Oxidative Phosphorylation

Question 1

What is the Structure of F-ATP synthase ?

Answer 1

• Half-channel I allows protons to move one at a time from the exoplasmic medium to the negatively charged side chain of Asp-61 in the centre of a c subunit near the middle of the membrane.
• The proton-binding site in each c subunit is shown as a dotted circle representing the negatively charge on the side chain of Asp-61.
• Half-channel II (Arginine residue) permits protons to move from the Asp-61 of an adjacent c subunit into the cytosolic medium.

Question 2

If the inner membrane is impermeable how does ADP & Pi (and other intermediates) enter the matrix and ATP leave?

Answer 2

A cascade of carriers embedded in the inner membrane that are driven either by Δψ or ΔpH

Question 3

Function of Adenine nucleotide translocase (antiporter) ?

Answer 3

Transports ATP from the matrix into the intermembrane space. Recall that “the outer mitochondrial membrane is semi-permeable to small molecules” and therefore, ATPs are now free to go out to the cytoplasm and participate in a number of reactions. ADP enters the matrix in exchange for the translocation of an ATP

Question 4

Function of Phosphate translocase (symporter) ?

Answer 4

Transports phosphate H2PO4- into the matrix. This is a symporter and one H+ enters with one molecule of H2PO4-.

Question 5

The H+ gradient is also used to ?

Answer 5

Drive some coupled transport processes

• Voltage gradient (ADP-ATP exchange)
• pH gradient (Pyruvate and phosphate import)

Question 6

What is a summary of the Chemiosmotic hypothesis?

Answer 6

ATP synthesis in the inner membrane of mitochondria is driven by the chemical potential (ΔpH) and electrical potential (Δψ ) of the electrochemical gradient of H+ in the intermembrane space compared to the inner matrix of mitochondria. These two potential differences across the membrane is the basis of proton-motive force (Δp) mV

Question 7

Addition of substrates ADP and Pi and succinate initiates ?

Answer 7

The increase of ATP synthesis and O2 consumption

Question 8

CN- inhibits ?

Answer 8

Electron Transport

- inhibits both ATP synthesis and oxygen consumption

Question 9

Ventruricidin and oligomycin inhibit ?

Answer 9

The F-ATP synthase

Question 10

DNP is ?

Answer 10

An uncoupler, a small hydrophobic compound that crosses membranes and releases H+ ions that dissipate the proton gradient

Question 11

Use of compounds that disrupt the inner membrane allows ?

Answer 11

Greater diffusion of H+ ions into the mitochondria

• Triton X100 – detergent
• Valinomycin – transports K+
• Uncouplers – transport H+

Question 12

Uncoupling protein 1 (UCP1) is ?

Answer 12

An integral membrane protein found in the mitochondrial inner membrane of brown adipose tissue, and facilitates the process of non-shivering thermogenesis in mammals

Question 13

Brown adipose tissue is revealed on ?

Answer 13

Exposure to cold

Question 14

Cyanobacteria use ?

Answer 14

Cytochrome b6f, Cytochrome c6, and plastoquinone for both oxidative phosphorylation and photophosphorylation

• In photophosphorylation, electrons flow (blue arrows) from water to NADP+.
• In oxidative phosphorylation, electrons flow from NADH to O2. Both processes are accompanied by proton movement across the membrane, accomplished by a Q cycle

Question 15

Mobile e- carriers in the chloroplast electron transport chain are:

Answer 15

Plastoquinone (Q); Plastocyanin pC; Ferredoxin (Fd).