Lipids

Question 1

What are lipids only soluble in?

Answer 1

Organic solevents

Question 2

What are the essential FA? and what happens if they’re defficient?

Answer 2

A-linolenic acid (n3) - decrease in IQ and visual/retinal activity
linoleic acid (n6) - dermatitis, decrease in growth and reproductive maturity.

Question 3

How do we make EFA?

Answer 3

We must desaturate and elongate to get FA from metabolites.
linoleic acid –> arachidonic acid –> pro inflammatory eicosanoid
a-linoleic –> eicosapentaenoic acid –> anti inflammatory eicosanoid

Question 4

What does FA have?

Answer 4

hydrophobic tail and hydrophilic head group

Question 5

FA naming: delta vs omega

Answer 5

Delta = numbering starts from carboxyl end. ie. 18:2delta^9,12
Omega = numbering starts from FA end. ie. 18:2n^6

Question 6

What are TAGs?

Answer 6

main dietary and storage lipid
ester bonds
3FA + glyceride

Question 7

What is a phospholipid?

Answer 7

more polar than TAG –> amphipathic
membranes

Question 8

what is a sterol?

Answer 8

cholesterol ester
bile acid production

Question 9

Lipid digestion: mouth

Answer 9

lingual lipase continously secreted (not rlly digested here)

Question 10

lipid digestion: stomach

Answer 10

gastric lipase and lingual lipase = stable at low pH

Question 11

lipid digestion: liver and gallbladder

Answer 11

make bile acids from cholesterol and storage of bile acids - emulsify lipids (released by hormones) because not soluble in water. This makes mixed micelles. the mixed micelles can access spaces between mv in the intestine by carrier mediated transporters.

Question 12

lipid digestion: SI

Answer 12

pancreatic enzymes - pancreatic lipase, cholesterol esterase (breaks ester bond), and phospholipase (BBE)

Question 13

Describe enterohepatic circulation

Answer 13

most bile is reabsorbed and only a little is lost in feces. soluble fiber reduces effeciency of enterhepatic circualtion which is good bcs we want more cholesterol to be lost to feces so your body can increase endrogenous production.

Question 14

Describe lipid absorption.

Answer 14

mix micelles have to break down and then form back up to go to the lymphatic (lacteal) system.

Question 15

Lipid transport: how are lipoproteins classified?

Answer 15

ratio to protein (density)
specific apolipoprotein content (Apo- receptor interations)

Question 16

Lipid transport: chylomicron/CR

Answer 16

high lipid low protein
ApoB-48, ApoC, ApoE

Question 17

Lipid transport: VLDL

Answer 17

high lipid low protein
ApoB-100, ApoC, ApoE

Question 18

Lipid transport: LDL

Answer 18

bad cholesterol - relative to VLDL, protein to lipid ratio increases
ApoB-100, ApoC, ApoE

Question 19

Lipid transport: HDL

Answer 19

good cholesterol - low lipid high protein
ApoA family

Question 20

Describe chylomicrons.

Answer 20

They enter the lymphatic system before entering the blood. Dietary lipids are availble to adipose tissue and muscle before arriving at blood.

Question 21

Chylomicrons: LPL

Answer 21

LPL (lipoprotein lipase) is located on the surface of the endothelial cells lining small blood vessels and capillaries. LPL is only expressed in muscle and adipose tissue and is activated by ApoC in chylomicrons and LPL hydrolyses the TAG in chylomicrons –> CR. This is insulin regulated.

Question 22

LDL

Answer 22

Delivers cholesterol to for essentiality and to unwanted places.
VLDL is the main transporter of newly synthesized hepatic TAG. The ApoE and ApoB-100 receptors on LDL initiates the liver to take up LDL via receptor mediated endocytosis.

Question 23

HDL

Answer 23

more cholesterol returning to liver through reverse cholesterol transport. But first LCAT (lectin-cholesterol) esterfies a FA to cholesterol to make a mature HDL. This can go right to liver via SR-B1 (scavenger receptor B1) which is an HDL receptor into the liver, or HDL–>VLDL + LDL by CETP (cholesterol ester transfer proteins) which transfers cholesterol ester from HDL to VLDL or LDL.

Question 24

3 fates of cholesterol

Answer 24

1. converted into bile acids to replenish
2. eliminated as feces
3. packaged into VLDL and send around body

Question 25

What will happen to those with high blood cholesterol if you decrease dietary cholesterol?

Answer 25

Decrease LDL

Question 26

Where do lipids fit into the previously discussed metabolic pathways: gluconeogensis

Answer 26

(inhibited by insulin) lipase hydrolyses ester linkages (lipolysis). In adipose tissue HSL (hormone sensitive lipase) cleaves a FA from glycerol backbone. This complete breakdown of 1TAG = 1 glycerol and 3 FA. The glycerol can go to glycolysis or gluconeogenesis and the FA can go to Boxid to generate E.

Question 27

Beta oxidation.

Answer 27

each round of B-oxidation removes 2 carbons and produces 1 NADH and 1 FADH2. ie. 10 carbon FA goes through 4 rounds of b oxidation and produces = 4 nadh and 4 fadh2 = (4x3) + (4x2) =20ATP

Question 28

Krebs cycle.

Answer 28

net energy produced = 3NADH + 1FADH + 1GTP = (3x3) + (1x2) + (1x1) = 12 ATP per 1 acetyl CoA

Question 29

Combine B oxidation and krebs. How many ATP are produced by complete oxidation of a 10C FA.

Answer 29

(12 x 5) - from krebs cycle acetyl CoA (you get 5 acetyl CoA from a 10C FA
+
(20) - from 4 rounds of b oxidation that produces 4 nadh and 4 fadh2 each
= 80ATP