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Biochemistry > Chapter 17 > Flashcards

Chapter 17 Flashcards

1
Q

Four major functions of lipids

A

structural components
energy reserves
vitamins
hormones

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2
Q

Summary of how lipids are transported

A

from the intestine as chylomicrons to the liver and other tissues
other tissues to liver as HDL
leaves the liver as VLDL that changes into LDL
LDL then moves to other tissues and the liver

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3
Q

Triaglycerols

A

glycerol bonded to three fatty acids
main storage form of fat

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4
Q

The release of fatty acids from triacylglycerols and phosphoacylglycerols is catalyzed by

A

lipases

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5
Q

the breakdown of a triacylglycerol creates

A

three fatty acids

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6
Q

Phospholipases D’s

A

destroy cell membranes

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7
Q

The release of fatty acids in adipocytes is under

A

hormonal control- epinephrine
cyclic AMP begins a kinase cascade that leads to phosphorylation and activation of the lipases

fatty acids are released and can then be oxidized to produce ATP in the mitochondria

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8
Q

Fatty acids are oxidized via _____ to produce ____

A

beta- oxidation
acetyl-CoA

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9
Q

Beta oxidation takes place in the

A

mitochondria

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10
Q

Acetyl CoA is used to generate energy via the

A

citric acid cycle
electron transport chain

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11
Q

Fatty acid activation

A

two steps catalyzed by acyl-CoA synthetase

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12
Q

A repeated sequence of four reaction that occur in the mitochondrial matrix

A

Beta oxidation of fatty acids

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13
Q

Goals of beta oxidation

A
  1. create a carbonyl group on the beta carbon by shortening the acyl group by two carbons
    - removed as acetyl-CoA
  2. generate energy by producing the reduced electron carriers FADH2 and NADH
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14
Q

The first reaction of beta oxidation

A

electron transfer reactions

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15
Q

The second reaction of Beta oxidation

A

addition of water

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16
Q

The third reaction of beta oxidation

A

NAD+ cofactor

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17
Q

fourth reaction of beta oxidation

A

release of acetyl-CoA

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18
Q

Beta oxidation- Electron transfer reactions are catalyzed by

A

acyl-CoA dehydrogenase

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19
Q

Beta oxidation- addition of water is catalyzed by

A

hydratase

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20
Q

Beta oxidation- NAD+ cofactor is catalyzed by

A

another dehydrogenase

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21
Q

Beta oxidation- release of acetyl-CoA is catalyzed by

A

thiolase

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22
Q

Energy yields from beta oxidation

A

1 NADH, 1 FADH2 and 1 acetyl-CoA

NADH and FADH2 generate ATP via electron transport chain and ATP synthase
acetyl-CoA enter the citric acid cycle to generate 1 FADH2, 3 NADH, 1 GTP

Total ATP 120

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23
Q

Fats are more ______ than sugars and amino acids

A

reduced

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24
Q

Beta oxidation of fatty acids steps

A
  1. oxidation of beta carbon generated FADH2
  2. Hydration of beta carbon generates -OH groups
  3. oxidation of beta carbon generates NADH and a carbonyl group
  4. cleavage between the alpha and beta carbons and formation of acetyl-CoA
    5 further cycles
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25
Q

Fatty acyl-CoA is shortened by 2 carbons from the

A

carbonyl end

26
Q

Beta oxidation repeats until

A

there are just two carbons left

27
Q

Fatty acids with ___ double bonds pose a problem for enzymes in beta oxidation

A

cis

28
Q

Cis double bonds are turned into trans double bonds by what enzyme

A

isomerase

29
Q

Why do unsaturated fatty acids yield less free energy than saturated fatty acids

A

creates fewer FADH2 due to having to use an isomerase to change a cis bond to a trans bond

30
Q

ODD chain length fatty acids beta oxidation difference

A

occurs until three carbons are left
propionyl-CoA created at the end

31
Q

in order to enter the citric acid cycle propionyl-CoA (created by odd numbered chain) must go through

A

carboxylation to methyl-malony-CoA and rearrangement to succinyl-CoA

32
Q

Beta oxidation of fatty acids produces metabolic water how?

A

FADH2 and NADH produce water in the electron transport chain

33
Q

Peroxisomes

A

enclosed by a single membrane and contain a variety of degradative and biosynthetic enzymes

34
Q

How does fatty acid oxidation in peroxisomes differ from that in mitochondria

A

enoyl-CoA product of the reaction is identical to the product of the mitochondrial acyl-CoA dehydrogenase reaction

35
Q

What happens if we don’t consume carbs

A

no glycolysis
rely on fatty acids for acetyl-CoA
Liver does gluconeogenesis making glucose
TCA stops because acetyl-CoA directed to make glucose for the brain

36
Q

In long fasts and starvation oxaloacetate is

A

consumed to make glucose by the gluconeogenic pathway so acetyl CoA accumulates

37
Q

Increased acetyl CoA makes

A

acetoacetate
beta hydroxybutyrate
acetone
All of these are ketone bodies

38
Q

Ketone bodies are made

A

in the liver mitochondria

39
Q

Production of ketone bodies

A

two acetyl-CoA are condensed to acetoacetyl-CoA
Another condensation with acetyl-CoA produces hydroxyl-alpha-methylglutaryl-CoA
HMG-CoA lyase releases acetyl-CoA to produce acetoacetate
Acetoacetate is either decarboxylated to acetone or reduced to alpha hydroxybutyrate

40
Q

Ketone bodies are used by the

A

brain as a fuel source during starvation

41
Q

Why is an excess of ketone bodies bad?

A

are acidic and can lower the pH of the blood
Ketoacidosis
- increased thirst, secretion of H+ into the urine
- symptom of untreated diabetes (type 1)

42
Q
A
43
Q

Anabolism of fatty acids happens in the

A

cytosol

44
Q

Anabolism of fatty acids is/is not a simple reversal of beta oxidation

A

NOT

45
Q

First step of anabolism is

A

exporting acetyl-CoA from the matrix to the cytoplasm via a citrate intermediate

46
Q

Formation of the main precursor to fatty acid synthesis of _____ is from the carboxylation of acetyl-CoA

A

malonyl-CoA

47
Q

Formation of malonyl-CoA is catalyzed by

A

acetyl-CoA carboxylase (ACCase) complex

48
Q

ACCase requires

A

biotin, Mn2+, and ATP

49
Q

Fatty acid synthesis priming groups

A
  1. two carbon acetyl group that will be lengthened is transferred from CoA to a Cys side chain of fatty acid synthesis
  2. malonyl group will donate an acetyl group to the growing fatty acyl chain is transferred from CoA to the ACP domain of the enzyme
50
Q

Subsequent steps of fatty acid synthesis

A
  1. condensation reaction- malonyl group is decarboxylated and the resulting two-carbon fragment attacks the acetyl group to form a four-carbon product
  2. 3-ketoacyl product of step 3 is reduced
  3. dehydration introduces a 2,3 double bond
  4. second NADPH dependent reduction completes the conversion of the condensation product to an acyl group
  5. acyl group is transferred from ACP to enzymes Cys group
    another malonyl group is loaded onto the free ACP
    ready for another condensation reaction
51
Q

free fatty acids are mostly found

A

incorporated within triacylglycerols and phosphoacylglycerols
synthesis of these compound occurs in the endoplasmic reticulum of liver or fat cells

52
Q

main point of regulatory control for fatty acid metabolism

A

ACCase

53
Q

phospholipid synthesis

A
  1. ATP phosphorylates the OH group of ethanolamine or choline
  2. phosphoryl group attacks CTP to form CDP-ethanolamine or CDP-choline. PPi product is hydrolyzed
  3. the C3 OH group of diacylglycerol displaces CMP to generate the glycerophospholipid
54
Q

Phosphatidylserine synthesis

A

head-group exchange reaction

55
Q

Phosphatidylinositol synthesis

A
  1. phosphatidase attacks CTP to form CDP- diacylglycerol
  2. an inositol group displaces CMP to produce phosphatidylinositol
56
Q

Every carbon of cholesterol is derived from

A

acetyl-CoA carbons

57
Q

Cholesterol is stored as

A

an ester
changed using acyl-CoA (cholesterol acyltransferase)

58
Q

Cholesterol synthesis inhibitors

A

Lipitor
lovastatin
simvastatin

59
Q

The body coordinates cholesterol production and transport among tissues

A

SREBP regulatory system

60
Q

Steroid hormones are synthesized from

A

cholesterol

Biochemistry (14 decks)

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