Digestion and absorption 3.3.3

Question 1

What is the definition of digestion?

Answer 1

• Larger biological molecules being hydrolysed into small molecules that can be absorbed in the blood.

Question 2

What is hydrolysed during the digestion of carbohydrates?

Answer 2

• Glycosidic bonds

Question 3

How does amylase act on starch?

Answer 3

• Amylase breaks down starch into maltose which can then be acted upon by the enzyme maltase.

Question 4

What are the 2 types of amylase?

Answer 4

• Salivary amylase
• Pancreatic amylase

Question 5

Why is there no carbohydrate digestion in the stomach?

Answer 5

• Salivary amylase is too acidic for the stomach.

Question 6

How are different carbohydrates absorbed?

Answer 6

• Glucose and galactose are absorbed by active transport using sodium ions.
• Fructose is absorbed by facilitated diffusion across a carrier protein.

Question 7

What hydrolysing happens when digestion of lipids happens?

Answer 7

• Hydrolysis of ester bonds.

Question 8

What are the products of digestion of lipids?

Answer 8

• One monoglyceride and 2 fatty acids

Question 9

What are the enzymes during lipid digestion and where are they made?

Answer 9

• Lipases catalyse lipid digestion and are produced in the pancreas and secreted in the small intestine.

Question 10

Outline points about bile salts?

Answer 10

• Bile salts are produced by the live.
• They lower the surface tension between lipids and water so large drops of lipid split into smaller ones. (EMULSIFY)

Question 11

How do the products of lipid digestion and bile salts interact?

Answer 11

• Products of lipid digestion stick to the bile salts to form micelles.

Question 12

What is the role of micelles?

Answer 12

• Micelles move products to epithelial cells by constantly breaking up and reforming, leading to the release of products.

Question 13

How are proteins hydrolysed?

Answer 13

• Hydrolysed by a variety of proteases that hydrolyse the peptide bonds to release amino acids.

Question 14

Outline the 3 different proteases…

Answer 14

1) Endopeptidases - Enzymes that act on hydrolysing peptide bonds within the protein molecule.
2) Exopeptidases - Enzymes that act on hydrolysing peptide bonds at the end of the protein molecule.
3) Membrane-bound dipeptidases - act on peptide bonds between peptide molecules.

Question 15

How are proteins absorbed?

Answer 15

• The co-transport using sodium ions.

Question 16

What are 5 adaptations of the ileum

Answer 16

1) Very long - allows time for diffusion and active transport of products of digestion.
2) Ileum lining is folded - villi form microvilli, allowing a large surface area or diffusion.
3) One cell thick epithelial walls allows a short diffusion distance.
4) Rich blood supply in the microvilli maintains a concentration gradient.
5) Many mitochondria allow provide energy for active transport.