Lecture 4: Cellular Respiration - Exam 3

Question 1

What is electron transport?

Answer 1

Electron transport refers to the current of electrons in the cell membrane of prokaryotes (and mitochondrial and chloroplast membranes).

Question 2

What is the Electron Transport Chain?

Answer 2

Electrons flow spontaneously down an energy gradient through a series of electron carriers.

Question 3

At specific points in the chain of carries, called coupling sites, something happens with protons. What is it?
There is also energy released in this process. What is it conserved as?

Answer 3

Protons are translocated across the membrane and an electrochemical proton potential is created at these sites.
The energy that is released is conserved as a proton motive force.

Question 4

Electron transport in membranes is referred to as?

Answer 4

Respiration

Question 5

What is the difference between aerobic and anaerobic respiration?

Answer 5

If oxygen is the final electron acceptor in the electron transport chain, this mechanism is referred to as aerobic respiration.
If other compounds are the final electron acceptors in the ETC, the mechanism is referred to as anaerobic respiration.

Question 6

The final e- acceptor can be _____ (oxygen, nitrate, sulfate) or _____ (fumarate).
The name of the respiration is derived from?

Answer 6

organic ; inorganic
The name of respiration is derived from the final electron acceptor.

Question 7

What is the main energetic purpose of respiratory electron transport pathway?

Answer 7

Is to convert redox potential (deltaEh) into a proton potential (deltap).

Question 8

What happens to the energy carriers, NAD+ and FAD+, during central metabolism processes (glycolysis, krebs cycle)?
What are NAD+ and FAD+?
What does NADH act as?

Answer 8

They are reduced (accept e-).
NAD+ and FAD+ are coenzymes (essential to the function of an enzyme).
NADH acts as primary electron donor to the ETC.

Question 9

How does ETC contribute to PMF?

Answer 9

Two electrons from NADH are removed by the first electron carrier protein complex in the cytoplasmic membrane (NADH Dehydrogenase).
- These electrons are then transferred to the next strongest
electron receptor and this transfer releases energy that allows
H+ to be pumped across the membrane, creating a PMF.
- Through multiple redox reactions, the electrons travel down the
ETC to the terminal electron receptor (oxygen in aerobic respiration).
As these protons re-enter the cell through ATP synthase, ATP is
generated

Question 10

What are redox reactions? Why are they important?

Answer 10

Are oxidation-reduction chemical reactions in which reactants undergo a change in their oxidation states and involve the transfer of electrons from one species to another.
They are important because in order for the cell to generate ATP, multiple redox reactions must occur.

Question 11

What is oxidation?
What is an oxidizing agent?

Answer 11

Oxidation = losing electron(s) (becoming more positive)
Electron acceptor = oxidizing agent = oxidant = substance that is getting reduced

Question 12

What is reduction?
What is a reducing agent?

Answer 12

Reduction = gaining electron(s)
Electron donor = reducing agent = reductant = substance that is getting oxidized.

Question 13

What is a good reducing agent? What is a good oxidizer?

Answer 13

A good reducing agent is one that readily donates electrons (NADH).
A good oxidizer is one that readily accepts electrons (oxygen)

Question 14

Oxidation of one molecule is always _____ with reduction of another molecule.

Answer 14

coupled

Question 15

The tendency to donate or accept electron(s) depends on the ______.

Answer 15

Redox pair

Question 16

What is reduction potential (Eh)?
How is it measured?
What kinds of molecules are better electron donors?

Answer 16

Tendency to either donate or accept electron(s) of a molecule.
Measured electrically in volts.
The molecules with more negative Eh are better e- donors = e- spontaneously flow to molecules with more positive Eh values.

Question 17

What is the redox potential equation?

Answer 17

ΔEh = Eh (acceptor) – Eh (donor)

Question 18

The larger the ΔEh is, the energy released in the reaction…?**

Answer 18

The larger the ΔEh is, the larger the energy released in the reaction.

Question 19

Describe the flow of electrons.

Answer 19

Electrons move through the ETC from a higher to lower energy state.

Question 20

What is the electron tower?

Answer 20

Bacteria go for the electron acceptor that yields the highest energy, and then moves down the tower when they are depleted.
Ex:

O2
H2O
(Aerobic)
—————————————————–
NO3
SO4
(Anoxic)
——————————————————
Iron
CO2
Hydrogen
(Anaerobic)