Enzymes Flashcards
What are anabolic reactions?
Larger molecules built up from smaller ones
Give examples of anabolic reactions
Protein synthesis and making polysaccharides
What are catabolic reactions?
Larger molecules are broken down
Give some examples of catabolic reactions
Digestion
Give an equation for metabolism
Catabolism + anabolism
What is a catalyst?
A substance that increases the rate of a reaction while remaining chemically unchanged itself
What are enzymes?
Biological catalysts
What is a substrate?
A molecule that binds to the active site of an enzyme to form an enzyme-substrate complex
What is the active site?
The small part of the enzyme that binds to its specific substrate and causes catalysis
Explain the induced fit hypothesis
Shape of the active site moulds to the substrate which is not an exact fit to start with. Binding with the active site causes the shape to change slightly so that it’s complementary
What is the activation energy?
The energy barrier that must be overcome before reactants reach their temporary transition state
How do enzymes increase the rate of reaction
Lowers the activation energy by offering an alternative reaction pathway which has a lower activation energy
Why are enzymes so specific?
Precise tertiary shape
Active site has specific shape
Substrate must be complementary with this
What is the transition state?
The unstable intermediate molecules form before the become products
What factors affect the rate of reactions on enzymes?
Temperature
pH
enzyme concentration
substrate concentration
How does temperature affect the rate of reaction of enzymes?
Increasing temp increase rate bc more kinetic energy - more collisions with more energy
Too much kinetic energy causes bonds to break. Shape of active site changes + no longer complementary
Too little Ke and not enough energy for enzyme-substrate complexes to form
What is the optimum temperature?
The temp at which the rate of an enzyme controlled reaction is fastest
What is the optimum pH?
The pH at which an enzyme catalysed reaction is fastest
How does pH affect rate of reaction of enzymes?
Affects hydrogen bonds
Changes bonding patterns
Changes the shape of the active site
No longer complementary
What is a limiting factor?
Any factor that limits the rate at which a reaction can occur
What is an enzyme inhibitor?
A substance that slows the rate of an enzyme-controlled reaction by preventing binding to the active site
How do competitive inhibitors work?
Similar shape to substrate
Complementary to active site
Blocks active site so substrate can’t bind
Reaction doesn’t take place
How do non-competitive inhibitors work?
Binds to allosteric site on the enzyme (not active site)
Change to 3D structure
Causes a change in the shape of the active site of the enzyme
Substrate no longer complementary
What is end product inhibition?
When the product of the late reaction in a series of reactions inhibits the enzyme controlling an earlier reaction
What type of proteins are enzymes?
Globular
How does the structure of enzymes link to their function?
Globlar - so they’re soluble bc hydrophillic R groups on the outside and hydrophobic on the inside. Good for transport.
What are intracellular enzymes?
Operate inside the cell
What are extracellular enzymes?
Operate outside the cell
How does increasing substrate concentration affect the rate of a reaction?
Increases rate of reaction at first bc more enzyme-substrate complexes
All active sites get used up so substrate is no longer the limiting factor
How does increasing enzyme concentration affect the rate of reaction?
Increases rate because of increased active site availability
What is reversible inhibition?
Binding of inhibitor is weak/temporary
Can leave enzyme and it returns to functioning normally
What is irreversible inhibition?
Permanently bound inhibitor
Enzyme cannot separate
Enzyme is denatured
