27 Flashcards
(28 cards)
Cells require
Energy
What is ATP
the major energy intermediate (currency) of the cell
What bonds do ATP consist of and what is their key feature
Phosphoanhydride bonds
- they are very high energy
If a cell is going to spend ATP, the cell needs an…
…ATP income (ATP synthesis)!
The ΔG (change of free energy) of a reaction tells us about:
- The relative abundance of the substrates and products
- The energy stored in the chemical bonds of the products and
substrates
ΔG < 0
ΔG < 0 for A —> B : reaction is spontaneous/ energy released/
energetically favourable
(Energy is higher then B)
ΔG = 0
ΔG = 0 for A —-> B : reaction is at equilibrium/ no change in energy
ΔG > 0
ΔG > 0 for A —-> B : is not spontaneous/ energy required/ energetically unfavourable
ATP hydrolysis is genergetically_______
ATP synthesis is genetically_______
ATP hydrolysis is energetically favourable (ΔG’ = -30 kJ/mol)
ATP synthesis is energetically unfavourable (ΔG’ = 30 kJ/mol)
Delta G is specific to…
- a specific reaction under specific conditions
Delta G’ under standard conditions
All reactants 1M
PH 7
Reaction coupling
If ΔG1 + ΔG 2 < 0 then coupled reaction is energetically favourable
Enzymes often couple reactions to drive necessary unfavourable reactions
Reaction coupling example - the hexokinase reaction (glycolysis first step) what does it do (in terms of coupling) to make glucose 6-phosphate.
Pathways for processing food molecules for ATP synthesis - two key reaction types?
1 . Those involving ADP and ATP
2. Redox reactions Fuel molecules get oxidized - something needs to be reduced (provide the oxidizing power)
Coenzymes: NAD and FAD are reduced
Redox reactions involve
Redox reactions involve the transfer of electrons (e -)
What to biological redox reactions involve? What kind of enzymes catalyse these reactions
Biological redox reactions often involve the transfer of hydrogen atoms (includes an e -)
Hydrogen referred to as a reducing equivalent
The enzymes that catalyse these reactions are often called dehydrogenases ( e.g. lactate dehydrogenase)
How much energy is realises from carbohydrate and lipid respectively.
Stepwise oxidation of fuel molecules occurs in the pathways - how does this compare to the direct burning of sugar?
- a number of little oxidation’s reassessing a little bit of energy each time to be captured in ATP
Features of co-enzymes and features of co-enzymes for the pathways
• Class of co-factors
• Small organic molecules
• Co-substrates
• Often derived from vitamins
Key features for the pathways:
• Low concentration in cells
• Act as carriers
• Exist in two forms
Nicotinamide adenine dinucleotide - what is it derived from? What is its structure and what does it do?
Derived from Niacin (vitamin B3)
Accepts a hydrogen and an electron in metabolic pathways (glycolysis, fatty acid oxidation, citric acid cycle)
NAD undergoes a ____-electron reduction
NAD undergoes a two-electron reduction ( accepts two reducing equivalents)
Two forms of NAD - and example of the reaction
NAD+ NADH
(oxidized form) (reduced form)
