Lecture 33

Question 1

What is the only thing you can do with lactate?

Answer 1

Convert it back into pyruvate

Question 2

What does Lactate dehydrogenase do?

Answer 2

Converts lactate back into Pyruvate

Question 3

Why would lactate in tissues be produced?

Answer 3

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

Question 4

What happens when lactate is oxidized?

Answer 4

It is converted to Pyruvate and NADH

Question 5

What does the production of lactate ensure?

Answer 5

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

Question 6

What is Lactic acid to Lactate?

Answer 6

Lactic acid is the conjugate base of lactic acid

Question 7

How does the production of Lactate affect pH?

Answer 7

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

Question 8

What happens to lactate after it is produced?

Answer 8

It is exported from muscle via a specific membrane trnasporter

Question 9

What transports lactate out of the muscle?

Answer 9

A symporter along with H+

Question 10

What causes the decrease in blood pH?

Answer 10

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

Question 11

What is the benefit of lactate being increased?

Answer 11

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

Question 12

What can lactate be used for?

Answer 12

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

Question 13

What does Lactate Dehydrogenase do?

Answer 13

Reduces pyruvate into lactate and oxidized NADH in the process

Question 14

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

Answer 14

Aerobic conditions

Question 15

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

Answer 15

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

Question 16

Which tissue is lactate a metabolic fuel for?

Answer 16

Cardiac tissue

Question 17

What can happen to lactate in the liver?

Answer 17

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

Question 18

What happens to Pyruvate anaerobically in yeast?

Answer 18

It is converted to ethanol

Question 19

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

Answer 19

Decarboxylation and Reduction

Question 20

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

Answer 20

Pyruvate ➡️ Acetylaldehyde ➡️ Ethanol and CO2 and NAD+

Question 21

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

Answer 21

•Reoxidize NADH to NAD+ under anaerobic conditions

Question 22

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

Answer 22

There is no consumption of NAD+

Question 23

What does Pyruvate Dehydrogenase do?

Answer 23

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

Question 24

What links glycolysis to the citric acid cycle?

Answer 24

Pyruvate dehydrogenase

Question 25

Where does Pyruvate Dehydrogenase work?

Answer 25

In the mitochondria matrix

Question 26

What processes occur in the matrix?

Answer 26

* Pyruvate dehydrogenase * Citric acid cycle * Oxidative phosphorylation * Beta-oxidation (fatty acids)

Question 27

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

Answer 27

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

Question 28

In which part of mitochondria does glycolysis generate pyruvate?

Answer 28

In the cytosol

Question 29

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

Answer 29

The mitochondrial matrix so the most inner part

Question 30

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

Answer 30

The pyruvate translocase

Question 31

Why is the outer mitochondrial membrane so porous?

Answer 31

Because it has porins

Question 32

What is the permeability of the inner mitochondrial membrane?

Answer 32

It is very difficult to get across so it is impermeable

Question 33

What does Pyruvate Translocase do?

Answer 33

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

Question 34

What is pyruvate converted to acetyl-CoA by?

Answer 34

The pyruvate dehydrogenase complex (PDC)

Question 35

How many carbons is pyruvate?

Answer 35

Three

Question 36

How is NADH affected by PDC?

Answer 36

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

Question 37

What are the reactants of Pyruvate Dehydrogenase?

Answer 37

Pyruvate, HS-CoA and NAD+

Question 38

What are the products of Pyruvate Dehydrogenase?

Answer 38

Acetyl CoA, CO2, NADH

Question 39

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

Answer 39

The carboxylate part

Question 40

Why is Acetyl-CoA a high energy molecule?

Answer 40

Because it contains a thioester

Question 41

When does Coenzyme become known as Acetyl-Coa?

Answer 41

When it has an acetyl group attached by a thioester bond

Question 42

What is Coenzyme A a derivative of?

Answer 42

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

Question 43

Why is the PDH important?

Answer 43

Because it is a significant committed step

Question 44

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

Answer 44

It can be metabolized for energy via the citric acid cycle

Question 45

What is the net reaction for the pyruvate dehydrogenase reaction?

Answer 45

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

Question 46

Why can the PDH reaction be described as a transacetylation?

Answer 46

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

Question 47

What are some of the cofactors required by PDH?

Answer 47

NAD+ FAD CoA This is 3 of 5

Question 48

What are the three separate enzyme activities of PDH?

Answer 48

* Decarboxylate * Transfer to CoA * Oxidation

Question 49

What is PDH regulated by?

Answer 49

Kinases and Phosphotases

Question 50

What are the advantages of multienzyme complexes?

Answer 50

* Speeds up reaction times (channelling) * Limits number of side reactions (channelling) * Enzymes controlled as a single unit

Question 51

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

Answer 51

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

Question 52

How will PDH be affected by calcium?

Answer 52

Its activity will be activated by calcium

Question 53

How will PDH be affected by Acetyl-CoA?

Answer 53

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

Question 54

Why is PDH heavily regulated?

Answer 54

Because it is irreversible and committed

Question 55

Can Acetyl-CoA be used to make glucose?

Answer 55

No it cannot

Question 56

What is PDH sensitive to?

Answer 56

ATP requirements

Question 57

What is PDH regulated by?

Answer 57

* NAD+/NADH ratio * Acetyl-CoA * Ca2+ concentration

Question 58

How can NAD+/NADH initially regulate PDH?

Answer 58

It can help regulate through the substrate product effect

Question 59

How can NAD+/NADH inhibit PDH?

Answer 59

Through allostery and activation of protein kinases which phosphorylate PDH

Question 60

How can Acetyl-CoA affect PDH?

Answer 60

It can inhibit it by activating protein kinases which phosphorylate it

Question 61

How can calcium affect PDH?

Answer 61

It can activate phosphatases which dephosphorylate PDH which activates it

Question 62

What are the activators of PDH?

Answer 62

High NAD+ conc and high Calcium

Question 63

What are the inhibitors of PDH?

Answer 63

High NADH and Acetyl-CoA