Enzymes Flashcards
For a reaction to proceed spontaneously, /\G must be…?
The rate of reaction is not affected by…?
-ve
magnitude of /\G
Which RNA molecules act as catalysts?
Ribozymes
Why do some reactions with -ve /\G occur slowly?
Energy input is needed to convert reactants into transition-state species
What are transition-state species?
Unstable molecular forms
Define activation energy
Ea
Energy barrier that prevents reactants becoming products spontaneously
What can increase the free energy of a reaction?
When is this not a feasible solution? Why?
Increase temp
- -> molecules have greater energy content
- -> can overcome activation energy barrier
Biological systems
- speeds up breakdown of membranes + proteins
How do enzymes generally work?
Alter the nature of transition-state species
- reduce energy level of transition state OR increase energy level of ground state
(=reduces energy barrier between ground + transition state)
How do enzymes reduce activation energy?
Enzymes release free energy when they bind to substrates
- free energy released when multiple weak bonds + interactions form between the enzymes + substrate
What are enzyme active sites complementary to?
The intermediate states
which substrates pass as they’re converted to products
What are the 3 chemical events that occur at active sites?
- Orient + bring together substrates
- Add charges to substrate
- Induce strain on substrate
How can enzymes prevent the hydrolysis of substrates?
Enzyme changes shape when it binds to substrate
- -> engulfs
- -> prevents water entering active site
What are the 7 enzyme groups?
Oxidoreductases Transferases Hydrolases Lyases Isomerases Ligases Translocases
What do oxidoreductases catalyse?
transfer of electrons to or from substrates
= reduces or oxidises
What do transferases catalyse?
transfer of functional groups e.g. phosphate between molecules
What do hydrolases catalyse?
cleavage of bonds by adding water
What do lyases catalyse?
removal of a group to form a double bond OR
addition of a group to a double bond
(doesn’t add anything??)
What do isomerases catalyse?
intramolecular rearrangements
What do ligases catalyse?
reactions where 2 molecules are joined
What do translocases catalyse?
transfers from 1 side of barrier to another e.g. across membranes
What can alter enzyme function?
Mutations
