4.1 Enzyme Action Flashcards
What is an enzyme?
biological catalysts
interact with substrate molecules to increase rate of reactions.
Usually globular proteins.
What is metabolism?
sum of all reactions in an organism
What are anabolic reactions?
reactions of metabolism
which construct larger molecules from smaller units.
Require energy from hydrolysis of ATP.
(building large molecules from smaller ones)
What are catabolic reactions?
reactions of metabolism
which break large molecules down into smaller units.
Releases energy.
(breaking large molecules into smaller ones)
Anabolic reactions [require/release] energy.
require
Catabolic reactions [require/release] energy.
release
What is the advantage of having enzymes within an organism?
increases rate of reaction without having to increase temperature/pressure to the point where it is unlivable for an organism.
What 2 requirements must be met for 2 reactant molecules to react?
- COLLISION of reactant molecules
- reactants collide more frequently with increase temperature & pressure
- enzymes cause more frequent collisions between reactant molecules
- reactants collide more frequently with increase temperature & pressure
- with SUFFICIENT ENERGY
- colliding molecules must have reached activation energy, Ea, in order to react
What are the 2 hypotheses for enzyme action?
- Lock and Key - only a specific, complementary substrate will “fit” active site
- Induced Fit - active site is flexible, conformational change induced as substrate enters
Describe what occurs in the Lock & Key model of enzyme action:
Active Site: area in tertiary structure, complementary + specific to substrate.
- Substrate successfully collides with active site in tertiary structure
- Substrate binds to active site - enzyme-substrate complex
- R groups on active site interact with substrate (catabolic)
- Puts strain on bonds within substrate
- Products released from enzyme-product complex
Enzyme is unchanged, can take part in subsequent reactions.
(In anabolic reactions, substrates are held in the active site orientated so bonds are formed)
Describe what occurs in the Induced Fit model of enzyme action:
- Substrate successfully collides with active site in tertiary structure
- Substrate enters enzyme - enzyme-substrate complex
- R-group interaction with substrate induces conformational change in active site
- Puts strain on bonds within substrate, breaking them.
- Products released from enzyme-product complex
- Enzyme is unchanged, can take part in subsequent reactions.
What are intracellular enzymes?
enzymes which function within cells
Give an example of an intracellular enzyme & it’s function:
Catalase
Catalyses hydrogen peroxide (toxin) made from metabolic pathways into water & oxygen
Found in both animal & plant cells
H2O2 ⟶ O2 + H2O
What are extracellular enzymes?
Enzymes which function outside of the cell which it originated from
usually digestive
What are extracellular enzymes used for?
Break down large substrates outside cell
into smaller subunits
which can be transported into cell
