Lecture 20 Fatty acid Metabolism, response to starvation

Question 1

on average how many KG of fat does a 70KG person have and how many Kcal is that

Answer 1

15kg and 141kcal

Question 2

Do you have a lot of glycogen?

Answer 2

no

Question 3

what does your liver make and gallbladder store to emulsify fats

Answer 3

Cholic acid (bile salts)

Question 4

What is cholic acid

Answer 4

a bile salt that is made by you liver release into small intestine to break down fats

Question 5

After releasing bile salts and emulsifying what do the fats turn into in your small intestine

Answer 5

mixed micelles

Question 6

What enzymes digest lipids in your small intestines

Answer 6

lipases (enzymes that digest lipids)

Question 7

What do lipases digest your triglycerols into and why is this important

Answer 7

glycerol and three fatty acids dur bc triglycerols cannot cross the membrane but the two smaller things can (so they can get into your lymphatic system and your circulatory system)

Question 8

what is the primary transporter of triglycerols in your circulatory systems

Answer 8

Chylomicron

Question 9

what is chylomicron

Answer 9

the primary transporter of triglycerols in your circulatory systems

Question 10

what happens after glycerol and fatty acids cross your intestinal mucosa

Answer 10

they are reassembled into triglycerols and given to chylomicron to carry through the circulatory system

Question 11

is there a reversible reaction form TGAs to free fatty acids

Answer 11

yes

Question 12

how does the TGA cross the membrane

Answer 12

by breaking them down into free fatty acids and glycerol

Question 13

how do lipases attack TAG

Answer 13

by attacking each ester bond individually forming three reactions so the TAG–>DAG—>MAG— >FA+ glycerol

Question 14

do different lipases target each ester bond in a TAG

Answer 14

yes

Question 15

how does glycerol enter central metabolism

Answer 15

through G3P (glycolysis)

Question 16

What are the general steps of prep for B oxidation

Answer 16

1. activate fatty acid by shoving a CoA on it
2. transport that into the mitochondria via the carnitine carrier system
3. beta oxidation

Question 17

where does activation step of fatty acids happen

Answer 17

in the cytoplasm

Question 18

how much ATP does beta oxidation activation take

Answer 18

2 ATP

Question 19

purpose of carnitine pathway

Answer 19

to get your activated fatty acids into the mitochondria so they can be beta oxidized

Question 20

steps of the carnitine pathway

Answer 20

1. transfer the activated fatty acyl coA onto a molecule called carnitine by taking off its CoA, that is then able to pass through the outer mtocontral membrane. (by using Carnitine Acyltransferase 1)
2. the whole thing then moves into the matrix bc carnitine has a special transporter form the intermembrane space into the matrix
3. Once in the matrix, you replace the carnitine again with coenzyme A (where it goes on its merry way) by using Carnitine Acyltransferase II
   ta da!

Question 21

does the carnitine pathway consume energy, does it go with is concentratioin gradiet

Answer 21

no, it goes with with concentration gradient

Question 22

how you you shit off FA degradation

Answer 22

shut off the carnitine pathway

Question 23

general steps of Beta oxidation and when is what produced

Answer 23

1.(acetyl CoA dehydrogenase) dehydrogenation (produce FADH2)

2. Hydration (has to be tras bond) (enoyl CoA hydratase) (shove on OH)
3. dehydrogenation (Beta hydroxyacyl-CoA dehydrogenase) (turn OH into carbonyl group) (produce NADH)
4. Thiolytic cleavage (thiolase)

Question 24

What is beta oxidation like? (in terms of mechanisms)

Answer 24

Amino acid degradation and citric acid cycle

Question 25

another name for FAD

Answer 25

flavin cofactor

Question 26

besides initial activation, where does the other ATP get used in the activation step of beta oxidation

Answer 26

putting back together the 2 inorganic phosphates that you broke apart after using the ATP

Question 27

Overall how many ATPs does it take to activate B oxidation

Answer 27

2

Question 28

balance sheet for one turn of the citric acid cycle if you start with one acetyl coa

Answer 28

A acetyl-CoA= 3 NADH + 1 FADH2 + 1 ATP (ie 10 ATPS)

Question 29

practice beta oxidation with regular 16 C chain (how many ATP???)

Answer 29

106net

Question 30

what are the two variations of the beta oxidations and how do we get around them

Answer 30

1. if you have an unsaturated bond you don't have to do the initial dehydrogenation (making of trans double bond) so you subtract an FADH2 from every double bond you have (+you also might have to isomerize it into a trans but that does not affect energy) 2. Odd chain fatty acid chains= at the end of oxidation you are left with a three carbon thing which you carboxylase using cofactor biotin and an ATP and HCO- (propionyl CoA Carboxylase) then you do some mutase reactions to form SUCCINYL CoA which can go into the citric acid cycle where it can generate 1 FADH2 and one NADH - so if you have uneven thing treat it as if it were even then at the end SUBTRACT 1 MORE ATP and ADD 1 NADH AND 1 FADH

Question 31

what is special about vitamin B12 and what's another name for it

Answer 31

Methylcobalamin and it can do radical chemistry which enables now enzyme mechanisms (make a tricyclic energetically unstable thing)

Question 32

where does normal fatty acid degradation take place?

Answer 32

in the mitochondria

Question 33

where does degradation of branched chain fatty acids and FA over =or more than 22C long (in humans and in plants)

Answer 33

in humans: Peroxisome In plants: Glyoxysome

Question 34

what scenario would you degrade FA in the peroxisome (or glyoxysome in plants) instead of the mitochondria?

Answer 34

if its branched or 22 or more C long

Question 35

where does FA biosynthesis happen

Answer 35

cytoplasm

Question 36

when beginning to synthesize FA what molecule do you mix with acetyl CoA to start adding carbons

Answer 36

Malonyl-Coa! is made by mixing Acetyl-Co2 and Cox

Question 37

what enzyme performs FA synthesis and what is special about it

Answer 37

Fatty Acyl synthetase (big polypeptide that has different domains that do different steps) special bc its is doing substrate channeling!!

Question 38

Steps of FA biosynthesis

Answer 38

1. Activation (Acetyl CoA +Co2 --> Malonyl CoA) using cofactor Biotin (the regulated step) 2. IDK IF I NEED TO KNOW THIS

Question 39

what cofactor is used for carboxylation

Answer 39

biotin

Question 40

what cofactor is used for decarboxylations

Answer 40

TPP

Question 41

What are the pros and cons of a multifunctional protein

Answer 41

pro: substrate channeling, correct stoichiometry, no need to encode binding surface con: no change for modularity (can't use it for other stuff)

Question 42

What is your system doing at time =0 since eating

Answer 42

release insulin

Question 43

why can't your brain use fatty acids as energy efficiently? (4 reasons)

Answer 43

1. hard to transfer them across the blood/ brain barrier 2. the ATP generation linked to beta oxidation demands more oxygen than glucose, which is risking neurons to become hypoxic 3. Beta oxidation leads to superoxides and other types of oxygen radicals which will damage the brain due to severe oxidative stress. 4. Also the rate of ATP generation is just overall slower than glucose

Question 44

What happens at t=2 hours since eating

Answer 44

drop insulin increase glucagon start breakdown glycogen

Question 45

What happens at t=4 hours since eating

Answer 45

glycogen is gone so start mobilizing FA for liver and muscle

Question 46

What happens at t >12 hours since eating

Answer 46

Formation of ketone bodies created to replenish glucose

Question 47

most common ketone body

Answer 47

Acetoacetate

Question 48

what is acetoacetate

Answer 48

a ketone body that feeds your brain when glucose is gone

Question 49

What does your brain do when it has no glucose

Answer 49

makes ketone bodies

Question 50

3 types of ketone bodies

Answer 50

Acetone, Acetoacetate, D-B-hydroxybutyrate

Question 51

The 2 uses of formed Acetyl CoA:

Answer 51

1. citric acid cycle 2. converted to ketone bodies

Question 51

Where do ketone bodies come from?

Answer 51

liver and Acetyl coa

Question 52

Tell me about the synthesis of ketone bodies

Answer 52

last 5 min of starvation lecture HELP

Question 53

where is glucose coming from after you run out of everything

Answer 53

proteins from your muscle then your organs

Question 54

can you live with no glucose in your body

Answer 54

NO