Chapter 5 (Digestion and Metabolism)

Question 1

List the different types of digestive enzymes.

Answer 1

• proteases/peptidases: break down proteins into small peptides and amino acids
• lipases: break down fats into free fatty acids and glycerol
• amylases: break down carbohydrates (starch and sugars) into simple sugars (like glucose)
• nucleases: break down nucleic acids into nucleotides

Question 2

passive absorption

Answer 2

directly across body wall

Question 3

endocytosis

Answer 3

• direct nutrient absorption at cellular level
• phagocytosis: cell “eating”
• pinocytosis: cell “drinking”

Question 4

mammalian dentition

Answer 4

specialization of teeth for different types of foods eaten

Question 5

functions of incisors, molars, and carnassials

Answer 5

• large incisors for gnawing (squirrels, beavers)
• many compact molars for grinding (ox)
• carnassials for shearing bone and tendon (lion)

Question 6

gastric ceca

Answer 6

• secretes digestive enzymes in invertebrates

- may be present instead of a stomach

Question 7

Name the 3 main cell types of gastric pits of the stomach lining and what they secrete.

Answer 7

• goblet cells: mucous
• parietal cells: HCl
• chief cells: pepsinogen

Question 8

Name the 3 parts of the small intestine (vertebrates) and their functions.

Answer 8

• duodenum: secretion of mucus and fluids
• jejunum: secretes fluids, digestion, absorption
• ileum: most nutrient absorption, some secretions

Question 9

Name and function of the following types of intestinal cells: enterocytes, goblet cells, interepithelial lymphocytes, enteroendocrine cells, epithelial cells within crypts of Lieberkuhn, Paneth cells at base of cryst of Lieberkuhn

Answer 9

• enterocytes: absorptive cells with microvili
• goblet cells: secrete mucus
• interepithelial lymphocytes: T cells, immunodefense
• enteroendocrine cells: secrete hormones controlling GI tract motility and digestion
• epithelial cells of crypts: secrete intestinal juice
• Paneth cells: secrete enzyme that breaks down bacterial cell walls

Question 10

carbohydrate transport into intestinal cells (enterocytes) under low glucose conditions

Answer 10

• SGLT-1 imports glucose

- fructose enters via facilitated diffusion on GLUT-5

Question 11

carbohydrate transport into intestinal cells (enterocytes) during increasing glucose levels

Answer 11

• GLUT-2 translocated to microvilli

- increased capacity for glucose intake

Question 12

bile salts

Answer 12

• amphipathic molecules present in the bile

- emulsifies fats into fat droplets with the help of lecithin

Question 13

emulsification

Answer 13

• breaking down of fats into smaller droplets

- increases surface area for lipase

Question 14

micelles

Answer 14

• formed by monoglycerides, fatty acids and bile salts

- cannot be absorbed

Question 15

methods of transport of amino acids vs. dipeptides/tripeptides through enterocytes

Answer 15

• amino acids: active transport or secondary active transport with Na+
• dipeptides/tripeptides: secondary active transport with H+
• amino acids can diffuse to blood capillary of villus

Question 16

Large proteins are broken down into large polypeptides by (1). Polypeptides are hydrolyzed into smaller polypeptides and peptides by (2). Proteolysis is completed by (3) to produce amino acids.

Answer 16

(1) pepsin
(2) proteases from pancreas (trypsin, chymotrysin, carboxypeptidase)
(3) intestinal aminopeptidases, carboxypeptidases, dipeptidases

Question 17

chylomicrons

Answer 17

• TAG (triacylglycerol) coated with lipoproteins in golgi apparatus
• lipid transport particles that can be circulated
• absorbed by diffusion into lacteal; circulate lymphatic system to blood stream to body