Lipid Metabolism: FA Synthesis Flashcards Preview

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Flashcards in Lipid Metabolism: FA Synthesis Deck (20):
1

What are the functions of lipids?

They provide:
-fuel stores
-structural components for LIPID MEMBRANE
-signaling molecules for transduction pathways for growth)

2

What are the FA derivatives?

glycerolipids, glycerophospholipids, sphingophospholipids

3

What is the major source for FA synthesis and why?

Dietary carbohydrates are the largest source for FA synthesis because of its ability to upregulate the transcription of proteins for FA synthesis through INSULIN RELEASE

4

Where does FA synthesis occur for the most part?

In the liver

Secondarily: adipose tissue, brain, kidney, mammary glands

5

What are the overall steps in FA synthesis?

1.) Cytosolic entry of Acetyl-CoA
2.) Generation of Malonyl-CoA
3.) FA Chain formation (7 Rxns via FA Synthase)

6

What is the rate-limiting step of FA synthesis?

Acetyl CoA Carboxylase--> the carboxylation of acetyl-CoA to Malonyl CoA

7

What are the key regulators of the rate-limiting step for Acetyl CoA Carboxylase?

(+) CITRATE, INSULIN
(-) GLUCAGON, EPINEPHERINE, PUFA, HIGH AMP, PALMITATE

8

Is Acetyl CoA Carboxylase (anabolic state) phosphorylated or not phosphorylated to be activated?

De-phosphorylated

9

What does ATP Citrate Lyase do? What are the regulators of it?

ATP Citrate lyase splits citrate--> OAA + Acetyl-CoA

Regulators:
(+) glucose, insulin
(-) PUFA, Leptin**

10

What happens to OAA after ATP Citrate Lyase splits Citrate?

OAA will become Malate:

Malate--> OAA (Malate Dehydrogenase) (malate-kg-transporter)
Malate--> Pyruvate + NADPH (Malic Enzyme)

11

Where is the NADPH produced from?

It is produced from the:
Pentose Phosphate Pathway (2-12 NADPH produced)
Malic Enzyme (converts Malate--> Pyruvate) (1 NADPH)

***NADPH necessary for FA Synthase activity***

12

What are the substrates for Acetyl CoA Carboxylase?

CO2, ATP, Biotin

13

Random but IMPORTANT: Is Malonyl CoA an inhibitor or activator of the rate-limiting enzyme in FA degradation- Carntitine Acyl Transferase I/ Carnitine Palmitoyl Transferase I?

****INHIBITOR

14

Describe the structure of FA Synthase Complex

Multi Enzyme Complex:
-2 identical dimers
-7 enzymes/ dimer
-Acyl Carrier Proteins

15

FA Synthesis Stoichiometry

1 Acetyl CoA + 7 Malonyl CoA + 14NADPH + 14 H+ --> Palmitic Acid + 14 NADPH+ + 8CoA + 6H20

16

FA Synthase- overall rxn flow

1.) condensation
2.) reduction
3.) dehydration
4.) reduction

17

What does Leptin do? What structural part of the body does it regulate? How does it regulate?

Leptin is a hormone released from the adipocytes that gives signals to the hypothalamus on the levels of fat storage. It regulates the satiety as well as FA synthase--> decreases FA Synthesis.

18

How are FAs longer than 16 chains made?

They are created in the mitochondria or Smooth Endoplasmic Reticulum

19

For longer chain FA synthesis, past 16-Chains, what compound is used for SER vs. Mitochondria?

SER- Malonyl CoA
Mitocondria- Acetyl CoA

20

Where does desaturation of FAs occur? What are the limitations of the human metabolism for FA Desaturation?
Which enzymes do we have?

FA Desaturation occurs:
**Smooth Endoplasmic Reticulum**

Human limitations: Can't go past C-9
Acyl CoA Desaturases of Humans: 4,5,6 and 9