Chapter 10

Question 1

Starting reactants and products of glycolysis, PDH reaction, Crebs cycle, and ETC.

Answer 1

Question 2

The conversion of pyruvate ______ carbon molecule to acetyl-coA _____ carbon molecule is an (oxidation/reduction) reaction.

Answer 2

3 carbon, 2 carbon, oxidation

Question 3

Steps of pyruvate dehydrogenase reaction:

Answer 3

1 glucose –> 2 pyruvates –> 2 Acetyl-coA, 2 NADH & 2 CO2

Question 4

What is the main purpose of the citric acid cycle?

Answer 4

To oxidize carbons in intermediates to CO2 and generate high energy electron carriers (NADH & FADH2) and GTP.

Question 5

What are some things that inhibit the PDH reaction?

Answer 5

Acetyl-CoA itself, NADH, ATP, pyruvate dehydrogenase kinase

Question 6

The production of acetyl coA is regulated by two important enzymes to ensure the body doesn’t overproduce or underproduce it. What are they?

Answer 6

Pyruvate dehydrogenase kinase - this enzyme phosphorylates the other enzyme PDH to turn it off when acetyl-CoA levels are high
Pyruvate dehydrogenase phosphatase - this enzyme dephosphorylates PDH to turn it on, when acetyl-CoA levels are low, and ADP levels are high

Question 7

What is the role of pyruvate dehydrogenase? What are characteristics of it?

Answer 7

It is a 3 enzyme complex with multiple subunits, in charge of the oxidation & decarboxylation of pyruvate to create acetyl-coA.

Question 8

What are other ways that Acetyl-CoA can be formed?

Answer 8

It can be formed from ketogenic amino acids, ketone bodies, alcohol, and fatty acids

Question 9

Describe the process of how acetyl-coA is created from fatty acids.

Answer 9

1. In the cytosol of the cell, a fatty acid couples with CoA forming fatty acyl CoA
2. This complex travels to the intermembrane space of the mitochondria where the acyl group is transferred to a molecule called carnitine
3. Acyl-Carntitine can cross the inner membrane, UNLIKE the CoA
4. Acyl group is transferred to a mitochondrial coA enzyme once again forming Acyl-coA
   5.Acyl-CoA undergoes beta-oxidation to form acetyl-CoA

Question 10

Where does the citric acid cycle occur?

Answer 10

Mitochondrial matrix; innermost compartment

Question 11

Citric Acid Cycle reactants and products

Answer 11

Question 12

What is the rate-limiting step of the TCA cycle?

Answer 12

The rate-limiting enzyme is isocitrate dehydrogenase which converts isocitrate to alpha-ketoglutarate. It is rate-limiting because this step is inhibited by elevated ATP & NADH.

Question 13

what is the net ATP yield from 1 glucose?

Answer 13

30-32 ATPs
2 ATP from glycolysis + 2 ATP from TCA cycle + 28 ATP from ETC chain = 32 max ATP

Question 14

1 NADH produces _____ ATP.
1 FADH2 produces _____ ATP.

Answer 14

NADH = 2.5
FADH2 = 1.5

Question 15

The electron transport chain generates a high concentration of protons in the (intermembrane space/mitochondrial matrix). The ETC is located in the (intermembrane space/inner membrane/matrix).

Answer 15

Intermembrane space; inner membrane

Question 16

What is oxidative phosphorylation, and where does it occur?

Answer 16

The process where energy is harnessed through a series of protein complexes embedded in the inner-membrane of mitochondria (called ETC and ATP synthase) to create ATP.
Occurs in the inner membrane of the mitochondria.

Question 17

Describe ATP synthase

Answer 17

Enzyme complex in the ETC chain made of two portions:
F0 - the non polar ion channel spanning the membrane, which allows protons to flow down their gradient
F1 - uses the energy released by the electrochemical gradient to phosphorylate ADP –> ATP

Question 18

What does the proton gradient do in the ETC? What is the significance of ADP for the enzyme ATP synthase?

Answer 18

The proton gradient provides energy for ATP synthase to rotate. to release an ATP molecule.
ADP is necessary because it is the substrate which allows it to be converted into ATP once bound to the enzyme.

Question 19

As the ETC chain progresses, the reduction potentials of each complex (increase/decrease).

Answer 19

Increase because the final electron acceptor O2 has the highest reduction potential

Question 20

Chemiosmotic coupling

Answer 20

Direct relationship which pairs the exergonic process of H+ traveling through the ATP synthase to the endergonic process of phosphorylating ADP.
Coupling refers to the energy released from one reaction driving the second reaction.

Question 21

How does the concentration of O2 affect the rate oxidative phosphorylation and NADH/FADH2.

Answer 21

Decreased O2 causes decreased oxidative phosphorylation and increased NADH/FADH2

Question 22

Complex I of ETC (NADH-CoQ oxoreductase)

Answer 22

Electrons passed from NADH –> FMN –> Fe-S subunit –> Coenzyme Q (ubiquinone) –> becomes CoQH2 (ubiquinol)
-4 protons pumped into intermembrane space

Question 23

Complex II of ETC (Succinate-CoQ oxidoreductase)

Answer 23

Electrons passed from succinate –> FAD which becomes FADH2 –> Fe-S subunit –> Coenzyme Q (ubiquinone) –> becomes CoQH2 (ubiquinol)
-No proton pumping occurs at this complex

Question 24

Complex III of ETC

Answer 24

Coenzyme Q from both Complex I and Complex II travels to Complex III to transfer its electrons to cytochrome C
Coenzyme Q also donates 2 protons to Complex III to be pumped into intermembrane space
-4 protons pumped into intermembrane space:
2 from Coenzyme Q and two from the reaction of transferring e- from coenzyme Q to cytochrome C

Question 25

Complex IV (cytochrome oxidase)

Answer 25

Electrons in the form of hydride ions are passed from cytochrome C to –> O2 –> which forms H2O
-Oxygen is the final electron acceptor
-Two protons pumped into intermembrane space

Question 26

How many electrons are required to fully reduce 1 molecule of O2? How many NADHs are needed? How many cytochrome c’s are needed?

Answer 26

4 electrons total
2 NADH (each NADH carries 2 e-)
4 cytochrome c (each carries 1 e-)

Question 27

What are coenzyme Q (also known as ubiquinone) and cytochrome C?

Answer 27

Both electron carriers.
Ubiquinones - lipid soluble, small organic molecules
Cytochrome C - heme containing proteins which handover e- to O2

Question 28

What is a flavoprotein? Draw the structure.

Answer 28

A subclass of electron carriers that are derived from riboflavin (vitamin B2). Examples: FAD and FMN

Question 29

Glycerol 3-phosphate shuttle

Answer 29

Electrons are transferred from cytosolic NADH to DHAP, forming glycerol 3-phosphate. These electrons can then be
transferred to mitochondrial FAD, forming FADH2.

Question 30

Malate-aspartate shuttle

Answer 30

In cytosol oxaloacetate îs reduced to malate by coupling with NADH –> Malate now carries the electrons that NADH once had –> malate travels through the two mitochondrial membranes –> malate is oxidized back to oxaloacetate and transfers its electrons to form mitochondrial NAD+ –> thus forming NADH inside the matrix
This shuttle produces 2.5 ATP for every NADH

Question 31

Once malate donates its electrons to mitochondrial NAD, it becomes oxaloacetate. Can oxaloacetate cross the mitochondrial membranes?

Answer 31

No, it can’t. Oxaloacetate is transaminated (swapping of ketone for NH2 group) to form aspartate. Aspartate then travels to the cytosol.

Question 32

What is the purpose of the malate aspartate shuttle?

Answer 32

To transport electrons from cytosolic NADH (produced from glycolysis) to inside the mitochondria so they can be used in the ETC

Question 33

What is the primary way NAD+ is regenerated in the cytosol under anaerobic conditions? and under aerobic conditions?

Answer 33

Anaerobic - fermentation (pyruvate –> lactate)
Aerobic - malate aspartate shuttle, glycerol-3-phosphate shuttle