Digestion And Absorption Flashcards
What happens in digestion?
Large biological molecules a hydrolyse to smaller molecules that can be absorbed across cell membranes
Give examples of large biological molecules in food
Starch/proteins (too large to be absorbed across the cell membrane
What does digestion break Large molecules such as starch on proteins down into and what does this mean?
Protein is broken into amino acid’s
Starch broken into glucose
Can be absorbed from the gut into the blood
What is amylase produced by?
Saliva re gland is (released into mouth)
Pancreas (released into small intestine)
Explain how starch (polysaccharide) is digested
- Amylase hydrolyses starch to maltose (polysaccharide to disaccharide)
- Membrane bound maltase (attached to epithelial cells lining ileum of small intestine) hydrolysed maltose to glucose (disaccharide to monosaccharide)
- Hydrolysis of glycosidic bonds
Where are membrane bound disaccharidases attached ?
Attached to epithelial cells lining the ileum of the small intestine
Give three examples of membrane-bound disaccharidases?
Maltase
Lactase
Sucrase
Explain how disaccharides are digested
Membrane-bound disaccharidases hydrolyse the disaccharide into two monosaccharides
MaltASE: maltose —> glucose + glucose
SucrASE: sucrose —> glucose + fructose
LactASE: lactose —> glucose + galactose
Hydrolysis of glycosidic bond
Talk about bile salts
Bile salt produced by the liver
Bile salts emulsify lipid to the smaller lipid droplets
Increasing surface area of lipids means lipases can work at faster rate
Where is lipase made?
Pancreas
Released into small intestine
Explain how lipase hydrolyses lipids
Lipase hydrolyses lipids —> three fatty acids + glycerol
Breaking ester bonds
Monoglycerides, fatty acids and bile salts stick together to form micelles
Endopeptidases
Hydrolyse peptide bonds within a protein/between amino acids in the central region
Breaking protein into two or more smaller peptides
Exopeptidases
Hydrolyse peptide bonds at the end of protein molecules
Removing a single amino acid
Dipeptidases are a type of…
Exopeptidase
Dipeptidases
Often membrane-bound in ileum of small in testing
Hydrolyse peptide bond between a dipeptide to produce two amino acids
Mechanisms for the absorption of the products of digestion by cells lining the ileum of mammals to include the role of micelles in the absorption of lipids
??????
Monoglycerides and fatty acids diffuse out of micelles in the lumen into epithelial cells
Because they are lipid soluble
——
Monoliths rides and triglycerides recombine to triglycerides which aggregate into globules
——
Globules coated with proteins to form chylomicrons
——
Leave via exocytosis and enter lymphatic vessels
——
Return to blood circulation
The concentration of glucose in the blood rises after eating a mill contain carbohydrates.
The rise of slow if the carbohydrate is start rather than screws. Explain why.
Digestion of sucrose occurs in one single step
Starch is digested to maltose and then digested to glucose
Group a actors as a control for the mouse yoghurt investigation. Explain the purpose of the control group. (2)
To show the effect of the inhibitor
To show the effects of yoghurt
Give two reasons why it is important that all the marks were given the same food each day
Different foods contain different amounts of glucose
To keep starch/fibre intake the same
Use your knowledge to suggest how the addition of the inhibitor of amylase could lead to lower blood glucose concentration (2)
FEWER ES COMPLEXES FORM
So less starch is digested to maltose
So less glucose from maltose
So less absorption of glucose from the gut
Reasons why results may not support use of the inhibitor of amylase to treat diabetes and mice (5)
No SDs
So don’t know if results are significant
Larger sample needed
Might not be representative (anomalies may have a bigger or smaller affect)
Investigation only lasted 20 days
Don’t know long term effects
Fall in blood glucose small
Mice with inhibitor still have a large rise of blood glucose levels
Blood glucose could continue to fall to really low levels
Which could be harmful
Where is Maltase produced?
On epithelium of small intestine
Describe the proteins are digested in the human gut (4)
Hydrolysis of peptide bonds
Endopeptidases break polypeptides into smaller peptide chains
Exopeptidase is remove terminal amino acids
Dipeptideases hydrolyse dipeptides into amino acids
