1 - Energetics

what is ATP + it’s role in the cell?

adenosine triphosphate - energy currency of the cell.

what happens when ATP is broken down into ADP?

releases energy

why is hydrolysis of ATP energetically favourable?

increases entropy, relieves electrostatic repulsion between phosphate groups and •released phosphate ion is resonance stabilised (means negative charge of Pi is spread out and stabalised)

what is Catabolism?

breaking molecules down to release energy

What is the process of the catabolism of glucose?

breaks down into pyruvate (by glycolysis) → converted into acetyl-CoA + enters TCA cycle → NADH + FADH₂ produced from that enter electron transport chain + drive ATP production

What is the process of the catabolism of Triglycerides?

Triglycerides → broken down into fatty acids → converted into acetyl-CoA + enters TCA cycle → NADH + FADH₂ produced from that enter electron transport chain + drive ATP production

what is the process of the catabolism of amino acids?

Amino acids → broken down → enter TCA cycle → NADH + FADH₂ produced from that enter electron transport chain + drive ATP productionNADH + FADH₂ → ETC → ATP

what is the first law of thermodynamics?

energy cannot be created or distroyed - only transfromed from one form to another.

what is enthalpy, enthalpy change and it’s units?

Enthalpy (H) is chemical bond energy. enthalpy change (ΔH) of a chemical reaction is the sum of energy used when bonds are broken during the reaction and the energy released when new bonds are formed. J/KJ.

what does it mean when ΔH is negative?

heat is lost from the molecules and released to the surroundings and the reaction is exothermic.

what does it mean when ΔH is positive?

heat is taken up by the molecules from the surroundings and the reaction is endothermic.

what is entropy?

entropy (S) is the level of disorder or number of ways somehting can be arranged.

ehat is the second law of themrodynamics?

all processes must increase the entropy of the universe.

what is Gibbs free energy change?

ΔG tells you whether a chemical reaction is energetically favourable and whether it can happen spontaneously or not.

what is the equation for ΔG and what does the answer tell you?

ΔG  = ΔH  -  T ΔS

•T is the temperature in Kelvin.

•ΔG has units, kJ mol^-1

reaction can occur spontaneously if ΔG is –ve

reaction cannot occur spontaneously if ΔG is +ve

what does exergonic

The reaction is energetically favourable

what does endergonic mean?

The reaction is not energetically favourable

how does the value of ΔG change as the reaction reaches equilibrium and what is it at eq?

the value becomes more positive and it is 0 at eq.

what are standard conditions?

•1M concentration of reactants and products

•25°C (298 K)

•pH = 7 (for biological systems)

what does the value of ΔG depend on?

the concentrations of reactants and products.

what is ΔG°’ and what can it be used for?

standard free energy change - Although conditions in the cell are not ‘standard’ , the value of ΔG°’ can give an indication of whether a reaction is likely occur spontaneously in the cell or not.

how does ΔG tell you about the direction of a reversible reaction?

A ⇌ B

ΔG depends on the relative concentrations of A and B.

• Lots of reactant, little product → reaction tends to go forward → ΔG is negative

• Little reactant, lots of product → reaction tends to go backward → ΔG is positive

• Balanced at equilibrium → neither direction is favoured → ΔG = 0

what equation relates ΔG  to ΔG°′?

how can an energetically unfavourable reaction in the cell be achieved?

by ‘coupling’ it to a favourable one (often hydrolysis of ATP)

what is oxidation + reduction?

O = loss of electrons + R = gain of electrons

what is an oxidising + reducing agent?

oa = accepts electrons + ra = donates electrons

what are redox carriers?

a molecule that carries electrons from one molecule to another during a redox reaction.

what is redox potential (E₀^l)?

value given to a redox carrier which tells you about it’s ability to donate its electrons to another electron acceptor molecule.

What does a lower E₀^{l mean?}

It is a better electron donator - electrons flow from more negative E₀^{l to more positive} E₀^l.

redox reaction example

what is the equation which relates ΔG^0’ and ΔE₀’?