Fat Metabolism

Question 1

What is the basic structure of tags

Answer 1

A glycerol backbone and 3 fatty acid chains

Question 2

What is the basic pathway for fat breakdown in a cell

Answer 2

The tag will be broken down into a glycerol and fatty acid.
The glycerol can be used to generate new glucose via gluconeogenesis in the liver
The fatty adds can undergo fatty auld oxidationor ßoxidation in muscle, liver, or other tissues

Question 3

What is the difference between acyl coa and acetal coa

Answer 3

Acetal COA is 2 molecules bound to con whereas acyl has a longer chain

Question 4

T/F. Acyl chains are trapped in the cell by covalent addition of coenzyme A

Answer 4

True

Question 5

What must be done to release acyl chains from the cell and be used in the cytoplasm

Answer 5

Acyl COA synthatase catalyzes a reaction to form fatty and acyl COA

Question 6

What drives the synthetase reaction forward

Answer 6

Pyrophosphate hydrolysis (ATP - amp)

Question 7

What kind of reaction is a acyl coA synthatase

Answer 7

Ligase

Question 8

Isn’t more favorable to convert ATP to ADP or to amp? Why?

Answer 8

It is easier to convert ATP to ADP because there must be a second ATP present to first convert the amp to ATP

Question 9

Describe the reaction needed to generate ATP from amp

Answer 9

Amp is converted into ADP via adenylate kinase and an ATP molecule will de sacrificed and form a second ADP molecule.
ATP synthase which can only bind to ADP will produce 2 ATPs

Question 10

What is needed for fatty acid activation

Answer 10

2 ATPs (1 for activation and one for production of ADP) and 1 water to hydrolyze PPi

Question 11

Where does ß oxidation take place

Answer 11

Mitochondrial matrix

Question 12

T/F. Acyl con can move across the outer and inner membrane.

Answer 12

False acyl coa can only move across outer membrane via porins. There are no transporters in the inner membrane to transport acyl coa and it is too large and water soluble

Question 13

Carnitine shuttle

Answer 13

Mechanism used to indirectly get acyl coa across membrane
It will regulate what comes into the mitochondria and whether we are breaking COA chains

Question 14

Describe how acyl coa enters the matrix

Answer 14

Carnitine acyltransferase 1 transfers act to a Carnitine , which will then be translated across the inner membrane while a new Carnitine gets shuttled out.
Carnitine acyltransferase 2 moves acyl back onto COA
Acyl esa can then be catabolized in ß oxidation

Question 15

How many rounds of oxidation are needed to breakdown 16:0 COA

Answer 15

Use formula (n/2-1)
You would need 7 rounds ,

Question 16

For each round of ß oxidation what is being consumed/produced

Answer 16

1 water and COA is being consumed

1 NADH, FADH, AND Acetyl CoA is produced

Question 17

What hormones are required for tag breakdown

Answer 17

Epinephrine and glucagon

Question 18

How does fatty acids move to the blood

Answer 18

They are bound to serum albumin and enter tissue

Question 19

How many ATP, are required to move fatty acids in the cytoplasm

Answer 19

2

Question 20

What is the rate limiting step in the citric acid cycle

Answer 20

Oxalacetate, because in order to start the CAC acetal coa must combine with oxaloacetate
To produce citrate

Question 21

What are the different ways oxalacetate can be made

Answer 21

By amino acids or pyruvate by enzyme pyruvate carboxylase

Question 22

Explain the 3 steps in fat synthesis

Answer 22

1. Acetal coa is transported to the citric acid cycle where it will be converted into citrate to cross the membrane via citrate synthase it will then be converted back into acetal COA regenerating a pyruvate molecule
   2.acetylco A is carboxylated by acetal co A carboxylase using ATP to form malonyl COA
2. Malonyl COA will be used to make the 16:0 fatty acid chains

Question 23

What is the significance of the CO2group on malonyl coa

Answer 23

It will help drive the fatty acid synthesis reaction forward

Question 24

What 2 enzymes are needed for fatty acid synthesis

Answer 24

Acetal coa carboxylase for conversion to malonyl coa and fatty acid synthase

Question 25

What does acetal esa carboxylate use as its reducing power? FA synthase?

Answer 25

ACC uses ATP
Fa uses nadph

Question 26

Regulatory steps for fat synthesis

Answer 26

ACC is regulated by PTM phosphorylation.
When ACC is phosphonylated by kinase it is inactivated. This happens in the catabolic state when epinephrine and glucagon signaling is on

In the anabolic state, insulin activates phosphates which will dephosphorylate ACC turning it on citrate can also stimulate ACC

Question 27

Describe the competitive regulatory processes in fat metabolism

Answer 27

Malonyl Col, product of conversion of acetal COA by ACC can inhibit CATI, preventing the conversion of acyl COA to acyl Carnitine trapping it in cytoplasm

Question 28

Describe the competitive regulatory processes in fat metabolism

Answer 28

Malonyl Col, product of conversion of acetal COA by ACC can inhibit CATI, preventing the conversion of acyl COA to acyl Carnitine trapping it in cytoplasm

Question 29

In step 3 of FA synthesis, what is the purpose of acyl carrier protein (acp)

Answer 29

It shuttles the intermediates between different reaction sites

Question 30

How many cycles are required for FA synthesis of 16:0

Answer 30

7 cycles (n/2-1) with acetyl coA and malonyl coA for cycle 1 and 6 more malonyl for the other cycles

Question 31

How much energy is used for FA synthesis

Answer 31

7 ATP and 14 NADPH