Transcript Enzymes & Digestion

ENZYMES & DIGESTION
Noadswood Science, 2012
Enzymes & Digestion
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Sunday, March 27, 2016
To know how the enzymes in the digestive system aid digestion
Digestive System
Digestive System
Mouth - putting food in your mouth is called feeding
or ingestion. Teeth grind the food down, and saliva
(produced from salivary glands) help make the food
moist, easing swallowing (as well as the enzyme
amylase which helps break down starch)
Mouth
Salivary gland
Oesophagus
(gullet or food pipe)
Small intestine
Stomach
Large intestine
Oesophagus (gullet) - when you swallow, the
trachea (windpipe) is shut off, and food passes
down the oesophagus. Muscles in the wall above the
food contract, making the piper narrower above the
food, pushing it down (this is why you can eat, even
when upside down)!
*Appendix
Rectum & anus
Stomach - food is churned up with the strong acid
(pH 1-2)
Digestive System
Small intestine - small molecules are absorbed
through the small intestine wall
Mouth
Salivary gland
Large intestine - food which we cannot digest (e.g.
fibre) is passed into the large intestine, where water
is removed. This forms a more solid material faeces
Oesophagus
(gullet or food pipe)
Small intestine
Stomach
Large intestine
*Appendix
Rectum & anus - faeces is stored in the rectum,
eventually being pushed out of the anus - faeces is
egested
Rectum & anus
*Appendix - in some animals, helps to break down
cellulose, but no known use in humans
Enzymes
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The enzymes involved in respiration, photosynthesis and protein synthesis
work inside cells
Other enzymes are produced by specialised cells and released from them
(the digestive enzymes are like this)
They pass out into the gut, where they catalyse the breakdown of food
molecules
Enzymes
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Enzymes are not living! They are special proteins which can break large
molecules down.
There are specific enzymes, which break down specific nutrients: 
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Amylase (carbohydrase) enzymes break down starch into simple sugars
Protease enzymes break down proteins into amino acids
Lipase enzymes break down fats into fatty acids and glycerol
Anylase - starch to sugar
Protease - protein to amino acids
Lipase - fats to fatty acids & glycerol
Carbohydrates (amylase enzyme)
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Carbohydrates are digested in the mouth, stomach and small intestine
Amylase is produced in the salivary glands, pancreas, and small intestine
Chew a piece of bread for long enough, it will taste sweet (as the starch is
broken down into simple sugars)
amylase
carbohydrates  simple sugars
Proteins (protease enzyme)
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Proteins are digested in the stomach and small intestine
Protease is produced in the stomach (called pepsin), pancreas and small
intestine
Stomach acid is strong hydrochloric acid, helping digestion and killing
harmful micro-organisms that may be in the food
protease
protein  amino acids
Fats (lipase enzyme)
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Fat is digested in the small intestine – bile (made in the liver) helps break
fat into small droplets that are easier for the lipase enzymes to work on
Lipase is produced in the pancreas and small intestine
lipase
fat  fatty acids + glycerol
Absoprtion
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Digested food molecules are absorbed in the small intestine, passing
through the wall of the small intestine into the bloodstream (where they are
carried around the body to where they are needed)
Only small, soluble substances can pass across the wall of the small intestine
Large insoluble substances cannot pass through - this is why we need
enzymes!
Digestion
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The stomach produces hydrochloric acid, helping to begin digestion (and
killing many harmful microorganisms that might have been swallowed along
with the food)
The enzymes in the stomach work best in acidic conditions (low pH)
Digestion
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After the stomach, food travels to the small intestine – the enzymes in the
small intestine work best in alkaline conditions, but the food is acidic after
being in the stomach
A substance called bile (produced in the stomach and stored in the gall
bladder) neutralises the acid to provide the alkaline conditions needed in
the small intestine (as well as breaking down fat)
Enzyme Locations
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Summary of enzymes involved with digestion, what reaction they catalyse
and where they are produced: -
Enzyme
Reaction Catalysed
Location Produced
Amylase
Starch  Sugars
Salivary glands; pancreas; small
intestines
Protease
Proteins  Amino Acids
Stomach; pancreas; small
intestines
Lipase
Lipids  Fatty Acids + Glycerol
Pancreas; small intestines
Summary
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Amylase catalyses the breakdown of starch into sugars in the mouth and
small intestine
Proteases catalyse the breakdown of proteins into amino acids in the
stomach and small intestine
Lipases catalyse the breakdown of fats and oils into fatty acids and
glycerol in the small intestine