Fatty acids and Membrane phospholipids biosynthesis Flashcards

1
Q

seeing as the carbons from an acetyl-coA are the ones used to elongate a fatty acid, what brings the acetyl into the cytosol?

A

the tricarboxylate transport system

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2
Q

the initiation of fatty acid synthesis takes place by?

A

the carboxylation of acetyl-coA to generate malonyl-coA

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3
Q

fatty acid synthesis carries out ? rxns at a time. It lengthens a fatty acid ? carbons at a time

A

7, 2

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4
Q

elongation and desaturation of Free fatty acids requires which enzymes?

A

elongases and desaturases

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5
Q

triacylglycerol are synthesized from ?

A

glycerol and fatty acids

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6
Q

fatty acid oxidation occurs where? Has which carrier group? Has what as an electron acceptor?

A

in the mitochondria. CoA as a carrier. FAD, NAD+ as acceptors.

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7
Q

what is the tricarboxylate transport system?

A

is it a citrate-malate-pyruvate shuttle. That provides cytosolic Acetyl -CoA and NADPH for fatty acid synthesis

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8
Q

what at the 3 sources of acetyl-coA

A

amino acid degradation (makes cytosolic). Fatty acid oxidation (makes mitochondrial). Glycolysis (cytosolic pyruvate) which is converted to acetyl-coA in mitochondria

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9
Q

how does the mitochondrial acetyl-coA enter the cytosol?

A

as citrate

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10
Q

How is citrate converted into pyruvate?

A

citrate + ATP citrate lyase = Oxaloacetate. +malate dehydrogenase = malate. + Malic enzyme = pyruvate

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11
Q

what is the Acetyl- carboxylase reaction?

A

It needs an ATP, a bicoarbonate ion, a Biotin enzyme
ATP is hydrolysed, the energy released form here is used to transfer the CO2 from bicarbonate to biotin.
This CO2 is then moved to acetyl-coA .
and this has formed malonyl-coA

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12
Q

acetyl-coA carboxylase, is inhibited by, and is activated by?

A

it is activated by citrate.

it is inhibited from long chain fatty acid

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13
Q

malonyl-coA inhibits

A

carnitine palmitoyl transferase I, which is a mitochondrial enzyme

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14
Q

explain the ACC hormones control. PKA

A

PKA senses CMP levels (controlled by glucagon levels). It can phosphorylate the carboxylase making it less sensitive to allosteric control

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15
Q

explain the ACC hormones control. AMP dependant kinase?

A

senses ATP/ADP levels in cells. Can phosphorylate carboxylate making it less sensitive

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16
Q

explain the ACC hormones control. protein phosphate 2A

A

dephosphorylation carboxylate making it more active

17
Q

what’s are the steps of biosynthesis of fatty acids

A

loading, condensation, reduction and dehydration, elongation, unload

18
Q

what is the loading step

A

has a malonyl/acetyl-transferase MAT. We load the acetyl group from acetyl-coA from the ACP. Then we load a malonate group from the malonyl-coA enzyme to the ACP. IN the end we have an acetyl group on the cysteine residue of FAS , and a malonate group on the ACP site of FAS. A coA is released

19
Q

explain the condensation reactive

A

The decarboxylation of the malonate group, that allows the nucleophilic attack on the thioester bond between the acetyl group on the cysteine residue on FAS .it is done by beta-ketoacyl-ACP synthase. It generates acetoacetyl-ACP . CO2 is released

20
Q

explain the reduction and dehydration steps

A

3: we reduce the ketone function of acetoacetyl-ACP by ACP reductase, and form hydroxybutyryl-ACP .
4: we have a dehydration reaction done by hydroxyacyl-ACP dehydrogenase, to form butenoyl-ACP
5: we have to make the double bond a single bond this is done by enoyl-ACP reductase, this forms butyryl ACP

21
Q

butyryl-ACP becomes?

A

palmitoyl-ACP after 7 rxns cycles. Then it gets hydrolysed by palmitoyl-thioesterase. Then forms palmitate

22
Q

list the domains of fatty acid synthase

A

ketoacyl synthase, malonyl synthase, dehydrase, enoyl reductase, ketoacyl reductase, thioesterase

23
Q

what are desaturases?

A

are enzyme that form a double bond. Mammals only have C9/6/4/5 fatty acyl-coA desaturases. This means that a C9,12 acid is obtained by the diet and not by the body. They need the energy of NADHP. go to slide 26

24
Q

how are dietary triacylglyerols turned into triacylglycerols for the body

A

they are acted upon by lipases, monoacylglycerol acyltransferase, diacylglycerol acyltransferase, and 2 coA groups are released (from the enzymes)

25
Q

sphingolipids are synthesized from?

A

palmitoyl-coA and serine

26
Q

prostaglandin synthesis from arachidonate is blocked by?

A

drugs

27
Q

what forms the myelin sheath?

A

sphingomyelin

28
Q

gangliosides are used for

A

brain neuron transmission

29
Q

tay sachs disease is caused by?

A

malfunction in hexoaminidase A