Lecture 4 - Intro to Bioenergetics

Question 1

What is the role of ATP?

Answer 1

ATP is the common currency for the exchange of energy in all living systems. It plays a central role in energy metabolism as a free energy donor for most energy requiring processes.

Question 2

How is ATP synthesised?

Answer 2

ATP synthesis is coupled by a process referred to as chemiosmosis

The membrane is impermeable to protons so proton pumps move protons from inside to outside the membrane generating a voltage difference

ATP synthase moves H+ back in through the membrane (other pumps will also do this)

Question 3

Define Chemisosmosis.

Answer 3

Chemiosmosis - the coupling of ion electrochemical gradients to carry out cellular work

Question 4

Bioenergetics equations

Answer 4

∆ûS+ = RT ln ([S]I/[S]O) + zF∆E

∆ûS+ = Electrochmeical potential (J/mol)
[S]I = Concentration of ions inside
[S]o = Concentration of ions outside
R = Gas constant
T = Temp in (K)
∆E = Electrochmeical difference (V)
Z = Charge

RT ln ([S]I/[S]O) = chemical potential gradient
zF∆E = electrical potential gradient

Question 5

How can chemiosmotic coupling of the proton circuit and ATP sunthesis be demonstrated?

Answer 5

Chemiosmotic coupling of the proton circuit and ATP synthesis can be demonstrated.
By using an uncoupler such as DNP (illegal weight loss drug - increases metabolism by reducing ATP production.) which makes the membrane leaky to H+ ions and generates heat.
Non-shivering thermogenesis uses this in babies and hibernating animals

Question 6

How do electron transport chains work?

Answer 6

The redox potential becomes more positive as you go down an electron transport chain to the terminal acceptor. The more negative the value means that the substance has a lower affinity for electrons and will therefore readily donate electrons.
Translocation of the H+ occurs through ATP synthase converting the electrochemical gradient to potential energy stored in the phophoanhydride bond of the ATP