B - 1 - Digestion and Absorption

Question 1

Which digestive enzyme breaks down starch?

Answer 1

Amylase

Question 2

Describe the structure of amylase?

Answer 2

Made of long chains of alpha glucose

Question 3

Where is amylase produced and released?

Answer 3

Produced - The salivary glands and the pancreas

Released - The mouth and the small intestine

Question 4

How does amylase work?

Answer 4

It catalyses hydrolysis reactions that break glycoside bonds in starch to produce maltose

Question 5

What are membrane bound Disaccharidases?

Answer 5

Enzymes that are attached to the cell membranes of epithelial cells lining the ileum

Question 6

What do membrane bound Disaccharidases do?

Answer 6

They help break down disaccharides into monosaccharides involving the hydrolysis of glycosidic bonds

Question 7

Which digestive enzyme catalyses the breakdown of lipids?

Answer 7

Lipase

Question 8

How does lipase work?

Answer 8

It catalyses the breakdown of lipids into monoglycerides and fatty acids. This involves the hydrolysis of ester bonds in lipids

Question 9

Where are lipids made and secreted?

Answer 9

Made - Pancreas

Secreted - Small Intestine

Question 10

What are bile salts?

Answer 10

A type of salt produced by the liver to aid the digestion of lipids

Question 11

What are micelles?

Answer 11

A microscopic structure composed of monoglycerides, fatty acids and bile salts

Question 12

Why are bile salts important for lipid digestion?

Answer 12

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.

Question 13

What happens after the lipid is broken down by lipase?

Answer 13

The monoglycerides and fatty acids stick with the bile salts to form tiny structures called micelles.

Question 14

What are Endopeptidases?

Answer 14

An enzyme that hydrolyses peptide bonds within a protein

Question 15

What are Exopeptidases?

Answer 15

Enzymes that hydrolyse the peptide bonds at the end of proteins to remove single amino acids

Question 16

What are Dipeptidases?

Answer 16

An endopeptidase enzyme that hydrolyses peptide bonds within a protein. They work specifically on dipeptides

Question 17

Where are Dipeptidases often located?

Answer 17

IN the cell surface membrane of epithelial cells on the small intestine

Question 18

How are monosaccharides absorbed across the ileum epithelium into the bloodstream?

Answer 18

Glucose - via active transport with sodium ions via a co transporter protein.
Fructose -Facilitated diffusion through a different transporter protein

Question 19

How are Monoglycerides and fatty acids absorbed across the ileum epithelium into the bloodstream?

Answer 19

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

Question 20

How are Amino Acids absorbed across the ileum epithelium into the bloodstream?

Answer 20

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.