N: LIPIDS: metabolism

Question 0

how is the glycerol component of fats metabolised?

Answer 0

glycerol enters the glycolysis pathway and is converted to carbohydrate (glucose)

then follows normal route ie. glucose -> pyruvate + CoA -> acetyl-CoA

Question 1

how are fats metabolised?

Answer 1

glycerol and fatty acid components metabolised separately

Question 2

where do fats enter cycle?

Answer 2

in 2 places
glycerol - glycolysis(conversion to acetyl-CoA)
fatty acid component - TCA cycle direct (broken into 2 carbon components combining with CoA to create lots of acetyl-CoA able to enter TCA cycle) ie. 16 carbon fatty acid = 8 acetyl-CoA molecules

Question 3

how is the fatty acid component of fats metabolised?

Answer 3

it’s taken apart 2 carbons at a time, combining with CoA to create lots of lil acetyl-CoAs -> feed into TCA cycle
2H atoms with high energy electrons also made and transferred to cofactors (NADH & FADH2) these go direct to ETC

Question 4

why do we get more energy out of fatty acids vs. carb?

Answer 4

129 ATPs per 16 chain fatty acid vs. 32 ATP per carb
why?
- longer chain
- mainly Carbon and Hydrogen, not as much oxygen
- glucose has already been partially oxidised
- number of Hydrogen per gram is higher = more potential energy

Question 5

where does fatty acid oxidation occur?

Answer 5

activation = outer mitochondria membrane
|
| - carrier molecules help it get through membrane
V
oxidation = inner compartment of mitochondrion

Question 6

when and why do ketone bodies come into play?

Answer 6

• > during fasting fatty acids from fat reserves provide most energy
• > BUT fatty acids => acetyl-CoA => TCA
• > TCA needs oxaloacetate to function, but during fasting body has low glucose levels => fat cannot utilise TCA cycle => acetyl-CoA buildup
• > acetyl-CoA => ketone bodies which can be used to provide energy

Question 7

what is the role of ketone bodies during fasting?

Answer 7

to keep brain functioning, ketone bodies can cross blood brain barrier

brain functions on carbs - fatty acids cannot penetrate

Question 8

by day 10 of fasting all energy needed for nervous system comes from?

Answer 8

ketone bodies

Question 9

characteristics of ketosis to conserve energy:

Answer 9

1) induces loss of appetite
2) lowers bodies metabolic rate
3) conserves reserves of fat & lean tissue

Question 10

what is the benefit of ketosis?

Answer 10

prolongs life during starvation for up to 2-3 months

Question 11

what is the affect of a low carb diet?

Answer 11

tricks the body into thinking its starving

• > glycogen reserves
• > glucose made from AAs in body’s protein
• > induce ketosis
• > metabolic rate reduced to conserve energy ..weight loss slowed

Question 12

what can initial weight loss often be attributed to?

Answer 12

water weight loss

due to water attached to glycogen, and glycogen stores depleted during diet