Bioenergetics

Question 1

Explain the concept of the ‘reduced bond’

Answer 1

is the oxidation state of C or N.

• C is oxidised: if H in C-H bond decrease & bonds to electroneg. atoms increase
• C is reduced: when the opposite happens

Question 2

How is the energy content of molecules estimated through the use of reduced bonds?

Answer 2

• C-C & C-H reduced bonds = -220kJ/mol
• N-C & N-H reduced bonds = -105kJ/mol
* calculation = # bonds x energy

Question 3

Where does most of the free energy from ATP come from?

Answer 3

from the gamma phosphate (high-energy) in ATP which is unstable and is easily lost during hydolisis

Question 4

If a bottle of ATP is exposed to water molecules in the air what prevents the formation of products through this method?

Answer 4

ATP hydrolysis has a high Ea (200-400kJ/mol) that must be reached for products to be formed. A rxn is least likely because the frequency of successful collisions is not possible w/ H2O(g)

Question 5

Describe coupled reactions

Answer 5

When an exergonic rxn drives an endergonic rxn: heat released from 1st rxn can be used in next rxn

Question 6

Describe hydrolysis of ATP

Answer 6

1. O from H2O binds to P on gamma PO4
2. P detaches off
3. left w/ inorganic phosphate formed + ADP

Question 7

List (& Describe) main e- carriers

Answer 7

• NAD+ & NADP
• FMN & FAD
• Ubiquinone
• Cytochrome proteins: has Fe in heme prosthetic group
• Iron-sulphur proteins: Fe not in heme but as a complex w/ S & joined to protein w/ cysteine residues

Question 8

Most chemical rxns result in: (i.e. the state/conditions that is favourable to be in)

Answer 8

• Low energy (enthalpy*)
• more stable state
• Greatest dispersal of emotional energy (entropy*)

Question 9

What are the laws of thermodynamics?

Answer 9

1st: Energy cannot be created or destroyed, it is transferred and converted from one form to another
2nd: All natural process occur to have minimum potential energy
2nd: Entropy increases (never decrease) i.e. more space=better

Question 10

Describe enthalpy (H)

Answer 10

Energy potential of a system

Question 11

Describe entropy (S)

Answer 11

Matter or energy spreading out (from Hi [ ] -> Lo [ ]) (same as Hi Energy -> Lo E). *Entropy always INCREASE (= + entropy).

Question 12

Describe Gibbs Free Energy (△G)

Answer 12

aka Free energy- energy to do work & makes changes. Tells how far rxn is from equilibrium. Determine if rxn is spontaneous. Only when properties of system is known:
- entropy and enthalpy changes in system & surroundings

Question 13

What does negative or positive free energy mean?

Answer 13

-△G: rxn is spontaneous (exergonic)

+△G: rxn is NOT spontaneous (endergonic)

Question 14

Whats the Gibbs free energy equation?

Answer 14

△G = △H - T△S

• T: temp. (K)
• △S: entropy

Question 15

What’s the equation for Gibbs free energy under STANDARD conditions?

Answer 15

△G = - RT ln K

• △G: energy @ standard cond.
• R: gas constant
• T: temp (K)
• ln: loge
• K: equilibrium constant

Question 16

What’s the equation for Gibbs free energy under NON-standard conditions?

Answer 16

△G = △G’º + RT ln Q

• △G’º: energy at biochemical standard cond.
• Q: actual [R] & [P] not their standard [ ]s

Question 17

What’s the diff. b/w heat & temp. in thermodynamics?

Answer 17

Heat: refers to transfer of energy (enthalpy)
Temp: △s in temp. (cold/hot) bc of the transfer of energy via heat