Digestion and Absorption

Question 1

Amylase

Answer 1

digestive enzyme catalysing starch to maltose
produced in salivary glands and pancreas
also found in small intestine
involves hydrolysis of glycosidic bonds

Question 2

membrane bound disaccharidases

Answer 2

enzymes attached to cell membranes of epithelial cells lining the ileum
Help break down disaccharides into monosaccharides
involves hydrolysis of glycosidic bonds

Question 3

Monosaccharides

Answer 3

can be transported across the cell membranes of the ileum epithelial cells via specific transporter proteins

Question 4

Lipid digestion

Answer 4

catalysed by lipase
into monoglycerides and fatty acids
involves hydrolysis of ester bonds
made in the pancreas
work in the small intestine

Question 5

Bile Salts

Answer 5

produced by the liver and emulsify lipids
(form small lipid droplets)
increases the surface area of lipids (single large to several small droplets) for lipase to work on
Once lipid has been broken down, monoglycerides and fatty acids stick with bile salts to form micelles

Question 6

Monoglyceride

Answer 6

a glycerol molecule with a fatty acid attached

Question 7

Endopeptidases

Answer 7

act to hydrolyse peptide bonds WITHIN a protein.
e.g. Trypsin and chymotrypsin
- synthesised in pancreas and secreted into small intestine
e.g. Pepsin
- released into stomach by cells in stomach lining
- only works in acidic conditions (i.e. HCL in stomach)
GIVE MORE ENDS FOR EXOS TO WORK ON

Question 8

Exopeptidases

Answer 8

act to hydrolyse peptide bonds AT THE END of protein - remove single amino acids from proteins

Question 9

Dipeptidases

Answer 9

exopeptidases that work specifically on dipeptides
hydrolyse the peptide bond between two amino acids
in membrane of epithelial cells in small intestine

Question 10

Monosaccharides absorption

Answer 10

Glucose - active transport w/Na+ via co-transporter proteins
Galactose = the same
Fructose - facilitated diffusion through different transporter protein

Question 11

Monoglycerides and fatty acids absorption

Answer 11

Micelles - move monoglycerides and fatty acids towards epithelium
constantly break up and reform to release products so they’re absorbed
products are lipid soluble - diffuse directly across epithelial cell membrane

Question 12

Amino Acids absorption

Answer 12

Absorbed in a similar way to glucose and galactose

co transport w/Na+

Question 13

Why is digestion necessary

Answer 13

Large molecules too big to cross cell membranes =>
molecules broken down into smaller molecules
=> more easily absorbed