2.5 Adaptations for Nutrition

Vocabulary list

• I have made a vocab / definition list for you to fill in for this section

Nutrition

• Nutrition is the process by which a living organism assimilates food and uses it for growth and for replacement of cells and tissues.

• There are 2 strategies for carrying out nutrition:autotrophic heterotrophic

Autotrophs

• Autotrophs use simple inorganic materials to manufacture complex organic compounds

• Examples?

• Autotrophs serve as a primary producer in a food chain.

• Plants obtain nutrition by harnessing light through photosynthesis (photoautotrophs)

• Some organisms obtain energy through oxidation (chemoautotrophs) to make organic substances from inorganic ones.

• Autotrophs do not consume other organisms; they are, however, consumed by heterotrophs.

Heterotrophs• Heterotrophs obtain energy by consuming other

organisms in a food chain• They must rely on an organic source of carbon

that has originated as part of another living organism.

• Heterotrophs depend either directly or indirectly on autotrophs for nutrients and food energy.

• There are several different strategies for heterotrophic nutrition.

Saprophytes (saprobionts)

• Absorptive form of nutrition• Saprophytes absorb nutrients from non-

living organic material by extracellular digestion.

• In this process they decompose the organic matter

• They feed by secreting enzymes onto food material

• The soluble products of digestion are then absorbed

• The products cross the cell membrane by diffusion

Rhizopus

The gut• Most heterotrophs have a gut• Food is processed as it passes along this gut• In simple organisms, the gut is a single tube.• It is undifferentiated (ie only one section)• This is because they feed on only one type of

foodstuff.

• In more advanced organisms, the gut is differentiated.

• Divided into different parts specialised to carry out different functions

1. Ingestion2. Digestion3. Absorption4. Egestion

(not excretion!)

(.wav)

Egestion of faeces

Excretion

CO2 H2O

Layers of the gut

• The gut wall consists of 4 layers of tissue:– Serosa– Longitudinal muscle layer– Circular muscle layer– Submucosa– Mucosa

1. The outermost portion of the gut wall consists of a layer of tough collagenous connective tissue. This covering protects and anchors that portion of the tract to surrounding structures. Digestive organs located below the diaphragm usually have an outer wrapping of peritoneum called the Serosa.

2. Generally, there is a double layer of smooth muscle consisting of an outer longitudinal layer and an inner circular layer. It is the combined action of these two layers that produces the muscular contractions of peristalsis.

3. The Submucosa is a layer of loose connective tissue inside the thick muscularis. Blood vessels, lymphatics and nerves are located here, as well as, glandular tissue.

4. The inner lining or Mucosa of the tract is essentially a mucous membrane. Overall its functions are:

– Secretion - mucous, digestive enzymes and hormones.– Absorption - end products of digestion, water, minerals.– Protection from infection.

Human alimentary canal

• Label what you can!

Alimentary canal

• Buccal cavity• Tongue• Salivary glands• Oesophagus

+ Liver & Pancreas

• Stomach• Duodenum• Ileum• Colon• Rectum• Anus

Glands

• An organ in the human or animal body that secretes particular chemical substances for use in the body or for discharge into the surroundings

• There are lots of glands in the digestive system producing digestive secretions

• Some glands are found in the wall of the gut and secrete directly into the gut cavityE.g.?

• Some glands are outside of the gut and secrete into the gut via ductsE.g.?

Digestion

• Organisms with a varied diet need more than one type of enzyme to be produced

• Usually more than one enzyme is needed to digest any one particular food substance to completion

• Not everything can always be completely digested by any given organism

• Mucus secretions lubricate the food as it passes along the gut and also protects the gut wall.

Carbohydrate digestionBuccal cavity Stomach Pancreas Small Intestine

Starch MaltoseGlucose

Maltose

Sucrose Glucose + Fructose

Lactose Glucose + Galactose

• Saliva contains amylase hydrolysing some starch to maltose.

• Pancreatic Juice also contains amylase completing the digestion of starch. Why do you need a second input of amylase?

• Maltose is digested by maltase in the small intestine. These enzymes are found in the membrane of the epithelial cells lining the small intestine.

• Sucrase and lactase are found on the membranes too.

Protein digestion

• 2 types of protein-digesting enzymes:– Endopeptidases (hydrolyse between amino acids in the middle of the chain)– Exopeptidases(hydrolyse between amino acids at the end of the chain)

Buccal cavity

Stomach Pancreas Small Intestine

Proteins

Small polypeptides

Amino acids and dipeptides

Small polypeptides

Amino acids

Lipid digestion

• Fats become globules when mixed with water• These have large vol:SA ratio, so are hard for

enzymes to work on• Releasing bile in the upper small intestine

helps

Buccal cavity Stomach Pancreas Small Intestine

TriglyceridesFatty Acid

+Glycerol

• Bile emulsifies fat globules. The muscles in the gut wall help break down big droplets into smaller ones

• Bile is alkaline keeping the optimum pH for lipase to work

• Lipase is secreted by the pancreas

Absorption

• Absorption of the end products of digestion takes place in the ileum, the surface area of which is increased by villi and microvilli

• Amino acids are water soluble. Absorbed partly by diffusion and partly by active uptake

• Glucose absorbed by a mixture of diffusion and active uptake

• Both the above are linked to active transport of Na ions from the gut

• They enter the capillaries and then travel to the liver via the hepatic portal vein

• Fatty acids and glycerol combine with bile salts to make micelles

• Micelles dissolve in cell surface membranes and dissolve into the cell cytoplasm

• They are repackaged and are passed into the lacteal

• Then into the lymphatic system to the blood stream opening at the thoracic duct.

• Most water is reabsorbed, along with soluble nutrients, in the small intestine.

• Active transport of Na ions, amino acids and glucose makes a diffusion gradient so water passes across by osmosis.

• The colon absorbs the remaining water, together with vitamins (secreted by microorganisms in the colon) in order to produce solidified faeces.

• Residues of undigested cellulose, bacteria and sloughed cells pass along the colon to be egested as faeces.

• Cellulose fibre is required to provide bulk and stimulate peristalsis.

• Glucose is absorbed from the blood by cells, for energy release in respiration, and any excess is converted to fat for storage.

• Amino acids are absorbed for protein synthesis;

• excess cannot be stored so is deaminated, whereby the removed amino groups are converted to urea and the deaminated remainder is converted to carbohydrate and stored.

• Lipids are used for membranes and hormones, and the excess is stored as fat.

Teeth

• Teeth are used in mechanical digestion in order to increase surface area for enzyme action.

• Animals can be classed as Herbivore, Carnivore or Omnivore

• Each have a number of adaptations of mouthparts/dentition and gut structure according to what it eats.

What features does each type show in terms of dentition?

pony

Wolf

Pig

Cougar

• Mammals have evolved different types of teeth with each type being specialised for a different function, incisors, canines, premolars and molars.

• There are differences between the teeth of carnivores and herbivores reflecting their differing diets.

• In herbivores the jaw moves in a horizontal plane whereas in carnivores the jaw moves vertically.

• The gut of a carnivore is short reflecting the ease with which protein is digested.

• Ruminants such as cow and sheep eat mainly grass, a large proportion of which consists of cellulose cell walls.

• Ruminants have a specialised stomach or rumen in which mutualistic bacteria live.

• The presence of these bacteria together with their modified gut enables ruminants to achieve a more complete breakdown of cellulose.

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