Fatty Acid Synthesis

Question 1

De novo synthesis mostly occurs where in the body

Where in the cell?

Answer 1

Liver, lactating mammary glands and some in adipose

Cytosol

Question 2

What is the rate limiting and regulated step for fatty acid synthesis?

Why is this important?

Answer 2

Carboxylation (adding carbon) of acetyl CoA to form malonyl CoA

Because malonyl CoA is the precursor for fatty acid synthesis

Question 3

Short term regulation of ACC is done by?

Answer 3

Protein kinase A and protein phosphatase

Question 4

Long term regulation of ACC is done by

Answer 4

Prolonged high calorie and high carb diet will increase ACC (increase fatty acid synthesis)

Prolonged low calorie or high fat diet will decrease ACC (reduces fatty acid synthesis)

Question 5

Once final fatty acid length is 16 carbons, there will be termination in synthesis with end product ___

What happens to this end product

Answer 5

Palmitoyl-S-ACP

Palmitoyl thioesterase cleaves the thioester bond releasing saturated palmitate (16:0)

Question 6

Two sources of NADPH

Answer 6

HMP shunt (mostly) and malate oxidation and decarboxylation by malic enzyme (one of first steps in handwritten note)

Question 7

Palmitate (16:0) is further elongated where?

Very long chain FAs need to be generated for?

Answer 7

Smooth ER

Brain lipids

Question 8

Structure of triacylglycerol (TAG)

Answer 8

Carbons of glycerol:
Carbon 1: saturated FA of varied length (often 16)
Carbon 2: unsaturated FA of varied length
Carbon 3: saturated or unsaturated FA of varied length

Question 9

3 qualities of TAG that come into play for its storage?

Answer 9

1. Only slightly soluble in water
2. Unable to form micelles independently
3. Able to coalesce (form oil droplets)

Question 10

Synthesis of TAG requires production of the following 2 TAG building blocks

Answer 10

1. Glycerol phosphate (initial acceptor of activated FAs during TAG synthesis)
2. Acyl CoA (FFAs must be converted to activated form)

Question 11

Glycerol Phosphate:

1. Two places where it is produced
2. Two pathways in which it is produced

Answer 11

1. Liver and adipose
2. Glycolytic pathway (glucose-> DHAP by glycerol phosphate dehydrogenase) and
   Free glycerol -> glycerol phosphate by glycerol kinase (in liver only)

Question 12

When will no TAG production occur?

Answer 12

When plasma glucose and insulin levels are low (because GLUT4 for adipose is insulin dependent - so adipose will not be able to synthesize glycerol phosphate without insulin)

Question 13

Converting FFA to acyl CoA is catalyzed by ?

Answer 13

Thiokinase

Question 14

4 reactions required to assemble TAG from glycerol phosphate and fatty acyl CoA

Answer 14

1. Sequential addition of 2 FAs from fatty acyl CoA to glycerol phosphate (by acyltransferase)
2. Removal of phosphate group by a phosphatase
3. Addition of a third FA by an acyltransferase

Question 15

How is TAG stored in adipose tissue?

Why?

Answer 15

As cytosolic lipid droplets.

FAs from TAG in this format are easily mobilized when fuel is required

Question 16

~small amount of TAG are stored in liver

1. How are they packaged?
2. Function of VLDL

Answer 16

1. With other lipids and apoproteins to form VLDLs

2. Secreted to blood and deliver endogenously synthesized lipids to peripheral tissues

Question 17

Difference between chylomicrons and VLDLs?

Answer 17

Chylomicrons deliver exogenous dietary acquired lipids (and TAG); VLDLs deliver de novo synthesized lipids