Enzymes And Digestion Flashcards
What does the oesophagus do
Carries food from the mouth to stomach
What’s the role of the stomach
Store and digest food, especially proteins. It has glands that produce enzymes which digest proteins
What’s the purpose of the ileum and how is it adapted to it
Absorbing the products of digestion into the blood stream
Food is further digested by enzymes produced by its walls and glands that pour their secretion into it
The inner walls of the ileum are folded into villi- giving them a large SA. SA can be further increased by the mircrovilli on the epithelial cells of each villus
What does the large intestine do
Absorb water- many of it is from the secretions of the many digestive glands
What is the role of the rectum
Faeces are stored here before being removed by the Anya in egestion
What do the salivary glands do
They pass their secretions via a duct in the mouth.
The secretions contain the enzyme amylase, which hydrolyses starch into maltose
What is the role of the pancreas
Produced a secretion called pancreatic juice. It contains proteases to hydrolyse proteins, looses to hydrolyse lipids and amylase to hydrolyse starch
What are the two stages of digestion
Physical breakdown
Chemical digestion
What happens during physical breakdown stage
Broken down into smaller pieces by teeth - Providing a large SA for chemical digestion and make it possible to ingest food
Food is churned by muscles in stomach wall this physically breaks it up
What happens during chemical digestion
It hydrolyses large, insoluble molecules into smaller, soluble ones.
Usually one enzyme hydrolyses a large molecule into sections and these sections are then hydrolysed into smaller molecules by one or more additional enzymes
What do all digestive enzymes function by
Hydrolysis
What are the three types of digestive enzymes
Carbohydrases- hydrolyse carbohydrates ultimately to monosaccharides
Lipases - hydrolyse lipids into glycerol and fatty acids
Proteases - hydrolyse proteins, ultimately to amino acids
How is Maltase produced by the lining of the ileum
Saliva contains amylase - starts hydrolysing any food to maltose (contains mineral salts to maintain the pH around neutral- where they work best)
Food is swallowed and enters stomach - acid denatures the amylase and prevents further hydrolysis of starch
Food is passed into small intestine, where it mixes with pancreatic juice- contains amylase - continuing the hydrolysis of remaining starch to maltose (alkaline salts produced by Pancreas and intestinal wall to maintain pH around neutral for amylase to function)
Muscles in intestine wall push food along ileum. Epithelial lining produces maltase(membrane bound disaccharide). Maltase hydrolyses the maltose from starch breakdown into a-glucose
What does sucrase hydrolyse
Single glycosidic bond in sucrose. Hydrolysis produces the two monosaccharides glucose and fructose
What does lactase hydrolyse
Single glycosidic bond in the lactose molecule. This hydrolysis produces glucose and galactose
Where are lipases produced and which bond do they hydrolyse
In the pancreas
they hydrolyse the ester bond
What are lipids split up into micelles by
Bile salts ( produced by liver)
In lipid digestion, what does emulsification do
Increase SA of the lipid so that the action of lipases is speeded up
What are the three types of peptidases
Endopeptidases
Exopeptidases
Dipeptidases
What does an endopeptidase do
Hydrolyse peptide bonds between amino acids in central region of a protein molecules forming a series of peptide molecules
What does an exopeptidase do
Hydrolyse the peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases. In this way they progressively release dipeptides and single amino acids
What do dipeptidases do
Hydrolyse bond between two amino acids of a dipeptide.
They are membrane bound, being part of the cell surface membrane of the epithelial cells lining the ileum
How do the villis properties increase the efficiency of absorption
Increase SA for diffusion
Very thin walled, reducing diffusion distance
Contain muscle, able to move - helps maintain diffusion gradient as their movement mixes the contents of the ileum
Supplied well with blood vessels - so that blood can carry away absorbed molecules and maintain a diffusion gradient
Epithelial cells lining the villi posses microvilli- further increase SA for absorption
What happens to the fatty acids and monoglycerides during absorption once inside the epithelial cells
Transported to endoplasmic reticulum- recombined to form triglycerides
Starting in endoplasmic reticulum and continuing in Golgi apparatus
Triglycerides associate with cholesterol and lipoproteins to form structures called chylomicrons(special particles adapted for transport of lipids)
Chylomicrons move out of epithelial cells by exocytosis
Enter lymphatic capillaries called lacteal and then the blood stream
