Week 12: Electron Transport Chain, Oxidative Phosphorylation, Glycogen Degradation

Question 1

How does phosphorolysis differ from hydrolysis?

In phosphorolysis a bond is broken by adding the elements of ______, whereas in hydrolysis a bond is broken by adding the elements of ________.

Answer 1

phosphoric acid, water

Question 2

You are planning to go on a strenuous hike and are advised to eat plenty of high-carbohydrate foods, such as bread and pasta. Your friend prefers to eat candy bars because she claims they will allow her to store as much glycogen from the sucrose they contain as compared to starchy food on a gram-for-gram basis. Is this true?

Sucrose provides ______, both of which can be converted readily to _______.

It is advantageous to eat complex carbohydrates, such as starch, to build up glycogen stores. Phosphorolysis of starch produces glucose-1-phosphate monomers, which require _______ (for glucose phosphorylation) to enter glycogen synthesis as compared to the _______ obtained from sucrose.

Answer 2

Yes

glucose and fructose, glucose-6-phosphate

one less ATP

unphosphorylated glucose and fructose

Question 3

______ and _______ are two important forms of control of enzymatic action. ______ plays a more important role in glycogen breakdown.

Answer 3

Allosteric effects, covalent modification

Covalent modification

Question 4

Which important energy molecule is created from the gradient set up by the electron transport chain?

Answer 4

ATP

Question 5

The energy stored in the proton gradient is used to phosphorylate ____ to produce _____.

Answer 5

ADP, ATP

Question 6

What is the role of FADH2 in the electron transport chain?

Answer 6

Reactant
FADH2 is consumed in the electron transport chain.

Question 7

Which protein has a greater affinity for electrons, cytochrome a or cytochrome c?

Answer 7

Cytochrome a

Question 8

The proteins in the electron transport chain are arranged in order of increasing ______.

Answer 8

electron affinity

Question 9

What is the role of water in the electron transport chain?

Answer 9

product

Question 10

The standard state free energy change for the phosphorylation of ADP to ATP is -30.5 kJ mol-1. Complexes ______ all have electron transfer reactions that are more exergonic than that. Therefore, all three of these complexes produce sufficient energy to be able to drive the _______ reaction.

The standard state free energy change for electron transfer reactions in complex II is -13.5 kJ mol-1, which is not sufficient to drive the ADP phosphorylation reaction.

Answer 10

I, III, and IV

ADP phosphorylation

Question 11

Cytochrome c oxidase, CoQH2-cytochrome c oxidoreductase, and succinate-CoQ oxidoreductase are isolated from mitochondria and are incubated in the presence of oxygen, cytochrome c, coenzyme Q, and succinate. What is the overall oxidation-reduction reaction that can be expected to take place?

Answer 11

Succinate + ½ O2 → Fumarate + H2O

Succinate can transfer electrons through complex II (succinate-CoQ oxidoreductase) to CoQ. The reduced CoQ can pass its electrons through complex III (CoQH2-cytochrome c oxidoreductase) to cytochrome c. Complex IV (cytochrome c oxidase) can then pass the electrons to O2 from cytochrome c. The net reaction would be the conversion of succinate to fumarate with the concomitant reduction of O2 to H2O.

Question 12

The Q cycle allows the two electrons carried by _____ or ______ to be separated onto ______.

Answer 12

NADH, FADH2
two cytochromes

The Q cycle allows a smooth transition from the two-electron carriers (NADH and FADH2) to one-electron carriers (cytochromes) in the electron transport pathway. Handing off two electrons simultaneously to two one-electron carriers would be much more difficult than cycling one electron back to a second carrier as the Q cycle does.

Question 13

The P/O ratio indicates the extent of coupling of ______ to _______.

Answer 13

ATP production, electron transport

The P/O ratio gives the number of moles of phosphate consumed in the reaction ADP + Pi → ATP in oxidative phosphorylation per mole of oxygen consumed in the reaction ½ O2 + 2H+ + 2e- → H2O at the end of the electron transport chain. The P/O ratio is a measure of the coupling of ATP production to electron transport.

Question 14

Why does ATP production via oxidative phosphorylation require an intact mitochondrial membrane?

The mitochondrial inner membrane allows a _______ to form, and this ______ powers ________.

Answer 14

hydrogen ion gradient
gradient
ATP production

Question 15

The whole point of _______ fuels to get those ______ electrons in citric acid cycle is so we can get them to _________ so that energy can be used to create a _______.

Answer 15

oxidizing
high-energy
electron transport chain
proton gradient

Question 16

Citric acid cycle, ETC, and oxidative phosphorylation occurs in the ______.

Answer 16

mitochondrial matrix

Question 17

The respiratory chain (ETC) catalyzes the flow of electrons from _______ carriers to _______ carriers (_____).

Energy is _____ when high energy electrons are transferred to _______.

Answer 17

low reduction potential
high reduction potential (exergonic)

released
oxygen

Question 18

Higher (more positive) standard reduction potential tells you there is a strong driving force for this half-reaction to happen _______.

Answer 18

in this direction

Question 19

Lower (more negative) standard reduction potential tells you there is NOT a strong driving force for this half-reaction to occur in this direction. In fact, this reaction is more likely to happen ________

Answer 19

in reverse (an oxidation process)

Question 20

When you pair two half-reactions, you can calculate the cell potential with:

Answer 20

E0 = E0red - E0oxid

(+) indicates galvanic –> spontaneous

Question 21

Oxygen forming water is a really _______ reaction.

Answer 21

favorable reduction
Ultimate spot for electrons

Question 22

∆Grxn under standard conditions:

Non-standard cell potentials:

Answer 22

∆Grxn = -n x F x E0cell

Ecell = E0cell - (RT/nF)lnQ

Question 23

Would there be more or less energy produced when electrons are transferred from NADH to Q, than when they are transferred from FADH2 to Q?

Answer 23

More energy when electrons are transferred from NADH to Q because bigger gap in energy on standard reduction potential table

Question 24

Electron transport chain is essentially sequential ______ reactions that carry electrons downstream to _____.

Along the way, energy is used to pump _____ out of the ____ into ______ setting up a _____

Answer 24

redox, oxygen

protons, matrix, intermembrane space
proton gradient

Question 25

Prosthetic groups included in the electron-transport chain:

Answer 25

Fe-S Heme groups Copper (CuA and CuB)

Question 26

Fe-S are iron-sulfur clusters Iron covalently bound to sulfur in the side chains of ______ groups

Answer 26

cysteine

Question 27

Complex I: Conformational change to ______ changes _____ of side chains, allowing them to act as a _____ and accept ______.

Answer 27

Q2- (negatively charged) pKa base, a proton

Question 28

Complex II is NOT a _____, but does provide ______ to complex III using ______.

Answer 28

proton pump electrons + protons ubiquinone

Question 29

Can lower the proton concentration in matrix in two ways: Both will ______ gradient.

Answer 29

1) pumping protons out to other side 2) bonding protons to some other molecule INCREASE

Question 30

Complex III: Ubiquitonal change ______ electrons, cytochrome c _______ protons

Answer 30

transferring pumping out

Question 31

Complex IV: Transfer of electrons through _____ and ______ to _____ to pump protons out of the matrix

Answer 31

copper, iron oxygen

Question 32

Electrons carried by FADH2 are not as energy-rich as those carried by NADH because FADH2 has a ________. Consequently, less _____ will be synthesized from the ______ of FADH2 as compared to NADH.

Answer 32

lower redox potential ATP, oxidation

Question 33

Which enzyme complex catalyzes the reduction of oxygen to water during oxidative phosphorylation?

Answer 33

cytochrome c oxidase

Question 34

Which carrier in the electron-transport chain is a protein (as opposed to a small molecule)?

Answer 34

cytochrome c

Question 35

Complex I enzyme: Tells you e- transferred from ...

Answer 35

NADH-coenzyme Q reductase Tells you e- transferred from NADH to coenzyme Q

Question 36

Complex II enzyme: e- picked up from ____; passed to _____ and then to ______

Answer 36

Succinate-coenzyme Q reductase succinate, FADH2, ubiquinone (Q)

Question 37

Complex III enzyme: Allows transfer of e- from ______ to ______

Answer 37

Cytochrome c Coenzyme Q Oxidoreductase coenzyme Q, cytochrome C

Question 38

Cytochrome c is a small _____ protein in the _______. Carries electrons to ______

Answer 38

peripheral, intermembrane space complex IV

Question 39

Complex IV enzyme: Electrons transferred from ______

Answer 39

Cytochrome oxidase cytochrome c

Question 40

The knob, or ______ is made up of ____ and ____ subunits It performs the _____ function (active site on ____ subunit)

Answer 40

αβ hexamer 3α, 3β catalytic, β ADP + Pi --> ATP occurs on these β subunits

Question 41

Rotor (AKA: central stalk, axel) ____ and ____ subunits spins _____

Answer 41

γ and ε subunits 360º

Question 42

Peripheral Stalk (AKA: stator) made up of ________ serves to stabilize _____ so it doesn't spin

Answer 42

a, b2, and δ stabilizes knob

Question 43

c ring is made up of _____ subunits spins _______ (______)

Answer 43

8-15 c subunits 360º (spins faster than rotor as its what causes the rotor to spin in the first place)

Question 44

______ of ATP synthase (______) causes formation of ______

Answer 44

Dimerization (grouping together), cristae (folds)

Question 45

The binding change mechanism accounts for the synthesis of _____ in response to _______.

Answer 45

ATP, proton flow

Question 46

The three catalytic β subunits of the F1 component can exist in three conformations: In the O (open form), nucleotides can ______ or _____ from the β subunit. In the L (loose form), nucleotides are _____ in the β subunit. In the T (tight form), ____ is synthesized from _____

Answer 46

bind to, be released from trapped ATP, ADP and Pi

Question 47

For every 360º turn of the F1 component, ___ ATP are released

Answer 47

3

Question 48

The number of c rings determines the number of ____ required to synthesize a molecule of _____ The c ring of vertebrates consist of ____ subunits, making vertebrate ATP synthase the most efficient known.

Answer 48

protons, ATP eight

Question 49

In muscle, electrons from cytoplasmic NADH can enter the electron-transport chain by using the ______ shuttle. The electrons are transported from _____ to _____ and subsequently to ____ to form ______.

Answer 49

glycerol phosphate NADH FADH2 Q QH2

Question 50

In the heart and liver, electrons from _____ NADH are used to generate _____ NADH through the _______ shuttle. The shuttle consists of ____ and ______.

Answer 50

cytoplasmic mitochondrial malate-aspartate two membrane transporters four enzymes

Question 51

The ______ enables the exchange of cytoplasmic ADP for mitochondrial ATP. ____ must enter the mitochondria for ____ to leave.

Answer 51

ATP-ADP translocase ADP, ATP

Question 52

The ______, the _____, and the _____ are associated with one another to form a large complex, the _____

Answer 52

ATP-ADP translocase phosphate carrier ATP synthase ATP synthasome

Question 53

Electrons do not flow through the electron-transport chain unless ______ is available to be converted into _____. The regulation of oxidative phosphorylation by ADP is called ______ control. This is an example of control by ____ charge.

Answer 53

ADP, ATP acceptor or respiratory energy

Question 54

The liver breaks down glycogen for release of glucose to the ________ while muscle cells break down glucose for ______ within the cell.

Answer 54

bloodstream energy use

Question 55

Glycogen is a highly branched ______ of glucose present in all tissues.

Answer 55

homopolymer (all monomers are glucose)

Question 56

Phosphoglucomutase is an _____

Answer 56

isomerase changes where phosphate group is (rearranges it) catalyzes Glucose-1-phosphate -> Glucose-6-phosphate

Question 57

Hormonal control of glycogen breakdown: When fasting, low glucose the pancreas will excrete ______ When exercising, the adrenal medulla will excrete _____

Answer 57

glucagon epinephrine

Question 58

Phosphorylase exists in two forms: b form: a form:

Answer 58

less active (without phosphates) more active (with phosphates)

Question 59

The a form differs from the b form in that a ______ residue 14 is _______.

Answer 59

serine phosphorylated

Question 60

Phosphorylation is stimulated by the hormones _____ and _____. R and T state are controlled by _____

Answer 60

glucagon epinephrine allosteric regulators

Question 61

Phosphorylated version (phosphorylase a) favors ____ state Unphosphorylated version (phosphorylase b) favors ____ state

Answer 61

R T

Question 62

Phosphorylation alters the active site such that ______ that block the active site in the ___ form are removed.

Answer 62

alpha helices b

Question 63

R state is more active site because those active sites are more ______.

Answer 63

open

Question 64

Default in liver is phosphorylase _____ - Can be in R or T state, but ____ state favored. - Glucose can bind. When it does, it stabilizes the ____ state and _____ activity, since more molecules are in the _____ state.

Answer 64

a (phosphorylated, more active) R T, reduces, T

Question 65

Default in muscle is phosphorylase ____ - Can be in R or T state, but ____ state favored. - High [AMP] will shift more to ____ state - High [ATP] or [glucose] will shift more to ____ state

Answer 65

b (not phosphorylated, less active) T R (positive effector) T

Question 66

At really high [glucose] _____ will cause cascade that causes ______

Answer 66

insulin dephosphorylation

Question 67

A key role of the liver is to maintain adequate ______ Thus, _______ is a negative regulator of liver phosphorylase, facilitating the transition from the R state to the T state.

Answer 67

blood levels of glucose glucose

Question 68

Glycogen degradation is turned off by several mechanisms: 1. The inherent ______ of the G protein renders these proteins inactive. 2. ________ converts _____ into _____, which does not stimulate _________. 3. _________ removes phosphoryl groups from _______ and ________, thereby inactivating the enzymes.

Answer 68

GTPase activity Phosphodiesterase cAMP, AMP, protein kinase A Protein phosphatase 1, phosphorylase kinase, glycogen phosphorylase

Question 69

Electron transport and oxidative phosphorylation are _______ processes. Electron transport requires the _______ complexes of the inner mitochondrial membrane, whereas oxidative phosphorylation requires _______, also located on the inner mitochondrial membrane. Electron transport can take place in the ______ of oxidative phosphorylation.

Answer 69

different respiratory ATP synthase absence

Question 70

What are two advantages of the components of the electron transport chain being embedded in the inner mitochondrial membrane? The components are in the proper ______ for the electrons to be ______ rapidly from one component to the next; if the components were in solution, speed would be limited to the rate of diffusion. A second advantage, which is actually a necessity, is that the components are properly ______ to facilitate the transport of protons from the ______ to the _________.

Answer 70

orientation, transferred positioned, matrix, intermembrane space

Question 71

The F1 portion of the mitochondrial ATP synthase, which projects into the matrix, is the site of ________.

Answer 71

ATP synthesis

Question 72

The F0 portion of mitochondrial ATP synthase lies within the inner mitochondrial membrane, but the ______ portion projects into the ______.

Answer 72

F1 matrix

Question 73

In what sense is mitochondrial ATP synthase a motor protein? The _____ part of mitochondrial ATP synthase has a stationary domain (the _____ domain) and a domain that rotates (the ______ domain). This is exactly the arrangement needed for a motor.

Answer 73

F1, α3 β3 δ γε

Question 74

One full turn of the citric acid cycle yields _______.

Answer 74

3 NADH, 1 FADH2, 1 GTP

Question 75

Match the following components of the electron transport chain with their reactants: Complex I: Complex II: Complex III: Complex IV:

Answer 75

NADH FADH2 QH2 Cytochrome C

Question 76

As electrons passed between electron carriers in the electron transport chain, the reduction potential of each carrier _______.

Answer 76

increases

Question 77

How many protons are transported across the inner mitochondrial membrane by Complex II?

Answer 77

0

Question 78

Which subunit of ATP synthase is responsible for the catalysis of ATP formation?

Answer 78

β

Question 79

What occurs when the catalytic subunit of ATP synthase is in the loose state?

Answer 79

ADP and Pi bind

Question 80

Given the standard reduction potentials of the half-reactions below, which of the following has the greatest tendency to be oxidized? Half-reaction ε°' (V) Fumarate2- + 2H+ + 2e- → succinate2- ε°' = 0.031 Ubiquinone + 2H+ + 2e- → ubiquinol + H2 ε°' = 0.045 NAD+ + H+ + 2e- → NADH ε°' = -0.320 a-ketoglutarate + CO2+ 2H+ + 2e- → isocitrate ε°' = -0.380

Answer 80

isocitrate

Question 81

Given the information below, calculate the actual reduction potential if the concentrations of pyruvate and lactate are 100 µM and 50 µM, respectively. Temperature = 37°C ε°' for pyruvate reduction = -0.185 V

Answer 81

-0.176 V 2 electron transfer (pyruvate is turning into lactate)

Question 82

In complex 1, _____ will give electrons to FMN. FMN then transfers electrons to ______ within the complex that will ultimately give two electrons to _____ to form _____. This _______ molecule will induce _______ changes within the complex that will modify the _____ of the amino acid residues present to allow them to _____ protons in the ______. These protons will be _____ from one amino acid to another until they eventually reach the _______. Two protons will also eventually make their way to ____ to form _____. Since protons are effectively being pulled from the matrix to the intermembrane space, a gradient is forming where there are more protons in the ______ than the _____. Ubiquinone (Q) serves as one of the first electron carriers that connects the _____ carriers from the citric acid cycle (NADH and FADH2) to the _____.

Answer 82

NADH iron-sulfur clusters ubiquinone (Q), Q2- negatively charged conformational pKas pick up matrix shuttled intermembrane space Q2-, QH2 intermembrane space, matrix high-energy electron electron transport chain

Question 83

What enzymes are required for the liver to release glucose into the blood when an organism is asleep and fasting?

Answer 83

Glycogen phosphorylase Transferase a-1,6-Glucosidase Phosphoglucomutase Glucose-6-Phosphatase

Question 84

What enzymes are required for the liver to release glucose into the blood when an organism is asleep and fasting? Describe the role of each. Glycogen phosphorylase: Cleaves ______ in the glycogen chain to release _______. Phosphoglucomutase: Converts ____ to ______ Transferase: Responsible for moving inaccessible branch residues in groups of _____ onto longer chain to allow ______ to cleave off the _______ and then let phosphorylase take over. a-1,6-Glucosidase: Cleaves ______ found on glycogen branch points to release ______ as well as allow for further degradation of the glycogen chain by phosphorylase. Glucose-6-Phosphatase: Hydrolyzes _____ into _______ that can be transported in the blood and carried to other tissues in the body.

Answer 84

alpha-1,4 bonds, glucose-1-phosphate G1P, G6P 3, glucosidase, branch point alpha-1,6 bonds, free glucose G6P, glucose

Question 85

Describe how ATP Synthase works to generate ATP. Start with the proton gradient and describe step by step what happens to generate the ATP. 1) The proton gradient is formed by pumping a large amount of protons from the matrix to the intermembrane space. This way, ________ >> _______. This can also be phrased as _________ < _______. 2) Protons will enter the a subunit of the _____ area of ATP synthase and specifically bind to the _____. As each proton binds to the _____, it will rotate slightly and build up tension. Once enough protons bind, the rotation will lead to the _____ rotating 120°, which will induce a ______ change in each of the three ______. 3) The αβ dimers can be found in one of three conformations: Loose, Tight, and Open. The loose conformation can ______. The tight conformation forces those two molecules close together to synthesize _____. The open conformation will ______. With each 120° rotation of the γ stalk, there is a release of ATP, so a full rotation of the c-ring will always release _____.

Answer 85

H+ in the intermembrane space >> H+ in the matrix pHintermembrane < pHmatrix F0, c-ring, γ stalk, conformational, alpha-beta dimers bind ADP and Pi ATP release ATP 3 ATP

Question 86

Glucagon or Epinephrine starts a signaling cascade that results in mass ______ of enzymes that will end up converting _____ to the _____ form, activating ______.

Answer 86

phosphorylation glycogen phosphorylase a glycogen degradation

Question 87

Glucose-6-phosphate stabilizes the ____ state of glycogen phosphorylase, which will ______ glycogen degradation.

Answer 87

T discourage

Question 88

AMP stabilizes the ___ state of glycogen phosphorylase, which will _____ glycogen degradation.

Answer 88

R increase