chapter 6

Chapter 6 NutritionChapter 6 Nutrition

6.1 Types Of Nutrition

Learning Outcomes

• State the types of nutrition• Explain autotrophic nutrition• Explain heterotrophic nutrition• Classify organisms according to the types

of nutrition

Types of Nutrition• Nutrition is the entire process by which

organisms obtain energy from food, for growth, maintenance and repair of damaged tissues.

• The substances that are required for the nourishment of an organism are called nutrients.

• Living organisms can be divided into two main groups based on their nutritional habits : autotrophs and heterotrophs.

Chapter 6 Nutrition

Types Of Nutrition

Nutrition

Autotrophs(autos: self;

trophos : feed)

Heterotrophs(heteros: other)

1) Autotrophic nutrition• Autotrophs (autos: self; trophos: feed) are

organisms which practice autotrophic nutrition.

• Autotrophs synthesise complex organic compounds from raw, simple inorganic substances, such as air and water, by using light or chemical energy.

• Autotrophs manufacture their own food, either by photosynthesis or by chemosynthesis.

a) Photosynthesis • (photo: light) is the process in which green

plants, called photoautotrophs, produce organic molecules from carbon dioxide and water using sunlight as a source of energy.

b) Chemosynthesis • (chemo : chemical) is the process in which

chemoautotrophs synthesise organic compounds by oxidising inorganic substances such as hydrogen sulphide and ammonia.

1) Autotrophic nutrition

Examples of autotrophs

Photoautotrophs - Trees

Chemoautotrophs- Bacteria

2) Heterotrophic nutrition• Heterotrophs (hetero: other) are organisms that

cannot synthesise their own nutrients but must obtain the nutrients from other organisms.

• Heterotrophic nutrition is a type of nutrition in which an organism obtains energy through the intake and digestion of organic substances, usually plant and animal tissues.

• Heterotrophs may practise holozoic nutrition, saprophytism or parasitism.

a) Holozoic nutrition• A type of nutrition which the organisms feed

by ingesting solid organic matter which is subsequently digested and absorbed into their bodies.

• Some examples are humans, herbivores, carnivores and some carnivorous plants such as pitcher plants and Venus flytraps.

2) Heterotrophic nutrition

Examples of heterotrophs

Carnivorous plants (Holozoic nutrition-Pitcher plants

Holozoic nutrition - Carnivores

b) Saprophytism• A type of nutrition which the organisms, called

saprophytes, feed on dead and decaying organic matter.

• Examples are bacteria and fungi which digest their food externally before absorbing the nutrients into their bodies.


Saprophytes-Fungi

c) Parasitism • Is a close association in which an

organism, the parasite, obtains nutrients by living on (ectoparasite) or in the body (endoparasite) of another living organism, the host.

• The parasite absorbs readily digested food from its host.

• Examples of parasites include fleas and lice, various bacteria, fungi and the worms which infest the human intestinal tract.


Parasites Lice‑

Chapter 6 Nutrition

Types Of Nutrition

Nutrition

Autotrophs

Photosynthesis

Chemosynthesis

Process of synthesis of food by using light energy

Process of synthesis of food by using chemical energy

Chapter 6 Nutrition

Types Of Nutrition

Nutrition

Heterotrophs

SaprophytismHolozoic Paratism

Hunts and eat other organisms.

Absorbs nutrient from dead and decaying organic matter.

• Absorb nutrient from living hosts.

• Ectoparasites and endoparasites.


6.2 Balanced Diet

Learning Outcomes• State the necessity for a balanced diet• explain the factors affecting the daily energy requirement

of the human body• Determine the energy value and nutrient content in food

samples• Explain the functions and sources of vitamins and minerals

in diet to maintain health• Explain the functions and sources of roughage or dietary

fibre in a diet • Explain the functions of water in the body• Justify the selection of an appropriate balanced diet for a

target group

Chapter 6 Nutrition

Balanced Diet

Contains correct proportions of all classes of food according to the needs of body.

Contains correct proportions of all classes of food according to the needs of body.

Balanced Diet

The Necessity for a

Balanced Diet

For various metabolic reactions.

Source of energy.

For growth and repair of damaged body tissue.

Chapter 6 Nutrition

Balanced Diet

Daily Energy Requirement

Energy value is quantity of heat released from the combustion of 1 gram of food.

During respiration, the energy is released in an oxidation process, which is similar to the combustion (burning) of food.

When the food is burnt, it releases energy, mainly in the form of heat

The assumption made is that respiration releases the same amount of energy as combustion does.

Chapter 6 Nutrition

Balanced Diet

Daily Energy Requirement

Unit of energy value = joule per gram (Jg-1).

Energy Content/ Value of food

• The amount of heat generated from the combustion of one gram of food is known as the energy value of the food.

• The unit used to describe energy values in food is joule per gram (J g-1).

• The amount of energy in food can also be expressed in terms of calories.

Energy content of food• Table 1 shows the calorific values for the three

main food classes.

Which class of food has the highest energy value?

Energy Content / Value of food• The energy content of a

particular food can be measured by burning a known mass of the food completely in the presence of oxygen in a bomb calorimeter

(Figure 1).• The bomb calorimeter is

used to calculate the energy value of various types of food samples.

• It consists of a container in which the food sample is sealed with excess oxygen.

• The electrical coil ignites the food sample.

Figure 1 : A food calorimeter or a bomb calorimeter

Figure 2: Apparatus set-up to determine the energy value in a food sample in the lab

• The energy content of a sample of food can be determined by first weighing the sample and then completely burning the food in an atmosphere of oxygen.

• The heat released by the burning food is transferred to a known volume of water, causing a rise in the temperature of the water.

• The energy value of food can be calculated as follows:

Energy Content / Value of food

• The following data show the results of an experiment to determine the energy value of a peanut.

Energy content of food

Nutrient Content in Food

• The nutrient content of different food samples can be determined by carrying out food tests.

• Certain foods are rich sources of a particular nutrient, for example, starch, proteins or lipids.

ITeach – Biology Form 4

Chapter 6 Nutrition

Balanced Diet


VitaminsVitamins

Fat Soluble VitaminsWater Soluble

Vitamins

For maintenance of good health and efficient metabolism

Can be stored in body fat

Can be stored in body fat

Vitamins A, D,E,K Vitamins A, D,E,K

Obtained from daily diet

Obtained from daily diet

Vitamin B and C Vitamin B and C


Chapter 6 Nutrition

Balanced Diet


MineralsMinerals

Macrominerals Microminerals

• Vital for maintenance of good health

• Must be obtained through diet

Ex: Calcium, phosphorus

Required in large quantity 100mg / day

Required less than 20 mg / day

Ex: Ferum, iodine,zinc

Chapter 6 Nutrition

Balanced Diet

Roughage or Dietary Fibre

Made up of cellulose.

Stimulate peristalsis and prevent constipation

Eliminate toxic substances which can cause bowel cancer

Constipation result from deficiency of roughage.


Chapter 6 Nutrition

Balanced Diet

WaterWater

Act as medium of transport for nutrients

Act as medium of transport for nutrients

Healthy adults need 2 to 2.5 litres of water a day.

Healthy adults need 2 to 2.5 litres of water a day.

Water loss need to be replaced to prevent dehydration.

Water loss need to be replaced to prevent dehydration.

Chapter 6 Nutrition

Balanced Diet

Selection of an Appropriate Balanced Diet

Lipids, salt and sugar

Meat and alternatives

Fruits and vegetables

Rice and alternatives

Level 4

Level 3

Level 2

Level 1

Which level we should take in a large quantity?


6.3 Malnutrition


Chapter 6 Nutrition

Malnutrition

MalnutritionOccurs when a person’s diet is not balanced.

Protein deficiency will lead to Kwashiorkor and Marasmus problems.

Deficiency diseases caused by inadequate intake of mainly vitamins, minerals and amino acids.

Osteoporosis result from a diet lacking in calcium.

Obesity will result in cardiovascular disease and diabetes mellitus.

Processing food can cause high blood pressure.

Kwashiorkor

Marasmus


6.4 Food Digestion


6.4 Food Digestion• The food we consume are complex organic

molecules which are too large to pass through plasma membranes and enter body cells.

• In order for food substances to be used by the human body, they have to be converted into a form that can be readily absorbed by the body cells.

• Digestion is the process that breaks down complex food substances into simpler, soluble molecules that are small enough for the body to absorb.

• Food digestion takes place in the alimentary canal, a long, muscular tract which extends from the mouth to the anus.

• The alimentary canal consists of the: • mouth• oral cavity • Pharynx• Oesophagus• Stomach• small intestine (duodenum, jejunum and ileum)• large intestine (appendix, caecum, colon,

rectum) • anus.

The Human Digestive System

• The small intestine constitutes two thirds of the length of the alimentary canal.

• Digestion breaks down:

carbohydrates into glucose moleculesproteins into amino acidslipids into glycerol and fatty acids.


Chapter 6 Nutrition

Food Digestion

Breaks down of larger food substances to simpler soluble molecules, tiny enough for body to assimilate.

Food Digestion

Starchdigest

Glucose

Protein Amino Acids

Lipids Glycerol + Fatty Acids

digest

digest

• These essential substances are required by the body cells to carry out metabolic processes.

• For example:glucose is oxidised to generate energyamino acids are used to synthesise

proteins such as enzymes and hormoneslipids form a major component of

plasma membranes.

• As the food passes through the alimentary canal, it is broken down in stages until the digestible material is dissolved and absorbed.

• The indigestible residue is removed through the anus.

• Digestion involves both physical and chemical processes.

1) Physical digestion

• involves the breaking down of large pieces of food into smaller pieces by mechanical means. It starts in the mouth with the slicing and chewing action of the teeth.

• continues to a smaller extent in the stomach by the churning action brought about by the contraction of the muscles of the stomach wall.

2) Chemical digestion

• Process of breaking down of complex food molecules into simple soluble molecules by digestive enzymes.

• This process normally involves hydrolysis reactions. (involved/need water)


Chapter 6 Nutrition

Food Digestion

Human Digestive System

Takes place in alimentary canal with aid of digestive juices.

Physical digestion - breaking down of large pieces of food into smaller pieces.

Chemical digestion - break down of complex food molecules by digestive enzymes into smaller molecules.

Oral cavity

Liver

Gall bladder

Rectum

Small intestine

Large intestine

Pancreas

Stomach

Oesophagus

PharynxSalivary glands

(A) Digestion in the mouth

• The digestive process starts in the mouth.

• The chewing action breaks down the food into smaller pieces and increases the surface area of the food for digestive enzymes to act on.

• The presence of food in the mouth triggers secretion of saliva by three pairs of salivary glands.

• Saliva contains the enzyme salivary amylase which begins the hydrolysis of starch to maltose.


Chapter 6 Nutrition

Food Digestion

Digestion in the Mouth

Peristalsis: A series of wave-like muscular contraction along oesophageal wall.

Starch + watersalivary

maltoseamilase

• The thoroughly chewed food is rolled into a mass called a bolus in preparation for swallowing.

• During swallowing, a cartilage flap called the epiglottis temporarily closes the airway to prevent food from entering the trachea.

• Next, the bolus enters the oesophagus, a muscular tube lined with epithelium and mucous glands.

• The mucus :lubricates the bolus aids the movement of the bolus along the

oesophagus by peristalsis, a series of wave-like muscular contractions along the oesophageal wall (Diagram 1).

• When the cardiac sphincter relaxes, the bolus enters the stomach.

• Cardiac sphincter is a ring of muscles which control the opening of the stomach.

Diagram 2 :Secretion of gastric juice in the stomach

Diagram 1: Peristalsis along the oesophagus


Chapter 6 Nutrition

Food Digestion

Digestion in the Mouth

Peristalsis: A series of wave-like muscular contraction along oesophageal wall.

Starch + watersalivary

maltoseamilase

(B) Digestion in the stomach• The stomach is a thick-walled, sausage-

shaped organ situated below the diaphragm.

• It is a muscular sac with a highly folded inner wall.

• The epithelial lining of the stomach contains gastric glands that secrete gastric juice (Diagram 2).

• Gastric juice contains mucus, hydrochloric acid and the enzymes pepsin and rennin.

Diagram 2 :Secretion of gastric juice in the stomach

(a) Hydrochloric acid• Creates an acidic condition (pH 1.5- 2.0)

which is optimal for the action of the enzymes in the stomach.

• Stops the activity of salivary amylase.• Helps to kill bacteria in food.

(b) Pepsin • starts the hydrolysis of large protein

molecules into smaller chains of

polypeptides by breaking specific peptide

bonds.

(c) Rennin • coagulates milk by converting the soluble

milk protein, caseinogen, into insoluble casein.

• Mucus, secreted by the goblet cells of the gastric gland, protects the stomach wall from the action of hydrochloric acid and digestive enzymes.

• Food stays in the stomach for a number of hours.

• During this period, the food is thoroughly churned and mixed with the gastric juice by the peristaltic contractions of the stomach wall.

• Eventually, the contents of the stomach become a semi-fluid called chyme.

• Relaxation of the pyloric sphincter allows the chyme to gradually enter the duodenum.

Food

Oesophagus

LungLung

Stomach

Diaphragm


Chapter 6 Nutrition

Food Digestion

Gastric glands secrete gastric juice.

Gastric juice consists of mucus, hydrochloric acid, enzyme pepsin and rennin.

High acidity (pH 2) - sufficient to destroy existence bacteria in food.

Digestion in the Stomach

Protein + waterpepsin

polypeptides

Caseinogenrennin

casein

Finally, chyme is produced.

stomach

(C) Digestion in the small intestine

• The small intestine consists of the duodenum, jejunum and the highly coiled ileum.

• The duodenum, the first part of the small intestine, receives chyme from the stomach and secretions from the gall bladder and pancreas.

2) Digestion in the ileum

• Glands in the wall of the ileum secrete intestinal juice which contains digestive enzymes needed to complete the digestion of peptides and disaccharides.

• The intestinal enzymes require an alkaline medium to act at an optimum rate.

• At the end of the digestive process, all carbohydrates are digested into monosaccharides such as glucose, fructose and galactose.

• Proteins are digested into amino acids and lipids into fatty acids and glycerol.

* Show summary

• Vitamins and minerals are extremely small and soluble and need not be digested.

• Dietary fibre cannot be digested in the human body as the enzyme cellulase is not produced in the human alimentary canal.

* Show summary

Ileum

Liver

PancreasDuodenum


Chapter 6 Nutrition

Food Digestion

Digestion in Small Intestine

Starch, protein and lipids are digested here

Receives chyme from stomach Produced bile that helps neutralise acidic chyme and optimises pH for enzyme action in duodenum

Secrete intestinal juice

Major site of nutrient absorption

Ileum

Liver

Pancreas

Secretes pancreatic juice that contains enzyme amylase, trypsin and lipase

Duodenum

Digestion of cellulose in ruminants and rodents

(a) The digestive system of ruminants• Herbivores like ruminants and rodents feed on

plants which contain a high percentage of cellulose, a polysaccharide which is extremely insoluble.

• Therefore, much of the energy in their diets is stored in this complex carbohydrate. The breakdown of cellulose requires the enzyme cellulase.

• Ruminants obtain most of their energy from the breakdown of cellulose of plant cell walls by cellulase.

Ruminants

• The herbivors that regurgitate food and rechew the food.

• Although ruminants do not produce cellulase, their digestive systems are specially adapted to carry out cellulose digestion.

• Ruminants like cows and goats have stomachs which are divided into four chambers, namely rumen, reticulum, omasum and abomasum.

Rumen

Omasum

Reticulum

Abomasum


Chapter 6 Nutrition

Food Digestion

Digestive System in Ruminants

Rumen

Cellulose is broken down by cellulase.

Omasum

Cellulose is hydrolysed.

Cud is swallowed again into mouth and chewed to break down cellulose.

Reticulum

Reswallowed cud is moved to omasum.

Large particle of food are broken down into smaller pieces by peristalsis.

Abomasum

Proteins and food substances are digested by digestive enzymes.

The food then passes through small intestine.

• This adaptation enables ruminants to carry out rumination, the process of regurgitating food and rechewing it.

• The first two chambers, the rumen and reticulum, are specialised compartments which have large communities of bacteria and protozoa.

• These microorganisms are able to secrete cellulase to digest cellulose.

• In many cases, the microorganisms also use the sugars and other products of cellulose digestion along with minerals to synthesise certain nutrients, such as vitamins and amino acids, which are essential to the ruminants.

• Diagram 4 shows the processes involved a cellulose digestion in the digestive system of a cow.

b) The digestive system of rodents and other Herbivores

• In rodents like rats and herbivores like rabbits, the caecum and appendix are enlarged to store the cellulase-producing bacteria.

• In herbivores like, the breakdown products pass through the alimentary canal twice.

• The faeces in the first batch are usually produced at night, and are soft and watery.

The digestive system of rodents and other Herbivores

• These are eaten again to enable the animals to absorb the products of bacterial breakdown as they pass through the alimentary canal for the second time.

• The second batch of faeces become drier and harder.

• This adaptation allows rabbits to recover the nutrients initially lost with the faeces.

Diagram 4: Digestion of cellulose by the digestive system of a rabbit

1

2

3

4


Chapter 6 Nutrition

Food Digestion

RodentsRodents

Have long and large caecum.Have long and large caecum.

Cellulose is digested in the caecum by bacteria.Cellulose is digested in the caecum by bacteria.

caecum

ileum


Chapter 6 Nutrition

Food Digestion

Comparison of Digestive Process in Humans, Ruminants and Rodents

Human

Cannot digest cellulose

No enzyme cellulase

Stomach has one chamber

Caecum is short

Ruminant

Digest cellulose in stomach

Enzyme cellulose is secreted in the stomachStomach has four

chambers

Caecum is short

Rodent

Digest cellulose in the caecum

Enzyme cellulose is secreated in the caecumStomach has one

chamberCaecum is long and

large

Problems associated with food digestion

• The function of the digestive system depends largely on proper nutrition.

• Proper nutrition can help the digestive system functions at its best.

• There are many problems associated with the digestion of food.

(1)Incomplete digestion

• Incomplete digestion of food may cause severe pain in the abdomen followed by nausea, vomiting and a bloated stomach.

• Incomplete digestion of food is caused by excessive intake of food, eating too much oily food or eating too fast.

(1) Incomplete digestion

• If the food is not chewed properly before swallowing, the stomach cannot digest the food properly and this decreases the effectiveness of the digestive enzymes.

• Eating moderately and chewing food properly help prevent incomplete digestion of food.

(2) Reduced production of specific digestive enzymes

• Reduced production of specific digestive enzymes can cause digestive problems.

• Adults usually find it difficult to digest lactose (milk sugar) compared to a baby or a child because of the lack of lactase. This condition is known as lactose intolerance.

(2) Reduced production of specific digestive enzymes

• Damage to organs such as the pancreas causes reduced production of digestive enzymes for the digestion of starch, proteins and lipids.

• As a result, digestion of these foods will be disrupted and the body will not be able to obtain sufficient nutrients.

(3) Gallstone preventing the flow of bile

• A person who often eats fatty food encourages the formation of gallstones in the bile duct and gall bladder.

• Gallstones are formed through the hardening of cholesterol. It is also caused by the excessive secretion of bilirubin and bile salts.

• The size of the gallstones may be as small as a grain of sand or as big as a golf ball.

(3) Gallstone preventing the flow of bile

• When the gallstones block the bile duct, bile cannot be channelled out. As a result, lipids cannot be emulsified and are difficult to digest.

• Formation of gallstones usually occurs in obese people.


6.5 Absorption And Assimilation Of Digested Food


Absorption And Assimilation Of Digested Food

• Digested food consists of small molecules which can pass through the plasma membranes of the body cells.

• To enter the body cells, nutrients in the lumen of the small intestine must be transported across the intestinal lining into the bloodstream.

• Ileum, the last part of the small intestine is the major site of nutrient absorption.

Adaptive Characteristics of the Small Intestines for Absorption

It is the longest section of alimentary canal (about 6m) for longer digestion time and greater absorption of nutrients.

The intestinal lining (inner wall) is highly folded and covered by tiny finger-like projections called villi.

The epithelial cells of a villus have a lining of microscopic projections called microvilli. Villi and microvilli increase the surface area for absorption of nutrients.

Villus, microvilli, blood capillaries and lacteal increase the rate of nutrient absorption and assimilation.

Chapter 6 Nutrition



Epithelial cells

Blood capillaries

Lacteal

Microvilli

Epithelial cell

Adaptive Characteristics of the Small Intestines for Absorption

The epithelial lining is only one cell thick to make the absorption of nutrients easy.

Each villus also has a network of blood capillaries and lymphatic vessel called lacteal ( blood vessels) to increase absorption and transportation of nutrients.

Villus, microvilli, blood capillaries and lacteal increase the rate of nutrient absorption and assimilation.

Chapter 6 Nutrition



Epithelial cells

Blood capillaries

Lacteal

Microvilli

Epithelial cell

(A) Absorption of Digested Food

Nutrient absorption involves both diffusion and active transport.

(a) In the blood capillaries:

(1) Absorption of glucose and amino acids

• Initially, they diffuse (facilitated diffusion) into the epithelial cells and are absorbed into the capillaries.

• Subsequently, the transport of the remaining nutrients across the epithelial lining involves active transport which energy is used.


(2) Absorption of mineral ions and water soluble vitamins B and C • Are absorbed by diffusion (facilitated

diffusion) into the blood capillaries.

(b) In the lacteals:

(1)Absorption of fatty acids and glycerols• Fatty acids and glycerol diffuse into the

epithelial cells of the villi and then they recombine to form droplets of lipid before enter the lacteals.


(b) In the lacteals:

(2) Absorption of fat soluble vitamins (ADEK)• Are also diffused (simple diffusion) and

absorbed into the lacteals.

(c) In the colon:

(1) 90% of water and some remaining mineral ions are reabsorbed into the cells lining the colon and subsequently into the bloodstream.


(c) In the colon:

(2) Vitamin K that is synthesized by the bacteria in the colon is also absorbed.

The absorbed nutrients are transported to body tissues or organs to be assimilated or to be stored.

Chapter 6 Nutrition


Absorption of Digested Food

Capillary network- allows transport nutrient to liver

Epithelial cell- allows rapid diffusion of nutrients

Lacteal- allows absorptions of fat

To liver – (glucose, amino acids, minerals)

To thoracic duct(fat droplets, Vitamin A,D,E,K)

(B) Assimilation of Digested Food

Assimilation: is a metabolic process where the

nutrients are used (utilised) to form complex compounds or structural components.

Happens in the liver and in the body cell.

(B) Assimilation of Digested FoodGlucose, amino acids, water soluble

vitamin B and C and minerals are transported by the blood vessels to the hepatic portal vein. (Textbook, page 119)

The hepatic portal vein then transports these nutrients to the liver to be processed for assimilation or metabolic processes.

The blood circulatory system transports the nutrients from the liver to the body cells for assimilation.

(B) Assimilation of Digested Food

The lipid droplets and fat soluble vitamins ADEK are transported by the thoracic duct to the left subclavian vein.

The nutrients then enter the blood circulatory system.

Assimilation in the Body Cells

Amino acids which enter the cells are used for the:

• Synthesis of new protoplasm • Repair the damaged tissues• Important building blocks in the

synthesis of enzymes and hormones.

Glucose is used to produce energy in cellular respiration.

Lipids represent the major energy store of the body. Excess lipids are stored in the adipose tissue.

Some lipids, eg: phospholipids and cholesterols are major components of plasma membranes.

Assimilation in the Body Cells

Functions of the LiverThe liver acts as a checkpoint which controls

the amount of nutrients released into the blood circulatory system.

(a) Regulation of blood glucose levels:• Excess glucose is converted by insulin to

glycogen and stored in the liver.• When the glycogen store in the liver is full,

excess glucose is converted into lipids by the liver.

• When the blood glucose level decreases, glycogen is converted by glucagon to glucose.

Functions of the Liver

(a) Regulation of blood glucose levels:

• Glucose is distributed throughout the body by the circulatory system.

• When the glucose molecules reach the cells, they are oxidized to release energy during cellular respiration.

(Textbook pg 119, Figure 6.12)

• When there is short supply of glucose and glycogen, the liver converts amino acids to glucose.

Functions of the Liver(b) Deamination:

• Excess amino acids cannot be stored in the body and are broken down in the liver by a process called deamination.

• Excess amino acids are converted to ammonia which is then converted to urea to be excreted.

Functions of the Liver(c) Detoxification:

• The liver cells remove the harmful substances from the blood. Bacteria are killed by phagocytic cells in the liver.

• The liver cells convert harmful substances to a compound which are less toxic by modified chemically and are eliminated.

Functions of the Liver

(d) Storage Function:• Stores fat soluble vitamins A and D, water

soluble vitamin B12 and mineral ions.

(e) Production of Bile:• Bile is transported to the duodenum to

emulsify fats.(f) Synthesis of Plasma Protein:• Site of synthesis fibrinogen and

prothrombin (components in blood clotting)


Chapter 6 Nutrition


Assimilation Of Digested Food

Assimilation is where nutrients are used to form complex compounds.

Deamination – Broken down process of excess amino acid in liver.

Detoxification - liver cells remove harmful substances from blood or convert them to less toxic compounds.

•Glucose --> Glycogen

•Glycogen -->Glucose

•Excess glucose --> Lipids

•Amino acid --> Plasma protein


6.6 Formation Of Faeces And Defaecation

Formation Of Faeces And DefaecationAfter absorption of nutrients has taken place in the

small intestine, the intestinal content enter the colon.

The intestinal contents are mixture of:

~water

~undigested food substances

~indigestible fibre (most is cellulose from plant

cell walls)

The movement of these undigested materials along the colon is slow and helped by peristalsis.

Formation Of Faeces And Defaecation

In the colon, about 90% of the water and mineral ions are reabsorbed from the undigested materials into the bloodstream.

Vitamin B12 and K that are synthesized by the symbiotic bacteria in the colon are also absorbed.

Finally, the remaining food residue is known as faeces.


Faeces consists of:

~undigested food residue

~dead epithelial cells (membranes of

intestine)

~bile pigments (bring colour to the faeces)

~toxic substances / bacteria

~water

~fibre


The wall of the colon secretes mucus to smoothen the movement of the faeces.

The faeces is kept in the colon for 12-14 hours.

The faeces is pushed into the rectum which is the temporary storage place.


When the rectum is full, pressure in the rectum increases, causing a desire to expel the faeces from the body.

Spinchter muscles relax and the rectal wall contracts.

The faeces are eliminated through the anus in a process called defecation.


Defecation is important to:

~eliminate undigested substances

~eliminate toxic substances

produced during fermentation by

bacteria.


Chapter 6 Nutrition


Formation of Faeces and Defaecation

Avoid toxicity in human body.

Excrete wastes and unwanted toxic substances.

Defective defaecation may lead to headache and lost appetite.

The formation of faeces in the colon

colon

rectum

solid waste

Role of Microorganism in the Colon The colon also serves as a habitat for a flourishing

population of bacteria.

The symbiotic microorganisms living in the human colon, eg:

~ Escherichia coli

1) synthesise vitamin B12 and K that can be

absorbed through the colon wall

2) maintain a stable environment in the alimentary

canal.

The microbial population in the colon can be killed due to excessive consumption of antibiotics.

Problem Related to Defecation1. Constipation • Difficulty elimination of feaces as the faeces become dry and

hard.

• This is caused by the extremely slow movement of faeces

through the colon.

• As a result, a greater amount of water is reabsorbed in the colon, making the faeces hard.

• Can be avoided :

~by drinking a lot of water

~by taking dietary fibre

• Chronic constipation can cause piles, which can cause bleeding during defecation.

Problem Related to Defecation

2. Haemorrhoids • Swollen veins in the rectum or anus due to

excessive pressure exerted to eliminate faeces.

3) Colon cancer• The symptoms are irregular frequency of

bowel (usus) movement and blood in faeces.


6.7 Evaluating Eating Habits


Earlier, we learned the importance of a balanced diet. It is also important that we practise good eating habits.

In recent times, we hear of increasing cases of eating disorders. Most cases of eating disorders reflect a disruption in normal eating habits.

Good eating habits mean taking food in the correct quantity at the correct time.

We should refrain from overeating or eating too little during a meal. For example, a balanced breakfast is essential as it provides all the nutrients required by the body.

Evaluating Eating Habits

A normal person should take in three meals a day: breakfast, lunch and dinner. He or she must also eat a variety of food to satisfy the body's nutrient requirement.

Sufficient amounts of fibre from fruits and vegetables must be included in the meals.

Drinking at least 2 to 3 litres of water a day is essential. This helps to flush out toxins from the body.

One should also avoid taking excessive fatty food and food rich in sugar.

Improper eating habits are associated with various health problems which affect a large number of the population.



Chapter 6 Nutrition


Good eating habits mean taking food in the adequate quantity at the right time.


Health Problem

Related to Bad Eating

Habits

Health Problem

Related to Bad Eating

Habits

Bulimia

Obesity

Anorexia nervosa

Gastritis

Health Problems Related To Eating Habits

(A) Gastritis

is a condition where the epithelial lining of the stomach becomes inflamed.

The stomach lining is normally covered with a layer of mucus which protects it from hydrochloric acid and digestive enzymes.

Gastric juice is secreted into the lumen of the stomach whenever one feels hungry.

If food is not taken at regular times, the absence of food in the stomach results in the acidic gastric juice acting on the epithelial lining of the stomach wall.

(A) Gastritis

Gastritis occurs when the protective mechanism in the stomach is disrupted and this results in damage to the stomach lining.

When the breach in the stomach lining develops into a hole, gastric ulcer may result.

For most types of gastritis, treatment involves taking medication such as antacids to reduce or neutralise stomach acids.



Excessive alcohol consumption and stress:

• can damage the stomach lining.

Taking aspirin and other pain relievers regularly:

• can also cause the stomach lining to become inflamed.

(B) Obesity

is defined as the excessive storage of energy in the form of fat.

This results from a lack of balance between food intake and energy expenditure.

Obesity is one of our nation's most critical health problems and is directly responsible for a huge number of deaths each year.


(B) Obesity

Obese people are predisposed to a number diseases including cardiovascular disease, hypertension and diabetes

For many, obesity leads to often life threatening diseases disorder such as anorexia nervosa and bulimia.


(C) Aneroxia nervosa

Experience an intense fear of gaining weight.

They intentionally deprive themselves of food to achieve a severe loss in body weight, often 15% or more below their normal body weight.

This condition is potentially fatal and is recognised as a

psychological disorder.

Individuals with this disorder have a distorted body image which convinces them they are fat.


(C) Aneroxia nervosa

In an attempt to boost their self-esteem, they refrain from eating to the extent that they become extremely emaciated.

They lose both fat and muscle and this eventually leads to disruptions of the functions of the heart, endocrine system and reproductive system.

Early treatment can correct some of the physical symptoms through nutrition and gradual restoration of body mass.


(D) Bulimia

may have a normal body mass.

Bulimia is characterised by sequences of excessive food intake and purging to counteract the effects of the binge.

The victims engage in consuming huge amounts of food within a short period of time.


(D) BulimiaThis is followed immediately by self-induced

vomiting or purging through laxative abuse.

Repeated purging results in serious injury to the digestive tract and can cause an imbalance of mineral ions in the blood.

This can lead to cardiovascular problems and kidney damage.


Nutrient Contents of Food

• Good eating habits also involve choosing the types of food we eat wisely.

• Are you aware of the contents of the food that you consume everyday?

• Do you normally check the food labels for information regarding the nutrient contents of the food you buy?

• Food manufacturers are required to provide nutritional labelling on commercially packaged food.

• The labels of food packets and containers provide complete information about the total calories per serving and the contents of various nutrients.

Nutrient contents of food

• As consumers we are able to make informed choices about the types of food we consume by studying the food labels.

• When buying food, we must consider the nutrients contents, freshness and various safety aspects

~ for example whether the food contains

additives which may have adverse effects

on our health.

• The nutritional information obtained from these sources will help reduce health problems related to poor eating habits.


6.8 The Importance Of A Healthy Digestive System



Chapter 6 NutritionThe Importance Of A Healthy Digestive System

The Importance Of A Healthy Digestive

System

The Importance Of A Healthy Digestive

System

Effects of a Defective Digestive

System on Health

Indigestion

Constipation

Haemorrhoids

Diarrhoea

Formation of bile stone

Too much spicy food Overeating

Prolonged constipation

Prevent the flow of bile to duodenum


Chapter 6 Nutrition

The Importance Of A Healthy Digestive System

Ways to Take Care of Digestive System

Good eating habit

Avoid junk food Eat nutritious food


6.9 The Importance Of Macronutrients And

Micronutrients In Plants



Elements required by plants• Green plants are able to synthesise their own nutrients.

• To do this, they require raw materials in the form of inorganic substances: carbon dioxide, water and mineral nutrients.

• Mineral nutrients are essential chemical elements required by plants to:

1) complete their life cycle

2) achieve optimal growth and development.

• What are the mineral elements required by plants?


Chapter 6 NutritionThe Importance Of Macronutrients And Micronutrients In Plants

The Importance of Macronutrients and Micronutrients in Plants

To accomplish their life cycle, growth and development.

Ex: Carbon (C), hydrogen (H) and Oxygen (O).



Elements required by plants

• Carbon (C), hydrogen (H) and oxygen (O) are three macronutrients that can be easily obtained from carbon dioxide in the atmosphere and water from the soil.

• Therefore, deficiency in these nutrients rarely occurs.

• They are the most abundant elements found in a plant and form the major ingredients of organic compounds, most of which are carbohydrates.

• The remaining mineral nutrients are obtained in the form of inorganic ions from the soil.



• The six macronutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S) are needed by plants in relatively large amounts.

• Micronutrients which include boron (B), copper (Cu), ferum (Fe), manganese (Mn), molybdenum (Mo) and zinc (Zn) are needed in very small amounts.

• To determine which elements are required for normal growth, plant seedlings are grown in a complete culture solution, also known as Knop's solution (Table 6.3).



• We can investigate whether a plant needs a particular mineral element by eliminating it from Knop's solution.

• Macronutrients and micronutrients are involved in the synthesis of chemical substances essential for the healthy growth of plants.

• They are also required for the various metabolic processes which take place within plants.

• The absence of one or more of these nutrients can lead to mineral deficiency in plants.

6.9 The Importance Of Macronutrients

And Micronutrients In Plants

• The symptoms of mineral deficiency depend on the functions of the mineral in the plant.

• For example, nitrogen (N) is the macronutrient that influences plant growth the most.

• It is a major component of proteins, nucleic acids, chlorophyll and enzymes of photosynthesis and respiration.

6.9 The Importance Of Macronutrients

And Micronutrients In Plants

• Nitrogen is important for the rapid growth of stems and leaves, and increases seed and fruit yield.

• The most common symptoms of nitrogen deficiency are chlorosis and stunted growth.

• In chlorosis, synthesis of chlorophyll is inhibited, resulting in pale yellow leaves.

• Table 6.4 The functions and effects of deficiency of other macronutrients



Function of Macronutrient in Plants

FunctionFunctionElementElement

Nitrogen

Phosphorus

Potassium

Calcium

Magnesium

To synthesis chlorophyll

Necessary for cell division

Protein synthesis, carbohydrate metabolism

Needed for formation of cell wall

To synthesis chlorophyll and protoplasm

Sulphur To synthesis protein and nucleic acids



The Effects of Macronutrient Deficiency

P

Mg

S

N

K

Ca Stunted growth Leaves become

distorted

Yellow-edged leaves Plant will die

Leaves turn yellow

Red or purple spots on old leaves

Red spots on leaves surfaces

Poor growth

General yellowing of affected leaves

The Functions And Effects of Deficiency of Micronutrients

• In addition to macronutrients, micronutrients or trace elements, are also essential for plant growth.

• Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients to growing plants.

• Table 6.5 shows the functions and effects of micronutrient deficiency in plants.



Function of Micronutrients in Plant

FunctionFunctionElementElement

Boron

Copper

Ferum

Manganese

Molybdenum

Necessary for the development of apical meristems

Reproductive growth and flower formation

To synthesis chlorophyll

Activate certain enzymes

For nitrogen metabolism

ZincFormation of leaves, synthesis of auxin



The Effects of Micronutrient Deficiency

Zn

Mn

BFe

Mo

Cu Brown spots Death of tips of

young shoots

Chlorosis

Yellowing of young leaves

Mottled leaves

Brown spots between the veins

Death of terminal buds, abnormal plant growth

Studying the Effects of Macronutrient Deficiencies In Plants1) Problem statement

• What are the effects of macronutrient decencies in plants?

2) Variables• Manipulated variable: Components of mineral elements in each

jar • Responding variable: Condition of the plants• Constant variables: The volume of the solution, the size and

type of maize seedlings, air that is pumped into

the jar

3) Hypothesis• Plant grows healthily in a complete Knop's solution (jar B).

4) Materials• Maize seedlings, potassium nitrate, potassium dihydrogen phosphate,

magnesium sulphate, calcium nitrate, iron(III) phosphate, distilled water, cotton wool and black paper.

The apparatus set-up to study the effects of macronutrient deficiencies in plants

5) Apparatus:• Glass jars, rubber bungs with holes, straight glass

tubes to fit into the holes of the rubber bungs, L-shaped delivery tubes to be connected to an air pump, and a knife.

6) Technique• Observe and record the conditions of seedlings at the

end of one month.

*Note:• The growth of green algae can deplete the nutrient

content of the culture solutions and affect the results of the experiment.

7) Procedure:

1 Eight glass jars labelled A to H are prepared.

2 The jars are filled with the solutions as given in Table 6.9.

3 The jars are wrapped with black paper to prevent the

growth of green algae.

4 Eight maize seedlings of almost the same size are chosen.

5 The glass jars are connected to an air pump to provide

aeration to the roots so that respiration can take place.

6 The culture solutions are replaced every week to replenish

the nutrients absorbed by the maize seedlings.

7 The growth of each seedling is observed at the end of one

month.

8 The colour, number, size and shape of leaves, height of

seedlings, length of roots, the growth of branches and the

strength of the stems are observed and recorded in a

table.

Table 6.9 Nutrient contents of glass jars A to H

Results

8) Discussion: • The maize seedling in jar B grows healthily the jar

contains Knop's solution. • The seedling in jar A does not show any growth as it does

not contain any nutrients.• The maize seedlings in the other jars show the effects of

macronutrient deficiencies. • The symptoms shown are related to the function of each

macronutrients in plants

9) Conclusion

• Plants will only grow healthily when the contents of the nutrient components in the jar are complete (jar B) . If there is a deficiency of a certain nutrient, the plant will have symptoms that show what is lacking. The hypothesis is accepted.


6.10 Photosynthesis



Chapter 6 NutritionPhotosynthesis

Discovery Of Photosynthesis

Jean Baptiste Van Helmont

1640

Joseph Priestly1772

Jan Ingenhousz1779

Study how plants grow

Show green plant restore O2

Discover plant release O2 in presence of sunlight

Jean Senebier1780

Robert Mayer1845

F.F Blackman1905

Prove plant release O2 when there is CO2 Find light energy convert to chemical energyDetermine photosynthesis involve light and dark reaction

1937Verify photosynthesis require sunlight, water and CO2

Photosynthesis = CO2 + Water light Carbohydrate + O2

(glucose)

Robert Hill


Chapter 6 Nutrition

Photosynthesis

Leaf Structure and FunctionLeaf Structure and Function

Xylem- Transports water from roots to the leaf

Phloem- Transports organic product away from the leaf

Palisade mesophyll- Contains many chloroplasts.- Absorbs sunlight.

Guard cells- Regulate opening and closures of pores

Spongy mesophyl cell-Allow diffusion of water and gases.

Stomata- Allows gaseous exchange between leaf and environment

Upper epidermis -Prevents loss of water.

Cuticle- Enables the leaf to trap sunlight


Chapter 6 Nutrition

Photosynthesis

Adaption of Plants from Different Habitats to Carry Out Photosynthesis

Adaption of Plants from Different Habitats to Carry Out Photosynthesis

Land plants Land plants

Plant floating on surface of water Plant floating on surface of water

Adaption of Plants from Different Habitats

Desert plants Desert plants

Ex: Hibiscus

• An abundant chloroplast in palisade cells and spongy mesophyll cells

• More stomata on the lower surface of the leaf

Ex: Water lily

• Chloroplast are found in leaves and stems

• Large, round and flat leaves

Ex: Cactus

• Leaves in thorn form

• Reduced leaves with sunken stomata

Adaptation of Land plants

The distribution of stomata is more on the lower epidermis layer to absorb more carbon dioxide and reduce transpiration

Chloroplasts can be found abundantly in the mesophyll palisade cells and spongy mesophyll cells to absorb more light for photosynthesis

Floating plants such as the lotus, have huge, round and flat leaves to enable them to absorb more sunlight.

The distribution of stomata on the upper layers of the leaves facilitates the absorption of carbon dioxide and the release of oxygen

Submerged plants usually do not have stomata

Chloroplasts are found on the leaves and stem of the plants

Adaptation of Aquatic plants

• Have a few stomata which are sunken to reduce transpiration

• The stomata are usually found on the lower layers of the surface of the leaves

• Chloroplasts can be found on the stems and leaves

Adaptation of Dessert plants


6.11 The Mechanism Of Photosynthesis

Two main stages in photosynthesis are light reaction and dark reaction.

Chapter 6 Nutrition

The Mechanism Of Photosynthesis

The Mechanism of Photosynthesis

Granum Stroma

Light reaction occur here.

Two main substances required: H2O,

sunlight

Dark reaction occur here Three main

substances required: hydrogen atom , CO2,

ATP Products: H2O +

Glucose

Products: H2O + O2 +

ATP

Mechanism of Photosynthesis1) Light Reaction

• The chlorophyll in the thylakoids absorbs light energy which excites the molecule of chlorophyll until it releases an electron.

• The light energy is used to break down/ split water molecules to become hydrogen ions (H+) and hydroxide ions (OH-).

• This reaction is known as photolysis of water.

• Electrons combine with the hydrogen ions to produce hydrogen atoms and chemical energy in the form of ATP which will be used in the dark reaction.


• Hydroxide ions release electrons to the chlorophyll to replace the excited electrons released from chloroplast and form hydroxide group.

• The combination of hydroxide group will form water and oxygen.


• After the light reaction is completed, the dark reaction takes place.

• The dark reaction does not involve the use of light.

• Try to remember which parts of the chloroplast absorb light. Your answer will explain why the dark reaction does not involve light.

Mechanism of Photosynthesis1) Dark Reaction (Calvin Cycle)

• The dark reaction occurs in the stroma.• Hydrogen atoms from the light reaction

react with carbon dioxide and produce glucose.

• This reaction is known as the reduction of carbon dioxide to glucose.

• This reaction is catalysed by enzymes and involves the use of energy, ATP.

Mechanism of Photosynthesis1) Dark Reaction

6 (CH2O)

• (CH2O) is the basic unit of glucose.

• Six units of (CH2O) combine to form one molecule of glucose.

• The glucose monomers then undergo condensation to form starch.

• Starch is temporarily stored as starch granules in the chloroplasts.

Mechanism of Photosynthesis1) Dark Reaction

• The following is a complete equation for photosynthesis:

• 6H2O + 6CO2 C6H1206+ 6O2

Mechanism of Photosynthesis

Light energy

chlorophyll

A comparison between the light reaction and dark

Use in cellular respiration

Undergoes condensation to form starch

Two main stages in photosynthesis are light reaction and dark reaction.

Chapter 6 Nutrition

Summary

The Mechanism of Photosynthesis

Granum Stroma

Light reaction occur here.

Two main substances required: H2O,

sunlight

Dark reaction occur here Three main

substances required: hydrogen atom , CO2,

ATP Products: H2O +

Glucose

Products: H2O + O2 +

ATP


6.12 The Factors Affecting Photosynthesis


Chapter 6 Nutrition

The Factors Affecting Photosynthesis

Factors Affecting Photosynthesis

Factors Affecting Photosynthesis

3 Factors Affecting

Photosynthesis

Light Intensity

Concentration of Carbon Dioxide

Temperature


Chapter 6 Nutrition

Light Intensity

When the concentration of CO2 and temperature are controlled at constant level, the rate of photosynthesis is directly proportional to light intensity up to a certain point.(P)

Beyond point P, no increase in rate of photosynthesis even if the light intensity increases. Concentration of CO2 or

temperature become the limiting factor because of insufficient.

The rate of photosynthesis will increase again by increasing the concentration of CO2 or temperature.

Light intensity

Rate of photosynthesis


Refer textbook pg 135, Figure 6.19

Rate of photosynthesis increases when concentration of CO2

increases.

At BC, increasing CO2

concentration will not increase the rate of photosynthesis because light intensity and temperature are limiting factors.


Chapter 6 Nutrition



Concentration of Carbon Dioxide


Concentration of carbon dioxide


Photosynthesis rate is high when light intensity and temperature are high.


Chapter 6 Nutrition


TemperatureTemperature

When temperature increase as much as 10oC, rate of photosynthesis increases doubly.

At temperature above 40oC, enzymes are denaturated cause rate of photosynthesis to decrease and stops.

Conclusion:

Optimum temperature: 25oC to 30oC.


Temperature

Optimum temperature


The difference in the rate of photosynthesis in plants throughout the

day• The rate of photosynthesis is not constant

throughout the day.

• In the morning and evening: is low • In the midday: is the highest• At night: stop

The difference in the rate of photosynthesis in plants throughout the

year• The rate of photosynthesis is not constant

throughout the year.

• In the summer: is the highest • In the autumn: is low• During winter: decrease (cease)


6.13 A Caring Attitude Towards Plants



Chapter 6 Nutrition

A Caring Attitude Towards Plants

The Importance of

A Good Attitude

towards Plants

The Importance of

A Good Attitude

towards Plants

Regulates normal climate

Plays important roles in ecosystem

Produces green foods

Maintains contents of O2 and CO2 in air

Provide wildlife and fish habitat


6.14 Technology Used In Food Production


6.14 Technology Used in Food Production

Introduction The need for improving the quality and quantity of food

• The rapid increase in the country's population imposes a greater demand on food supply.

• There is a need to improve the quality and quantity of food production to meet the demands of the growing population.

• In order to improve the quality and quantity of food, the Agriculture Ministry of Malaysia has drawn up several strategies to sustain the production of food in the country.

• Among these are strategies to raise productivity in food production and support the food industries.

• The ministry has also given priority to the production of food such as rice, fruits, vegetables, fishes and poultry.

The efforts by various agencies to diversify food production

1) Ulam • is a type of salad which includes fresh leaves, fruits and other

plant parts which are eaten raw.

• It is a traditional Malay dish but it is now well accepted by other races.

• Examples of ulam include pegaga (Centella asiatica), shoots of papaya, kacang botor, petai (Parkia speciosa) and kemangi (Ocimum sanctum).

• They are rich in mineral ions, vitamins and fibre. Some of these plants are also used in the preparation of herbal medicines and drinks.


2) Chicken, fish and meat. • In order to diversify the sources of protein, the government

encourages the consumption of rabbit meat, quail meat, ostrich meat, freshwater fish and prawns.

• Rabbit meat is rich in protein but low in fat and cholesterol. The meat has a soft texture and is suitable for young children.

• Ostrich meat is nutritious, rich in protein and low in fat.• Freshwater fish like tilapia, jelawat and haruan are low in

cholesterol. Fish protein is easily digestible and is much needed by growing children for healthy development.

Photograph 6.8 The diverse sources of food


3) Mushrooms• Another nutritious source of food is mushrooms.

• There is a wide variety of mushrooms available in our country, for example, button mushrooms, abalone mushrooms and shittake mushrooms.

• These mushrooms have a high nutrient content and some, like the shittake mushrooms, are believed to be able to increase the body's immunity.

Methods used to improve the quality and quantity of food production

• These include:• Direct seeding for rice• Hydroponics for vegetables• Aeroponics for vegetables• Breeding of plants and animals• Tissue culture• Genetic engineering• Crop rotation• Soil management • Biological control.


Chapter 6 Nutrition

Technology Used In Food Production

Technology Used In Food Production

Method used to improve the quality and

quantity of food production

Crop rotation

Direct seeding

Hydroponics

Aeroponics

Breeding of plant

Animal breeding

Biological control

x

1) Direct seeding • is a method by which seeds are sown directly into the soil by

using special machines.

• The seeds are covered with soil while they are being sown.

• This technique does not involve transplanting of seedlings and therefore results in less damage to the roots of the seedlings.

• The plants achieve faster growth and this increases the yield.

• Less water is needed to irrigate the fields.

• This method is widely used in the planting of paddy to obtain higher yields of rice.

2) Hydroponics

• a commercial technique for growing certain crop plants in culture solutions rather than soil (Photograph 6.9)

• The roots of the plants are immersed in a solution which contains all the macronutrients and micronutrients required by the plants in the correct proportion.

• The plants are supported by a medium such as pebbles.

• The culture solution is aerated to provide sufficient oxygen for respiration.

3) Aeroponics

• is a modified technique of hydroponics. • In this method, the plants are suspended in

a special chamber with the roots exposed to the nutrient are sprayed onto the roots of the plants at suitable intervals.

• This enables the plant roots to absorb more oxygen in between the periods of spraying.

• Almost all types of vegetables like spinach, lettuce, tomatoes and chillies can be cultivated by using hydroponics and aeroponics methods.

• Both methods have a lot of benefits compared to planting in

soil:

1) Light intensity and temperature can be controlled to ensure that the environmental factors are at an optimum level for maximum growth.

2) The plants can be grown all year round and higher yields

can be obtained.

3) Plants achieve faster growth because the culture solutions

provide nutrients in a form that can be readily absorbed by

the roots and used by the plants to carry out living processes.

4) Selective Breeding (in Plants)• In this technique, different plant varieties with certain

beneficial characteristics are selectively bred.• The resulting varieties of plants (hybrid plant)

inherit the beneficial characteristics of both parent plants.

• Beneficial characteristics of hybrid plant:

~ have increased nutritional value

~ higher yields

~ show greater resistance to diseases and

climatic changes.

• In Malaysia, the most widely planted variety of oil palm is Tenera sp.

4) Selective Breeding (in Plants)• It is a variety produced by crossing the

parent varieties of Dura sp. and Pisifera sp.

• Tenera sp. possesses the beneficial characteristics of Dura sp. and Pisifera sp.

• It produces fruit with less fibre and more oil content (Photograph 6.10).

• The fruit do not drop off easily from the bunch.

• Many varieties of paddy, maize, sugar cane and vegetables have also been cross-bred by scientists.

• Photograph 6.10 The Tenera sp. variety has a big kernel, a thick mesocarp and a thin endocarp

5) Animal breeding • involves the cross breeding of two different

breeds of animals. • Animals have been selectively bred to enhance

the yields of milk, meat and other products. • In Malaysia, the hybrid cattle called Mafriwal is

bred in farms for its milk. • Mafriwal is a cross between a Friesian cow

and a Sahiwal bull. • Mafriwal produces more milk with low fat

content.• Many breeds of goats, sheep, chickens and

ducks have also been cross-bred in Malaysia.

Mafriwal

6) Tissue culture• This process involves tissue culture in which an

entire plant can be regenerated from the cells or tissues of a parent plant.

• The cells or tissues(explant) taken from the parent plant are grown in a sterile culture medium or culture solution which contains the necessary nutrients and growth hormones.

• Plantlets which are produced can then be transplanted to nurseries.

• In Malaysia, tissue culture of plant tissues enables commercial propagation of clones which have all the beneficial characteristics of the parent plants.

• This method helps increase the agricultural yield of many crop plants like papayas, pineapples and starfruits.

Photograph 6.11

Producing clones through tissue culture technique

7) Genetic engineering

• is a technique that has great potential in improving the quality and quantity of food to meet the needs of an increasing world population.

• This technique enables the characteristics of an organism to be altered by changing the genetic composition of the organism.

• It involves the transfer of beneficial genes from one organism to another organism.

• For example, genes from plants can be inserted into the DNA of animal cells and vice versa.

7) Genetic engineering

• The genetically modified organism (GMO) is called a transgenic organism.

• Developments in genetic engineering have enabled transgenic crop plants such as wheat, tomatoes, legumes, soya beans and potatoes to be cultivated commercially.

• These crop plants contain genes from other organisms to enhance growth, nutritional properties and resistance against diseases.

8) Soil Management

• Another method of increasing productivity is to practise proper soil management.

• Soil should be cultivated in a controlled manner

• So that not all minerals are removed from it at any one time.

• Regular addition of organic or inorganic fertilisers returns the nutrients to the soil.

• Ploughing helps increase aeration in the soil.

9) Crop Rotation• Many countries practise crop rotation to maintain

and improve soil fertility and prevent the build-up of pests which are peculiar to certain crop species.

• In this method, different plants are cultivated in succession on the same plot of land over a period of time. In a typical four-stage rotation, legumes are an important source of nitrogen for the soil. Other crops that can be included are leafy plants, plants that bear fruits like watermelons and root plants like onion and garlic.

• Steps must also be taken to reduce soil erosion and the leaching of nutrients from the soil. Addition of organic matter promotes humus formation and improves the soil structure. This helps promote plant growth.

10) Biological control

• Is the control of pests by biological means. • This is achieved by introducing a natural enemy of the pest,

such as a predator or a parasite. • The predator or parasite either feeds on or kills the pest. • In Malaysia, owls and snakes have been used successfully

to control the rat population in oil palm plantations. • In Australia, the population of the prickly pear cactus

(Opuntia sp.) is controlled by introducing the cactus moth (Cactoblastis cactorum).

• This method of pest control is beneficial as it reduces a number of problems associated with chemical control which uses pesticides.

• However, care must be taken to avoid upsetting the natural ecological balance, for example, a particular predator may harm other species which are beneficial.


6.15 Technological Development In Food Processing



Chapter 6 Nutrition

Technological Development In Food Processing



Process of preparing food to make it more attractive, more edible and last longer

The Necessity for Food Processing

To preserve food from food spoilage

Expanding the uses of food substances

To enhance its commercial value

To withstand long periods of transportation and storage


The necessity for food processing:• Food processing is the process of preparing

food to make it more attractive, more palatable and to last longer.

• So that it can withstand long periods of transportation and storage

• To preserve food by overcoming the factors that cause food spoilage. This avoids wastage of food and prevents food poisoning due to food spoilage.

• To increase its commercial value.

• Photograph 6.12 The various processed food found on the supermarket shelf


Chapter 6 Nutrition


Involves methods of preparing food to increase lifespan of food.

Food Preservation

What causes food spoilage?

What causes food spoilage?

Oxidation of foodOxidation of food

The action of microorganism on food

The action of microorganism on food

Infestation by insects and rodents

Infestation by insects and rodents


• Food preservation involves methods of preparing food to extend the lifespan of food so that it can be stored for future use.

• Food substances are processed in various ways to ensure that there is a continuous supply for the population.

What causes food spoilage? • One of the causes is the action of microorganisms on food,

especially decomposing bacteria and fungi which act on carbohydrates and proteins in food to produce carbon dioxide, water, ammonia, hydrogen sulphide and other organic substances.

• The presence of these substances spoils the food and makes it toxic.

• Food preservation prevents bacterial and fungal decay and contamination of food, which can cause food poisoning.


• Another cause for food spoilage is the oxidation of food.

• Have you noticed how apples turn brown very quickly when cut and exposed to air?

• This condition is due to oxygen reacting with enzymes and chemicals released by the cells in the fruit.

• What happens to fried food that is exposed to air for an extended period of time?

• Oily food becomes rancid, smells and tastes different as a result of oxidation.

• Rancid food is harmful to the body.

Correlating the food processing methods with factors causing food spoilage

• Microorganisms, like other living organisms, require food, water, oxygen and a suitable temperature for growth and reproduction. In addition, microorganisms can only survive in conditions with optimum pH and solute concentrations.

• Food can be preserved by destroying the microorganisms present in the food or by stopping the activities of these microorganisms.


Chapter 6 Nutrition


Types of Processing MethodTypes of Processing Method

7 Types of Processing

Method

Cooking

Pickling

Fermentation

Drying

Pasteurisation

Canning

Refrigeration

Correlating the food processing methods with factors causing food spoilage

1) Cooking • is the easiest way to prevent food spoilage. Heating food

at high temperatures can kill microorganisms and denature the enzymes that cause the breakdown of food.

2) Treating food with salt or sugar • causes the microorganisms to lose water due to osmosis. • Pickling food such as chillies with vinegar reduces the pH

and prevents microorganisms from growing. • Vegetables and fruits are normally preserved by using

this method.

3) Fermentation • Fruit juices and other food substances can be fermented by

adding yeast. • Fermentation of fruit juices produces ethanol which, at high

concentrations, prevents the juices from becoming spoiled. • The ethanol produced has great commercial value.

Traditional food such as tapai is produced by the fermentation of pulut rice or tapioca.

4) Drying • Fish, meat and fruits can be dried to preserve them. Drying

under the hot sun removes water from food• This prevents the microorganisms from growing. • The ultraviolet rays of the sun also kill bacteria and many

other microorganisms.

5) Pasteurisation• Milk is preserved by pasteurisation to destroy

bacteria which cause diseases such as those of tuberculosis and typhoid.

• This method of preservation retains the natural flavour of milk.

• Nutrients like vitamin B are not destroyed. In this process, milk is heated to 63°C for 30 minutes or to 72°C for 15 seconds followed by rapid cooling to below 10°C.

• The pasteurised milk can then be refrigerated to last for a few days.

• Fruit juices and soups can also be preserved this way.

6) Canning • Uses heat sterilisation to kill microorganisms

and their spores. • The food is packed in cans and steamed at

high temperatures and pressure to drive out air.

• The cans containing food are then sealed while the food is being cooled.

• The vacuum created within the cans prevents growth of microorganisms.

7) Refrigeration (Freezing)• Is a common method employed at home to

keep food such as meat and fish from spoiling. • Food stored at temperatures below 0°C can

remain fresh for a long period of time. • The extremely low temperatures prevent the

growth of microorganisms or the germination of spores.

Photograph 6.13 Examples of pasteurised milk

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