Chapter 14: Digestion

Question 1

Digestion is facilitate by a diverse set of which enzymes

Answer 1

Hydrolytic enzymes

Question 2

All products from the breakdown of biomolecules are finally converted to….

Answer 2

Acetyl CoA

Question 3

Components and characteristics of Acetyl-CoA

Answer 3

Acetyl (COCH3) : 2 C
CoA (Coenzyme A): Serves as a carrier

Will enter the citric acid cycle to make energy

Question 4

Digestion in Mouth

Answer 4

• Where digestion begins
• Chewing —-> Slurry
• The slurry is more readily attacked by hydrolytic enzymes
• Saliva contains: Na+, K+, Cl-, HCO3- and mucoproteins

Question 5

Digestion in Stomach

Answer 5

• Site of food breakdown
• Chemical breakdown of protein begins
• Delivers Chyme to small intestine
• Acidic environment generated by H+/K+ ATPase
• Gastric amylase and Gastric lipase (initiate emulsification) have minor roles for other nutrients.

Question 6

Enzyme involved in protein breakdown in stomach

Answer 6

Pepsin (active form) - immune to denaturation in high acidic solutions
Pepsinogen (inactive form)
- endopeptidase activated pepsinogen

Question 7

Zymogen

Answer 7

• inactive enzyme or inactive precursor
• also called pro-enzymes
• get activated in site of digestion
• Allows control of the location of digestion —> i.e. compartmentalization

Question 8

Exocrine role of Pancreas

Answer 8

• Extensive biochemical breakdown
• Secretes pancreatic enzymes/proenzymes

Question 9

Endocrine role of Pancreas

Answer 9

• Coordinate whole body tissue response to feeding
• Secretes hormones
• Insulin with feeding ( high blood glucose levels)
• Glucagon when not fed (low blood glucose levels)

Question 10

The Pancreas secretes…..

Answer 10

bicarbonate to neutralize stomach acid

Question 11

Enteropeptidase

Answer 11

• Also called enterokinase
• Produced in the intestine to activate pancreatic enzymes

Question 12

Role of small intestine

Answer 12

Digestion:
- Site of action for pancreatic enzymes
- Brush border enzymes
Absorption:
- Massive surface area via villi and microvilli

• intestinal tract lines with epithelial cells also called enterocytes

Question 13

Secretin

Answer 13

• Stimulates pancreas to release sodium bicarbonate in intestine (neutralize the acidity of products entering)

Question 14

Cholecystokinin (CCK)

Answer 14

• Stimulates pancreas to release digestive enzymes
• Stimulates the gall bladder to secrete bile salts

Question 15

Protein digestion

Answer 15

• digested into oligopeptides
• Peptidases on surface of intestinal cells cleave oligopeptides
• a.a are subsequently released into blood by antiporters

Question 16

Celiac Disease

Answer 16

• gluten enteropathy -> intestinal inflammatory disorder
• Genetically predisposed
• Mount an inflammatory response to gluten derived peptides found in Rye and Barley.
  
  • Gluten proteins and rich in glutamine and proline –> may be linked to pattern of peptides produced during digestion
• Inflammatory response damages the intestinal lining –> impairs nutrient absorption

Question 17

Carbohydrate Digestion

Answer 17

• Breakdown to monosaccharides inside the gut lumen and at enterocyte surface
• Sucrose and lactose digested by sucrase and lactase
• Galactose, glucose and fructose absorbed into enterocyte via transporters

Question 18

which bonds do a-amylase , a-glucosidase and a-dextrinase cleave

Answer 18

a- amylase : cleaves a-1,4 bonds in starch and glycogen
a-glucosidase: ‘maltase’, cleaves a-1,4 bonds in starch and glycogen
a-dextrinase: cleaves a-1,6 bonds (debranching enzyme)

Question 19

Bile Salts…

Answer 19

insert into lipid droplets rendering them more accessible to digestion by lipases

Question 20

Lipases,….

Answer 20

convert the triacylglycerols into 2 fatty acids and monoacylglycerol
- digestion products are carried as micelles to intestinal epithelium

Question 21

Examples of emulsification for fat digestion

Answer 21

• body temperature and peristalsis
• salivary and gastric lipase release fatty acids that act as surfactants
• Carboxy end interacts with water
• Bile salts

Question 22

Chylomicron description

Answer 22

• lipoprotein
• transport particles
• exterior: phospholipid monolayer, apoproteins (ApoB-48) and cholesterol
• interior: TAGs and Cholesterol esters