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Biocheem > Lecture 33 > Flashcards

Lecture 33 Flashcards

1
Q

What is the only thing you can do with lactate?

A

Convert it back into pyruvate

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2
Q

What does Lactate dehydrogenase do?

A

Converts lactate back into Pyruvate

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3
Q

Why would lactate in tissues be produced?

A

Because NAD+ needs to be oxidized so glycolysis can still occur

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4
Q

What happens when lactate is oxidized?

A

It is converted to Pyruvate and NADH

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5
Q

What does the production of lactate ensure?

A

That we maintain the concentration of NAD+ so glycolysis can continue in anaerobic condtions

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6
Q

What is Lactic acid to Lactate?

A

Lactic acid is the conjugate base of lactic acid

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7
Q

How does the production of Lactate affect pH?

A

It does not to a decrease in pH because it consumes a proton

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8
Q

What happens to lactate after it is produced?

A

It is exported from muscle via a specific membrane trnasporter

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9
Q

What transports lactate out of the muscle?

A

A symporter along with H+

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10
Q

What causes the decrease in blood pH?

A

Pyruvate being converted to lactate to maintain the citric acid cycle (NADH being oxidized to NAD+) and then lactate is transported out of the muscle cells along with H+ which is a symporter causing an decrease in pH

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11
Q

What is the benefit of lactate being increased?

A

Because it is transported out using a symporter, that also transports H+ it causes blood pH to decrease which stabilized the T state of Hb causing increased oxygen unbinding

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12
Q

What can lactate be used for?

A

It can be converted back to pyruvate by oxidation and reducing NAD+ to NADH and the pyruvate can be used as fuel

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13
Q

What does Lactate Dehydrogenase do?

A

Reduces pyruvate into lactate and oxidized NADH in the process

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14
Q

Under what conditions can we take lactate and convert it back to pyruvate?

A

Aerobic conditions

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15
Q

What is reduced or oxidized when Pyruvate is converted to Acetyl-CoA?

A

NAD+ is reduced to NADH when pyruvate is converted to acetyl-CoA

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16
Q

Which tissue is lactate a metabolic fuel for?

A

Cardiac tissue

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17
Q

What can happen to lactate in the liver?

A

It can be oxidized to pyruvate which can then be converted to glucose through gluconeogenesis

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18
Q

What happens to Pyruvate anaerobically in yeast?

A

It is converted to ethanol

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19
Q

What are the two steps in the conversion of Pyruvate to Ethanol in yeast?

A

Decarboxylation and Reduction

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20
Q

What are the final products in the conversion of Pyruvate to Ethanol in yeast?

A

Pyruvate ➡️ Acetylaldehyde ➡️ Ethanol and CO2 and NAD+

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21
Q

What is the biochemical purpose for the production of lactate in muscle cells?

A

•Reoxidize NADH to NAD+ under anaerobic conditions

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22
Q

What is the net consumption of NAD+ under anaerobic conditions?

A

There is no consumption of NAD+

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23
Q

What does Pyruvate Dehydrogenase do?

A

Converted Pyruvate to Acetyl-CoA which can be used in the citric acid cycle

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24
Q

What links glycolysis to the citric acid cycle?

A

Pyruvate dehydrogenase

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25
Q

Where does Pyruvate Dehydrogenase work?

A

In the mitochondria matrix

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26
Q

What processes occur in the matrix?

A
  • Pyruvate dehydrogenase
  • Citric acid cycle
  • Oxidative phosphorylation
  • Beta-oxidation (fatty acids)
27
Q

What is a characteristic of all the processes that occur in the mitochondrial matrix?

A

They are aerobic because they heavily rely on the electron transport chain

28
Q

In which part of mitochondria does glycolysis generate pyruvate?

A

In the cytosol

29
Q

In which part of the mitochondria is pyruvate converted to acetyl-CoA?

A

The mitochondrial matrix so the most inner part

30
Q

How can pyruvate be brought to the mitochondrial matrix to be converted to acetyl-CoA?

A

The pyruvate translocase

31
Q

Why is the outer mitochondrial membrane so porous?

A

Because it has porins

32
Q

What is the permeability of the inner mitochondrial membrane?

A

It is very difficult to get across so it is impermeable

33
Q

What does Pyruvate Translocase do?

A

It allows for the transport of pyruvate across the inner mitochondrial membrane along with H+

34
Q

What is pyruvate converted to acetyl-CoA by?

A

The pyruvate dehydrogenase complex (PDC)

35
Q

How many carbons is pyruvate?

A

Three

36
Q

How is NADH affected by PDC?

A

NAD+ is reduced to NADH in the process of pyruvate dehydrogenase converting pyruvate to acetyl-CoA

37
Q

What are the reactants of Pyruvate Dehydrogenase?

A

Pyruvate, HS-CoA and NAD+

38
Q

What are the products of Pyruvate Dehydrogenase?

A

Acetyl CoA, CO2, NADH

39
Q

Which part of pyruvate is converted to carbon dioxide in Pyruvate Dehydrogenase?

A

The carboxylate part

40
Q

Why is Acetyl-CoA a high energy molecule?

A

Because it contains a thioester

41
Q

When does Coenzyme become known as Acetyl-Coa?

A

When it has an acetyl group attached by a thioester bond

42
Q

What is Coenzyme A a derivative of?

A

Vitamin B5 is linked to an adenosine nucleotide which has a functional portion of a sulfhydryl group (thiol) which is able to form a thioester

43
Q

Why is the PDH important?

A

Because it is a significant committed step

44
Q

Once Acetyl-CoA is made what can it be used for?

A

It can be metabolized for energy via the citric acid cycle

45
Q

What is the net reaction for the pyruvate dehydrogenase reaction?

A

Pyruvate + CoA + NAD+ ➡️ Acetyl-CoA + NADH + CO2

46
Q

Why can the PDH reaction be described as a transacetylation?

A

Because the acetyl portion of pyruvate is being transferred onto Acetyl-CoA

47
Q

What are some of the cofactors required by PDH?

A

NAD+
FAD
CoA
This is 3 of 5

48
Q

What are the three separate enzyme activities of PDH?

A
  • Decarboxylate
  • Transfer to CoA
  • Oxidation
49
Q

What is PDH regulated by?

A

Kinases and Phosphotases

50
Q

What are the advantages of multienzyme complexes?

A
  • Speeds up reaction times (channelling)
  • Limits number of side reactions (channelling)
  • Enzymes controlled as a single unit
51
Q

How will PDH be affected by the ATP/ADP ratio?

A

Its activity will be slowed by a high ATP/ADP ratio

52
Q

How will PDH be affected by calcium?

A

Its activity will be activated by calcium

53
Q

How will PDH be affected by Acetyl-CoA?

A

Its activity will be slowed because acetyl-CoA is a product

54
Q

Why is PDH heavily regulated?

A

Because it is irreversible and committed

55
Q

Can Acetyl-CoA be used to make glucose?

A

No it cannot

56
Q

What is PDH sensitive to?

A

ATP requirements

57
Q

What is PDH regulated by?

A
  • NAD+/NADH ratio
  • Acetyl-CoA
  • Ca2+ concentration
58
Q

How can NAD+/NADH initially regulate PDH?

A

It can help regulate through the substrate product effect

59
Q

How can NAD+/NADH inhibit PDH?

A

Through allostery and activation of protein kinases which phosphorylate PDH

60
Q

How can Acetyl-CoA affect PDH?

A

It can inhibit it by activating protein kinases which phosphorylate it

61
Q

How can calcium affect PDH?

A

It can activate phosphatases which dephosphorylate PDH which activates it

62
Q

What are the activators of PDH?

A

High NAD+ conc and high Calcium

63
Q

What are the inhibitors of PDH?

A

High NADH and Acetyl-CoA

Biocheem (38 decks)

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