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LIFE PROCESSES

Looking at living things

Living things Although all living things look different from each other, they all have seven things in common.

These seven things are called life processes.

Something is only alive if it does all seven processes.

THE SEVEN LIFE PROCESSES

1

All living things move

Animals move their whole bodies to get from one place to another.

Plants turn towards the light and their roots grow down into the soil.

2

All living things reproduce

Animals have babies.

New plants grow from seeds.

3

All living things are sensitive

All living things respond to changes. Living things notice changes in their surroundings and react to them.

Eg. Plants grow towards the light.

Eg. People react to the temperature around them.

4

All living things need nutrition

Food is used to provide energy.

Green plants make their own food using sunlight.

Animals eat plants or other animals.

5

All living things excrete

Waste substances must be removed from the body.

Plants and animals both need to get rid of waste gas and water.

6

All living things respire

Plants and animals use the oxygen in the air to turn food into energy.

7

All living things grow

Babies grow into adults.

Seedlings grow into plants.

The seven life processes1 Move

2 Reproduce3 Sensitive4 Nutrition5 Excrete6 Respire7 Grow

Use the first letter from each process to help you remember them.

Move Reproduce Sensitive NutritionExcrete Respire Grow

They spell MRS NERG

This is MRS NERG !

Can you remember what each of the letters in her name stand for ?

Move Reproduce Sensitive NutritionExcrete Respire Grow

Well done !

Nutrients :-

The components of food like carbohydrates, fats, proteins vitamins and minerals are called nutrients.

Nutrients help living organisms :-

i) To build their bodies.

ii) To grow.

iii) To repair the damaged parts of their bodies.

iv) To provide energy to carry out life processes.

The mode of taking food by an organism and its utilization in the body is called

nutrition.

Modes of nutrition :- There are two main modes of nutrition in living organisms. They are autotrophic

nutrition and heterotrophic nutrition.

i) Autotrophic nutrition :- is nutrition in which organisms can prepare their own

food.

Organisms which can prepare their own food are called autotrophs.

ii) Heterotrophic nutrition :- is nutrition in which organisms get their food directly or indirectly from plants.

Organisms which get their food directly or indirectly from plants are called

heterotrophs.

nutrition

What is photosynthesis?

Plants make their own food. This process is called photosynthesis.

Where does photosynthesis occur?

Photosynthesis occurs in the leaves of a plant.

What is needed for photosynthesis to occur? Light is needed for photosynthesis to occur. The

plant’s leaves use the light to make a sugar called glucose.

Why do plants need glucose?

Glucose is the food for the plant. It gives the plant energy to grow.

How much glucose does a plant make? Plants make enough glucose to be used during the night and

on cloudy days when they don’t get sunlight. The extra glucose is stored in the plant’s leaves and other parts.

How does photosynthesis help us? During the process of photosynthesis, oxygen is

produced. We use this oxygen to breathe.

Photosynthesis - Food making process in plants :-

Photosynthesis is the process by which plants prepare their own food by using sunlight, water, carbon dioxide and chlorophyll.

Photosynthesis take place in the leaves.

i) Sunlight is obtained from the sun.

ii) Water is absorbed by the roots and transported to the leaves.

iii) Carbon dioxide is taken from the air through small pores in the leaves called stomata.

iv) Chlorophyll are the green pigments present in the leaves.

Chlorophyll uses the energy from sunlight to prepare food by using water and carbon dioxide. The food prepared is carbohydrate which is then converted into starch. During photosynthesis oxygen is released. Equation of photosynthesis :- SunlightCarbon dioxide + Water Carbohydrate + Oxygen Chlorophyll

Synthesis of proteins :-

The soil has some bacteria which convert nitrogen from the air into usable nitrogen in the soil. Farmers also add fertilisers containig nitrogen into the soil. Plants absorb this nitrogen from the soil along with water and

other constituents to prepare proteins and fats.

Outline

I. PhotosynthesisA. Introduction

B. Reactions

II. Cellular RespirationA. Introduction

B. Reactions

Photosynthesis

Method of converting sun energy into chemical energy usable by cells

Autotrophs: self feeders, organisms capable of making their own food– Photoautotrophs: use sun energy e.g. plants photosynthesis-makes

organic compounds (glucose) from light– Chemoautotrophs: use chemical energy e.g. bacteria that use sulfide or

methane chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methane

Photosynthesis

Photosynthesis takes place in specialized structures inside plant cells called chloroplasts– Light absorbing pigment molecules e.g. chlorophyll

Overall Reaction

6CO2 + 12 H2O + light

energy → C6H12O6 + 6O2+ 6H2O Carbohydrate made is glucose Water appears on both sides because 12 H2O molecules are required and 6

new H2O molecules are made

Water is split as a source of electrons from hydrogen atoms releasing O2 as a byproduct

Electrons increase potential energy when moved from water to sugar therefore energy is required

Light-dependent Reactions

Overview: light energy is absorbed by chlorophyll molecules-this light energy excites electrons and boosts them to higher energy levels. They are trapped by electron acceptor molecules that are poised at the start of a neighboring transport system. The electrons “fall” to a lower energy state, releasing energy that is harnessed to make ATP

Energy Shuttling

Recall ATP: cellular energy-nucleotide based molecule with 3 phosphate groups bonded to it, when removing the third phosphate group, lots of energy liberated= superb molecule for shuttling energy around within cells.

Other energy shuttles-coenzymes (nucleotide based molecules): move electrons and protons around within the cellNADP+, NADPH NAD+, NADP FAD, FADH2

Light-dependent Reactions

Photosystem: light capturing unit, contains chlorophyll, the light capturing pigment

Electron transport system: sequence of electron carrier molecules that shuttle electrons, energy released to make ATP

Electrons in chlorophyll must be replaced so that cycle may continue-these electrons come from water molecules, Oxygen is liberated from the light reactions

Light reactions yield ATP and NADPH used to fuel the reactions of the Calvin cycle (light independent or dark reactions)

Calvin Cycle (light independent or “dark” reactions)

ATP and NADPH generated in light reactions used to fuel the reactions which take CO2 and break it apart, then reassemble the carbons into glucose.

Called carbon fixation: taking carbon from an inorganic molecule (atmospheric CO2) and making an organic molecule out of it (glucose)

Simplified version of how carbon and energy enter the food chain

Harvesting Chemical Energy

So we see how energy enters food chains (via autotrophs) we can look at how organisms use that energy to fuel their bodies.

Plants and animals both use products of photosynthesis (glucose) for metabolic fuel

Heterotrophs: must take in energy from outside sources, cannot make their own e.g. animals

When we take in glucose (or other carbs), proteins, and fats-these foods don’t come to us the way our cells can use them

Cellular Respiration Overview

Transformation of chemical energy in food into chemical energy cells can use: ATP

These reactions proceed the same way in plants and animals. Process is called cellular respiration

Overall Reaction:– C6H12O6 + 6O2 → 6CO2 + 6H2O

Cellular Respiration Overview

Breakdown of glucose begins in the cytoplasm: the liquid matrix inside the cell

At this point life diverges into two forms and two pathways– Anaerobic cellular respiration (aka fermentation)– Aerobic cellular respiration

C.R. Reactions

Glycolysis– Series of reactions which break the 6-carbon glucose molecule down into

two 3-carbon molecules called pyruvate– Process is an ancient one-all organisms from simple bacteria to

humans perform it the same way– Yields 2 ATP molecules for every one glucose molecule broken down– Yields 2 NADH per glucose molecule

Anaerobic Cellular Respiration

Some organisms thrive in environments with little or no oxygen– Marshes, bogs, gut of animals, sewage treatment ponds

No oxygen used= ‘an’aerobic Results in no more ATP, final steps in these pathways serve ONLY to

regenerate NAD+ so it can return to pick up more electrons and hydrogens in glycolysis.

End products such as ethanol and CO2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

Aerobic Cellular Respiration

Oxygen required=aerobic 2 more sets of reactions which occur in a specialized structure

within the cell called the mitochondria– 1. Kreb’s Cycle– 2. Electron Transport Chain

Kreb’s Cycle

Completes the breakdown of glucose– Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen

atoms end up in CO2 and H2O– Hydrogens and electrons are stripped and loaded onto NAD+ and FAD to

produce NADH and FADH2 Production of only 2 more ATP but loads up the coenzymes with

H+ and electrons which move to the 3rd stage

Electron Transport Chain

Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chain-like a series of steps (staircase).

As electrons drop down stairs, energy released to form a total of 32 ATP

Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water

Energy Tally

36 ATP for aerobic vs. 2 ATP for anaerobic

– Glycolysis 2 ATP

– Kreb’s 2 ATP

– Electron Transport 32 ATP 36 ATP

Anaerobic organisms can’t be too energetic but are important for global recycling of carbon

Other modes of nutrition in plants :-

Parasitic plants :- are plants which do not have chlorophyll and cannot prepare their own food. They get their food from other plants called host . Eg :- Cuscuta ( Amarbel)

Insectivorous plants :- are plants which feed on insects. Eg:- Pitcher plant. The leaf of the pitcher plant is modified into a pitcher. The end of the pitcher has a lid which can open and close. When an insect enters the pitcher, the lid closes.

The insect is then digested by digestive juices inside the pitcher. Other example is Venus flytrap, Nepenthes, Serracenia and Cephalotus

Saprotrophs :- are plants which do not have chlorophyll and cannot prepare their on food. They get their food from dead and decaying organic matter. Eg :-

mushroom, bread mould etc. They produce digestive juice on the dead and decaying organic matter and convert it into a solution and then absorb the

nutrients from the solution.

Symbiotic relationship :- Some plants live together and share shelter and nutrients. Eg :- lichens. In lichens, an alga and a fungus live together. The

fungus provides shelter, water and minerals to the alga. The alga provides food to the fungus which it prepares by photosynthesis.

How food is absorbed?Mechanisms for the movement of nutrients into a

body system

Types of Nutritional Gain

Holozoic nutrition method by which humans and other mammals feed

Saprotrophic nutrition method by which fungi and many prokaryotes feed

Parasitic nutrition method of feeding which has evolved in many different

groups of organisms, including various kinds of worms and fungi and a few plants.

Cellular Structure

Glucose

indirect active transport involving the co-

transport of sodium ions.

Then facilitated diffusion and simple diffusion ,into the tissue fluid inside the villus and then into blood capillary.

Amino-acids

In a fetus a newly born baby , some entire undigested proteins can be absorbed by pinocytosis. This is how babies are able to

absorb some of their mother’s antibodies from the milk. This can also happen to a small extent in adults.

Absorbed into the villus cells by active transport and pass out of the opposite side by diffusion.

Fatty acids and glycerol

Easily absorbed across the cell surface membrane of the villus by simple diffusion.

Once inside the cells, they are taken to the smooth endoplasmic reticulum, then to the Golgi apparatus, where they are surrounded in a coat of protein.

These tiny structures ranging from 100 to 600nm in diameter ,are moved out of the villus by exocytosis.

Too big for blood so they absorb into the lymph inside the lacteals from a milky emulsion, which is what gives these structures their name. (‘Lact’ means ‘to do with milk’).

Vitamins

Absorbed in the small intestine The fat-soluble vitamins A, D, and E can simply cross

the cell surface membranes by diffusion The water –soluble vitamins, such as vitamin C and

the many types of B vitamins are moved across the cells surface membranes by specific transport. Vitamin B can only be adsorbed in combination with intrinsic

factor.

Water and Inorganic Ions

Considerable amounts of sodium, chloride, calcium, and irons are also adsorbed in small intestine

Calcium is helped by the presence of vitamin D. Iron is helped by citrate ions and ascorbic acid, both

of which is found in citrus fruits. Why fresh fruits and vegetables in the diet can help to

prevent anemia. On the other hand, drinking to much tea can hinder irons

absorption, because tannins in the tea react with irons to produce compounds which cannot be adsorbed.

Digestion

Overview

Organic Molecule Pathways

Liquid vs. Pill

Liquid vs. Pill

Liquid vs. Pill

Liquid vs. Pill

Liquid vs. Pill

Liquid vs. Pill

Liquid vs. Pill

Liquid vs. Pill

Liquid vs. Pill

Vitamin Filtering Begins

Liquid vs. Pill

Pill Vitamin Looses 0.8 Ounces In Filtering Process

Liquid vs. Pill

Liquid Vitamin Looses 0.2 Ounces In Filtering Process

Liquid vs. Pill

Pill PillLiquid Liquid

Nutrient Requirements

• Humans require eight essential amino acids. • All are available in milk, eggs, or meat, but not in all

vegetables. • Thus, vegetarians must eat a mix of foods.

NUTRITION IN ANIMAL

Heterotrophic Nutrition: When an organism takes food from another organism, it is called heterotrophic nutrition. Different heterotrophic organisms follow different methods to take and utilize food. Based on this, heterotrophic nutrition can be divided into two types:

(a) Saprophytic Nutrition: In saprophytic nutrition, the digestion of food takes place before ingestion of food. This type of nutrition is usually seen in fungi and some other microorganisms. The organism secretes digestive enzymes on the food and then ingests the simple substances. Saprophytes feed on dead materials and thus help in decomposition dead remains of plants and animals.

(b) Holozoic Nutrition: In holozoic nutrition, the digestion of food follows after the ingestion of food. Thus, digestion takes place inside the body of the organism. Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.

MENU OF THE DAY

• Describe the functions of main regions of the alimentary

canal and the associated organs: mouth, salivary glands,

oesophagus, stomach, duodenum, pancreas, gall

bladder, liver, ileum, colon, rectum, anus, in relation to

ingestion, digestion, absorption, assimilation and

egestion of food, as appropriate.

• Functions of a typical amylase, protease and lipase

(listing the substrate and end-products)

Nutrition in animals

How does…..

“ You are what you eat.”- Jean Anthelme Brillat-Savarin

Holozoic nutrition: feeding on ready-made complex organic matter.

Holozoic nutrition

The taking in of food (chemical energy) by the body & converting it into living matter

What is Nutrition?

INGESTION

DIGESTION

ABSORPTION

ASSIMILATION

EGESTION

Taking in food

Breakdown of complex food substances into smaller

soluble food substances

Digested food is absorbed Into body cells

Absorbed food is use to provide energy or form

new protoplasm

Removal of undigested food

5 processes in digestion

Feeding/ Ingestion – intake of food into the mouth.

Feeding/ Ingestion

Digestion – large food molecules are broken down into small, soluble and diffusible molecules.

2 types: Physical and chemical digestions

Digestion

1. Physical digestion refers to the mechanical break up of food into small particles which increases its surface area for chemical digestion. (E.g. Chewing, stomach churning). It also mix the digestive enzymes with the food particles

2 types of digestions

1. Chemical digestions – breaking of biomolecules like proteins, starch and fats into small soluble molecules which can be absorbed by the cells. It involves digestive enzymes and chemical reactions like hyrolysis.

2 types of digestions

Why must food molecules be broken down into smaller, simpler forms before it can be absorbed

by the cells for other uses?

Cell membranes are partially permeable and only allow small molecules to pass

through.

Absorption – digested food materials are taken into the body cells.

Absorption

Assimilation – absorbed food materials are converted into new protoplasm or used to provide energy.

Assimilation

Egestion – elimination of undigested food materials (faeces)

Egestion

Do not confuse

Ingestion with

Egestion!!!

Digestive enzymes

Starch

Proteins PROTEASE

Lipids/ Fats

AMYLASE

LIPASE fatty acids &

glycerol

amino acids

maltose

Alimentary canal

The Digestive System

Consists of:

1) The gut or alimentary canal (9 m) from mouth to anus.

2) Glands (A cell, tissue, or organ that secretes a chemical substance).

3) Associated organs.

The Alimentary Canal

Mouth and buccal cavity

Oesophagus Stomach

Small intestines

Large intestine Anus

Mouth & Buccal Cavity

The Mouth & Buccal Cavity

Buccal Cavity

The Mouth & Buccal Cavity

1. Food enters through the mouth. This process is called ingestion.

2. Teeth cuts food into small pieces. This increases surface area to volume ratio for enzyme to act more efficiently.

The Mouth & Buccal Cavity

1. Salivary glands produce saliva to moisten food.

2. Saliva also contains salivary amylase to break down starch to maltose.

3. pH of saliva is neutral (around pH 7).

The Mouth & Buccal Cavity

Salivary Glands

The Mouth & Buccal Cavity

Starch Maltose Salivary Amylase

Salivary amylase is active at pH 7.

The Mouth & Buccal Cavity

1. Tongue rolls food into boli.

2. Food is swallowed and enters the pharynx.

Human Alimentary Canal

• Made up of a tubular gut called the alimentary canal.

• Food travels through our body along the alimentary canal which is a continuous tube beginning at the mouth and ending at the anus.

• The parts of the gut includes: mouth, pharynx, oesophagus, stomach, small intestine, large intestine and anus.

mouth

stomach

oesophagus

small intestine

pharynx

large intestine

anusRectum

Mouth & salivary glands Pharynx, Oesophagus Stomach Small intestine- duodenum & ileum

Associated organs-liver, gall bladder, pancreas

Large intestine- colon, rectum Anus

The Alimentary Canal & Associated Organs

mouth

stomach

oesophagus

duodenum

pharynx

colon/ large intestine

anus

livergall bladder

pancreas

ileum

rectum

jejunum

Alimentary Canal & Associated Organs

salivary gland

• Nutrition (Definition)

• 5 Processes of Nutrition

• Digestive Enzymes

• Alimentary Canal

• Alimentary Canal & Accessory Organs

What we learn today.

liver

gall bladder

pancreas

ileum

rectum

jejunum

Alimentary Canal & Associated Organs

salivary gland

colon/ large intestine

anus

duodenum

oesophagus

mouth

pharynx

stomach

Human Digestion

HUMAN DIGESTION

Human digestive system

GI (gastrointestinal) tract = alimentary canal

Digestion

Digestion is the breakdown of large, complex organic molecules into smaller components that can be used by the body.

Molecules need to be small enough to diffuse across plasma membranes.

Five Components of Digestion Ingestion – this is the consumption of or taking in of

nutrients. Digestion – the chemical breakdown of large organic

molecules into smaller components by enzymes. Absorption – the transport or delivery of digested nutrients

to body tissues. Assimilation – absorbed food materials are converted into

new protoplasm or used to provide energy. Egestion – the elimination of food waste materials from the

body.

Ingestion

Food enters the human digestive tract through the mouth or oral cavity.

Humans are considered chunk feeders because they consume chunks of food that are then mechanically broken down.

Alimentary Canal

The human digestive tract is often referred to as the alimentary canal.

The alimentary canal of a normal adult is approximately 6.5 to 9 meters long.

Ingestion Mouth

◦ mechanical digestion teeth

breaking up food◦ chemical digestion

saliva amylase

enzyme digests starch mucin

slippery protein (mucus) protects soft lining of digestive system lubricates food for easier swallowing

buffers neutralizes acid to prevent tooth decay

anti-bacterial chemicals kill bacteria that enter mouth with food

Mechanical Digestion

Physical breakdown of food begins with the teeth grinding the food and increasing its surface area. An increase surface area allows for easier chemical digestion

Bacteria living in the mouth can feed off of nutrients sticking to the teeth and cause tooth decay.

Saliva

Saliva is released from the salivary glands and begins chemical digestion of starches. Saliva contains the enzyme salivary amylase which breaks down starches into simpler carbohydrates.

Taste Buds

As the food particles dissolve in the saliva they penetrate the cells of the taste buds located on the tongue and cheeks.

Humans can differentiate between sweet, sour, salty and bitter.

Swallowing

Saliva also lubricates the food and helps to form a bolus, the ball of food that is swallowed.

Esophagus

The bolus of food moves down the esophagus propelled by wave-like muscular contractions known as peristalsis.

Peristalsis moves food all the way through the gastrointestinal tract.

mouthbreak up fooddigest starchkill germsmoisten food

MouthChemical and mechanical digestion.

Food is chewed (masticated) mechanically.

A bolus (lump) is formed with saliva and the tongue.

The mouth and buccal cavity :- Food is taken into the body through the mouth. This process is called ingestion. In the mouth the food is broken down into smaller pieces by the teeth. The mouth has salivary glands which secrete saliva. The saliva breaks down starch into sugars. The tongue helps to mix the food with saliva and swallow the food.

Babies do not have teeth. Humans grow two sets of teeth. The first set of teeth begins to grow during infancy. This set of teeth is called milk teeth. These fall off between the ages of six and eight. The second set of teeth, which replaces the milk teeth, is called the permanent teeth. This set lasts throughout our life, unless it falls off during old age.Teeth help in breaking down the food into smaller particles so that swallowing of food becomes easier. There are four types of teeth in human beings. They are incisors, canines, permolars and molars.

The incisor teeth are used for cutting the food. The canine teeth are used for tearing the food and for cracking

hard substances. The premolars are used for coarse grinding of food. The molars are used for fine grinding of food. Number of teeth Type of teeth Lower jaw Upper jaw TotalIncisors 4 4 8Canines 2 2 4Premolars 10 10 20molars

Dental Formula Dental formula for milk teeth in humans is 2120/2120. It means that each half of

upper jaw and lower jaw has 2 incisors, 1 canine and 2 premolars. Molars are absent in milk teeth. There are 20 teeth in the milk teeth set.

Dental formula for permanent teeth in human is 2123/2123. It means that each half of upper jaw and lower jaw has 2 incisors, 1 canine, 2 premolars, and 3 molars.

The dental formula in dogs (carnivore) is 3142/3143 The dental formula in rabbits (herbivore) is 2033/1023

Structure of Tooth The vertical section of tooth shows the following parts• The crown − the part lying above the gums• The neck − it connects the crown with the root• The root − it lies buried inside the gums and supports the toothThe white part of the tooth is called the enamel, it consists of calcium salts.Inner to the enamel is the dentine which is a solid tissue and contains strands of cytoplasm in it.The dentine encloses a cavity known as the pulp cavity. This cavity supplies the tooth with nerves and blood capillaries.At the root of the tooth is a bone like material called the cement which holds the tooth firmly to the socket.

Tooth decayA number of bacteria are present in our mouth, though not all of them are harmful. However, irregular and improper cleaning of teeth can lead to the growth of several harmful bacteria in our mouth. These bacteria break down the sugar present in leftover food particles and release acids in the mouth, which damage the teeth. This is known as tooth decay. This condition can lead to severe toothache. It can also result in untimely loss of teeth.Tooth decay can occur because of consuming chocolates, sweets, cold drinks, and other sugar products.

How can tooth decay be prevented?

Tooth decay can be prevented by maintaining oral hygiene, which

includes the proper cleaning of teeth. Teeth must be brushed twice a day after meals using dantun or dental

floss.

Tongue :- The tongue has taste buds to detect different tastes of food. The different regions of the tongue detect different tastes.

Swallowing (& not choking)

Epiglottis ◦ flap of cartilage◦ closes trachea (windpipe) when swallowing◦ food travels down esophagus

Peristalsis ◦ involuntary muscle contractions to move food

along

Which type of digestion is the following?

1. Chewing a saltine? -

2. Saliva breaking the saltine down into molecules of glucose? -

3. Your tongue breaking pieces of a hamburger apart?

4. Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids?

Pharynx The back of the throat.

Larynx- passage for air, closes when we swallow.

Is approximately 15cm long.

Digestive Glands Groups of specialized secretory cells.

Found in the lining of the alimentary canal or accessory organs.

series of involuntary wave-like muscle contractions which move food along the digestive tract

Peristalsis

Stomach

The stomach acts as a temporary storage site for food. Food usually spends about 4 hours in the stomach. It has ridges which allow it to expand to store about 1.5 litres of food.

The stomach is also the site of initial protein digestion.

Stomach Movement of food into and out of the

stomach is controlled by circular muscles known as sphincters.

One at the top of the stomach allows food from the esophagus to enter and prevents food from going back up into the esophagus.

Another located at the bottom slowly releases partially digested food into the small intestine. The partially digested food is called chyme.

Stomach Millions of cells lining the stomach secrete various fluids

known collectively as gastric fluids. Gastric fluid consists of mucus, hydrochloric acid,

pepsinogens and other substances. Mucus coats and protects the lining of the stomach.

Hydrochloric acid kills any harmful substances that have been ingested and it also converts pepsinogen into pepsin.

Pepsin is a protein digesting enzyme that breaks large protein chains into smaller chains.

Stomach pH

The pH environment of the stomach normally ranges between 2.0 and 3.0 on the pH scale.

The high acidity allows pepsin to work and makes the HCL effective at killing pathogens

Stomach Ulcers

An stomach ulcer is a lesion in the lining of the stomach. It occurs when the protective mucus lining breaks down and the cell membranes are exposed to the HCl and pepsin

Most stomach ulcers are linked to the bacterium shown on the right known as Heliobacter pylori.

Endoscopy

An endoscope (shown on the right) can be used to view things such as stomach ulcers or as shown below, a tumor growing in the large intestine.

The endoscope can also extract small pieces of tissue for a biopsy.

Stomach Food is temporarily stored here.

Gastric juices are secreted.

Has layers of muscle that line the inside.

Mechanically and chemically breaks down food.

Stomach Functions

◦ food storage can stretch to fit ~2L food

◦ disinfect food HCl = pH 2

kills bacteria

◦ chemical digestion pepsin

enzyme breaks down proteins

But the stomach is made out of protein!What stops the stomach from digesting itself?

mucus secreted by stomach cells protects stomach lining

stomachkills germs break up fooddigest proteinsstore food

sphincter

sphincter

mouthbreak up fooddigest starchkill germsmoisten food

Gastric Juices Secreted by the stomach.

Acidic (pH 1.5-2.5) (HCl).

Pepsin- an enzyme that breaks down large proteins into amino acids.

Food is further broken down into a thin liquid called chyme.

Accessory Organs

PancreasGall BladderSpleen

Gall bladder

Pouch structure located near the liver which concentrates and stores bile

Bile duct – a long tube that carries BILE. The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine.

BILE

Bile emulsifies lipids (physically breaks apart FATS)

Bile is a bitter, greenish-yellow alkaline fluid, stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.

Pancreas

An organ which secretes both digestive enzymes (exocrine) and hormones (endocrine)

** Pancreatic juice digests all major nutrient types.

Nearly all digestion occurs in the small intestine & all digestion is completed in the SI.

Pancreas Digestive enzymes

◦ digest proteins trypsin, chymotrypsin

◦ digest starch amylase

Buffers ◦ neutralizes

acid from stomach

Liver Function

◦produces bile bile stored in gallbladder until needed breaks up fats

act like detergents to breakup fats

bile contains colors from old red blood cells collected in liver =iron in RBC rusts & makes feces brown

bile contains colors from old red blood cells collected in liver =iron in RBC rusts & makes feces brown

pancreasproduces enzymes to digest proteins & starch

stomachkills germs break up fooddigest proteinsstore food

mouthbreak up fooddigest starchkill germsmoisten food

liverproduces bile

- stored in gall bladderbreak up fats

Small and Large Intestine

The intestines are named for their diameter, not length.

The small intestine is up to 7 m in length but only 2.5 cm in diameter.

The large intestine is only 1.5 m in length but 7.6 cm in diameter.

Small Intestine

In mammals the length of the small intestine is directly related to their diet.

Due to the fact that meats are easier to digest than plant materials, carnivores (lion) will have a shorter intestine than herbivores (rabbit). The length of the digestive tract of omnivores falls somewhere in the middle.

Anatomy of the Small Intestine

The majority of chemical digestion occurs in the first of three sections of the small intestine known as the duodenum.

This section also contains an opening from the bile duct and pancreatic duct through which bile and pancreatic enzymes enter the small intestine.

Small Intestine Food enters the small intestine

as a semi-solid mixture known as chyme. The chyme is acidic due to the HCl in the stomach so it needs to be neutralized.

The presence of chyme in the small intestine triggers the conversion of prosecretin into secretin which is absorbed into the blood stream and carried to the pancreas

Small Intestine Most chemical

digestion takes place here.

Simple sugars and proteins are absorbed into the inner lining.

Fatty acids and glycerol go to lymphatic system.

Lined with villi, which increase surface area for absorption, one cell thick.

Small intestine Function

◦ chemical digestion major organ of digestion & absorption

◦ absorption through lining over 6 meters! small intestine has huge surface area = 300m2

(~size of tennis court) Structure

◦ 3 sections duodenum = most digestion jejunum = absorption of nutrients & water ileum = absorption of nutrients & water

Duodenum 1st section of small intestines

◦ acid food from stomach ◦ mixes with digestive juices from:

pancreas liver gall

bladder

stomachkills germs break up fooddigest proteinsstore food

mouthbreak up fooddigest starchkill germsmoisten food

pancreasproduces enzymes to digest proteins & starch

Absorption in the SI Much absorption is thought to occur directly through

the wall without the need for special adaptations

Almost 90% of our daily fluid intake is absorbed in the small intestine.

Villi - increase the surface area of the small intestines, thus providing better absorption of materials

Absorption by Small Intestines Absorption through villi & microvilli

◦ finger-like projections◦ increase surface area for absorption

VILLI

Pancreas The pancreas is an accessory

organ of the digestive system. It releases chemicals to aid in digestion.

Secretin will stimulate the pancreas to release a solution containing bicarbonate ion into the small intestine where it will neutralize the acidic chyme and raise the pH from 2.5 to 9.0. This inactivates the pepsin.

Pancreas and Digestion

The pancreas also releases digestive enzymes that break down the three macromolecules: carbohydrates, lipids and proteins.

Pancreas & Proteins

Trypsinogen, a protein-digesting enzyme is released into the small intestine where it is convertes into trypsin and it breaks down large protein chains into smaller chains.

The final step in protein digestion occurs with the release of erepsins from the pancreas and they break the smaller chains into individual amino acids.

Pancreas and Carbohydrates

Amylase enzymes are released from the pancreas that break large carbohydrate chains into small chains called disaccharides.

Then the small intestine releases disaccharide enzymes which break those small chains into individual sugars.

Pancreas and Lipids

The pancreas also releases enzymes known as lipases that break down fats into fatty acids and glycerol.

The lipases include pancreatic lipase and phospholipase.

Before lipids can be broken down by lipases they must first be emulsified.

Liver

The liver is a large accessory organ of the digestive system that is constantly producing a fluid known as bile.

Bile is stored in the gall bladder until it is needed in the small intestine.

Liver and Gall Bladder

The presence of lipids in the small intestine trigger the release of the hormone cholecystokinin (CCK) which triggers the release of bile from the gall bladder.

Bile contains bile salts that emulsifies fats which means it breaks them into smaller droplets so they can be digested.

Gallstones

Bile contains cholesterol which can acts as a binding agent and cause bile salts to crystallize into gallstones.

Gallstones can block the bile duct and inhibit fat digestion while causing a lot of pain.

Jaundice

Jaundice is a yellow discoloration of the skin and tissues caused by a collection of bile pigments in the blood.

The pigments are a result of the liver breaking down hemoglobin from red blood cells and the products are stored in the gall bladder.

Detoxification and the Liver The liver is also able to

detoxify many substances in the body by making them soluble and they can then be dissolved in the bloodstream and eliminated in urine.

One example would be alcohol. Alcohol can damage liver cells which are replaced by connective tissues and fat. The result is cirrhosis of the liver (shown left).

Absorption of Materials

Chemical digestion of nutrients is completed by the time it reaches the large intestine.

Now that nutrients are small enough they need to be absorbed into the blood stream so they can diffuse inside cells.

Large Intestine

The large intestine or colon stores waste products long enough so that water can be reabsorbed from the wastes.

Along with the water, some inorganic salts, minerals and vitamins are absorbed.

Large Intestine

The large intestine is home to several different types of bacteria.

These bacteria use waste materials to synthesize vitamins B and K. This is an example of a symbiotic relationship.

Cellulose

Cellulose is a long chain carbohydrate found in the cell wall of plant cells.

Humans cannot digest cellulose however it provides bulk which promotes the movement of the waste products out of the colon.

Cellulose

Cellulose is more commonly known as fiber. Fiber helps to remove wastes and therefore toxins from the body.

If you have a diet low in fiber you will have fewer bowel movements which means toxins remain in your body for longer periods of time.

Absorption of Nutrients

Most nutrients are absorbed in the small intestine.

The small intestine is lined with millions of small finger-like projections known as villi. The villi increase the surface are of the small intestine which increases it’s ability to absorbed digested nutrients.

Structure of the Villus

Each villus contains a capillary network along with a lacteal.

End products of protein and carbohydrate digestion enter the capillary network.

End products of fat digestion are absorbed into the lacteal. The lacteal is a vessel of the lymphatic system.

Microvilli

Large intestines (colon) Function

◦ re-absorb water use ~9 liters of water every

day in digestive juices > 90% of water reabsorbed

not enough water absorbed diarrhea

too much water absorbed constipation

Large Intestine Solid materials pass

through the large intestine.

These are undigestible solids (fibers).

Water is absorbed. Vitamins K and B are

reabsorbed with the water. Rectum- solid wastes exit

the body.

You’ve got company! Living in the large intestine is a

community of helpful bacteria◦ Escherichia coli (E. coli)

produce vitamins vitamin K; B vitamins

generate gases by-product of bacterial metabolism methane, hydrogen sulfide

AppendixVestigial organVestigial organ

Rectum

Last section of colon (large intestines)◦ eliminate feces undigested materials

extracellular waste mainly cellulose

from plants roughage or fiber

masses of bacteria

Digestive Homeostasis Disorders

ULCERS – erosion of the surface of the alimentary canal generally associated with some kind of irritant

CONSTIPATION – a condition in which the large intestine is emptied with difficulty.

Too much water is reabsorbed

and the solid waste hardens

Digestive Homeostasis Disorders

Digestive Homeostasis Disorders

DIARRHEA – a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine.

This results in increased, multiple, watery feces.

This condition may result in severe dehydration, especially in infants

Digestive Homeostasis Disorders

APPENDICITIS – an inflammation of the appendix due to infection

Common treatment is removal of the appendix via surgery

Digestive Homeostasis Disorders

GALLSTONES – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder

Can either be “passed” (OUCH!!) or surgically removed

Digestive Homeostasis Disorders

ANOREXIA NERVOSA - a psychological condition where an individual thinks they appear overweight and refuses to eat.

Weighs 85% or less than what is developmentally expected for age and height

Young girls do not begin to menstruate at the appropriate age.

Digestive Homeostasis Disorders

HEART BURN – ACID from the stomach backs up into the esophagus.