Lecture 2.5 Study Guide –Cellular Respiration (2)

Question 1

List the following for the CAC: 
 location? 
inputs? 
outputs?
 net yield?

Answer 1

location: mitochondrial matrix
inputs: 6 NADH, 2 FADH2
outputs: ATP, NADH, FADH2 and CO2
net yield:

Question 2

Describe the reactions used by cells to fully oxidize the remaining two carbons from glucose that are present in acetyl CoA.

Answer 2

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Question 3

Describe key regulatory steps in the citric acid cycle.

Answer 3

the CAC is regulated by feedback inihton at multiple points, where the molecules of NADHand ATP inhibitors of the CAC

Question 4

Compare and contrast glycolysis and the citric acid cycle.

Answer 4

Glycolysis is a linear metabolic pathway for the complete oxidation of glucose into pyruvate lactate and thus generating ATP. CAC is a cyclic pathway involving the oxidation of acetyl CoA into CO2 and H2O.

Question 5

Describe the location & components of the electron transport chain and how a proton gradient is established.

Answer 5

location: inner mitochondrial membrane
components:
Complex 1, Complex 2, Ubiquinone, Complex 3, Cytosone C, Complex 4, ATP synthase

Question 6

Trace the flow of electrons from NADH and FADH2 through the electron transport chain to O2.

Answer 6

“Visible” ATP:

In the citric acid cycle, there is only one reaction which indirectly produces an ATP and this is at step 7.

Connections to Electron Transport and ATP:

Reactions 4, 6, and 10 involve oxidations of an alcohol group to a ketone group with the coenzyme NAD+, which result in the removal of 2 hydrogens and 2 electrons. This is the entry point into electron transport chain. Recall that starting with NAD+, results in the production of 3 ATP for each use of the electron transport chain.

Electron Transport Diagram

How many ATP are produced from one turn of the citric acid cycle starting with NAD+ in the electron transport chain?

Steps 4 = NAD+ = 3 ATP
Steps 6 = NAD+ = 3 ATP
Steps 10 = NAD+ = 3 ATP
NET ATP from = NAD+ = 9 ATP

Step 8 is another oxidation involving the coenzyme FAD. Since FAD is part of the second enzyme complex, only 2 ATP are made with the electron transport chain.

Step 8 = FAD = 2 ATP

Question 7

Explain how the action of ATP synthase to make ATP is dependent on a proton motive force.

Answer 7

The proton-motive force created by the pumping out of protons by the respiratory chain complexes is in the mitochondria of most tissues mainly used to translocate protons through the ATP synthase complex, leading to the formation of ATP from adenosine diphosphate (ADP) and phosphate.

Question 8

Explain the difference between substrate-level and oxidative phosphorylation.

Answer 8

Substrate-level phosphorylation is directly phosphorylating ADP with a phosphate and energy provided from a coupled reaction. … As protons move through ATP synthase, ADP is turned into ATP. The production of ATP using the process of chemiosmosis in mitochondria is called oxidative phosphorylation.

Question 9

acetyl-CoA

Answer 9

a cofactor formed by the oxidative decarboxylation and of pyruvate in glycolysis. this cofactor gets reduced in the CAC

Question 10

ATP

Answer 10

this energy bearing molecule splits into ATP + Pi. ATP isn’t ready to be used immediately

Question 11

ATP Synthase

Answer 11

a turbine in the inner mitochondrial membrane that rotates to make ATP as protons pass-through. Rotation of the central shaft within the lollipop head F1 ATPase pushes α/β dimers through three successive conformations. Successive conformational changes result in ATP synthesis.

NOTE: this protein is considered to be part of the ETC but it is not involved in the transport of electrons;

Question 12

CoA (coenzyme A)

Answer 12

main function is to deliver the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production.

Question 13

complex 1

Answer 13

aka NADH dehydrogenase; oxidizes NADH and transfers the two electrons through proteins containing FMN prosthetic groups and Fe -S cofactors to reduce an oxidized form of ubiquinone (Q). Four H+ are pumped out of the matrix to the intermembrane space

Question 14

complex 2

Answer 14

aka Succinate dehydrogenase; oxidizes FADH2 adn transfers the two electrons through proteins containing Fe-S cofactors to reduced an oxidized form of Q. this complex is also used in CAC step 6

Question 15

complex 3

Answer 15

aka cytochrome c reductase; oxidizes Q and transfers one electron at a time through proteins containing heme prosthetic groups adn Fe-S cofactors to reduce an oxidized form of cytochrome C. A total of 4H+ ions per 2 electrons is transported from the matrix to the intermembrane space

Question 16

complex 4

Answer 16

aka cytochrome c oxidase; oxidizes cytochrome c and transfer each election thru protein contains heme prosthetic groups to reduce oxygen gas which picks up 2 H+ from the matrix to produce water. two additional H+ are pumped out of the matrix to the intermembrane space

Question 17

Cytochrome C

Answer 17

reduced by accepting a single electron from complex 3 and move along eh surface of the ETC, where it is then oxidized by complex 4

Question 18

Electron transport chain (ETC)

Answer 18

aka final step of anaerobic respiration that occurs in the inner mitochondrial membrane; a process that moves hydrogen ions across a membrane to produce large amounts of ATP

Question 19

FAD/FADH2

Answer 19

this electron carrier gets reduced in CAC step 6

Question 20

feedback inhibition

Answer 20

a cellular control mechanism in which an enzyme’s activity is inhibited by the enzyme’s end product. This mechanism allows cells to regulate how much of an enzyme’s end product is produced.

Question 21

fermentation

Answer 21

state process of complete glucose oxidation that occurs under anaerobic conditions

Question 22

glucose oxidation

Answer 22

this process (vis cellular respiration) is a 4-step process involving glycolysis, pyruvate oxidation, the CAC, the ETC, and oxidative phosphorylation

Question 23

H+ electrochemical gradient

Answer 23

The electrochemical proton gradient across the inner mitochondrial membrane is used to drive ATP synthesis in the critical process of oxidative phosphorylation

Question 24

Inner mitochondrial membrane

Answer 24

the site of the last phase of anaerobic respiration

Question 25

Mitochondria

Answer 25

the site of cellular respiration and fermentation

Question 26

Mitochondrial matrix

Answer 26

the space within the inner membrane that serves the site of CAC reactions

Question 27

NAD+/NADH

Answer 27

this electron carrier gets reduced CAC step 3 and 5, and becomes oxidized again in CAC step 8

Question 28

Oxidative decarboxylation

Answer 28

a chemical reaction removes the presence of the carboxyl (COOH) groups and releases a carbon footprint

Question 29

Oxidative phosphorylation

Answer 29

the process in which ATP is formed as a result of the transfer of electrons from NADH or FADH 2 to O 2 by a series of electron carriers.

Question 30

Redox reaction

Answer 30

reactions that involve the transfer of electrons between chemical species

Question 31

Regulatory site

Answer 31

an allosteric site that allows molecules to either activate or inhibit (or turn off) enzyme activity

Question 32

Substrate-level phosphorylation

Answer 32

formation of ATP from ADP and a phosphorylated intermediate, rather than from ADP and inorganic phosphate,

Question 33

Ubiquinone (Q)

Answer 33

reduced by complexes 1 and 2 and move thru the hydrophobic interior of the ETC membrane, where it is oxidized by complex 3

Question 34

acetyl-CoA

Answer 34

a molecule that conveys the carbon atoms from glycolysis (pyruvate) to the citric acid cycle to be oxidized for energy production

Question 35

CAC step 1

Answer 35

Step 1. In the first step of the citric acid cycle, acetyl \text{CoA}CoAstart text, C, o, A, end text joins with a four-carbon molecule, oxaloacetate, releasing the \text{CoA}CoAstart text, C, o, A, end text group and forming a six-carbon molecule called citrate.

Question 36

CAC step 2

Answer 36

Step 2. In the second step, citrate is converted into its isomer, isocitrate. This is actually a two-step process, involving first the removal and then the addition of a water molecule, which is why the citric acid cycle is sometimes described as having nine steps—rather than the eight listed here^3

Question 37

CAC step 3

Answer 37

Step 3. In the third step, isocitrate is oxidized and releases a molecule of carbon dioxide, leaving behind a five-carbon molecule—α-ketoglutarate. During this step, \text{NAD}^+NAD
+
start text, N, A, D, end text, start superscript, plus, end superscript is reduced to form \text{NADH}NADHstart text, N, A, D, H, end text. The enzyme catalyzing this step, isocitrate dehydrogenase, is important in regulating the speed of the citric acid cycle.

Question 38

CAC step 4

Answer 38

Step 4. The fourth step is similar to the third. In this case, it’s α-ketoglutarate that’s oxidized, reducing \text{NAD}^+NAD
+
start text, N, A, D, end text, start superscript, plus, end superscript to \text{NADH}NADHstart text, N, A, D, H, end text and releasing a molecule of carbon dioxide in the process. The remaining four-carbon molecule picks up Coenzyme A, forming the unstable compound succinyl \text{CoA}CoAstart text, C, o, A, end text. The enzyme catalyzing this step, α-ketoglutarate dehydrogenase, is also important in regulation of the citric acid cycle.

Question 39

CAC step 5

Answer 39

Step 5. In step five, the \text{CoA}CoAstart text, C, o, A, end text of succinyl \text{CoA}CoAstart text, C, o, A, end text is replaced by a phosphate group, which is then transferred to \text{ADP}ADPstart text, A, D, P, end text to make \text{ATP}ATPstart text, A, T, P, end text. In some cells, \text{GDP}GDPstart text, G, D, P, end text—guanosine diphosphate—is used instead of \text{ADP}ADPstart text, A, D, P, end text, forming \text{GTP}GTPstart text, G, T, P, end text—guanosine triphosphate—as a product. The four-carbon molecule produced in this step is called succinate.

Question 40

CAC step 6

Answer 40

tep 6. In step six, succinate is oxidized, forming another four-carbon molecule called fumarate. In this reaction, two hydrogen atoms—with their electrons—are transferred to \text{FAD}FADstart text, F, A, D, end text, producing \text{FADH}_2FADH
2
​
start text, F, A, D, H, end text, start subscript, 2, end subscript. The enzyme that carries out this step is embedded in the inner membrane of the mitochondrion, so \text{FADH}_2FADH
2
​
start text, F, A, D, H, end text, start subscript, 2, end subscript can transfer its electrons directly into the electron transport chain.

Question 41

CAC step 7

Answer 41

Step 7. In step seven, water is added to the four-carbon molecule fumarate, converting it into another four-carbon molecule called malate.

Question 42

CAC step 8

Answer 42

Step 8. In the last step of the citric acid cycle, oxaloacetate—the starting four-carbon compound—is regenerated by oxidation of malate. Another molecule of \text{NAD}^+NAD
+
start text, N, A, D, end text, start superscript, plus, end superscript is reduced to \text{NADH}NADHstart text, N, A, D, H, end text in the process.

Question 43

describe how NADH function as a regulator of the CAC

Answer 43

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Question 44

more free energy is harvested during the CAC than during glycolysis, but 1 mole of ATP is produced for each mole of acetyl CoA that enters the cycle. Most of the remaining free energy released during the CAC is

A) converted to KE
B) lost as heat 
C) used to reduce electron carriers 
D) used to reduce pyruvate 
E) used to synthesize ATP

Answer 44

Most of the remaining free energy released during the CAC is
A)

Question 45

Which of the following statements about Coenzyme Q is correct? Select all that apply.
A) between Complex III and Complex IV.
B) It is an integral membrane protein.
C) It accepts electrons directly from NADH and FADH2.
D) It donates electrons to Complex III.
E) It is a small lipid-soluble molecule.

Answer 45

It is the mobile electron carrier that shuttles electrons

A) between Complex III and Complex IV.

Question 46

If mitochondria in which Coenzyme Q has been removed are incubated in the presence of O_{2}, NADH, FADH_{2}, ADP, & Pi, what will be the redox of each of the complexes in the ETC? Select all that apply.

Answer 46

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Question 47

Which of the following statements about Cytochrome C is correct?
It donates electrons to Complex IV.
b
It donates electrons to O_{2}.
c
It is soluble in water.
d
It is the mobile electron carrier that shuttles electrons between Complex II and Complex III.
e
It is a peripheral membrane protein.

Answer 47

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Question 48

If mitochondria in which Cytochrome C has been removed are incubated in the presence of O_{2}, NADH, FADH_{2}, ADP, & Pi, what will be the redox of each of the complexes in the ETC? Select all that apply.

a
Complex I will be reduced.
b
Complex I will be oxidized.
c
Complex II will be reduced.
d
Complex II will be oxidized.
e
Complex III will be reduced.
f
Complex III will be oxidized.
g
Complex IV will be reduced.
h
Complex IV will be oxidized.

Answer 48

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Question 49

Kearns-Sayre syndrome (KSS) is a myopathy (i.e., disease of muscle tissue) associated with mitochondrial disease. KSS results from deletions in mtDNA that cause symptoms including difficulty opening the eyelids, cardiac conduction abnormalities, muscle weakness, cerebellar ataxia, and hearing loss. The most common deletion of mtDNA in KSS results in loss of NADH dehydrogenase.

Which of the following would result if NADH dehydrogenase is deleted? Select all that apply.
The pH difference across the inner membrane would decrease.
b
NADH would not be oxidized.
c
FADH_{2} would not be oxidized.
d
H_{2}O production would decrease.
e
ATP synthesis by oxidation phosphorylation would be increased.

Answer 49

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Question 50

Mitochondrial DNA (mtDNA) is the DNA located in mitochondria, which constitutes only a small portion of the DNA in a eukaryotic cell. In humans, mtDNA encodes only 37 genes, of which 13 encode proteins necessary for mitochondrial function (the remaining 24 encode tRNAs and rRNAs).
One of the genes in mtDNA is the enzyme in Complex I of the ETC. What is the name of this enzyme?

Answer 50

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Question 51

In the electron transport chain, why is the amount of ATP generated by electrons from an NADH molecule more than the amount of ATP generated by electrons from an FADH_{2}. molecule?
Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer.
a
There is more NADH than FADH_{2} made for every glucose molecule that enters cellular respiration.
b
One NADH contributes two electrons whereas one FADH_{2} contributes one electron to the electron transport chain.
c
With NADH, the final electron acceptor is complex I whereas with FADH_{2}, the final electron acceptor is complex II.
d
More protons are pumped across the inner mitochondrial membrane when NADH is the electron donor than when FADH_{2} is the electron donor.
e
More H_{2}O is produced when NADH is the electron donor than when FADH_{2} is the electron donor

Answer 51

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Question 52

Solution A has a pH of 9, solution B has a pH of 3, and solution C has a pH of 8. Which two solutions can be paired across a membrane to create the greatest potential energy gradient, and in which direction will the flow of protons release this energy?
Solution A → Solution B.
b
Solution A → Solution C.
c
Solution B → Solution A.
d
Solution B → Solution C.
e
Solution C → Solution A.
f
Solution C → Solution B.

Answer 52

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Question 53

Which of the following particles can pass through the ATP synthase channel? Select all that apply.
Multiple answers:
Multiple answers are accepted for this question
Select one or more answers and submit. For keyboard navigation...SHOW MORE
a
ADP.
b
ATP.
c
Inorganic phosphate (Pi).
d
Protons.

Answer 53

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