Chapter 28 and 29 - Lipid Biosynthesis

Question 1

fatty acid synthase (FAS)

Answer 1

a multi enzyme complex that synthesize fatty acids

Question 2

FA chain length is increased by sequential addition of …

Answer 2

2-carbon units

Question 3

elongation of FA stops with the formation of..

Answer 3

palmitate

Question 4

site of fatty acid biosynthesis

Answer 4

cytosol

Question 5

transport of acetyl CoA out of mitochondria in the form of..

Answer 5

citrate

Question 6

ATP-citrate lyase

Answer 6

cleaves citrate at the cost of a molecule of ATP to yield cytoplasmic acetyl CoA and oxaloacetate

Question 7

malonyl CoA

Answer 7

activated form of acetyl CoA

Question 8

acetyl CoA carboxylase

Answer 8

catalyzes the first and rate limiting step of FA biosynthesis

• carboxylation of acetyl CoA to malonyl CoA
• irreversible

Question 9

acetyl CoA carboxylase has a ______ prosthetic group

Answer 9

biotin

Question 10

fatty acid synthase

Answer 10

a complex of distinct enzymes that data;yzes the synthesis of saturated long chain FA from acetyl CoA, malonyl CoA, and NADPH

Question 11

fatty acid synthase in bacteria, plants

Answer 11

seven activities in seven separate polypeptides

Question 12

fatty acid synthase in yeast

Answer 12

seven activities in two separate polypeptides

Question 13

fatty acid synthase in vertebrates

Answer 13

seven activities in one large polypeptide

Question 14

acetyl transacylase

Answer 14

catalyze the formation of acetyl ACP from Acetyl CoA

Question 15

malonyl transacylase

Answer 15

catalyze the formation of malonyl ACP from malonyl-CoA

Question 16

Intermediates of FA synthesis remain attached to FAS via…?

Answer 16

2 thiol groups

Question 17

REVIEW

Answer 17

FAS steps

Question 18

FAS stops at ….

Answer 18

palmitate, 16C

Question 19

most fatty acids are long that…

Answer 19

palimatate.. 18-26C

Question 20

fatty acid elongation

Answer 20

• occurs in ER

- 2 carbons added at a time from malonyl CoA

Question 21

how does fatty acid elongation work?

Answer 21

reactions use malonyl CoA to add two-carbon units sequentially to the carboxyl ends of both saturated and unsaturated acyl CoA substrates

Question 22

fatty acid desaturation

Answer 22

introduction of CIS double bonds

-catalyzed by desaturase enzymes (specific for location of double bond)

Question 23

Humans lack ___ and ___ desaturases.

Answer 23

delta12 and delta15; therefore, linoleate and a-linoleate are considered essential fatty acids

Question 24

Cholesterol is a lipid synthesized by virtually all cells, but especially…

Answer 24

liver

Question 25

functions of cholesterol

Answer 25

- structural component of membranes | - precursor of bile salts, steroid hormones, and vit D.

Question 26

cholesterol structure

Answer 26

- 27 carbons - all C-atoms come from acetyl CoA - synthesized in cytosol and ER - 4 fused rings, a hydrocarbon tail, -OH group on C3 and double bond at C5 and C6

Question 27

cholesterol biosynthetic pathways

Answer 27

acetyl CoA to cholesterol - 25 rxns - 4 stages

Question 28

step 1 of cholesterol biosynthetic pathway

Answer 28

- synthesis of mevalonate - catalyzed by 3-hydroxy-3-methylglutaryl CoA reductase - irreversible

Question 29

Cholesterol is stored as....

Answer 29

cholesterol ester

Question 30

cholesterol is transported by...

Answer 30

lipoproteins - TA: chylomicrons and VLDL - cholesterols: LDL and HDL

Question 31

How is cholesterol synthesis regulated?

Answer 31

- balance between synthesis and dietary uptake | - feedback inhibition by cholesterol

Question 32

famililal hypercholesterolemia

Answer 32

- High cholesterol levels promote atherosclerosis - characterized by high concentrations of cholesterol and LDL in the plasma - cholesterol is deposited in various tissues because of the high concentration of LDL cholesterol in the plasma (defective LDL receptors)

Question 33

famililal hypercholesterolemia treatment

Answer 33

statins (cholesterol lowering drugs): competitive inhibitors of HMG CoA reductase

Question 34

acyltransferase

Answer 34

catalyze sequential attachment of fatty acids to glycerol backbone (ester bond)

Question 35

synthesis of phsophatidylcholine

Answer 35

liver possesses an enzyme, phosphatidylethanolamine methyltransferase, that synthesizes phosphatidylcholine from phosphatidylethanolamine when dietary choline is insufficient.

Question 36

eicosanoid

Answer 36

- specialized fatty acids - signaling molecules, hormone-like actions - 20C polyunsaturated fatty acid (arachidonate)

Question 37

biological actions of eicosanoid

Answer 37

vasodilation, constriction, platelet aggregation, inhibition of platelet aggregation, contraction of smooth muscle, chemotaxis of leukocytes, release of lysosomal enzymes

Question 38

excess eicosanoid production symptoms

Answer 38

pain, inflammation, fever, nausea, vomiting

Question 39

phospholipase A2

Answer 39

release arachidonate

Question 40

eicosanoids are derived from..

Answer 40

arachidonate

Question 41

arachidonate

Answer 41

a 20:4 fatty acid derived from linoleate | -major precursor of several classes of signal molecules (prostaglandins, leukotrienes: called eicosanoids)