Week 12: Electron Transport Chain, Oxidative Phosphorylation, Glycogen Degradation Flashcards
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 ________.
phosphoric acid, water
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.
Yes
glucose and fructose, glucose-6-phosphate
one less ATP
unphosphorylated glucose and fructose
______ and _______ are two important forms of control of enzymatic action. ______ plays a more important role in glycogen breakdown.
Allosteric effects, covalent modification
Covalent modification
Which important energy molecule is created from the gradient set up by the electron transport chain?
ATP
The energy stored in the proton gradient is used to phosphorylate ____ to produce _____.
ADP, ATP
What is the role of FADH2 in the electron transport chain?
Reactant
FADH2 is consumed in the electron transport chain.
Which protein has a greater affinity for electrons, cytochrome a or cytochrome c?
Cytochrome a
The proteins in the electron transport chain are arranged in order of increasing ______.
electron affinity
What is the role of water in the electron transport chain?
product
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.
I, III, and IV
ADP phosphorylation
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?
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.
The Q cycle allows the two electrons carried by _____ or ______ to be separated onto ______.
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.
The P/O ratio indicates the extent of coupling of ______ to _______.
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.
Why does ATP production via oxidative phosphorylation require an intact mitochondrial membrane?
The mitochondrial inner membrane allows a _______ to form, and this ______ powers ________.
hydrogen ion gradient
gradient
ATP production
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 _______.
oxidizing
high-energy
electron transport chain
proton gradient
Citric acid cycle, ETC, and oxidative phosphorylation occurs in the ______.
mitochondrial matrix
The respiratory chain (ETC) catalyzes the flow of electrons from _______ carriers to _______ carriers (_____).
Energy is _____ when high energy electrons are transferred to _______.
low reduction potential
high reduction potential (exergonic)
released
oxygen
Higher (more positive) standard reduction potential tells you there is a strong driving force for this half-reaction to happen _______.
in this direction
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 ________
in reverse (an oxidation process)
When you pair two half-reactions, you can calculate the cell potential with:
E0 = E0red - E0oxid
(+) indicates galvanic –> spontaneous
Oxygen forming water is a really _______ reaction.
favorable reduction
Ultimate spot for electrons
∆Grxn under standard conditions:
Non-standard cell potentials:
∆Grxn = -n x F x E0cell
Ecell = E0cell - (RT/nF)lnQ
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?
More energy when electrons are transferred from NADH to Q because bigger gap in energy on standard reduction potential table
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 _____
redox, oxygen
protons, matrix, intermembrane space
proton gradient
Prosthetic groups included in the electron-transport chain:
Fe-S
Heme groups
Copper (CuA and CuB)
Fe-S are iron-sulfur clusters
Iron covalently bound to sulfur in the side chains of ______ groups
cysteine
Complex I:
Conformational change to ______ changes _____ of side chains, allowing them to act as a _____ and accept ______.
Q2- (negatively charged)
pKa
base, a proton
Complex II is NOT a _____, but does provide ______ to complex III using ______.
proton pump
electrons + protons
ubiquinone
Can lower the proton concentration in matrix in two ways:
Both will ______ gradient.
1) pumping protons out to other side
2) bonding protons to some other molecule
INCREASE
Complex III: Ubiquitonal change ______ electrons, cytochrome c _______ protons
transferring
pumping out
Complex IV: Transfer of electrons through _____ and ______ to _____ to pump protons out of the matrix
copper, iron
oxygen
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.
lower redox potential
ATP, oxidation
Which enzyme complex catalyzes the reduction of oxygen to water during oxidative phosphorylation?
cytochrome c oxidase
Which carrier in the electron-transport chain is a protein (as opposed to a small molecule)?
cytochrome c
Complex I enzyme:
Tells you e- transferred from …
NADH-coenzyme Q reductase
Tells you e- transferred from NADH to coenzyme Q
Complex II enzyme:
e- picked up from ____; passed to _____ and then to ______
Succinate-coenzyme Q reductase
succinate, FADH2, ubiquinone (Q)
Complex III enzyme:
Allows transfer of e- from ______ to ______
Cytochrome c Coenzyme Q Oxidoreductase
coenzyme Q, cytochrome C
Cytochrome c is a small _____ protein in the _______.
Carries electrons to ______
peripheral, intermembrane space
complex IV
Complex IV enzyme:
Electrons transferred from ______
Cytochrome oxidase
cytochrome c
The knob, or ______
is made up of ____ and ____ subunits
It performs the _____ function (active site on ____ subunit)
αβ hexamer
3α, 3β
catalytic, β
ADP + Pi –> ATP occurs on these β subunits
Rotor (AKA: central stalk, axel)
____ and ____ subunits
spins _____
γ and ε subunits
360º
Peripheral Stalk (AKA: stator)
made up of ________
serves to stabilize _____ so it doesn’t spin
a, b2, and δ
stabilizes knob
c ring is made up of _____ subunits
spins _______ (______)
8-15 c subunits
360º (spins faster than rotor as its what causes the rotor to spin in the first place)
______ of ATP synthase (______) causes formation of ______
Dimerization (grouping together), cristae (folds)
The binding change mechanism accounts for the synthesis of _____ in response to _______.
ATP, proton flow
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 _____
bind to, be released from
trapped
ATP, ADP and Pi
For every 360º turn of the F1 component, ___ ATP are released
3
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.
protons, ATP
eight
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 ______.
glycerol phosphate
NADH
FADH2
Q
QH2
In the heart and liver, electrons from _____ NADH are used to generate _____ NADH through the _______ shuttle.
The shuttle consists of ____ and ______.
cytoplasmic
mitochondrial
malate-aspartate
two membrane transporters
four enzymes
The ______ enables the exchange of cytoplasmic ADP for mitochondrial ATP.
____ must enter the mitochondria for ____ to leave.
ATP-ADP translocase
ADP, ATP
The ______, the _____, and the _____ are associated with one another to form a large complex, the _____
ATP-ADP translocase
phosphate carrier
ATP synthase
ATP synthasome
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.
ADP, ATP
acceptor or respiratory
energy
The liver breaks down glycogen for release of glucose to the ________ while muscle cells break down glucose for ______ within the cell.
bloodstream
energy use
Glycogen is a highly branched ______ of glucose present in all tissues.
homopolymer (all monomers are glucose)
Phosphoglucomutase is an _____
isomerase
changes where phosphate group is (rearranges it)
catalyzes Glucose-1-phosphate -> Glucose-6-phosphate
Hormonal control of glycogen breakdown:
When fasting, low glucose the pancreas will excrete ______
When exercising, the adrenal medulla will excrete _____
glucagon
epinephrine
Phosphorylase exists in two forms:
b form:
a form:
less active (without phosphates)
more active (with phosphates)
The a form differs from the b form in that a ______ residue 14 is _______.
serine
phosphorylated
Phosphorylation is stimulated by the hormones _____ and _____.
R and T state are controlled by _____
glucagon
epinephrine
allosteric regulators
Phosphorylated version (phosphorylase a) favors ____ state
Unphosphorylated version (phosphorylase b) favors ____ state
R
T
Phosphorylation alters the active site such that ______ that block the active site in the ___ form are removed.
alpha helices
b
R state is more active site because those active sites are more ______.
open
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.
a (phosphorylated, more active)
R
T, reduces, T
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
b (not phosphorylated, less active)
T
R (positive effector)
T
At really high [glucose] _____ will cause cascade that causes ______
insulin
dephosphorylation
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.
blood levels of glucose
glucose
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.
GTPase activity
Phosphodiesterase cAMP, AMP, protein kinase A
Protein phosphatase 1, phosphorylase kinase, glycogen phosphorylase
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.
different
respiratory
ATP synthase
absence
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 _________.
orientation, transferred
positioned, matrix, intermembrane space
The F1 portion of the mitochondrial ATP synthase, which projects into the matrix, is the site of ________.
ATP synthesis
The F0 portion of mitochondrial ATP synthase lies within the inner mitochondrial membrane, but the ______ portion projects into the ______.
F1
matrix
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.
F1,
α3 β3 δ
γε
One full turn of the citric acid cycle yields _______.
3 NADH, 1 FADH2, 1 GTP
Match the following components of the electron transport chain with their reactants:
Complex I:
Complex II:
Complex III:
Complex IV:
NADH
FADH2
QH2
Cytochrome C
As electrons passed between electron carriers in the electron transport chain, the reduction potential of each carrier _______.
increases
How many protons are transported across the inner mitochondrial membrane by Complex II?
0
Which subunit of ATP synthase is responsible for the catalysis of ATP formation?
β
What occurs when the catalytic subunit of ATP synthase is in the loose state?
ADP and Pi bind
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
isocitrate
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
-0.176 V
2 electron transfer
(pyruvate is turning into lactate)
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 _____.
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
What enzymes are required for the liver to release glucose into the blood when an organism is asleep and fasting?
Glycogen phosphorylase
Transferase
a-1,6-Glucosidase
Phosphoglucomutase
Glucose-6-Phosphatase
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.
alpha-1,4 bonds, glucose-1-phosphate
G1P, G6P
3, glucosidase, branch point
alpha-1,6 bonds, free glucose
G6P, glucose
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, ________»_space; _______. 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 _____.
H+ in the intermembrane space»_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
Glucagon or Epinephrine starts a signaling cascade that results in mass ______ of enzymes that will end up converting _____ to the _____ form, activating ______.
phosphorylation
glycogen phosphorylase
a
glycogen degradation
Glucose-6-phosphate stabilizes the ____ state of glycogen phosphorylase, which will ______ glycogen degradation.
T
discourage
AMP stabilizes the ___ state of glycogen phosphorylase, which will _____ glycogen degradation.
R
increase
