Cell Integrity

Question 1

Where is the bulk of cellular ATP generated?

Answer 1

During oxidative phosphorylation in the inner membrane

Question 2

Where does the Krebs cycle take place?

Answer 2

The matrix of the mitochondria

Question 3

What is the equation for the re oxidisation of NADH?

Answer 3

NADH + 1/2 O2 + H+ —>
NAD+ + H2O

DG= -223 kJ/mol

Question 4

What is the equation for the re oxidisation of FADH2?

Answer 4

FADH2 + 1/2 O2 + H+ —>
FAD + H2O

DG= -170 kJ/mol

Question 5

How many and what type of electron carriers does the electron transport chain consist of?

Answer 5

4 membrane proteins

2 mobile

Question 6

What are the four membrane proteins in the ETC?

Answer 6

Complex I
NADH dehydrogenase

Complex II
Succinate dehydrogenase

Complex III
Q-cytochrome C oxidreductase

Complex IV
Cytochrome C oxidase

Question 7

What are the two mobile carriers involved in the electron transfer chain?

Answer 7

Co enzyme Q (ubiquinone)

Cytochrome C

Question 8

What do complexes I II and IV do in terms of electrons?

Answer 8

Accept them, and in doing so a proton (H+) is pumped into the inter membrane space

Question 9

What is the role of Succinate dehydrogenase (complex II)?

Answer 9

It is an enzyme of the TCA cycle and sits in the inner mitochondrial membrane. It uses FAD as a cofactor and communicates directly with coenzyme Q.

Electrons are passed from FADH2 to coenzyme Q it also picks up a pair of protons, regenerating FAD and forming QH2

Question 10

Does FADH2 or NADH release more protons into the inter membrane space when re oxidised?

Answer 10

NADH

Question 11

Where do NADH and FADH2 enter the electron transport chain?

Answer 11

NADH at complex I

FADH2 art complex II

Question 12

What is the ability of a redox couple to accept/donate electrons called?

Answer 12

Redox potential

Question 13

What does a negative standard redox potential (E0) imply

Answer 13

The redox couple has the tendency to donate electrons and therefore has more reducing power than hydrogen

Question 14

What does a positive E0 imply?

Answer 14

The redox couple has the tendency to accept electrons and there has a greater oxidising power than hydrogen

Question 15

ATP synthase is a multimedia enzyme consisting of two parts. What are these?

Answer 15

F0 : membrane bound

F1 : projects into the matrix

Question 16

What does the oxygen electrode do?

Answer 16

Measures the oxygen concentration in a solution housed within a small chamber

Question 17

What is the oxygen electrode made of?

Answer 17

The base is a Teflon membrane permeable to oxygen. Below this there is a compartment containing a platinum cathode (-ve) and a silver anode (+ve)

Question 18

What happens when around 0.6 V is applied? (Include equations at the anode and cathode)

Answer 18

Oxygen diffuses through the Teflon and is reduced to water at the cathode:
O2 + 4e- + 4H+ —> 2 H2O

The circuit is completed at the anode which is slowly oxidised to AgCl by the KCl electrolyte:

4Ag+ + 4Cl- —> 4AgCl + 4e-

The resulting current is proportional to the oxygen concentration

Question 19

Rough how many grams of ATP do humans possess at a time?

Answer 19

250g

It is recycled ~300 times a day

Question 20

What is respiratory control?

Answer 20

The control of the uptake of oxygen by mitochondria due to the concentrations of ADP and Pi

Question 21

What are metabolic poisons?

Answer 21

Molecules that interfere with either the flow of electrons along the ETC or the flow of H+ through ATP synthase

Question 22

How do cyanide and azide act as metabolic poisons?

Answer 22

They bind with high affinity to the ferric form of the harm group in the cytochrome oxidase complex plucking the final step of the ETC

Question 23

How does Malonate act as a metabolic poison?

Answer 23

It’s shape closely resembles that of succinate so it acts as a competitive inhibitor of succinate dehydrogenase. It slows down the flow of electrons from succinate to ubiquinone

Question 24

How does rotenone act as a metabolic poison?

Answer 24

It’s an isoflavone found in the roots and seeds of some plants. It inhibits the flow of electrons from complex I to ubiquinone

Question 25

How does oligomycin act as a metabolic poison?

Answer 25

It is an antibiotic produced my streptomyces that binds to the stalk of ATP synthase blocking the flow of protons through the enzyme

Question 26

How does dinotrophenol (DNP) act as a metabolic poison?

Answer 26

It is a proton ionophore which can shuttle protons across the inner mitochondrial membranes