Extracting energy from food molecules Flashcards
What is ATP?
Phosphates are joined by phosphoanhydride bonds which are high energy bonds - lots of energy stored in bonds hence when it is broken energy is released and this energy is used to do cellular work
What is gibbs free energy?
G < 0 then reaction is spontaneous, energy is released, more energy in A than there is in B
G = 0 then reaction is at equilibrium, no change in energy
G > 0 the reaction is non-spontaneous, energy is required, more energy in B than there is in A
What is ATP hydrolysis and ATP synthesis?
ATP hydrolysis - adding a phosphate releases energy, G = -ve
ATP synthesis - removing a phosphate requires energy, G = +ve
Can interchange between the two types
What is reaction coupling?
If one reaction is energetically unfavourable i.e. G=+ve we can couple it with a energetically favourable reaction to drive the necessary unfavourable reaction - reaction coupling
To find the total ∆G we can add the two ∆G together
What is hexokinase reaction coupling?
Hexokinase reaction is the first reaction in glycolysis for glucose to be able to be used for energy, originally an unfavourable reaction but coupled with ATP causing favourable reaction
What is a redox reaction?
Redox reaction - reaction involving transfer of electrons from one molecule to another
OIL RIG - oxidation is the loss of electrons, reduction is the gain of electrons
Thing being oxidised is the reductant/reducing agent and provides reducing power
Thing being reduced is the oxidant/oxidising agent and provides oxidising power
Energy is released in oxidation reactions
What are coenzymes?
Coenzymes are in low concentrations in cells, they can act as carriers and can exist in two forms
What is NAD?
Niacin is used to make NAD
Nicotinate accepts a hydrogen and an electron in metabolic pathways
NAD is involved in redox reactions where two electrons are transferred
NAD can be found in its oxidised form, NAD+, and its reduced form, NADH
What is FAD?
FAD is derived from riboflavin
It accepted two hydrogens in pathways. Flavin enzymes are tightly bound to proteins which they interact with
NAD is in solution whereas FAD always remains tightly associated with the enzymes it interacts with
FAD undergoes a two-electron reduction (accepts two reducing equivalents)
What is CoA?
CoA is derived from pantothenic acid and is not a carrier of electrons (not involved in redox reactions). It carries acyl groups (chains of carbons) and can exist in its free form (CoASH) or in a form where its acyl group attached (Acyl-CoA)
In free form there is nothing bound to CoA (SH), the acyl group is added to the CoA and S in Acyl-CoA form
