9 Fat absorption

Question 1

What are the 4 stages of Beta-oxidation?

Answer 1

oxidation
hydration
oxidation
cleavage

Question 2

How much ATP does Beta oxidation produce per acetyl unit liberated?

Answer 2

34 ATP

Question 3

Which vitamins are fat soluble?

Answer 3

A,D,E,and K

Question 4

A - overdosing and deficiency

Answer 4

overdosing - disposing of lipophilic substances, hair loss

deficiency - night blindness

Question 5

D - deficiency

Answer 5

impaired bone mineralisation (rickets, osteomalacia), and cancer

Question 6

E - deficiency

Answer 6

neurological problems, poor nerve conduction

Question 7

K - key roles

Answer 7

blood coagulation
bone metabolism
deposition of calcium salts in arterial vessel walls

Question 8

What is tocopherol?

Answer 8

organic compounds with Vitamin E activity

Question 9

What 3 fatty acids can’t be derived endogenously?

Answer 9

linoleic acid
linolenic acid
arachidonic acid

Question 10

What is the composition of fat intake?

Answer 10

90% triglycerides
5% phospholipids
rest are sphingolipids

Question 11

What does lipase do, and what then happens to the products?

Answer 11

releases a single fatty acid from triglycerides, long fatty acids insolube at acidic pH, in micelles droplets
medium and short fatty acids ionised in solution

Question 12

What happens to lipase in those with pancreatic insufficiency?

Answer 12

extended lipase activity in duodenum, alleviates fat absorption

Question 13

What do the fatty acids stimulate once in the duodenum?

Answer 13

CCK release by duodenal I cells

Question 14

What 4 things does pancreatic lipase need to work?

Answer 14

colipase (for ligand binding conformation), alkaline pH, bile salts, fatty acids

Question 15

Why do we need colipase?

Answer 15

lipase only active at oil-water interface of droplets, so colipase acts a an anchor site

Question 16

What 3 barriers need to be overcome to absorp fats?

Answer 16

mucous
unstirred water layer
apical membrane

Question 17

Why are shorter chain fatty acids easier to absorb?

Answer 17

they’re hydrophilic

Question 18

What breaks down micelles droplets near the enterocyte surface?

Answer 18

Acidic enrionment created by Na-H transporter

Question 19

How are the fatty acids actually absorbed?

Answer 19

non-ionic diffusion

collision and incorporation into the cell membrane

Question 20

What happens just before re-esterification in the cell?

Answer 20

long-chain acids bounds to protein, ensuring it goes to SER

Question 21

What does re-esterification do?

Answer 21

converts fatty acids into chylomicrons

Question 22

What happens to chylomicrons on endothelial surfaces?

Answer 22

encounter lipoprotein lipase, hydrolysing them into fatty acids and glycerol