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M104 T2 > M104 T2 L3 > Flashcards

M104 T2 L3 Flashcards

1
Q

Why is pyruvate useful?

A

bc it can turn into whatever molecule the cell needs it to be

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2
Q

Which enzyme helps pyruvate turn into lactase?

A

lactase dehydrogenase

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3
Q

What can pyruvate turn into?

A

lactase
oxaloacetate
alanine
acetyl-CoA

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4
Q

Which enzyme helps pyruvate turn into oxaloacetate?

A

pyruvate carboxylase

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5
Q

Which enzyme helps pyruvate turn into alanine?

A

alanine aminotransferase

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6
Q

Which enzyme helps pyruvate turn into acetyl-CoA?

A

pyruvate dehydrogenase complex

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7
Q

In what conditions does pyruvate turn into acetyl-CoA?

A

aerobic conditions

with the enzyme pyruvate dehydrogenase complex

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8
Q

What happens to pyruvate under aerobic conditions when turning into acetyl-CoA?

A

it is oxidised

it is completely degraded

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9
Q

Where in the cell does pyruvate turn into acetyl-CoA?

A

in the mitochondria

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10
Q

Where in the cell does glycolysis occur?

A

in the cytosol

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11
Q

In what conditions does glycolysis occur?

A

aerobic and anaerobic conditions

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12
Q

Where does pyruvate have to move from in the cell to turn into acetyl-CoA?

A

was made in the cytosol

has to move to the mitochondria

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13
Q

Where does the TCA cycle occur?

A

in the mitochondria

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14
Q

What are other names for the TCA cycle?

A

Krebs cycle

citric acid cycle

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15
Q

What is gained from the TCA cycle?

A

energy is produced

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16
Q

What can FAs be activated by?

A

the addition of an acyl group

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17
Q

How are activated FAs transported into the mitochondria?

A

via carnitine shuttles

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18
Q

What happens to activated FAs in the mitochondria?

A

they are used to generate acetyl CoA

this enters the TCA cycle

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19
Q

How is pyruvate transported into a mitochondrion?

A

via the MCP-2 carrier protein embedded in the mitochondrial membrane in aerobic conditions

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20
Q

What is the name of the reaction by which pyruvate is converted into acetyle CoA?

A

oxidative decarboxylation

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21
Q

What does pyruvate turn into after oxidative decarboxylation?

A

Acetyl CoA

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22
Q

What is the equation by which pyruvate is converted into acetyl CoA?

A

Pyruvate + CoA + NAD+

acetyl CoA + CO2 + NADH + H+

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23
Q

Is the oxidative decarboxylation of pyruvate reversible?

A

no
the reaction is irreversible
acetyl CoA can’t turn back into pyruvate

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24
Q

How many carbons are in pyruvate?

A

three C

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25
Q

How many carbons are in acetyl CoA?

A

two C

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26
Q

What two stages of metabolism are linked by the oxidative decarboxylation of pyruvate?

A

links glycolysis and the TCA cycle

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27
Q

What is the role of the PDH complex?

A

to convert pyruvate to acetyl-CoA

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28
Q

What does a PDH complex consist of?

A

3 enzymes

5 co-enzymes

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29
Q

Why is the TCA cycle known as a final COMMON pathway for the oxidation of fuel molecules?

A

bc it doesn’t matter which metabolic fuel is being used, so whether it’s a glucose or lipids or proteins
all of them end up in the TCA cycle

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30
Q

How many steps are in the TCA cycle?

A

8 steps

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31
Q

What happens overall in the TCA cycle?

A

acetyl residues from acetyl CoA

they are oxidised to co2

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32
Q

What is the formula for acetyl residues?

A

(CH3-CO-)

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33
Q

What is the role of reducing equivalents?

A

to transfer one electron in redox reactions

34
Q

Where are the reducing equivalents transferred to? What do they form?

A

NAD+ or FAD to form NADH and FADH2

35
Q

Why is the generation of NADH and FADH2 useful?

A

bc later on they will be transferred to the respiratory chain and used to generate ATP

36
Q

What happens overall in the TCA cycle carbon-wise?

A

a 4C unit condenses with a 2-C unit.
as the cycle goes on, 2Cs leave the cycle in the form of two CO2 mlcs
the 4-C unit is regenerated

37
Q

How many redox reactions occur through one TCA cycle?

A

four redox reactions

38
Q

What substances are produced for each molecule of acetyl CoA entering the TCA cycle?

A

NADH x3
CO2 x2
FADH2
GTP (directly makes ATP)

39
Q

What happens to the GTP molecule produced from one TCA cycle?

A

it goes on to directly generate a molecule of ATP

40
Q

What are the eight different intermediates of the TCA cycle?

A 
1 - citrate
2 - isocitrate
3 - a-ketoglutarate
4 - succinyl CoA
5 - succinate
6 - fumerate
7 - L-malate
8 - oxaloacetate
41
Q

How can you remember the eight intermediates of the TCA cycle?

A

A Certificate In Kama Sutra Should Further My Orgasm

After Class I Keep Some Specific Facts More Or-less

42
Q

Of the eight enzymes involved in the TCA cycle, which three do you need to know?

A

1 - citrate synthase
3 - isocitrate dehydrogenase
4 - a-ketoglutarate dehydrogenase

43
Q

Why are there only three enzymes of the eight in the TCA cycle that you need to know?

A

they are very important regulatory points of control for the TCA cycle
their activity is controlled IOT control the speed of the TCA cycle

44
Q

Which reaction in the TCA cycle does citrate synthase catalyse?

A

condensation reaction

reaction 1

45
Q

What happens during the condensation reaction (reaction 1) of the TCA cycle?

A

oxaloacetate + acetyl CoA < citrate

46
Q

Which reaction in the TCA cycle does isocitrate dehydrogenase then a-ketoglutarate catalyse?

A

iso - reaction 3

aket - reaction 4

47
Q

Which enzyme in the TCA cycle is part of the respiratory chain?

A

succinate dehydrogenase

48
Q

At which two points of the TCA cycle is the flow of C-atoms TIGHTLY regulated at?

A

when pyruvate is converted into acetyl-CoA (under PDH enzyme control)
the entry of acetyl-CoA into the TCA cycle (citrate synthase reaction)

49
Q

At which additional lesser two points of the TCA cycle is the flow of C-atoms regulated at?

A

at the isocitrate dehydrogenase reaction

at the a-ketoglutarate dehydrogenase reaction

50
Q

What happens if the E levels in a cell are high?

A

the activity of the TCA cycle will be inhibited

51
Q

What molecules in high levels indicate the presence of high E levels in a cell?

A

ATP
acetyl CoA
FAs
NADH

52
Q

What molecules in high levels indicate the presence of low ATP levels in a cell?

A

AMP (present when ATP has been used up)
CoA
NAD+
Ca 2+

53
Q

Why can calcium ions increase the rate of the TCA cycle?

A

they stimulate muscle contraction

they act as second messengers in some cells

54
Q

What are alternative sources of acetyl CoA (other than glucose)?

A

FAs

amacs (less common)

55
Q

Why are intermediate compounds of the TCA cycle constantly being replenished?

A

bc they have other biological roles in their cells

56
Q

How are the intermediate compounds of the TCA cycle replenished?

A

via anaplerotic reactions

57
Q

What is the role of anaplerotic reactions?

A

to maintain the concentrations of TCA cycle intermediates so that the cycle can function efficiently

58
Q

How many turns of the TCA cycle occur from one glucose mlc (6C)?

A

two turns, so twice the amount of products than from just one mlc of acetyl CoA (3C)

59
Q

What happens to the products of the TCA cycle that have been reduced in the process?

A

they are re-oxidised by the electron transport chain

60
Q

When NADH is produced by glycolysis, where is it located and where does it need to go?

A

located - in the cytoplasm, this is where glycolysis occurs

going - the mitochondrial inner membrane, this is where the electron transport chain occurs

61
Q

Why can’t NADH get across the mitochondrial inner membrane?

A

the inner membrane is impermeable to NADH

there’s no carrier in the membrane to transport NADH across

62
Q

What happens to the NADH product of glycolysis?

A

shuttles transfer two electrons from each NADH mlc into the mitochondria rather than transferring the NADH itself

63
Q

When NADH is produced by glycolysis, why does it need access to the mitochondrial inner membrane?

A

this is where the electron transport chain occurs

the NADH needs to be re-oxidised

64
Q

What are the two types of shuttles involved in giving NADH electrons from the electron transport chain?

A

the glycerol-3-phosphate shuttle

the malate-aspartate shuttle

65
Q

What areas is the glycerol-3-phosphate shuttle especially prevalent in?

A

the brain and muscle

66
Q

What areas is the malate-aspartate shuttle especially prevalent in?

A

in the liver and the heart

67
Q

What is the role of shuttles?

A

to give NADH e-s to the electron transport chain and regenerate NAD+
if the G3P shuttle is used, 1.5 mols of ATP is produced
if the MAS shuttle is used, 2.5 mols of ATP is produced

68
Q

What does the amount of ATP produced from shuttles depend on?

A

the type of shuttle used

69
Q

What is DHAP reduced to and how?

A

G3P by accepting electrons from NADH

at the same time, NADH is oxidised back into NAD+

70
Q

The redox reaction involving the reduction of DHAP and the oxidation of NADH is catalysed by what enzyme?

A

G3P dehydrogenase

71
Q

What is special about G3P?

A

this molecule is able to diffuse into the inter membrane space of mitochondria

72
Q

What happens to G3P once it is in the inter membrane space of mitochondria?

A

is oxidised back into DHAP by donating its two electrons to FAD

73
Q

What is FAD reduced to?

A

FADH2

74
Q

What happens to the DHAP once it has been converted from G3P?

A

it is able to diffuse back into the site of the cytosol

the process starts again

75
Q

What is the effect of FAD turning into FADH2?

A

the FADH2 goes through the electron transport chain and results in the production of 1.5 M of ATP

76
Q

Overall what happens in the G3P shuttle reactions?

A

a molecule of NADH / FADH2 transfers electrons into the mitochondria via a G3P shuttle
1.5 M of ATP is produced

77
Q

What does the malate-aspartate shuttle involve?

A

two pools of NADH and NAD+, one in the mitochondrial matrix and the other in the cytosol

78
Q

How does the process of the malate-aspartate shuttle start?

A

oxaloacetate in the cytosol accepts electrons from NADH and is reduced to malate

79
Q

What happens to NAHD once it has donated electrons in the malate-aspartate shuttle?

A

it is oxisised back to NAD+

80
Q

In the malate-aspartate shuttle, what is oxaloacetate converted into? What happens to it?

A

aspartate
transported out of the mitochondria again in exchange for a molecule of glutamate
once in the cytosol it turns back into oxaloacetate
cycle begins again

81
Q

Overall what happens in the malate-aspartate shuttle reactions?

A

NADH electrons are transported into the mitochondrial matrix
used to reduce a mlc of NAD+, generates NADH
the electrons are passed onto the electron transport chain

M104 T2 (15 decks)

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