The roles of ATP in living cells and the mechanisms of production of ATP Flashcards
Define metabolism
Metabolism: integrated set of enzymatic reactions comprising both anabolic and catabolic reactions
Define anabolism and catabolism
Anabolism: synthesis of complex molecules from simpler ones (necessary energy usually derived from ATP)
Catabolism: breakdown of energy- rich molecules to simpler ones (CO2 H2O and NH3)
How is energy released from catabolism?
(energy released is ‘captured’ as adenosine triphosphate (ATP) and stored for later use in anabolic reactions
Which processes make up metabolism?
Anabolism: synthetic reactions - the pathways end in ‘genesis’ e.g. glycogenesis (synthesis of glycogen from glucose)
Catabolism: breakdown reactions - the pathways end in ‘lysis’ e.g. glycolysis (breakdown of glucose to pyruvate)
What is energy required for?
§Motion (muscle contraction)
§Transport (of ions/molecules across membranes)
§Biosynthesis of essential metabolites
§Thermoregulation
Why is stored energy needed?
Timing of these energy-requiring processes does not necessarily coincide with feeding times so storage forms of food are required
What is an isothermal system?
- Cells are isothermal systems
- Heat flow cannot be used as a source of energy (heat can only do work when it passes to an area or an object at a lower temperature)
- Free energy (energy available to perform work) is acquired from nutrient molecules
Define
Gibbs free energy
Enthalpy
Entropy
- Gibbs free energy (G) – energy capable of doing work at constant temperature and pressure
- Enthalpy (H) – the heat content of the reacting system
- Entropy (S) – the randomness or disorder in a system
What is the gibbs free energy equation?
What is the gibbs free energy of a reaction?
Gibbs free energy of a reaction – maximum energy that can be obtained from a reaction at constant temperature and pressure
For the reaction A -> B
State what will happen if -
If greater concentration of B than A at equilibrium:
If greater concentration of A than B at equilibrium:
What is an exogernic reaction?
Products have less free energy than reactants and so are more stable than the reactants. Formation of product is “downhill” (spontaneous)
What is an endogernic reaction?
Products have more free energy than reactants and so are less stable than the reactants. Formation of product is ‘uphill’
What kind of reaction is this and is the gibbs free energy positive or negative?
What kind of reaction is this and is the gibbs free energy positive or negative?
What is coupling of reactions?
An endergonic reaction can be driven in the forward direction by coupling it to an exergonic reaction through a common intermediate
How would these reactions be coupled?
What is the role of ATP?
- ATP provides most of the free energy required for anabolism
- ATP is the energy currency of the cell
What is gibbs free energy in relation to ATP?
•Gibbs free energy: the energy derived from the oxidation of dietary fuels to generate ATP
Energy is conserved as _____ and is transduced into useful work
ATP
Complete the diagram on the structure of ATP
What is the role of Mg2+ in ATP?
- ATP in the cytosol is present as a complex with Mg2+
- Mg2+ interacts with the oxygens of the triphosphate chain making it susceptible to cleavage in the phosphoryl transfer reactions
What is the result of a Mg2+ deficiency?
A Mg2+ deficiency impairs virtually all metabolism
Label the compounds
What is Substrate level phosphorylation (SLP)?
- Formation of ATP by phosphate group transfer from a substrate to ADP
- Known as SLP to distinguish it from respiration-linked phosphorylation
How is the difference between substrate level phosphorylation and respiration-linked phosphorylation?
- SLPs require soluble enzymes and chemical intermediates
- Respiration-linked phosphorylations involve membrane-bound enzymes and transmembrane gradients of protons and require oxygen
Label the diagram on substrate level phosphorylation
What are enzymes and how do they work?
- Biological catalysts that accelerate the rate of chemical reactions
- Creates a new pathway for the reaction; one with a lower activation energy
Draw an energy profile with and without a catalyst
Do enzymes change the gibbs free energy?
Complete the table on enzyme classification
What are cofactors?
•Cofactors are non-protein molecules necessary for enzyme activity e.g. metal cations
What are coenzymes?
•Most coenzymes are organic molecules derived from vitamins
What is the role of coenzymes and cofactors?
- Participate in enzymatic reactions
- Cycle between oxidised and reduced forms
Complete the diagram on types of cofactors
How do coenzymes/cosubstrates work?
Have a loose association with their enzyme
Diffuse between enzymes carrying e-
What are prosthetic groups?
- Non-protein cofactor that is covalently bound to the enzyme
- Not released as part of the reaction
- Acts as a temporary store for e- or intermediates
Name 2 vitamin precursers of imporant coenzymes/cofactors/prosthetic groups
B2 (Riboflavin)
Niacin
Complete the table on vitamin precursers
What are the major redox coenzymes/prosthetic groups?
•Major redox coenzymes/prosthetic groups involved in transduction of energy from dietary foods to ATP: NAD+ / FAD / FMN
How do redox coenzymes/prosthetic groups work?
- Electrons are transferred from dietary material to these carriers -> coenzymes are reduced
- In each case two electrons are transferred but the number of H+ moved varies
e.g. NAD+ is reduced to NADH
FAD is reduced to FADH2
What is the role of Nicotinamide adenine dinucleotide (NAD+)?
NAD+ and NADP+ accept pairs of electrons to form NADH or NADPH
It is the nicotinamide that is the functional part of the molecule
i) NADH for ATP synthesis
ii) NADPH for reductive biosyntheses
What is the reduced and oxidised form of Nicotinamide adenine dinucleotide (NAD+)?
How does Re-oxidation of redox coenzymes occur?
- Recycling of NADH and FADH2 is via the respiratory chain in the mitochondria
- This is coupled to ATP synthesis - process of oxidative phosphorylation
Where does this happen?
Where does glycolysis occur?
Cell cytoplasm
Complete the diagram
Each reaction from G-3-P occurs ______ for every glucose molecule metabolised
Each reaction from G-3-P occurs twice for every glucose molecule metabolised
SLP: substrate level phosphorylation
Label the diagram of glycolysis
What reaction happens at the priming stage?
Priming stage
- uses 2 ATP and produces two C3 molecules which are interconvertible:
DHAP⇄ GAP
What is produced from the payoff stage?
Payoff stage
- generates 4 ATP and 2 NADH and various intermediates
What are the 2 possible fates of pyruvate?
- Under aerobic conditions, oxidation and complete degradation
- In hypoxic conditions, it can be reduced to lactate
Why has this system of lactate production evolved?
To allow glycolysis to continue in anaerobic conditions by oxidising NADH to NAD+ for use in glycolysis