27 Flashcards
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)
Flavin adenine dinucleotide
- what is it derived from?
- what does it do?
Accepts two hydrogens in pathways (fatty acid oxidation, citric acid cycle)
Flavin coenzymes are tightly bound to the proteins with which they interact (flavoproteins)
FAD undergoes a ___-electron reduction
FAD undergoes a two-electron reduction
(accepts two reducing equivalents) (gains to hydrogens
Coenzyme A: what os it derived from? What does it carry? What are its two forms?
Derived from pantothenic acid (vitamin B5)
Not a carrier of electrons (not reduced/oxidized)
Carries: acyl groups
CH 3 (CH2 )n CH2COO-
Two forms: free coenzyme A: CoASH
acyl group attached: Acyl-CoA (AcCoA)
Structure of free CoASH and structure of acyl group attached to Acyl-CoA
In free form nothing is bound to the SH
In Acyl-CoA from the acyl groups gets added to the S group
