Chapter 4 - Enzymes Flashcards
What are enzymes
Biological catalysts
Globular proteins
What type of reactions do enzymes catalyse
Anabolic and catabolic
Anabolic reactions
Building up eg. Condensation reactions
Catabolic reactions
Breaking down eg. Digestion
What is the active site
An area within the tertiary structure of the enzyme that is complementary to the shape of a specific substrate
How does enzyme bind to the subrate
R-groups in the tertiary structure in the active site form temporary bonds with the substrate
Lock and key hypothesis
The specificity of the active site to the substrate
Induced fit hypothesis
The active site changes shape to fit the substrate after it binds
The initial reaction is weak but it induces a change to the tertiary structure of the enzyme to strengthen the binding
Intracellular enzymes
Enzymes that catalyse reactions inside cells
Example of intracellular enzyme
Catalase breaks down H2O2 into O2 and H2O to prevent accumulation in cells as it is toxic
Extracellular enzymes - amylase
- starch molecules to large to be absorbed into blood
- amylase (in saliva) breaks starch down partially into maltose
- maltase in the small intestine breaks maltose into glucose which can be absorbed
Extracellular enzymes - trypsin
Trypsin (a protease) in pancreas breaks down proteins into smaller peptides which can be easier broken down into amino acids by other proteases for absorption into the blood
Temperature coefficient
Q10 - how much rate increases per 10 degree Celsius rise (usually 2)
Vmax
The maximum rate
When all enzyme active sites are occupied or no more substrate
What is an inhibitor
Molecules that prevent enzymes from carrying out their normal function
Competitive inhibitor
- Same shape as substrate to fit into the active site
- blocks substrate and prevents catalysis which slows rate
- normally temporary and reversible
- can still reach Vmax by increasing substrate concentration
Non-competitive inhibitors
- bind to allosteric site
- changes tertiary structure of enzyme and active site
- specificity lost
- irreversible
- cannot reach Vmax
End product inhibition
Non-competitive reversible inhibition
Prevents excess product being formed
What do co-factors and co-enzymes do
Non-protein helper components that help enzymes carry out their function
Co- factors
Inorganic molecules or ions
Examples of co-factors
- Cl- for amylase
- Zn2+ prosthetic group for carbonic anhydrase
Co-enzymes
Organic molecules
Where do coenzymes come from
Usually found in vitamins
