Lecture 17: Digestion

Question 1

Breakdown of carbs, proteins and lipid for digestion steps (2)

Answer 1

1. Digestion: Large molecules are broken into smaller units via hydrolysis. Lipids- Fatty acids and Glycerol, Polusaccharides-Monosaccharides, Proteins-Amino acids
2. Metabolism: Small molecules can be uptaken by cells and enter metabolic pathways to generate cellular energy

Question 2

Mechanical digestion

Answer 2

Purely physical breakdown that does not change the chemical nature of the molecules

Question 3

Chemical digestion

Answer 3

Enzymes break chemical bonds to produce smaller molecules

ex: Proteins-> amino acids

Question 4

Absorption

Answer 4

Metabolites produced from digestion are absorbed into the bloodstream

Question 5

Saliva contains

Answer 5

a-amylase to digest carbohydrates and lipase to digest lipids

*However, majority of digestion occurs later

Question 6

Digestion in the stomach (2)

Condition+enzyme

Answer 6

• Acidic conditions (PH 1-2) causes protein denaturation (denatured proteins are better substrates for proteases)
• Protease pepsin is activated under low PH conditions and catalyzes protein degradation

Question 7

Pepsin

Answer 7

Hydrolyzes denatured protein into shorter polypeptides

Question 8

Proteases

Answer 8

Break peptide bonds with water to produce short peptides and amino acids

Question 9

Pancreas role (2)

Answer 9

• Partially digested products in stomach triggers hormones that signals the pancreas to release:
  1. sodium bicarbonate (NaHCO3) to neutralize PH as food travels from the stomach to the small intestines
  2. Release host of enzymes into the small intestines to digest proteins, lipids and carbohydrates

Question 10

Proteases are released as

Answer 10

zymogens to prevent them from digesting the pancreas
Inactivated form of enzyme to prevernt enzyme from digesting pancreatic tissue

Question 11

Zymogens are activated by

Answer 11

proteolysis (Protein cleavage) from other proteases

Question 12

Lipase

Answer 12

Lipids-> fatty acids and glycerol

Question 13

Broken down products are

Answer 13

absorbed into the bloodstream and distributed to cells throughout the body

Question 14

Pancreatic proteases and intestinal peptidases

Answer 14

degrade proteins to small peptides and amino acids

Question 15

Carbohydrate digestion in the intestines (3):

Done by what+ how

Answer 15

• Done by a-amylase with degrades starch
• a-amylase cleaves a-1,4 bonds in starch but not a-1,6 bonds or terminal glucose residues (1,4 bonds)
• Disaccharide degradation by sucrase, lactase,matase

Question 16

Lactase cleaves lactose into

Answer 16

Galactose and glucose

Question 17

Maltase cleaves maltose into

Answer 17

glucose and glucose

Question 18

Sucrase cleaves sucrose into

Answer 18

Glucose and fructose

Question 19

Monosaccharides are taken up by

Answer 19

the intestinal cells and exported into the bloodstream

Question 20

Ways of lipid digestion in the intestines (2):

Answer 20

• Gallbladder releases Bile salts into the small intestines
• Bile salts are amphipathic molecules that facilitate emulsification (combine two ingredients together which do not ordinarily mix easily).
• Lipase

Question 21

Bile salts roles (2)

Answer 21

• Render triacygycerols more easily digestible by lipases
• Help package lipid degradation products into micelles

Question 22

Emulsion

Answer 22

A mixture of lipid droplets and water

Question 23

Lipase breaks down…

Answer 23

Triacyglycerol into fatty acids and monoacyglycerol (composed of a molecule of glycerol linked to a fatty acid via an ester bond)

Question 24

Phospholipase

Answer 24

degrade cell membrane

Question 25

Collagenase and hyaluronidase

Answer 25

Degrade connective tissues