the roles of ATP in living cells Flashcards
what is metabolism?
integrated set of enzymatic reactions comprising both anabolic and catabolic reactions
what is anabolism?
synthesis of complex molecules from simpler ones (necessary energy usually derived from ATP.) Pathways end in genesis
what is catabolism?
breakdown of energy rich molecules to simpler ones (CO2, H2O, NH3). Pathways end in lysis
what happens to energy when it is released from certain reactions?
energy released is captured as adenosine triphosphate (ATP) and stored for later use in anabolic reactions
what is energy required for? 4
what about timing?
- Motion
- Transport
- Biosynthesis of essential metabolites
- Thermoregulation
- Timing of these processes does not necessarily coincide with feeding times so storage forms of food are required.
what type of systems are cells?
what does this mean? 2
- Cells are isothermal systems *maintain constant temperature)
- Heat flow cannot be used as a source of energy (heat can only do work when it passes to an area at a lower temperature)
- Free energy (energy available to perform work) is acquired from nutrient molecules
what is Gibbs free energy (g)? 5
- Energy capable of doing work at a constant temperature and pressure
- Enthalpy (H)= the heat content of the reacting system
- Entropy (S)= the randomness or disorder of a system
- change in Gibbs free energy= change in enthalpy - (temperature x change in entropy)
- the maximum energy that can be obtained from a reaction at a constant temperature and pressure
what does change in enthalpy reflect? 2
the kinds and numbers of chemical bonds that are broken and formed
Positive when energy is absorbed by the reaction
what does change in entropy reflect? 2
the formation of large complex molecules from smaller molecules or vice versa
It is positive when randomness increases (breaking up a big molecule into smaller molecules)
for the reaction A-> B
- What if there is a greater concentration of B than A at equilibrium? 3
- what if there is a greater concentration of A than B at equilibrium? 3
spontaneous or exergonic reaction
- Free energy is defined as negative
- Energy is liberated by the reaction
- Unfavourable or endergonic reaction
- Free energy is defined as positive
- Energy input is required to start the reaction
describe exergonic reactions? 3
- Products have less free energy than reactants and are more stable than the reactants. Formation of product is downhill (spontaneous)
- CATABOLISM= exergonic reactions
- Change in Gibbs free energy will be negative
describe endergonic reactions? 3
- Products have more free energy than the reactants and are less stable. Formation of products is uphill
- ANABOLISM- endergonic reactions
- Change in Gibbs free energy is positive
describe coupling of reactions?
An endergonic reaction can be driven in the forward direction by coupling it to an exergonic reaction through a common intermediate
what is ATP? 6
- adenosine triphosphate
- Provides most of the free energy required for anabolism
- ATP is the energy currency of the cell
- Achieved by phosphate group transfer
- Gibbs free energy: the energy derived from the oxidation of dietary fuels to generate ATP
- Energy is conserved at ATP and is transduced into useful work
what are ATP/ADP Mg2+ complexes? 3
- 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
- An Mg2+ deficiency impairs virtually all metabolism
what is substrate level phosphorylation? 4
- Formation of ATP by phosphate group transfer from a substrate to ADP
- Known as SLP to distinguish it from respiration linked phosphorylation
- SLPs require soluble enzymes and chemical intermediates
- Respiration linked phosphorylation’s involve membrane bound enzymes and transmembrane gradients of protons and require oxygen
what are enzymes? 3
- Biological catalysts that accelerate the rate of chemical reactions
- Creates a new pathway for the reaction; one with a lower activation energy
- Do not influence the free energy change of a reaction
what types of enzyme classification are important to know? 2
- oxidoreductases, transfer of electrons
- transferases, transfer of functional groups
what are cofactors, coenzymes? 5
- Cofactors are non-protein molecules necessary for enzyme activity (metal cations)
- Most coenzymes are organic molecules derived from vitamins
- Participate in enzymatic reactions
- Cycle between oxidised and reduced forms
- Coenzymes/cosubstrates have a loose association with their enzyme and diffuse between enzymes carrying electrons
what are prosthetic groups? 3
- Non protein cofactor that Is covalently bound to the enzyme
- Not released as part of the reaction
- Acts as a temporary store for electrons or intermediates
name two vitamins and the coenzymes they create?
- B2 (riboflavin)= FAD or FMN
- niacin= NAD+
describe the redox coenzymes and prosthetic groups? 5
- Major redox coenzymes/prosthetic groups involved in transduction of energy from dietary foods to ATP= NAD+/ FAD/ FMN
- 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 varied
- NAD+ is reduced to NADH
- FAD is reduced to FADH2
what is NAD+? 5
- 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
- NADH for ATP synthesis
- NADPH for reductive biosynthesis
describe the re-oxidation of redox coenzymes? 2
- Recycling of NADH and FADH2 is via the respiratory chain in the mitochondria
- This is coupled to ATP synthesis- process of oxidative phosphorylation
give an overview of energy metabolism? 7
- proteins, carbohydrates, lipids
- amino acids, glucose, fatty acids and glycerol
- glycolysis
- pyruvate
- acetyl-CoA
- citric acid cycle
- oxidative phosphorylation
give an overview of the intermediates in the timing stages of glycolysis? 10
- glucose (ATP->ADP with hexokinase)
- glucose-6-phosphate (G-6-P)
- fructose-6-phosphate (F-6-P) (ADP->ATP with PRK-1, committed step)
- fructose-1,6-biphosphate (FBP)
- dihydroxyacetone (DHAP)/ glyceraldehyde-3-phosphate(G-3-P) (the one that moves on) (NAD+–>NADH)
- 1,3-biphosphoglycerate (1,3-BPG) (ADP->ATP)
- 3-phosphoglycerate
- 2-phosphoglycerate
- phosphoenolpyruvate (ADP->ATP with pyruvate kinase)
- pyruvate
what are the different fates of pyruvate? 2
- Under aerobic conditions, it is completely oxidised and completely degraded
- In hypoxic conditions, it can be reduced to lactate
