Bioenergetics

Question 1

Structure of the Mitochondria:

Answer 1

1. Outer membrane
2. Inner membrane (Mostly Impermeable)
3. Intermembrane space (Small area of total space, means it has a small volume. Therefore with a small amount of solutes you can have a high concentration)
4. Matrix

Question 2

Biogenesis of a Mitochondrion:

Answer 2

Fusion: 2 Mitochondira become 1
Fission: 1 Mitochondrion becomes 2

Directed by proteins within the outer an inner membranes:
mfn1 and mfn2 (mitofusin proteins) are involved in fusion.
Drp1 (a cytoplasmic GTPase, forms a ring that constricts, like cytokinesis) is involved in fission.

Question 3

Mitophagy

Answer 3

The degradation of a mitochondrion.
Is usually triggered by starvation, in order to regain the constituent parts.
Is regulated by PINK1 (Which is linked to Parkinsons). Build up of PINK1 leads to ubiquitination of a protein channel called VDAC, leading to degradation of the mitochondrion.

Question 4

How much free energy is in a proton gradient? (Formula for chemical, and for electrical)

Answer 4

FOR ANY CHEMICAL GRADIENT:
ΔG = R * T * ln([inside]/[outside])

Gas constant ‘R’ = 8.314 J K^-1 mol^-1
T = absolute temperature (K)

FOR ANY ELECTRICAL GRADIENT:
ΔG = n * F * Δψ

Δψ = Difference in voltage between the intermembrane space and the matrix (Note: Matrix minus IMS)
n = charge on ion to move
Faraday constant F = 96.5 kJ mol^-1 V^-1

Simplified equation:
Δp (mV) = Δψ - 61ΔpH
This equation shows that voltage (x 1) is the stronger force than pH (x -61).

Question 5

Redox Potential

Answer 5

A measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and thereby be reduced or oxidised.

Measured in volts (V), or millivolts (mV).

Question 6

How are electrons transferred within proteins?

Answer 6

By cofactors:
e.g. rubredoxin (1 e- at a time)
flavins (FAD etc.) (2 e- at a time)
haem (1 e- at a time)

Question 7

How are electrons transferred outwith and between proteins?

Answer 7

In the lipid bilayer:
e.g. Ubiquinone 
Menaquinone 
Demethylmenaquinone
(quinones can carry 2 electrons at a time)

Question 8

Before Complex BLANK of the Electron Transport Chain, electrons are contributed to a BLANK.

Answer 8

Before Complex III of the Electron Transport Chain, electrons are contributed to a quinone pool.

Question 9

Chemical Uncouplers

Answer 9

Make the inner membrane permeable to H+ by inserting themselves within the bilayer.
The free energy is released as heat.
Occurs naturally in brown adipose tissue (BAT)
Big interest in understanding BAT to treat obesity.