Metabolism Flashcards
What is metabolism?
The sum of all chemical reactions that take place in a cell or in an organism
Are metabolic pathways similar in diverse groups of organisms?
Yes, they are highly conserved. Indicates they evolved a long time ago
Does every organism have the same metabolic pathways?
No, some pathways like photosynthesis are limited to specific groups of organisms
What are the two purposes of metabolism?
To obtain energy from the environment
To create the molecules that cells require to live and grow
Where do photoautotrophs obtain energy and carbon from?
Energy comes from light, carbon comes from inorganic sources, namely CO2
Where do chemoheterotrophs obtain energy and carbon from?
Both from organic molecules
How is the chemical energy in organic molecules unlocked?
Breaking it down with aerobic respiration
What is catabolism? Is it oxidative or reductive? Exergonic or endergonic?
Breaking down molecules to obtain energy and building blocks. It is oxidative and exergonic and releases electrons and energy
What is anabolism? Is it oxidative or reductive? Exergonic or endergonic?
Building larger molecules from building blocks and energy. It is reductive and endergonic and requires an input of energy and electrons
What 3 biological macromolecules can be used as biological fuels?
Proteins, lipids, carbohydrates
What determines the direction and spontaneity of a reaction?
Free energy change: the DeltaG
When deltaG is negative:
a) which direction is spontaneous?
b) exergonic or endergonic?
Forward direction, exergonic
When deltaG is positive:
a) which direction is spontaneous?
b) exergonic or endergonic?
Reverse direction, endergonic. The forward direction requires energy input to go
When deltaG is zero:
a) which direction is spontaneous?
b) exergonic or endergonic?
Neither. The reaction is at equilibrium
What is the difference between deltaG° and deltaG°’?
deltaG°’ is the biochemical standard state, which also has the solute concentration at 1 mol/L, T = 298 K, P = 1 atm, but also has pH = 7
What is a metabolic pathway?
A series of consecutive, enzyme catalyzed steps
Are the reactions in a metabolic pathway spontaneous?
Yes, they all have to be energetically favourable and directional
What is the deltaG of a reversible reaction?
Close to 0
What determines the direction of a reversible reaction?
The ratio of products to reactants
What controls the rate of a reversible reaction?
The concentrations of reactants and products. The enzymes aren’t regulated
What is the deltaG of an irreversible reaction?
Negative
What controls the rate of an irreversible reaction?
They are regulated, and can be the rate limiting step that determines the overall rate of a reaction
How can an enzyme catalyzing an irreversible reaction be regulated?
- Amount of enzyme made or activated
- Controlling enzyme activity
- Controlling availability of substrate
What are opposing pathways?
One pathway goes from A -> Z and the other goes from Z -> A
