B - 1 - Digestion and Absorption Flashcards
Which digestive enzyme breaks down starch?
Amylase
Describe the structure of amylase?
Made of long chains of alpha glucose
Where is amylase produced and released?
Produced - The salivary glands and the pancreas
Released - The mouth and the small intestine
How does amylase work?
It catalyses hydrolysis reactions that break glycoside bonds in starch to produce maltose
What are membrane bound Disaccharidases?
Enzymes that are attached to the cell membranes of epithelial cells lining the ileum
What do membrane bound Disaccharidases do?
They help break down disaccharides into monosaccharides involving the hydrolysis of glycosidic bonds
Which digestive enzyme catalyses the breakdown of lipids?
Lipase
How does lipase work?
It catalyses the breakdown of lipids into monoglycerides and fatty acids. This involves the hydrolysis of ester bonds in lipids
Where are lipids made and secreted?
Made - Pancreas
Secreted - Small Intestine
What are bile salts?
A type of salt produced by the liver to aid the digestion of lipids
What are micelles?
A microscopic structure composed of monoglycerides, fatty acids and bile salts
Why are bile salts important for lipid digestion?
Several small lipid droplets have a bigger surface area than a single large droplet, so the formation of small droplets greatly increases the surface area of lipid that’s available for lipases to work on.
What happens after the lipid is broken down by lipase?
The monoglycerides and fatty acids stick with the bile salts to form tiny structures called micelles.
What are Endopeptidases?
An enzyme that hydrolyses peptide bonds within a protein
What are Exopeptidases?
Enzymes that hydrolyse the peptide bonds at the end of proteins to remove single amino acids
What are Dipeptidases?
An endopeptidase enzyme that hydrolyses peptide bonds within a protein. They work specifically on dipeptides
Where are Dipeptidases often located?
IN the cell surface membrane of epithelial cells on the small intestine
How are monosaccharides absorbed across the ileum epithelium into the bloodstream?
Glucose - via active transport with sodium ions via a co transporter protein.
Fructose -Facilitated diffusion through a different transporter protein
How are Monoglycerides and fatty acids absorbed across the ileum epithelium into the bloodstream?
Micelles help to move monoglycerides and fatty acids towards the epithelium. Because micelles constantly break up and reform they can ‘release’ monoglycerides and fatty acids allowing them to be absorbed - whole micelles are not taken up across the epithelium. Monoglycerides and fatty acids are lipid - soluble, so can diffuse directly across the epithelial cell membrane
How are Amino Acids absorbed across the ileum epithelium into the bloodstream?
Amino acids are absorbed in a similar way to glucose and galactose. Sodium ions are actively transported out of epithelial cells into the ileum itself. They then diffuse back into the cells through sodium dependent transporter proteins in the epithelial cell membranes carrying the amino acids with them.
