Ch 10: Carbohydrate Metabolism 2

Question 1

Acetyl-CoA

Answer 1

contains a high-energy thioester bond that can be used to drive other reactions when hydrolysis occurs

Question 2

Pyruvate dehydrogenase complex

Answer 2

five enzyme complex in the mitochondrial matrix that forms acetyl-CoA from pyruvate but is also inhibited by acetyl-CoA and NADH

Question 3

Pyruvate dehyrdrogenase (PDH)

Answer 3

oxidizes pyruvate, creating CO2; it requires thiamine pyrophosphate (vit B1, TTP) and Mg2+

Question 4

Dihydropropyl transacetylase

Answer 4

oxidizes the remaining two-carbon molecule using lipoic acid, and transfers the resulting acetyl group to CoA, forming acetly-CoA

Question 5

Dihydrolipoyl dehydrogenase

Answer 5

uses FAD to reoxidize lipoic acid, forming FADH2 which can later transfer electrons to NAD+, forming NADH that can feed into the electron transport chain

Question 6

Pyruvate dehydrogenase kinase

Answer 6

phosphorylates PDH when ATP or acetyl-CoA levels are high, turning it off

Question 7

Pyruvate dehydrogenase phosphatase

Answer 7

dephosphorylates PDH when ADP levels are high, turning it off

Question 8

Acetyl-CoA can be formed from

Answer 8

• fatty acids, which enter the mitochondria using carriers

fatty acid couples with CoA in the cytosol to form fatty acyl-CoA, which moves to the intermembrane space

the acyl (fatty acid) group is then transferred to carnitine to form acyl-carnitine, which crosses the inner membrane.

the acyl group is then transferred to a mitochondrial CoA to re-form fatty acyl-CoA, which can undergo B-oxidation to form acetyl-Coa

• carbon skeletons of ketogenic amino acids, ketone bodies, and alcohol

Question 9

Citric Acid Cycle takes place

Answer 9

in the mitochondrial matrix

Question 10

Citric Acid Cycles main purpose is

Answer 10

to oxidize acetyl-CoA to CO2 and generate high-energy electron carriers (NADH and FADH2) and GTP

Question 11

In CAC, Citrate synthase

Answer 11

couples acetyl-CoA to oxaloacetate and then hydrolyzes the resulting product, forming citrate and CoA-SH

regulated by negative feedback from ATP, NADH, succinyl-CoA, and citrate

Question 12

In CAC, Aconitase

Answer 12

isomerizes citrate to isocitrate

Question 13

In CAC, Isocitrate dehydrogenase

Answer 13

oxidizes and decarboxylates isocitrate to form alpha-ketoglutarate

generates the first CO2 and NADH of the cycle and is the

rate limiting step of the citric acid cycle so it is heavily regulated: ATP and NADH are inhibitors, ADP and NAD+ are activators

Question 14

In CAC, alpha-ketoglutarate dehydrogenase complex

Answer 14

acts similarly to PDH complex, metabolizing alpha-ketoglutarate to form succinyl-CoA

generates second CO2 and NADH

inhibited by ATP, NADH, and succinyl-CoA
activated by ADP and Ca2+

Question 15

In CAC, Succinyl-CoA synthetase

Answer 15

hydrolyses the thioester bond in succinyl-CoA to form succinate and CoA-SH. This enzyme generates the one GTP formed in CAC

Question 16

In CAC, Succinate dehydrogenase

Answer 16

oxidizes succinate to form fumarate

flavoprotein (since covalently bonded to FAD) anchored to the inner mitochondrial membrane because it required FAD, which is reduced to FADH2, only one generated in cycle

Question 17

In CAC, Fumarase

Answer 17

hydrolyzes alkene bond of fumarate, forming malate

Question 18

In CAC, Malate dehydrogenase

Answer 18

oxidizes malate to oxaloacetate

enzyme generates the third and final NADH of the cycle

Question 19

Electron Transport Chain

Answer 19

final common pathway that utilizes the harvested electrons from different fuels in the body; it is not the flow of electrons but the proton gradient that ultimately produces ATP
takes place on the matrix-facing surface of the inner mitochondrial membrane

Question 20

NADH donates electrons to the ETC that are

Answer 20

passed from one complex to the next
as ETC progresses, reduction potentials increase until oxygen, which has the highest reduction potential, receives the electrons

Question 21

Complex I (NADH-CoQ oxidoreductase)

Answer 21

uses an iron-sulfer cluster to transfer electrons from NADH to flavin mononucleotide (FMN) and then to coenzyme Q (CoQ) forming CoQH2. Four protons are translocated by complex I

Question 22

Complex II (Succinate-CoQ oxidoreductase)

Answer 22

uses an iron-sulfer cluster to transfer electrons from succinate to FAD and then to CoQ forming CoQH2. No proton pumping occurs here

Question 23

Complex III (CoQH2-cytochrome c oxidoreductase)

Answer 23

uses an iron-sulfer cluster to transfer electrons from CoQH2 to heme, forming cytochrome c as part of the Q cycle. Four protonns are translocated by Complex 3.

Question 24

Complex IV (cytochrome c oxidase)

Answer 24

uses cytochromes and Cu2+ to transfer electrons in the form of hydride ions (H-) from cytochrome c to oxygen, forming water. Two protons are translocated by Comple 4

Question 25

NADH cannot cross the

Answer 25

inner mitochondrial membrane. This means shuttle mechanisms must be used to transfer electrons in the mitochondrial matrix

Question 26

Glycerol 3-phosphate shuttle

Answer 26

electrons are transferred from NADH to dihyfroxyacetone phosphate (DHAP), forming glycerol 3-phosphate. these electrons are then transferred to mitochondrial FAD, forming FADH2

Question 27

Malate-aspartate shuttle

Answer 27

electrons are transferred from NADH to oxaloacetate, forming malate. Malate can then cross the inner mitochondrial membrane and transfer the electrons to mitochondrial NAD+, forming NADH

Question 28

What is the difference between Oxidative Phosphorylation and the ETC?

Answer 28

ETC is made up of the physical set of intermembrane proteins located on the inner mitochondrial matrix, and they undergo redox reactions as they transfer electrons to oxygen, the final electron acceptor. As electrons are transferred, a proton-motive force is generated in the intermembrane space. Oxidative phosphorylation is the process by which ATP is generated via harnessing the proton gradient, and it utilizes ATP synthase to do so

Question 29

What links Oxidative Phosphorylation and the ETC?

Answer 29

By splitting up electron transfer into several complexes, enough energy is released to facilitate the creation of a proton gradient at many locations, rather than just one. Greater the proton gradient, the greater the ATP generation will be. Direct reduction of oxygen by NADH would release a significant amount of energy to the environment, resulting in inefficient electron transport

Question 30

Proton-motive force

Answer 30

electrochemical gradient generated by the electron transport chain across the inner mitochondrial membrane. The intermembrane space has higher conc of protons than the matrix; this gradient stores energy which can be used to form ATP via chemiosmotic coupling

Question 31

ATP synthase

Answer 31

enzyme responsible for generating ATP and ADP and an inorganic phosphate (Pi)

Question 32

Under ATP synthase, the Fo portion is

Answer 32

an ion channel allowing protons to flow down the gradient from the intermembrane space to the matrix

Question 33

Under ATP synthase, the F1 portion uses

Answer 33

the energy released by the gradient to phosphorylate ADP to ATP

Question 34

Glycolysis generates

Answer 34

2 NADH and 2 ATP

Question 35

Pyruvate dehyrogenase generates

Answer 35

1 NADH per molecule of pyruvate; since each glucose molecule forms two molecules of pyruvate, this complex produces a net of 2 NADH

Question 36

Citric Acid Cycle generates

Answer 36

3 NADH, 1 FADH2, and 1 GTP (6 NADH, 2 FADH2, and 2 GTP per molecule of glucose)

Question 37

Each NADH yields

Answer 37

2.5 ATP;

10 NADH forms 25 ATP

Question 38

Each FADH2 yields

Answer 38

1.5 ATP;

2 FADH2 from 3 ATP

Question 39

GTP are converted to

Answer 39

ATP

Question 40

32 (30-32) ATP per molecule of glucose from

Answer 40

2 ATP from glycolysis
2 ATP (GTP) from citric acid cycle
25 ATP from NADH
3 ATP from FADH2