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55 Cards in this Set

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Which enzyme most resembles Pyruvate Dehydrogenase?

**
Alpha-Ketoglutarate Dehydrogenase
The oxygen that we require for aerobic metabolism is excreted as:

***
Water
An uncoupler of oxidative phosphorylation facilitates/promotes:

**
The passage of protons into the mitochondrial matrix
The transamination of two of the intermediates of the citric acid cycle generates:

**
Aspartate and Glutamate
What are the characteristics of the Pyruvate Dehydrogenase Complex?

**
1. It contains several different catalytic activities

2. It's regulated by phosphorylation/dephosphorylation

3. It's inhibited by NADH

4. It's inibited by acetyl CoA

5. Coenzyme A is a substrate
What is the order of the intermediates of the citric acid cycle?

****
1. Citrate

2. Isocitrate

3. Alpha Ketoglutarate

4. Succinyl Coa

5. Succinate

6. Fumarate

7. Malate

8. Oxaloacetate
Why is the citric acid cycle said to be strictly aerobic?

*****
Because the reoxidation of reduced cofactors requires molecular oxygen

For the reoxidation of NADH and FADH2
What is Complex II?

*
Succinic Dehydrogenase
Which enzyme requires the cofactor FAD?

*
Succinate Dehydrogenase
Why is the citric acid cycle said to be amphibolic?

*
Because it is both catabolic and anabolic
Acetyl CoA, the fuel for the citric acid cycle is produced from what class of foods?

*
Carbohydrates

Proteins

Fats
Which of the intermediates of the citric acid cycle is a substrate for the synthesis of heme?

**
Succinyl CoA
Which of the enzymes of the citric acid cycle is also a member of the electron transport chain?

**
Succinate Dehydrogenase
Which are the fates of pyruvate?

*
1. Carboxylation to Oxaloacetate

2. Oxidation to Acetyl CoA

3. Reduction to Lactate

4. Transamination to Alanine
What is the enzyme that connects glycolysis with the citric acid cycle?

*
Pyruvate Dehydrogenase
In the process of oxidative phosphorylation, ATP synthesis is directly driven by:

*
Proton flow out of the mitochondrial matrix
Which are the results of uncoupling oxidative phosphorylation?

**
1. Increase the rate of oxygen consumption, by enhancing the rate of oxygen uptake

2. Increase the rate of electron transport

3. Increase temperature

4. Decrease ATP synthesis

5. Increase in fuel catabolism
What is the structure of oxaloacetate?

**
COO ???????
How many moles of NADH are produced in one round of the citric acid cycle?

***
3 moles of NADH
During oxidative phosphorylation, protons:

*
Are pumped out of the mitochondrial matrix
Which enzyme in the citric acid cycle generates a nucleoside triphosphate (GTP) as a product?

**
Succinate Thiokinase generates GTP
Acetyl CoA is a positive allosteric effector for:

****
Pyruvate Carboxylase
Enzyme/Cofactor or Substrate pairing in the citric acid cycle:

**
Malate Dehydrogenase ---> NAD

Citrate Synthase ---> Oxaloacetate

Alpha Ketoglutarate Dehydrogenase ---> CoASH

Succinic Dehydrogenase ---> FAD

Succinic Thiokinase ---> GTP
The synthesis of citrate by citrate synthase is strongly favored by the hydrolysis of what transient intermediate?

**
Citryl CoA
Characteristics of the Citric Acid Cycle:

*
1. Produces reduced NAD and FAD for oxidative phosphorylation

2. The citrate produced in the first step is a regulator of glycolysis

3. GTP is a direct product of the cycle

4. Aspartate and glutamate are each produced in one step from cycle intermediates

5. Succinyl CoA provides the carbon for the synthesis of heme
The rate of the citric acid cycle is controlled by:

*
1. The availability of Acetyl CoA

2. The availability of oxygen

3. The energy charge (proportion of ATP vs. ADP and AMP)
How does insulin stimulate the activity of pyruvate dehydrogenase?

*
By activating Pyruvate Dehydrogenase Phosphatase
Which is the principal anaplerotic enzyme for the citric acid cycle ?

**
Pyruvate Carboxylase
Why can a lipophilic weak acid act as an uncoupler of oxidative phosphorylation?

*
Because it facilitates the passage of protons across the membrane

Allows it to conduct H+ ions across the membrane by association and dissasociation
The process of oxidative phosphorylation is totally dependent upon the permeability of the inner mitochondrial membrane to:

*
Protons
In which complexes do protons move in or out of the mitochondrial matrix?

*
Complex 1: NADH/CoQ Reductase

Complex 3: CoQ/Cytochrome c Reductase

Complex 4: Cytochrome Oxidase

Complex 5: ATPase
Characteristics of brown adipose tissue:

**
1. Contains many mitochondria

2. Thermogenin is a constituent of BAT inner mitochondria

3. Contains cytochromes which makes it brown
What is the structure for alpha ketoglutarate?

*
COO - C=O - CH2 - CH2 - COO
How many moles of reduced cofactors are produced by the oxidation of one mole of acetyl CoA by the citric acid cycle?

*
4 moles
What are the names for the complexes in the electron transport chain?

*
Complex 1: NADH/CoQ Reductase

Complex 2: Succinate Dehydrogenase

Complex 3: CoQ/Cytochrome c Reductase

Complex 4: Cytochrome Oxidase

Complex 5: ATPase
Which of the members of the electron transport chain is a lipid soluble quinone?

*
Coenzyme Q
It pumps protons! It accepts electrons from cytochrome C!! It makes water!!! It is....

*
Cytochrome Oxidase!
What are some examples of uncouplers of oxidative phosphorylation?

*
DNP (dinitrophenol): a hydrophobic weak acid

TNT
Where does oxidative phosphorylation take place?

*
In the inner mitochondrial matrix
Which enzyme of the citric acid cycle requires no cofactor and only water as cosubstrate?

*
?????
What are the catabolic roles of the citric acid cycle?
1. Generation of energy thru the brakdown of acetyl CoA into CO2 and energy products

2. Generation of reduced cofactors (NADH and FADH) for oxidative phosphorylation

3. Generation of GTP fro GDP
What are the anabolic roles of the citric acid cycle?
Citric acid cycle gives rise to intermediates important of other important compounds

CAC produces:

1. Citrate: Carbon for fatty acid synthesis

2. Ketoglutarate:
Glutamate (important neurotransmitter)

3. Succinyl CoA: Carbon for heme synthesis

4. Oxaloacetate: Aspartate for protein synthesis which can be converted to feed gluconeogenesis
What is the fuel for the citric acid cycle? What metabolites is it derived from?
Acetyl CoA which is derived from pyruvate via pyruvate dehydrogenase
Where in the cell does the citric acid cycle occur?
In the mtichondrial matrix
Where in the cell does oxidative phosphorylation take place?
In the inner mitochondrial matrix
How many molecules of reduced cofactors ar produced by the oxidation of one molecule of acetyl CoA by the citric acid cycle?
3 NADH

1 FADH2
How many ATP's are generated thru oxidative phosphorylation during the oxidation of NADH? FADH2? Why are these numbers approximate?
1 molecule of NADH ---> 3 ATP

1 molecule of FADH2 ---> 2 ATP

These numbers are approximate because coupling of ATP yield to these cofactors is indirect. Remember NADH and FADH2 don't directly produce ATP, they only power the proton pumps which can set up the gradient for the ATP synthase
What other high energy compound is generated directly by the citric acid cycle?
GTP
Why is pyruvate carboxylase an important enzyme?
Because it it the mechanism of replenishing oxaloacetate within the citric acid cycle when intermediates are removed for synthesis of other compounds

Pyruvate carboxylase has acetlyl CoA as it's allosteric effector
Why is pyruvate dehydrogenase an important enzyme?
Important in determining the fate of pyruvate.

Ensures pyruvate enters the citric acid cycle

Determines the fate of pyruvate

It's not an actual enzyme of the citric acid cycle, but it links the citric acid cycle with glycolysis

Pyruvate dehydrogenase catalyzes the conversion of pyruvate into acetyl CoA, which is not a substrate for gluconeogenesis

This essentially ensures that pyruvate enters the citric acid cycle and NOT gluconeogenesis
The oxidation of one mole of glucose via glycolysis and the citric acid cycle produces how many moles of ATP?
30
What is the role of the proton gradient in oxidative phosphorylation? How is it generated?
The proton gradient in oxidative phosphorylation is the driving force in the production of ATP. As protons flow down specific proton pores it will power ATP synthase to produce ATP from ADP and Pi

The various electron transport complexes, uses the reducing potentials of NADH and FADH2, to pump H+ across the inner mitochondrial membrane, setting up the gradient
What are the two characteristics of an uncoupler of oxidative phosphorylation? How does an uncoupler work?
Uncouplers can involve themselves in the oxidative phosphorylation because they are characterized as both hydrophilic and as a weak acid

Its hydrophilicity allows it to pass thru the inner mitochondrial matrix relatively easy. Once inside, its weak acid allows it to pick up protons near the surface of the outer mitochondrial matrix. Then it passes the proton from an uncoupler to uncoupler via "bucked brigade" and unloads the proton in the mitochondria or in the matrix

This results in a futile cycle as the enzymes of oxidative phosphorylation work to pump protons out, and the uncouplers bring them back into the matrix, causing a break in the proton gradient

As a result energy is lost as heat
What is P50 and how does it change with a right shift?
P50 is the partial pressure of oxygen at which half of the Hb is saturated with oxygen. With a right shift P50 will increase

A right shift also occurs with decrease pH, increase CO2 and 2,3-bpg
What is the structure for oxaloacetate?

*
COO - C=O - CH2 - COO