6.9 enzymes and digestion Flashcards
Glands in our body release enzymes
What do these do
They hydrolyse large molecules into small ones ready for absorption
What does the oesophagus do in digestion
It is the tube that carries food from the mouth to the stomach
What are the major parts of digestive system in order
Mouth (salivary glands)
Oesophagus
Stomach
Pancreas
Small intestine
Large intestine
Rectum
What does the stomach do in digestion
. It is a muscular sac with an inner layer that produces enzymes
. The muscles can churn the food in physical breakdown
. Its role is to store and digest food, especially proteins
. It has glands to produce enzymes eg pepsin
What does the ileum do in digestion
What adaptations does it have
. Long muscular tube in the small intestine
. Enzymes are in it that are produced by the walls and by glands that pour their secretions into it, to digest food
. Inner walls of it are folded into villi which give it a large surface area, with millions of microvilli on the epithelial cells of each villus
. This adapts the ileum for absorbing the products of digestion into the bloodstream
What does the large intestine do in digestion
It absorbs water, and most of the water that is absorbed is water from secretions of many digestive glands
What does the rectum do in digestion
It is in the final section of the intestines.
Faeces is stored here before being removed via anus by egestion
What two things do the salivary glands do in digestion
Situated near the mouth, where they pass their secretions via a duct in the mouth
. These secretions contain the enzyme amylase to hydrolyse starch into maltose
Also, they contain mineral salts to help maintain the PH to neutral which is the optimum PH for enzymes to work
What does the pancreas do in digestion
. It is a large gland below the stomach that secretes pancreatic juices
. These juices contain many proteins eg
Proteases to hydrolyse proteins
Lipase to hydrolyse lipids
Amylase to hydrolyse statch
What are the two stages of digestion in humans
. Physical breakdown
. Chemical digestion
Describe the physical breakdown of food
If food is large it is broken down into smaller pieces by structures eg the teeth
This makes it possible to ingest food, and also provides a large surface area for chemical digestion
. Food is also churned by muscles in the stomach wall which physically breaks it up
What are the 3 types of enzyme in digestion
. Carbohydrases: Hydrolyse carbohydrates into monosaccharides eventually
. Lipases: Hydrolyse lipids into glycerol and fatty acids
. Proteases: Hydrolyse protein into amino acids
What occurs in chemical digestion
How do all enzymes function
Chemical digestion hydrolyses large, insoluble molecules into small soluble ones
It is carried out by enzymes
ALL enzymes do hydrolysis to split up large molecules into smaller ones by adding water to break the chemical bonds that hold them together
What is the first stage of carbohydrates getting broken down with amylase
What is the second enzyme after this and where is it found
Where does it occur
Where else is this enzyme found
In the mouth, the enzyme amylase is present and it hydrolyses the glycosidic bonds in starch molecules to produce the disaccharide maltose
Then maltose is hydrolysed into alpha glucose by maltase which is produced in the lining of the ilium
Pancreas also produces amylase
Describe process of digestion of carbohydrates
. Saliva enters mouth from salivary glands and is thoroughly mixed with food whilst chewing
. Saliva contains the enzyme amylase which hydrolyses starch to maltose. It also contains mineral salts to keep PH neutral in the mouth for the amylase
. The food is swallowed and enters the stomach where it is acidic, and the acid denatures amylase and prevents further hydrolysis of starch
. Then, food goes to small intestine where it mixes with pancreatic juices that contain amylase
So this amylase continues the hydrolysis of starch to maltose
The PH is neutral again for amylase in the small intestine due to alkaline salts produced by pancreas and intestine wall
. Muscles in intestine wall push the food to the ilium which produces the maltase enzyme to break down maltose into glucose
. It is released by epithelium cells in the lining but never enters the lumen of the ilium so is a membrane bound disaccharidase
Describe the maltase enzyme and how it breaks down the maltose
It is in the epithelium cells in the lining of the ileum and stays in the lining
So is membrane bound
It hydrolyses the disaccharide maltose into two constituent glucose by breaking the glycosidic bond
There are two other disaccharides in the diet that are hydrolysed
Sucrose and fructose
How are these hydrolysed
. Sucrase hydrolyses sucrose to make fructose and glucose monosaccharides
It hydrolyses the glycosidic bond in sucrose
. It is also a membrane bound enzyme
. Lactase hydrolyses lactose to glucose and galactose by breaking the glycosidic bond
It is membrane bound also
Describe the role of lipids in digestion
What is the enzyme
Where does this digestion occur
Lipases hydrolyse lipids by hydrolysing the ester bond in triglycerides to form fatty acids and glycerol
Lipases are produced in the pancreas, so is a pancreatic juice which then
It occurs in the small intestine, before the ileum
What is bile, where is it made from
. Bile is made in liver but is stored in gall bladder
. It is released into the small intestine where it….
Emulsifies lipids by breaking them down into smaller molecules
And neutralises the stomach acid whilst entering the small intestine which needs a neutral PH for enzymes to work
How do lipases digest lipids
. Lipids are split up into droplets called micelles by bile
. This is emulsification which increases surface area of lipids so the lipase enzyme can work
. Lipase will hydrolyse the ester bond between a glycerol and fatty acids
How are proteins digested
- Proteins are large and complex molecules
- They are hydrolysed by peptidases (proteases) to break them down into amino acids
What are the 3 types of proteases
. Endopeptidase: Hydrolyse peptide bonds between amino acids in the central region of a protein molecule forming a series of peptide molecules
.Exopeptidase: Hydrolyse peptide bonds on the terminal amino acids of peptide molecules formed by endopeptidases
In this way they produce dipeptides and single amino acids
. Dipeptidases: Hydrolyse the bond between two amino acids in a dipeptide produced by exopeptidase
These are membrane bound enzymes and are part of the cell membrane of epithelial cells lining the ileum
