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biochem > lecture 8 > Flashcards

lecture 8 Flashcards

1
Q

fatty acids

A

hydrocarbon chin with carboxyl group, can have a double bond that introduces a kink

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2
Q

most abundant dietary lipids, triglycerides

A

found in both animal and plant foods

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3
Q

essential fatty acids

A

linoleic and linolenic acid, found in most vegetables, must be ingested

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4
Q

fatty deposits in adipose tissues provide

A

-a protective cushion around body organs
-an insulating layer beneath the skin
-an easy-to-store concentrated source of energy

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5
Q

Dietary fats

A

-help body to absorb vitamins
-are a major energy fuel hepatocytes and skeletal muscle
-Are a component of myelin sheaths and all cell membranes

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6
Q

prostaglandins function in

A

-smooth muscle contraction
-control of blood pressure
-inflammation

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7
Q

cholesterol

A

stabilizes membranes and is a precursor of bile salts and steroid hormones

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8
Q

the liver

A

-Synthesizes lipoproteins for transport of cholesterol and fats
-Makes tissue factor, a clotting factor
-Synthesizes cholesterol from acetyl CoA
-Uses cholesterol to form bile salts

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9
Q

certain endocrine organs

A

use cholesterol to synthesize steroid hormones

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10
Q

sphingolipids

A

often found in neural coverings

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11
Q

ester bonds

A

how fatty acids are linked

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12
Q

both glycerol and fatty acids

A

are metabolized in distinct ways

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13
Q

cells obtain fatty acid fuel from 3 sources

A

-fats consumed in the diet
-fats stored in cells as lipid droplets
-fats synthesized in one organ for export to another

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14
Q

most products of fat metabolism

A

are transported in lymph as chylomicrons

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15
Q

cytosol

A

glycolysis
pentose phosphate pathway
fatty acid synthesis

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16
Q

mitochondrial complex

A

citric acid cycle
oxidative phosphorylation
ketone body formation
beta oxidation of fatty acids

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17
Q

interplay of both cytoplasm and mitochondria

A

gluconeogenesis
urea synthesis

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18
Q

lipids in chylomicrons are

A

hydrolyzed by plasma enzymes and absorbed by cells

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19
Q

only neutral fats

A

are routinely oxidized for energy

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20
Q

catabolism of fats involves two seperate pathways

A

glycerol pathway
fatty acid pathway

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21
Q

major component of chylomicron

A

triglycerides

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22
Q

phospholipid surface

A

polar headgroups face outward

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23
Q

trglycerols are found in the interior

A

make up >80% of the mass

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24
Q

Apolipoproteins on exterior

A

serve as signals for chylomicron uptake & metabolism

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25
Q

Glycerol is converted to glyceraldehyde 3-phosphate (GAP)

A

-GAP is ultimately converted into acetyl CoA
-Acetyl CoA enters the Krebs cycle

26
Q

Fatty acids undergo beta oxidation which produces

A

-Two-carbon acetic acid fragments, which enter the Krebs cycle
-Reduced coenzymes, which enter the electron transport chain

27
Q

lipids hydrolyze triacylglycerols

A

-free fatty acids
-glycerol

28
Q

fatty acids form acetyl coa

A

-citric acid cycle

29
Q

glycerol phosphorylated

A

oxidized to DHAP
converted to GAP

30
Q

GAP enters glycolysis

A

payoff phase

31
Q

3 steps are required for fatty acid breakdown

A
  1. Lipids must be mobilized: triglycerols degraded into fatty acids & glycerol. Subsequently released from adipose tissue into energy-requiring tissues.
  2. Fatty acids must be activated and transported into mitochondria for degradation.
  3. Fatty acids broken down, step-by-step, into acetyl-CoA which is fed into the Krebs/TCA cycle.
32
Q

mobilization of triglycerols

A

triglycerols degrades into fatty acids and glycerol. Subsequently released from adipose tissue into energy requiring tissue

33
Q

low blood glucose

A

stimulates glucagon release

34
Q

Glucagon activates receptor-G protein-adenylate cyclase system

A

activates hormone-sensitive lipases (HSL)

35
Q

PKA phosphorylation of perilipin permits

A

access of HSL to triglycerols in fat droplets

36
Q

Fatty acids released from adipocyte into bloodstream

A

bind to serum proteins, transported to other cells (i.e., myocytes) for use as energy source

37
Q

hormone sensitive lipase

A

responsive to glucagon and insulin

38
Q

activation of fatty acids

A

and transportation into mitochondria for degradation

39
Q

carnitine is converted to acyl carnitine

A

acyl carnitine is brought into cell where it is converted back to carnitine

40
Q

stage 1 of fatty acid oxidation

A

beta oxidation of fatty acids

41
Q

stage 2

A

acetyl CoA oxidized to CO2

42
Q

stage 3

A

electrons transferred from NADH/FADH2 to ETC for ATP synthesis

43
Q

degradation of even-numbered saturated fatty acids into acetyl-CoA

A

respective sequence of:
-oxidation
-hydration
-oxidation
-thiolysis

44
Q

trans delta 2 enoyl CoA

A

very important intermediate for even and odd degradation

45
Q

oxidation of palmitate

A

produces 8 molecules of acetyl CoA

46
Q

b-Oxidation of Monounsaturated Fatty Acids

A

requires 1 additional enzyme:enoyl-CoA isomerase and loses 2 ATP per double bond

47
Q

ß-Oxidation of Polyunsaturated Fatty Acids

A

Requires 1 additional enzyme (in addition to the additional enoyl CoA isomerase required for monounsaturated): 2,4-dienoyl-CoA reductase
lose 3 ATP per additional double bond

48
Q

ß-Oxidation of Odd-Chain Length Fatty Acids

A

Same as oxidation of saturated FA’s but end with 3C
converted to succinyl CoA

49
Q

excess dietary glycerol and fatty acids undergo lipogenesis to form

A

triglycerides

50
Q

glucose easily converts to fats since acetyl coa is

A

An intermediate in glucose catabolism
The starting molecule for the synthesis of fatty acids

51
Q

lipolysis

A

the breakdown of stored fat, is essentially lipogenesis in reverse

52
Q

Oxaloacetate

A

necessary for the complete oxidation of fat
otherwise ketogenesis begins

53
Q

When diet provides carbohydrate fuel

A

oxidation of fats is unnecessary

54
Q

Two enzymes key for coordinated regulation

A

1) acetyl-CoA carboxylase (ACC)
2) carnitine acyl transferase I

55
Q

ACC

A

first enzyme in FA synthesis pathway

56
Q

Carnitine acyl transferase I

A

regulates transport of FA into mitochondrial matrix for b-oxidation

57
Q

high carb meal

A

stimulates insulin release

58
Q

Insulin-dependent protein phosphatase

A

dephosphorylates ACC (activates enzyme)

59
Q

ACC catalyzes

A

formation of malonyl-CoA (first intermediate in FA synthesis)

60
Q

Malonyl-CoA inhibits

A

carnitine acyltransferase I (prevents FA entry into mitochondrial matrix)

61
Q

When blood glucose drops between meals

A

Glucagon release activates PKA
PKA phosphorylates ACC (inactivates enzyme)
Malonyl-CoA levels decrease (FA entry into mitochondria is restored)
FA oxidation in mitochondria major form of fuel
Glucagon also stimulates mobilization of FA from adipose tissue, FA available from bloodstream

biochem (9 decks)

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