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
