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Biochemistry > fatty acids > Flashcards

fatty acids Flashcards

1
Q

fatty acids

A
  • energy storage and production
  • structural components of membranes
  • some hormones are derived from fatty acids
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2
Q

lipids

A

fatty acidsare conjugated with glycerol to form lipids -3 fatty acids linked to glycerol by an ester bond

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3
Q

lipids are..

A

highly hydrophobic and not easily transporte

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4
Q

TAG

A

triacylglycerol

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5
Q

TAG as an energy source

A

not used until glucose supplies are low

-broken down in adipose tissue (fat tissue) is catalysed by triacylglycerol lipase

TAG + 3H2O –> glycerol and 3 fatty acids

-fatty acids are transported into the blood stream with albumin

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6
Q

what catalysis the break down of TAG

A

triacylglycerol lipase

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7
Q

what activates lipase

A

hormonally activated by glucagon

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8
Q

saturated fatty acids

A

no double bonds

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9
Q

unsaturated fatty acids

A

contains one or more double bonds (of cis configurations )

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10
Q

fatty acids usually have an ….. number of C atoms

A

even

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11
Q

what are fatty acids synthesised from

A

C2 precursor: acetyl CoA

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12
Q

oxidation of fatty acids (3)

A

step 1: free fatty acids in the cytosol are activated formation fatty acylCoA step 2: fatty acyl-CoA uptake into mitochondria Step 3: beta-oxidation pathway in mitochondria

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13
Q

only organ in the body than cannot use fat as an energy source

A

the brain

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14
Q

step 1 of oxidation of fatty acids

A

-fatty acid activation- formation of any; CoA in cytoplasm -costs the equivalent of 2ATPs -AMP +ATP= 2 ADP

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15
Q

step2 of oxidation of fatty acids

A

fatty acyl CoA uptake by mitochondria - in animals, fatty acids are oxidised in mitochondria -the inner mitochondrial membrane is not permeable to fatty acids ro fatty acyl CoA and instead the carnitine shuttle is used to transport fatty acyl CoA from the cytoplasm to the mitochondrial matrix

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16
Q

carnitine shuttle

A

transports fatty acyl CoA from the cytoplasm to the mitochondrial matrix

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17
Q

step 3 of oxidation of fatty acids

A

Beta oxidation of fatty acids in mitochondria - called B oxidation because the B carbon (C3) is oxidised 1.H removed from alpha and B carbons by acyl CoA dehydrogenase. Contains FAD cofactor. Electrons delivered to Coenzyme Q in ETC 2. Hydration of double bond- to produce hydroxyacly-CoA 3. C-OH oxidised to C=O. NADH formed is oxidised by ETC to produce ATP 4. CoASH attacks B carbon (red) to produced acetyl CoA and a fatty acyl CoA which is now 2 C atoms shorter Acetyl Co A oxidised by citric acid cycle

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18
Q

in a even chained fatty acid (oxidation)..

A

all molecules are converted into acetyl CoA

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19
Q

ATP yield from oxidation of palmitate

A

16 carbons long -cost of activation to palmitoyl-CoA= 2 ATP -7 rounds of b-oxidation -8 acetyl coA -8 x 10 ATP=80 ATP 7NADH -7x 2.5 ATP=17.5 ATP

20
Q

what can convert fatty acids to sugars and what cant

A

animals can convert fats to sugars and animals cannot

21
Q

plants and fungi can convert acetyl CoA into

A

sugars- because they have the glyoxylate acid cycle

22
Q

glyoxylate cycle

A

occurs in specilsiased organelles called glyoxysomes

23
Q

overall reaction in glyoxyate cycle

A

2Acetyl CoA–> malate–> oxaloacetate

24
Q

oxaloacetate can then be used to produce glucose vi

A

glucoseneogenesis

25
Q

odds chain fatty acids yield..

A

ATO and propionyl CoA

26
Q

although animal are incapable of producing glucose from acetyl CoA.. they can..

A

make glucose from propionyl CoA

27
Q

mammals can produce glucose from

A

odd chain fatty acids

28
Q

Fatty acid synthesis: first step

A

energy to form C-C bonds is supplied indirectly by synthesising malonyl CoA from acetyl CoA using AT and CO2 - reaction is catalysed by Acetyl CoA carboxylase (uses biotin as a cofactor)

29
Q

what cofactor does acetyl co A carboxylase use

A

biotin

30
Q

Step 1 of biosynthesis

A

an acetyl (2C) group is added using Malonyl CoA as the donor. Loss of CO2 drives the reaction Malonyl CoA s synthesised by the carboxylation of acetyl CoA Acetyl CoA + CO2 + ATP malonyl CoA +ADP + Pi

31
Q

Step 2 of biosynthesis

A

the C=O group on the C3 (B carbon) is reduced to C-OH by NADPH

32
Q

step 3 of biosynthesis

A

dehydration generates a duble and between the alpha and beta carbons (C2 and C3)

33
Q

step4 of biosynthesis

A

reduction of double bond to single bond

34
Q

step 5 biosynthesis

A

fatty acyle-ACP, now 2C longer, can re-enter the process or the process is stopped by removing ACP (using fatty acyl-ACP thioesterase)

35
Q

what removes ACP and stops fatty acid synthesis

A

fatty acyl-ACP thiesterase

36
Q

basics on fatty acid synthesis

A

same intermediates as B oxidation -occurs in cytosol different carrier (acyl carrier protein instead of acetyl CoA) -diff cofactors

37
Q

substrates of synthesis of fatty acids

A

acetyl CoA and NADPH

38
Q

citrate shuttle

A

used to transport acetyl CoA from the mitochondria to the cytoplasm

39
Q

sources of NADPH for fatty acid synthesis

A

pentose phosphate pathway and the citrate shuttle

40
Q

acetyl CoA carboxylase

A

is a biotin-dependent enzyme that catalyzes the irreversible carboxylation of acetyl-CoA to produce malonyl-CoA

41
Q

acetyl CoA carboxylase is tightly regulated

A

inhibited by phosphorylation- AMP kinases is one of the major kinases–> others are controlled by glucagon and adrenaline

42
Q

insulin signalling favours…

A

fatty acid synthesis by activating phosphatase that dephosphorylates acetyl CoA carboxylase.

43
Q

what is reciprocally regulated

A

fatty acid synthesis and breakdown

44
Q

glucagon promotes

A

release of fatty acids from ADIPOCYTES- high levels of fatty acyl CoA inhibits acetyl CoA carbboxylase

45
Q

malonylCoA made by acetyl CoA carboxylase inhibits..

A

carnitine acyle transferase I and prevents fatty acid oxidation by blocking entry into the mitochondrion

46
Q

summary of fatty acids

A

Summary

♣ Lipids have a range of functions- cell membrane, energy storage and cell signalling

♣ Fatty acid degradation (b-oxidation) occur in the mitochondria

♣ Animals cannot produce sugars from even chain length fatty acids (but can odd length)

♣ Fatty acid synthesis occurs in the cytoplasm

♣ Synthesis and degradation are tightly regulated.

Biochemistry (18 decks)

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