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Biology B5e-h Cheat Sheet by

biology     gcse

Functions

salivary glands
produce saliva that moistens food and contains carboh­ydrase enzymes
stomach
produces hydroc­hloric acid and protease enzymes
pancreas
produces carboh­ydrase, protease and lipase enzymes
liver
produces bile
gall bladder
stores bile
small intestine
produces carboh­ydrase, protease and lipase enzymes, and absorbs digested food
large intestine
absorbs water

Positi­oning

 

Physical vs Chemical Digestion

Physical digest­ion breaks food into smaller pieces by:
-chewing in the mouth
-squeezing in the stomach This is done so that:
-food can pass more easily through the digestive system
-a larger surface area is provided for enzymes to work on
Chemical digest­ion uses digestive enzymes to breakdown large food molecules into smaller ones so they can be absorbed into the blood. The products of chemical digestion are absorbed into the body in the small intestine:
-sugars and amino acids pass into the bloods­tream by diffusion
-fatty acids and glycerol pass into the lymph

Enzymes

enzyme
breaks down...
into...
in the...
carboh­ydrase
starch
sugar
mouth + small intestine
protease
protein
amino acids
stomach + small intestine
lipase
fat
fatty acids + glycerol
small intestine
Stomach acid provides the correct pH for stomach protease to function properly.

Breakdown of starch

1. starch --> maltose
2. maltose --> glucose
 

Small intestine adapta­tions

-it has a thin lining
-it has a good blood supply
-it is very long and has a large surface area
-villi provide a large surface area for absorption to take place
-villi have a rich supply of blood vessels to carry away absorbed molecules.

pH differ­ences

Why is the pH in the mouth and small intestine alkaline, but the pH in the stomach is at acidic levels?
The enzymes there work at different optimum pH levels.

Bile purpose

What is the purpose of bile?
To lower the pH of food as it moves from the stomach to the small intestine.
How does bile (from the gall bladder) improve fat digestion?
It emulsifies (breaks down) fats in the small intestine. This provides a larger surface area in which the lipases can work.

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