Digestion & Absorption

Question 1

what is the function of vitamins A, C and D?

Answer 1

A - vision
C - antioxidant
D - calcium absorption

Question 2

what are the functions of calcium and iron minerals?

Answer 2

calcium - bone mineralisation
iron - oxygen transport

Question 3

what are the 3 main types of carbohydrates?

Answer 3

monosaccharide, disaccharide, polysaccharide

Question 4

what are the 3 types of monosaccharides?

Answer 4

glucose, fructose, galactose

Question 5

how does the body digest large molecules in food?

Answer 5

breaks down into smaller molecules that the body can absorb
e.g protein -> peptide -> amino acid

Question 6

what is the definiton of digestion?

Answer 6

the process of food being broken down into components simple enough to be absorbed into the intestine

Question 7

what enzyme secretions aid digestion?

Answer 7

glandular cells (mouth)
chief cells (stomach)
exocrine cells (pancreas)
enzymes bound to apical membrane of enterocytes

Question 8

what 3 glands produce saliva?

Answer 8

parotid, submandibular, sublingual

Question 9

what is the function of saliva?

Answer 9

begins carbohydrate digestion (using alpha amylase)
begins lipid digestion (using lingual lipase)

Question 10

what is a zymogen?

Answer 10

an inactive precursor (protein containing an inactive enzyme) that is activated by the cleavage of a specific peptide bond

Question 11

what does bile do in digestion?

Answer 11

emulsifies fats to allow enzymes to access them

Question 12

what are bile acids derived from?

Answer 12

cholestorol

Question 13

how is bile conjugated and what does it become?

Answer 13

conjugated to amino acid, becomes amphipathic (both hydrophobic/hydrophilic components)

Question 14

explain the functions of each small intestine component in digestion

Answer 14

duodenum - mixing secretions with food, acid neutralisation, further digestion, absorption
jejunum - completing breakdown, nutrient absorption
ileum - nutrient absorption

Question 15

explain how enterokinase activates various digestive proteins in the pancreas

Answer 15

enterokinase in the duodenum turns inactive trypsinogen into active trypsin, which can activate various other digestive proteins
(e.g proelastase -> elastase)

Question 16

what are the brush border enzymes? give examples

Answer 16

enzymes tethered to plasma membrane composed of numerous microvilli
examples - peptidases, lactase, sucrase, maltase

Question 17

what is mastication and what does the food become after mastication?

Answer 17

chewing
breaks up food and moistens it, becomes bolus

Question 18

what digestion occurs in the stomach?

Answer 18

protein digestion - HCL denatures proteins and activates pepsin (endopeptidases that break down proteins into small peptides)
lipids - gastric lipase present but minor contribution

Question 19

what carbohydrate digestion occurs in the duodenum?

Answer 19

alpha amylase digests starch
brush border enzymes turn disaccharides into monosaccharides

Question 20

what protein digestion occurs in the duodenum? (+ naming the enzymes)

Answer 20

cleaved by trypsin, chymotrypsin, elastase and carboxypeptidases to produce smaller peptides
brush border enzymes turn peptides into amino acids

Question 21

what lipid digestion occurs in the duodenum?

Answer 21

pancreatic lipase digests lipids to monoglycerides and fatty acids
phospholipase digests phospholipids to lysolecithin and fatty acids

Question 22

what 3 ways are nutrients absorbed?

Answer 22

passive absorption (diffusion)
facilitated transport (involved membrane carrier)
active transport (ATP needed)

Question 23

how are lipids absorbed?

Answer 23

in mixed micelles, they diffuse down conc. gradients into cells

Question 24

how do chylomicrons form and enter circulation?

Answer 24

triglycerides of above 12 carbons are formed into a chylomicron
then secreted into lymphatics through lacteals, where they end up in the bloodstream eventually

Question 25

how are monosaccharides absorbed?

Answer 25

sodium co-transporters, transported across basolateral membrane by glut-2 transporter

Question 26

how are amino acids absorbed?

Answer 26

sodium co-transporters and facilitated diffusion