Year 11 Biology Digestion 1
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What is digestion?
It is a chemical and mechanical breakdown of large organic molecules into smaller units that can pass across the plasma membrane.
It is the first important step that must occur after the food has been eaten.
Why is digestion necessary?
- - food must be broken down
- - the smaller units are then able to be absorbed by cells
What are the 4 main steps for substances to become available to cells?
- - Ingestion of food: when food is captured and taken into an aminals mouth. (eating)
- - Mechanical breakdown of ingested food:Large pieces of food are broken down into smaller pieces
Describe what ingestion of food involves:
Describe mechanical digestion and why it is important.
What happens in the mouth?
- Chemical and Mechanical digestion:
- Chemical when the amalyse in saliva starts to break down starch; and
- Mechanical when the teeth chew up the food into smaller pieces.
- The mixture forms a 'bolus' that is swallowed.
In what way do the teeth of herbivores, carnivores and omnivores differ?
Carnivore - such as the Tasmanian devil, have well developed canine teeth for tearing meat from bones.
Herbivore - such as the whiptail wallaby, have incisor teeth that enable them to clip the grass and other vegetation that they eat. There is an absence of canine teeth.
Omnivore - such as humans, have teeth that are appropriate for a varied diet.
Gnawing Animal - such as rats, have well developed incisor teeth that enable them to gnaw through heavy grasses, twigs and in some cases, trees.
Describe peristalsis, and where does this occur?
Peristalsis is the movement of food along the gut by means of contraction and relaxation of muscles in the gut wall.
What does the oesophagus do?
it is a soft muscular tube that transports food from mouth to stomach by paristalsis.
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