Lipid Anabolism

Question 1

Which intermediate of glycolysis is used as the glycerol backbone in lipid synthesis?

Answer 1

DHAP gets converted into glycerol and is used as the backbone in triacylglyercol synthesis

Question 2

In what tissues is fatty acid synthesis prodominently take place?

Answer 2

Liver and adipose tissue

Question 3

Function of Lipids

Answer 3

Fuel stores

Structural component

Signaling molecules

Temperature homeostasis

Question 4

What form of lipid in the body is fat stored?

Answer 4

Triacylglycerol

Question 5

Where is the body are triacylglycerol mostly stored

Answer 5

Adipose tissues

Question 6

Where in the body does beta-oxidation occur?

Answer 6

Liver

Question 7

How many phases of fatty acid synthesis?

Answer 7

Three

Phase 1 - Cytosolic Entry of Acteyl-CoA

Phase 2 - Generation of Malonyl-CoA

Phase 3 - Fatty acid chain formation

Question 8

What is the rate-limiting step in Fatty Acid Syntheis

Answer 8

Generation of Malonyl-CoA

Carboxylase (adds CO2) Acetyl-CoA to create Malonyl-CoA

Question 9

How does Aceytl-CoA get from the mitochondria into the cytoplasm

Answer 9

Citrate Transport

Acetyl-CoA is combine with oxaloacetate into citrate

Citrate is then transported into the cytosol from the mitochondria

Acetyl-CoA and OAA are then regenerated in the cytoplasm

Question 10

What controls ATP Citrate Lyase?

Answer 10

Activates - Glucose, Insulin (fed state)

Inactivates - PUFA, leptin (full/too fat state)

ATP Citrate Lysases converts Citrate back into Acetyl-CoA and OAA in the cytosol

Question 11

What enzyme converts Citrate back into Acetyl-CoA and OAA in the cytosol?

Answer 11

ATP Citrate Lyase

Question 12

What happens to the OAA after Acetyl-CoA is recreated back in the cytosol?

Answer 12

OAA ⇒ Malate ⇒ Pyruvate

Question 13

Function and Control of Aceytl-CoA Carboxylase

Answer 13

Carboxylate Acetyl-CoA into Malonyl-CoA

Rate-limiting step in Fatty Acid Synthesis

Activates - citrate, insuline (fed state)

Deactivates - Glucagon (fasting), epinephrine (exercise), high [AMP], PUFA, Palmitate

Question 14

Coenzyme for Acetyl CoA Carboxylase

Answer 14

Biotin - Vit B9

Question 15

Importance of Malonyl-CoA

Answer 15

Substrate of Fatty Acid Synthesis

Inhibits Carnitine Acyltransferase (rate-limiting step of Fatty Acid Degradation)

Helps prevent degradation during synthesis

Question 16

To make palmitate how many malonyl-CoA are required?

Answer 16

7 Malonyl-CoA

Question 17

How many NADPH are oxidized per palmitate?

Answer 17

14 NADPH

Question 18

Order of Reactions in Fatty Acid Synthesis

Answer 18

Condensation

Reduction

Dehydration

Reduction

Mnemonic: C ouR DR

Question 19

What reducing power does FAS require?

Answer 19

NADPH

Question 20

Sources of NADPH

Answer 20

Malic enzyme - 1

Pentose phosphate pathways - 2-12

Question 21

Regulation of Phase I of FAS

Answer 21

ATP Citrate Lyase

Activation (Dephosphorylated) - Citrate, Insulin,

Deactivation (Phosphorylate) - Long-chain fatty acids, epinephrine, glucagon, high [AMP]

Question 22

Conditions Increase Synthesis

Answer 22

High carb/low fat dies

Insulin and glucocoritcoid hormones

Question 23

Conditions that decrease FAS

Answer 23

High amounts of PUFA, high fat diets, starvation

Question 24

Where does elongation of parmitate occur in the cell?

Answer 24

Smooth ER or Mitochondria

Smooth ER uses Malonyl-CoA as source of carbon

Mitochondria uses Acetyl-CoA as carbon donor

Question 25

At which carbons can humans make double bonds?

Answer 25

Alpha end - 4, 5, 6 and 9

Thats why we need omega-3 and omega-6 fatty acids in our diets

Question 26

Essential Fatty Acids

Answer 26

Linoleic acid - (18C:2Sat)

Linolenic acid - (18C:3Sat)

Question 27

What are the essential fatty acids produced into?

Answer 27

Linoleic acid - arachidonic acid - omega 6

Linolenic acid - eicosapentanoic acid and docsahexanoic acid - omega 3