Digestion and absorption

Question 1

What is carbohydrates are broken down into?

Answer 1

-Disaccharides and then monosaccharides

Question 2

What is fats are broken down into?

Answer 2

-Fatty acids and monoglycerides

Question 3

What is proteins are broken down into?

Answer 3

-Amino acids

Question 4

Where does amylase is produced?

Answer 4

-The salivary glands (release amylase into mouth) and pancreas (releases amylase into the small intestine)

Question 5

What do amylase catalyse?

Answer 5

Catalyses the conversion of starch (polysaccharide) into the smaller sugar maltose (disaccharide)

Question 6

What are membrane-bound disaccharidases?

Answer 6

-Enzymes that are attached to the cell membranes of epithelial cells lining the ileum.
-Help break down disaccharides into monosaccharides
-Involves the hydrolysis of glycosidic bonds

Question 7

What disaccharidases breaks down maltose and what are the products?

Answer 7

Maltase breaks down maltose into 2 glucose molecules

Question 8

What disaccharidases breaks down sucrose and what are the products?

Answer 8

Sucrase breaks down sucrose into glucose and fructose

Question 9

What disaccharidases breaks down lactose and what are the products?

Answer 9

Lactase breaks down lactose into glucose and galactose

Question 10

How do lipids break down?

Answer 10

-Lipase enzymes catalyse the breakdown of lipids into monoglycerides and fatty acids- involves the hydrolysis of the ester bonds in lipids
-Lipases are made in the pancreas- work in the small intestine
-Bile salts are produced by the liver and emulsify lipids- cause lipids to form small droplets
-Several small lipid droplets have a bigger surface area than a single large droplet- increases the surface are of lipid thats available for lipases to work on
-Once they broke down, monoglycerides and fatty acids stick with the bile salts form micelles.

Question 11

What are proteins broken down by?

Answer 11

-Endopeptidases and exopeptidases

Question 12

What are proteases?

Answer 12

-Enzymes that catalyse the conversion of proteins into amino acids by hydrolysing the peptide bonds between amino acids

Question 13

Endopeptidases-

Answer 13

-Act to hydrolyse peptide bonds within a protein
-Trypsin and chymotrypsin are two examples of endopeptidases- synthesised in the pancreas and secreted into the small intestine
-pepsin released into the stomach by cells in the stomach lining-Only works in acidic conditions, provided by HCL in the stomach

Question 14

Exopeptidases-

Answer 14

-Act to hydrolyse peptide bonds at the ends of protein molecules- remove single amino acids from proteins
-Dipeptidases are exopeptidases that work specifically on dipeptides- act to separate the two amino acids that make up a dipeptide by hydrolysing the peptide bond between them
-Located in the cell surface membrane of epithelial cells in the small intestine.

Question 15

How does glucose and galactose absorbed across cell membranes after digestion?

Answer 15

-Absorbed across the epithelial cells of the ileum by active transport with sodium ions via a co-transporter protein

Question 16

How does fructose absorbed across cell membranes after digestion?

Answer 16

-Absorbed across the epithelial cells of the ileum via facilitated diffusion through a different transporter protein

Question 17

How does monoglycerides and fatty acids absorbed across cell membranes after digestion?

Answer 17

-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 they can diffuse directly across the epithelial cell membrane

Question 18

How does amino acids absorbed across cell membranes after digestion?

Answer 18

-Absorbed via co-transport, in a similar way to glucose and galactose
-Na ions are actively transport out of the ileum epithelial cells into the blood. This creates a Na ion conc gradient. Na ions can then diffuse from the lumen of the ileum into the epithelial cells through sodium dependent transporter proteins, carrying the amino acids with them.