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Biochem 2 > Lipid Metabolism (mini-test 1 AND 2) > Flashcards

Lipid Metabolism (mini-test 1 AND 2) Flashcards

1
Q

What is the major lipid in the body?

A

triglycerides

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2
Q

What is triglyceride also known as?

A

-TG
-triacylglycerol
-TAG
-glycerol w/ 3 FAs
-fat

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3
Q

Do we store FAs?

A

no, FAs are acidic but we do convert them to fat and store fat

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4
Q

TGs break down to FAs. What is this called?

A

lipolysis/mobilization

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5
Q

Which hormone stimulates lipolysis?

A

glucagon

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6
Q

What is another name for lipolysis?

A

mobilization

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7
Q

Does lipolysis occur in a fed state or fasting state?

A

fasting state

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8
Q

FAs are broken down to acetyl CoA. What is this called?

A

B oxidation

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9
Q

Acetyl CoA can make cholesterol. What is this called?

A

cholesterologenesis or cholesterol biosynthesis

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10
Q

Cholesterol can be converted to steroids. What is this called?

A

steroidogenesis

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11
Q

Does cholesterologenesis/ cholesterol biosynthesis occur during fed state or fasting state?

A

fed state

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12
Q

Acetyl CoA can be converted to ketone bodies. What is this called?

A

ketogenesis

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13
Q

Does ketogenesis occur in a fed state or fasting state?

A

fasting state

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14
Q

What else can make acetyl CoA besides FAs?

A

carbs and AAs can also make acetyl CoA

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15
Q

Acetyl CoA can make FAs. What is this called?

A

lipogenesis

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16
Q

Which hormone stimulates lipogenesis?

A

insulin

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17
Q

Is lipogenesis during a fed state or fasting state?

A

fed state

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18
Q

Do we get FAs from our diet?

A

yes

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19
Q

FAs can make TGs. What is this called?

A

esterification

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20
Q

Why is lipolysis also called mobilization?

A

because you’re mobilizing fats

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21
Q

Mobilization/lipolysis is where lipases hydrolyze the TG stored in the adipocytes to produce….

A

FAs and glycerol

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22
Q

How do FAs gets from the adipocyte to the blood?

A

simple diffusion

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23
Q

How do FAs get transported within the blood?

A

bound with albumin

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24
Q

How does glycerol get to the blood from adipocytes?

A

simple diffusion

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25
Q

How does glycerol move within the bloodstream?

A

freely, does NOT need a carrier protein (glycerol is water soluble)

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26
Q

What hormones trigger lipolysis/mobilization first?

A

glucagon or epi interact with AC first and make cAMP to start cascade

note: you have to feel hungry and if you wait to eat then the fats will start to get mobilized

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27
Q

What is the RLE in lipolysis/mobilization?

A

hormone sensitive lipase, also known as TG lipase

note: it removes a FA from either carbon 1 or 3 (DG lipase will be used on DGs, and MG lipase will be used on MGs)

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28
Q

What is the active form of TG lipase?

A

with phosphate attached

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29
Q

Can FAs convert to glucose?

A

Short answer no, but glycerol can

Exception- out of all the FAs, only odd chain FAs can convert to glucose (bc of propionyl CoA)

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30
Q

After mobilization/lipolysis, 2 glycerols will go to the liver because of an enzyme to make glucose (2 glycerols are needed to make glucose). What enzyme is used?

A

glycerol kinase

2 glycerols with glycerol kinase will make 2 glycerol 3 phosphate (which then will make DHAP and GAP, then F6P. F6P will convert to G6P with F1,6BPtase. G6P will then convert to glucose with G6Ptase)

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31
Q

FAs can go to any tissue that does not require glucose (RBCs, adrenal medulla, CNS, and gametes require glucose). Where do FAs usually go?

A

to liver (albumin will be left behind in blood while FA can simply diffuse into liver)

32
Q

Acyl means….

A

FA

33
Q

What is the first stage of FA metabolism (lipolysis)?

A

-after entering a liver cell, free FAs are immediately converted to fatty acyl coA
-fatty acid + SHCoA (thio CoA) + 2 ATP undergo reaction with acyl CoA synthetase/thiokinase to make fatty acyl CoA and AMP
-this enzyme requires vitamin B5
-this process is called fatty acid activation

34
Q

What is stage 1 of FA metabolism/ lipolysis called?

A

FA activation

35
Q

Where is acyl CoA synthetase/thiokinase located?

A

in the cytoplasm of liver cells

36
Q

What does acyl CoA synthetase/thiokinase require?

A

vit B5 and 2 ATP

37
Q

What is fatty acyl CoA also known as?

A

FA-SCoA, acyl CoA, or acyl SCoA, palmitoyl CoA (this one specifically is also known as palmitate)

38
Q

What is stage 2 of lipolysis/FA metabolism?

A

-basically- FAs transport to mitochondria
-this is for FAs that are 12+ carbons bc they need a carrier
-the carrier is carnitine and its a VIP molecule
-this stage is the rate limiting stage

-acyl CoA binds with carnitine with the help of carnitine acyl transferase 1 (CAT1) and the CoA will stay in the cytoplasm, whereas acyl carnitine will now be on the outer membrane of the mitochondria
-acyl carnitine will be transported to inner mitochondrial membrane and then undergo reaction with CAT2 and 1 CoA molecule to separate acyl and carnitine
-carnitine will go back out to cytoplasm and repeat, whereas acyl CoA will move onto beta oxidation stage

39
Q

What is stage 3 of FA breakdown called?

A

beta oxidation of FAs

40
Q

What is the beta oxidation stage of FA metabolism?

A

-an acetyl CoA is stripped off every turn of the oxidation spiral
-each turn generates 1 FADH2, 1 NADH, and 1 acetyl CoA
-there are 4 steps in 1 turn

41
Q

What is generated after 1 turn of beta oxidation with a FA like palmitate?

A

-1 FADH2
-1 NADH
-1 acetyl CoA

42
Q

What are the 4 steps of beta oxidation called?

A

1) oxidation/dehydrogenation
2) hydration
3) oxidation/dehydrogenation
4) thiolytic cleavage

43
Q

What is step 1 of beta oxidation?

A

-its an oxidation/dehydrogenation step
-acyl CoA undergoes a reaction with acyl CoA DH to make 1 FADH2 and enoyl CoA
-this creates a double bond between the alpha and beta carbons

44
Q

Which enzyme connects beta oxidation with ETC?

A

acyl CoA DH (its one of the enzymes that is a part of complex 2)

45
Q

What is step 2 of beta oxidation?

A

-hydration reaction (add water)
-enoyl CoA undergoes a reaction with enoyl CoA hydratase to make L hydroxyacyl CoA
-the water in this reaction opens the double bond between the alpha and beta carbons that was previously made in 1st step

46
Q

What is step 3 of beta oxidation?

A

-oxidation/dehydrogenation
-L hydroxyacyl CoA undergoes a reaction with hydroxyacyl CoA DH to make beta ketoacyl CoA and 1 NADH

47
Q

What is step 4 of beta oxidation?

A

-thiolytic cleavage
-beta ketoacyl CoA undergoes a reaction with beta ketothiolase and SCoA to make acyl CoA (now 2 carbons shorter) and 1 acetyl CoA
-the bond between alpha and beta carbons were cleaved to create the acetyl CoA and acyl CoA
-beta oxidation will repeat starting from step 1 until the FA is completely broken down and generates 2 acetyl CoAs

48
Q

How many carbons and/or double bonds does palmitate have?

A

16:0 (so its a saturated FA “SFA”)

49
Q

How many rounds of beta oxidation does it take to fully break down palmitate?

A

7 rounds

50
Q

How do you calculate number of rounds for even chain FAs?

A

total number of carbons / 2 and then subtract that number with 1

51
Q

How many FADH2 are generated with palmitate breakdown?

A

7

52
Q

How many NADH are generated with palmitate breakdown?

A

7

53
Q

How many acetyl CoA are generated with palmitate breakdown?

A

8 (for even chains, add 1 to number of rounds to get # of acetyl CoAs generated)

54
Q

How many ATP (net yield) are generated with palmitate breakdown?

A

129 ATP

55
Q

How do you calculate ATP generated from NADH?

A

multiply number of rounds by 3

56
Q

How do you calculate ATP generated from FADH2?

A

multiply number of rounds by 2

57
Q

How do you calculate ATP generated from acetyl CoA?

A

number of rounds + 1 and then multiply it by 12

58
Q

How do you calculate total ATP generated from FA breakdown

A

add together ATP generated from NADH, FADH2, and acetyl CoA

and then subtract total by 2 (because 2 ATP was used during activation step of FAs)

59
Q

How many carbons and/or double bonds does stearate have?

A

18:0

60
Q

How many ATP are generated from 20:0?

A
61
Q

How is beta oxidation of unsaturated FAs different from the usual saturated FAs?

A

for each double bond in a FA, one less FADH2 is generated

62
Q

How is beta oxidation of odd chain FAs different from saturated or unsaturated FAs?

A

all the steps are the same HOWEVER there is a different end product- instead of 2 acetyl CoAs at end there will be 1 acetyl CoA from that round and a propionyl CoA

for an odd chain unsaturated FA the NADH and acetyl CoA will be the same number as the turns but the FADH2 will be different because 1 less FADH2 is generated per double bond

63
Q

Which FA chain make glucose?

A

ONLY odd chain fatty acid bc of the propionyl CoA

even chain or unsaturated chains cannot

64
Q

Odd chain FAs are the only FAs that can make glucose because of propionyl CoA. to do this, propionyl CoA will undergo a reaction with what enzyme to make methylmalonyl CoA?

A

propionyl CoA carboxylase

65
Q

Odd chain FAs are the only FAs that can make glucose because of propionyl CoA. to do this, propionyl CoA will undergo a reaction with proprionyl CoA carboxylase to make methylmalonyl CoA. What is required here?

A

-ATP
-vitamin B7/ biotin
-carbon dioxide

66
Q

Odd chain FAs are the only FAs that can make glucose because of propionyl CoA. to do this, propionyl CoA will undergo a reaction with proprionyl CoA carboxylase to make methylmalonyl CoA. Then methylmalonyl CoA will undergo a reaction with what enzyme to make succinyl CoA (which will then go to TCA and then eventually convert to glucose)?

A

methylmalonyl CoA mutase

67
Q

Odd chain FAs are the only FAs that can make glucose because of propionyl CoA. to do this, propionyl CoA will undergo a reaction with proprionyl CoA carboxylase to make methylmalonyl CoA. Then methylmalonyl CoA will undergo a reaction with methylmalonyl CoA mutase to make succinyl CoA (which will then go to TCA and and then eventually convert to glucose). What does methylmalonyl CoA mutase require?

A

vit B12/ cobalamin

68
Q

Any reactions with a carboxylase will require what?

A

ABC
-A= ATP
-B= biotin/ vit B7
-C= CO2

69
Q

If theres an increase in methylmalonyl CoA, then what will it become and what does this indicate?

A

-indicates vitamin B12 deficiency/ cobalamin
-methylmalonyl CoA will be converted to methylmalonate in the blood (can be detected in blood test)

70
Q

What 2 things did we talk about that cause a vitamin B12/ cobalamin deficiency?

A

1) strict vegetarians bc B12 is only found in animal products
2) intrinsic factor deficiency (common in 50+ y/o)

71
Q

When theres a B12 deficiency and/or biotin deficiency, then there will be an increase in propionyl CoA in the body and this can lead to….

A

damaged myelin/demyelination which will ultimately cause peripheral neuropathy

72
Q

How is lipolysis regulated?

A

1) fat mobilization is regulated by TG lipase
2) malonyl CoA inhibits CAT1 which inhibits beta oxidation by preventing acyl CoA from entering the mitochondria
3) high citrate levels inhibit beta oxidation (because once citrate levels are high it means the body needs FAs so they shouldn’t be broken down)

73
Q

Fat mobilization is regulated by what?

A

TG lipase

74
Q

What inhibits CAT1 and therefore inhibits beta oxidation by preventing acyl CoA from entering mitochondria?

A

malonyl CoA

75
Q

High levels of what molecule inhibits beta oxidation?

A

high levels of citrate (because once citrate levels are high it means the body needs FAs so they shouldn’t be broken down)

Biochem 2 (13 decks)

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