Bioenergetics

Question 1

What are the 3 forms of energy for the TCA cycle?

Answer 1

NADH
FADH2
GTP

Question 2

Is TCA exergonic or endergonic? Why?

Answer 2

Exergonic, because it cleaves the acetyl coA which releases energy

Question 3

Describe how carbohydrates are broken down to acetyl coA for the TCA cycle.

Answer 3

Glucose -> 2 Pyruvate -> 2 Acetyl CoA

Question 4

Describe how lipids are broken down to acetyl coA for the TCA cycle.

Answer 4

TAGs -> Fatty acids -> Acetyl CoA

*Via Beta Oxidation

Question 5

Describe how proteins are broken down to acetyl coA for the TCA cycle.

Answer 5

Amino acids -> Acetyl coA

Question 6

Describe the energy output for NADH and FADH2

Answer 6

1 mol of NADH=2.5 mol ATP

1 mol FADH2=1.5 mol ATP

Question 7

In what way does TCA produce GTP?

Answer 7

via Substrate level phosphorylation

Question 8

How does Pyruvate enter the mitochondria?

Answer 8

Mitochondrial Pyruvate Carrier

Question 9

What enzyme converts pyruvate to acetyl coA and where does this occur?

Answer 9

Pyruvate Dehydrogenase Complex

This occurs in the mitochondria, before the TCA cycle

Question 10

What is the coenzyme for the pyruvate dehydrogenase complex?

Answer 10

Thiamine Pyrophosphate (TPP)

Question 11

What are the 2 major reasons the TCA cycle is anapleurotic and what does this mean?

Answer 11

Anapleurotic means “fill up” reactions that provide intermediates that replenish the TCA cycle

2 major ones:
Degradation of amino acids

Carboxylation of pyruvate

Question 12

Which amino acid feeds into alpha ketoglutarate in the TCA cycle?

Answer 12

Glutamate

note that alpha ketoglutarate can also be broken down into glutamate

Question 13

During lipid synthesis, which molecule from the TCA cycle plays a role in the synthesis of fatty acids?

Answer 13

Citrate, which is made from the combination of oxaloacetate and acetyl coA

Citrate leaves the mitochondria and is broken down into acetyl coA, which is used to make fatty acids

Question 14

What are the 4 classic TCA cycle disorders?

Answer 14

2-Oxoglutaric aciduria (alpha-ketoglutaric acid)
Fumarase deficiency
Succinyl Coa Synthetase deficiency
Mitochondrial depletion syndrome

Question 15

What does 2-Oxoglutaric aciduria (alpha-ketoglutaric acid)

cause?

Answer 15

Global developmental delay and neurological problems in infants such as mental retardation

Question 16

What does Fumarase deficiency cause?

Answer 16

Severe neurological impairment. Fatal by 2 years of age.

Question 17

What 2 mutations cause Succinyl Coa Synthetase deficiency?

Answer 17

SUCLA2
SUCLG1

These genes encode Succinyl Coa Synthetase

Question 18

Describe the difference between fission and fusion of the mitochondria.

Answer 18

Fission- the mitochondria appears a priori to be an essential event in proliferating cells. It essentially cuts off parts of the mitochondria that are not self sufficient.

Fusion- the movement of organelles moves the mitochondria pieces together to rescue less functional pieces.

*Note that these are essentially opposites of each other,

Question 19

What are the 3 goals of oxidative phosphorylation in order to be successful?

Answer 19

1. Transfer of electrons from NADH and FADH2 -> O2
2. To establish a proton gradient across the inner mitochondrial membrane and inner membrane space
3. To synthesize ATP

Question 20

When establishing the proton gradient, what are the two most important factors that constitute the proton-motive force (pmf) used to drive ATP synthesis?

Answer 20

1. PH gradient

2. Membrane potential

Question 21

What antibiotics inhibit which of the 5 complexes of the ETC?

Answer 21

PARM- inhibit complex 1

Malonate- inhibits complex 2

Antimycin- inhibits complex 3

Carbon Monoxide, Cyanide, Hydrogen Sulfur- inhibits Complex 4

Oligomycin- inhibits complex 5

Question 22

How does DNP (Ninitrophenol) and Aspirin affect the TCA cycle?

Answer 22

They uncouple it from ATP, therefore causing an increase in temperature and less ATP being made

Question 23

NADH cannot be made in the mitochondria, so what system is in place so NADH can be generated in the mitochondrial matrix?

What 3 tissues does this occur in?

Answer 23

Malate-Aspartate Shuttle

This occurs in the heart, liver, and kidneys

*Note that NADH only enters the mitochondria at complex I

Question 24

FADH2 cannot be made in the mitochondria, so what system is in place so FADH2 can be generated in the mitochondrial matrix?

What 2 tissues does this occur in?

Answer 24

Glycerophosphate shuttle

Occurs in skeletal muscle and the brain

*Note that FADH2 joints to the ETC at CoQ

Question 25

What is the rate limiting step of the TCA cycle?

What are the 3 regulatory enzymes of the TCA cycle?

Answer 25

Isocitrate Dehydrogenase

Citrate Synthase
Isocitarte Dehydrogenase
Alpha-Ketoglutarate Dehydrogenase

Question 26

Which molecule from the TCA cycle is used to make glucose? What is the name of this process?

Answer 26

Malate, Malate is taken from TCA and converted into Oxaloacetate, which is formed into PEP, then ultimately Glucose

Gluconeogenesis

Question 27

Describe the flow of protons through each of the complexes during the mitochondrial ETC.

Answer 27

Flow from the matrix into the intermembrane space for complexes I, III, and IV

Complex V moves protons from the intermembrane space back into the matrix

Question 28

Which complex uses its electrons to convert oxygen into water?

Answer 28

Complex IV

Note that this complex pumps hydrogen ions into the intermembrane space while oxygen is the final electron acceptor and is converted into water within the matrix.