Exam 2:

Question 1

Redox reaction

Answer 1

Reaction in which electrons move from a donor (reductant/reducing agent) to an acceptor (oxidant/oxidizing agent)

Question 2

Reducing agent

Answer 2

Electron donor in a redox reaction

Question 3

Oxidizing agent

Answer 3

Electron acceptor in a redox reaction

Question 4

E’

Answer 4

Standard reduction (electrode) potential 
The equilibrium constant for a redox reaction 
Measure of the tendency of the reductant to lose electrons 
More negative reduction potential = more likely to donate (electrons flow towards final acceptor which has the highest potential)

Question 5

deltaG naught’

Answer 5

Free energy released when electrons move from a reductant to an oxidant with a more positive potential

= -nFdeltaE’ where n = # electrons transferred, F = Faraday constant, and delta E’ = (E’acceptor - E’donor)

Question 6

Faraday constant

Answer 6

96.5kJ/mole/volt

Question 7

Types of electron carriers

Answer 7

Flavoproteins
Quinones
Iron-sulfur proteins
Cytochromes

Question 8

Flavoproteins

Answer 8

Protein-composed hydrogen and electron carrier molecules containing Flavin prosthetic group which bonds the H+ and e-
e.g. FAD, FMN

Question 9

Quinones

Answer 9

Lipid-composed hydrogen and electron carrier molecules, contain benzyl ring which confers electron carrying ability
e.g. coenzyme Q, ubiquinone

Question 10

Iron-sulfur proteins

Answer 10

Protein-composed electron carriers containing FeS clusters that act as prosthetic groups to bond the e-
e.g. Ferridoxin

Question 11

Cytochromes

Answer 11

Protein-composed electron carriers with heme prosthetic group that binds the e-
e.g. cytochrome c

Question 12

Complex I

Answer 12

NADH-ubiquinone oxioreductase
First complex in ETC
Coupled to proton extrusion

Question 13

Complex II

Answer 13

FADH2-succinate dehydrogenase
Second complex in ETC
Not coupled to proton extrusion

Question 14

Complex III

Answer 14

Ubiquinone-cytochrome c oxidoreductase, AKA bc1 complex
Third complex in ETC
Coupled to proton extrusion

Question 15

Complex IV

Answer 15

Cytochrome c oxidase, AKA cytochrome aa3
Fourth complex in ETC
Coupled to proton extrusion

Question 16

Coupling sites

Answer 16

Complexes in the ETC that couple electron transfer with extrusion of protons, generating a proton gradient across the membrane that contributes to the proton motive force

Question 17

protons extruded by ETC after electron donation by NADH

Answer 17

6 (donates to complex I, therefore three coupling sites are involved which each extrude 2 protons)

Question 18

protons extruded by ETC after electron donation by FADH2

Answer 18

4 (donates to complex II, therefore two coupling sites are involved which each extrude 2 protons)

Question 19

Differences in bacterial ETC compared to mitochondrial

Answer 19

1. Different pathways to oxygen
   - e.g. may send electrons to cyt 0 either after CII or CIII, bypassing CIV or CIII and CIV
2. Different final acceptor than oxygen
   - e.g. nitrate (inorganic), fumarate (organic)

Question 20

Photobacterium electron transport chain

Answer 20

ETC generates light
NADH donates electrons to flavoprotein, which shunts them to FMN (instead of the cytochrome complexes)
Electrons are then transferred to O2 in a process that uses an enzyme called luciferase and a long chain hydrocarbon to generate light
Both FMN and the hydrocarbon are oxidized as oxygen is reduced
Usually only use this pathway when colonizing tissues of marine animals (symbiotic, help fish to attract mates and deter predators)

Question 21

Oxidative phosphorylation

Answer 21

Process by which energy (proton gradient) from ETC is used to make ATP
ATP synthesis driven by influx of protons and catalyzed by F1F0ATPase
1 ATP generated for every 2 protons extruded by ETC that pass through ATPase on the way back in

Question 22

Chemiosmotic Theory

Answer 22

Membranes pump protons out, generating gradient that can then be used to do useful work (e.g. generation of ATP, flagella rotation, solute transport)

Question 23

deltaP

Answer 23

Proton motive force (mV)
Sum of all charges (proton concentration gradient and other) between cytoplasm and outside of cell
deltaP = deltaPsi - 60 delta(pH)
Most bacteria maintain deltaP between -60mV (minimum needed to do work) and -200mV (max membrane can withstand)

Question 24

delta Psi

Answer 24

All charges of the membrane potential except the proton gradient, contributes to the deltaP of a membrane

Question 25

delta pH

Answer 25

The proton gradient accross membrane, contributes to the deltaP

Question 26

Relative contribution of delta Psi and delta pH to delta P in neutrophiles

Answer 26

both delta psi and delta pH contribute to delta P

Question 27

Relative contribution of delta Psi and delta pH to delta P in acidophiles

Answer 27

delta P almost entirely contributed by delta pH

Question 28

Relative contribution of delta Psi and delta pH to delta P in alkaliphiles

Answer 28

delta P almost entirely contributed by delta Psi

Question 29

Measurement of delta Psi

Answer 29

Measured indirectly using a cation combined with an ionophore or a lipophilic cation

Question 30

Measurement of delta pH

Answer 30

Add radioactively labelled weak acid or base, uncharged molecule freely diffuses, becomes protonated (weak acid) or deprotonated (weak base) - measure radioactivity taken up by cells

for a weak acid: