Membrane Dynamics Flashcards
Enzymes
Metabolism
The sum of all the chemical reactions that occurs within a living cell/tissue/organism
What is a metabolic pathway?
A series of steps beginning with a molecule (metabolite) with a different enzyme that catalyses each step
What is a catabolic pathway?
They release energy by breaking down complex molecules into simple compounds
What is an example of a catabolic pathway?
Cellular respiration (sugar broken down to CO2 and water in the presence of oxygen)
What are anabolic pathways?
They consue energy to build complex molecules from simpler compounds
What is an example of an anabolic pathway?
Amino acid synthesis
What are the advantages of multi-step pathways?
- Multiple points to control how fast the reactions occur
- Ability to divert ‘pathway intermediates’ to other pathways to do other things
- Changes to metabolism through evolution
All the pathways are interconnected by what?
Metabolic webs/grids
What are the forms of energy?
Kinetic energy
Thermal energy
Potential energy
Chemical energy
What is the 1st Law of Thermodynamics?
Energy cannot be created or destroyed, only converted or transformed
What is the 2nd Law of Thermodynamics?
Entropy increases in isolated systems
Increase in entropy can cause a process to proceed..
Spontaneously (doesn’t require energy) (does not mean instantaneously)
Are energy transformations 100% efficient?
No
Some energy is lost as heat
Do we need a continuous input of energy to keep order in the system?
Yes (ex. eating)
What is free energy?
The amount of energy in the system
Reactants have an initial free energy state
Products have a final free energy state
Does breaking bonds take or release energy?
Take
Does forming bonds take or release energy?
Release
Does metabolism reach equilibrium?
NO (the cell would be dead)
What are the 3 kinds of work the cell does?
- Chemical work
- Transport work
- Mechanical work
What is broken by hydrolysis to release energy in ATP?
The P-O bond
Why do enzymes speed up reactions?
Because they are catalysts
Enzymes bind the reactant molecules so that they put stress of specific bonds of the reactant which lowers the activation energy making the bonds easier to break
What is energy coupling?
Using energy from an exergonic reaction to drive an endergonic process
What is activation energy?
The energy required to get the molecule ready to break
What speeds up the rate of a specific reaction without being consumed themselves or changing the overall G of the reaction?
Enzymes
What is the reactant molecule?
The enzyme’s substrate
What is an enzyme-substrate complex?
When an enzyme binds to the substrate
What has a specific 3D configuration to bind to the substrate?
The R-groups in the active site
What is the induced-fit model?
A theory that suggests that the active site and substrate are not a perfect match initially, but rather the substrate induces a change in shape in the enzyme
(shaking hands)
The rate at which the enzyme facilitates the reaction is determined by?
The concentration of the substate (more substrate = faster reaction to a limit)
Enzyme shape dictates?
Function
How does the environment in which the enzyme occurs affects its activity?
Increased temperature can speed up a reaction until it denatures
pH can denature a protein (proteins have differences in their optimal pH)
What are cofactors?
Helpers for initiate catalysis
Drugs and toxins work by?
Inhibiting enzymes
What is substrate inhibition?
A competitive inhibitor molecules resembles the substrate and binds to the active site so that the actual substrate can’t bind, slowing the rate of the reaction
What is feedback inhibition?
The inhibitor molecule binds elsewhere on the enzyme, changing the enzyme shape and the active site cannot bind with the substrate
What is allosteric regulation?
Occurs in enzymes with quaternary structures where each subunit has an active site
What is cooperativity?
A substrate binds to one unit, which stabilizes the active state on the other units (ATP and ADP regulate enzymes in cellular respiration this way)
What is allosteric activation?
A regulatory molecule binds to a regulatory site which stabilizes the active state
What is allosteric inactivation?
A regulatory molecule binds to a regulatory site which stabilizes the inactive state
