Biosynthesis of Fatty Acids Flashcards Preview

Digestive, Endocrine, and Metabolic Systems > Biosynthesis of Fatty Acids > Flashcards

Flashcards in Biosynthesis of Fatty Acids Deck (28):
1

What is the starting material for fatty-acid synthesis?

Acetyl co-a (in mitochondria), which itself is mostly from pyruvate

2

True or false: acetyl co-a is only found in mitochondria.

False. Citrate from the TCA cycle can pass through the mitochondrial membranes into the cytosol. It is then broken down to oxaloacetate and acetyl co-a by ATP cirate lyase; the oxaloacetate passes back into the mitochondria once converted back to pyruvate (via malate).

3

In the cytosol, acetyl co-a gets converted to ___________ by acetyl co-a carboxylase.

malonyl co-a

4

Fatty acid synthase converts malonyl co-a to __________.

palmitate

5

Desaturation of palmitate is accomplished by ____________.

the ER

6

Both the mitochondria and ER can __________ palmitate.

elongate

7

In naming unsaturated fatty acids, the double bonds are named for ____________.

the carbon they start on; for instance, 20:2(5,8) means a 20-carbon chain with two double bonds that go from 5 to 6 and from 8 to 9

8

Why can't people make linoleic acid and alpha-linoleic acid?

Because human cells lack enzymes to put double bonds from carbon 9 to the end of the chain.

9

What are three important uses for fatty acids?

- Compose the cell membrane
- Act as triglyceride storage
- Precursors for eicosanoids

10

______________ is the precursor to arachidonic acid.

Linoleic acid

11

Formation of malonyl co-a is stimulated by ____________ and inhibited by __________.

citrate (a sign of nutrient excess); long-chain fatty acyl co-a (the immediate downstream product)

12

____________ has many (seven) different activities.

Fatty acid synthase

13

The first two carbons in fatty acid synthesis are from ___________, while all subsequent carbons are from ____________.

acetyl co-a; malonyl co-a

14

NADPH is used in ______________.

the reducing steps of fatty acid synthesis

15

In addition to being produced in the hexose monophosphate shunt, NADPH can also be made by ____________.

NADH + NADP+ -> NAD+ NADPH

16

What things stimulate and inhibit fatty acid synthesis?

Stimulate:
- high carbohydrate levels leading to lots of acetyl co-a
- high insulin levels

Inhibit:
- high fat/low carb diets leading to increased cytosolic acyl co-a
- high glucagon levels

17

Insulin promotes the conversion of acetyl co-a to malonyl co-a by _______________.

dephosphorylating acetyl co-a carboxylase (via protein phosphatase)

18

Vmax directly correlates with ______________.

enzyme concentration

19

Almost all of the endogenous fatty acids are in the ______ configuration.

cis

20

High levels of ATP lead to increased fatty-acid synthesis by what mechanism?

ATP inhibits isocitrate dehydrogenase, leading to accumulation of citrate.

21

Fatty acid synthase ultimately produces __________.

palmitic acid (a 16-carbon molecule)

22

What enzyme is activated when polymerized and deactivated when depolymerized?

Acetyl co-a carboxylase

23

What enzyme synthesizes triglyceride?

Acyltransferase

24

Why does alcohol consumption promote fatty acid synthesis?

Alcohol is metabolized to acetyl co-a

25

The rate-limiting enzyme in fatty acid synthesis is _____________.

acetyl co-a carboxylase

26

The family of enzymes that elongate fatty acids is called ______________.

fatty acid elongase

27

What do mixed function oxidases do?

Introduce double bonds

28

Fatty acids must be ____________ before being activated to triglycerides.

activated by binding co-a

Decks in Digestive, Endocrine, and Metabolic Systems Class (133):