2.3 TCA, ETC, PDH

Question 1

PDH function

Answer 1

Converts pyruvate to acetyl-CoA

Question 2

Where do PDH and TCA occur?

Answer 2

Mitochondrial matrix

Question 3

Where does the ETC occur?

Answer 3

Mitochondrial inner membrane

Question 4

Function of TCA cycle

Answer 4

To oxidize acetyl CoA to Co2

Question 5

TCA is the final common oxidative pathway for ___

Answer 5

Carbohydrates, fats, and amino acids

Question 6

All of the TCA enzymes are soluble, except for

Answer 6

Succinate dehydrogenase

Question 7

Does the TCA cycle directly consume oxygen?

Answer 7

No

Question 8

How can vitamin deficiencies affect the TCA cycle?

Answer 8

Vitamins act as a cofactor for enzymes, so a deficiency in them causes reduced activity of enzymes resulting in lactic acidosis and neurological defects

Question 9

Is the TCA a closed or open loop cycle?

Answer 9

Closed

Question 10

Why is the TCA cycle considered an aerobic pathway?

Answer 10

B/c the NADH and FADH2 produced must transfer electrons to the ETC, which needs oxygen

Question 11

End products of TCA cycle

Answer 11

6 NADH
2 GTP
(b/c cycle turns twice)

Question 12

TCA cycle is a source of ___

Answer 12

Biosynthetic precursors
(important source for other building blocks in the cell)

Question 13

Steps of TCA cycle

Answer 13

1. Acetyl-CoA + oxaloacetate + citrate synthase = citrate
2. Citrate + aconitase = Isocitrate
3. Isocitrate + isocitrate dehydrogenase = alpha-Ketoglutarate
4. Alpha-ketoglutarate + alpha-ketoglutarate dehydrogenase complex = succinyl-CoA
5. Succinyl-CoA + syccinyl-CoA synthetase = Succinate
6. Succinate + succinate dehydrogenase = fumarate
7. Fumarate + fumarase = malate
8. Malate + malate dehydrogenase = oxaloacetate

Question 14

In which steps of the TCA cycle is CO2 released?

Answer 14

Decarboxylation of isocitrate to alpha-ketoglutarate

Decarboxylation of alpha-ketoglutarate to succinyl-CoA

Question 15

Which step in the TCA cycle is GTP released?

Answer 15

Conversion of succinyl-CoA to Succinate through substrate level phosphorylation

Question 16

What steps of the TCA cycle is NADH released?

Answer 16

Conversion of isocitrate to alpha-ketoglutarate
Conversion of alpha-ketoglutarate to succinyl-CoA
Conversion of malate to oxaloacetate

Question 17

What step of the TCA is FADH2 released?

Answer 17

Conversion of succinate to fumarate

Question 18

What’s significant about FADH2 when it’s released?

Answer 18

2 electrons immediately go to the ETC

Question 19

What enzymes regulate the TCA cycle?

Answer 19

Citrate synthesis
Isocitrate dehydrogenase
alpha-ketoglutarate dehydrogenase

Question 20

Electrons donated by NADH and FADH2 flow through the ___, causing protons to be pumped from the matrix to the intermembrane space

Answer 20

ETC

Question 21

The ___ in the ETC are passed to ___, which combines with protons to form water

Answer 21

Electrons

Oxygen

Question 22

The protons form a concentration gradient in the ETC, which power the ___

Answer 22

Catalytic action of ATP synthase

Question 23

Where do H+ ions build up in in the ETC

Answer 23

intermembrane space

Question 24

The ETC and ATP synthase process is called

Answer 24

Oxidative phosphorylation

Question 25

What are the 2 electron carriers in the ETC?

Answer 25

Coenzyme Q and cytochrome C

Question 26

Complex 1 in ETC is called and what does it do?

Answer 26

NADH dehydrogenase accepts electrons from NADH and transfers them to coenzyme Q NADH + H+ = NAD+

Question 27

Complex II in the ETC is called what and what's its function

Answer 27

Succinate dehydrogenase Accepts e- from FADH2 and transfers them to Coenzyme Q NOT a proton pump

Question 28

Name of complex III in ETC and what's its function

Answer 28

Ubiquinone-Cytochrome C Reductase/Cytochrome Reductase | Accepts e- from coenzyme Q and transfers them to cytochrome C

Question 29

Name of complex IV and what's its function?

Answer 29

Cytochrome oxidase Accepts e- from cytochrome C to reduce oxygen to H2O Also known as a proton pump

Question 30

What's the sequence of e- passage in the ETC?

Answer 30

``` From complex I or II to Coenzyme Q From Coenzyme Q to complex III From complex III to cytochrome C From cytochrome C to complex IV From complex IV to oxygen (to form H2O) ```

Question 31

Describe ATP synthase

Answer 31

Also called complex V (5) Made of 2 parts: F0 in the inner mitochondrial membrane and F1 in the mitochondrial matrix 3-4 protons move through this machine to convert a molecule of ADP and Pi to ATP

Question 32

The synthesis of ATP is brought about by the ___

Answer 32

Rotary motion - Large electrochemical potential flows through F0 subunit and causes a rotation, and subsequently F1 leading to ATP synthesis - The mechanical energy is converted into chemical energy

Question 33

What do inhibitors of the ETC result in?

Answer 33

Decreased O2 consumption Increased intracellular NADH/NAD+ and FADH2/FAD ratio Decreased ATP

Question 34

What does cyanide do?

Answer 34

Acts as an irreversible enzyme inhibitor of cytochrome C oxidase (complex IV) - Stops oxidative phosphorylation and ATP production

Question 35

What does Oligomycin do?

Answer 35

It's an ATP synthase inhibitor - It blocks Fo subunit and prevents reentry of protons into the matrix and prevents phosphorylation of ADP to ATP - H+ ions stay in the inner membrane space

Question 36

What are the types of uncouplers of oxidative phosphorylation?

Answer 36

Drugs (uncouplers) and proteins (uncoupling proteins)

Question 37

What do uncouplers of oxidative phosphorylation do?

Answer 37

Inhibit phosphorylation of ADP

Question 38

Describe dinitrophenol (DNP)

Answer 38

Acts as a protonophore - Allows protons to leak across the inner mitochondrial membrane and bypass ATP synthase Used as a weight loss Generates a lot of heat

Question 39

___ protein is an inner mitochondrial membrane protein found in brown adipose tissue and present in newborn babies

Answer 39

Uncoupling protein

Question 40

Describe metformin

Answer 40

A prescription drug used to treat type 2 diabetes | Inhibits complex I

Question 41

Describe the pyruvate dehydrogenase (PDH) complex

Answer 41

Connects the TCA cycle and subsequent oxidative phosphorylation to glycolysis

Question 42

Where is PDH located?

Answer 42

Mitochondria

Question 43

Net result of pyruvate to acetyl-CoA

Answer 43

2 NADH and 5 ATP

Question 44

Pyruvate loses ___ when converting to acetyl-CoA

Answer 44

Co2

Question 45

What are the enzymes associated with PDH?

Answer 45

``` Pyruvate dehydrogenase (E1) Dihydrolipoyl transacetylase (E2) Dihydrolipoyl dehydrogenase (E3) ```

Question 46

What are the coenzymes associated with PDH?

Answer 46

``` TPP Lipoic Acid FAD NAD+ CoASH ```

Question 47

PDH coenzymes are derived from ___

Answer 47

Vitamins

Question 48

alpha-Ketoglutarate dehydrogenase (KDH) is structurally similar to ___

Answer 48

PDH

Question 49

What happens when there is a high and low energy charge in the PDH?

Answer 49

High energy = slows down glycolysis and conversion of pyruvate to acetyl-CoA Low energy = speeds up reaction and activates PDH

Question 50

Phosphorylation of PDH is mediated by ___

Answer 50

Pyruvate dehydrogenase kinase (PDHK)

Question 51

What enzyme in PDH is activated by insulin?

Answer 51

PDH phosphatase

Question 52

What enzyme is activated by glucagon and wants to inhibit PDH reaction?

Answer 52

PDH kinase It pulls off ATP