enzymes Flashcards
(20 cards)
What are enzymes?
Globular protein biological catalysts that speed up biochemical reactions without being consumed.
Essential for life—working in metabolism, digestion, DNA replication, etc.
What is the structure of enzymes?
Enzymes have a specific three-dimensional (tertiary) structure due to folding and bonding (hydrogen, ionic, disulfide).
What is the active site of an enzyme?
A small region that binds substrate(s), forming the enzyme–substrate complex.
What is the Lock & Key model of enzyme action?
An early model where the enzyme’s active site is rigid and complements the substrate exactly.
What is the Induced Fit model of enzyme action?
The active site changes shape slightly to fit the substrate when it binds, lowering activation energy.
What evidence supports the Induced Fit model?
X-ray crystallography showing shape change in enzymes like hexokinase.
How do enzymes lower activation energy?
By stabilising the transition state, speeding up reactions.
What happens to enzymes during chemical reactions?
They form and release products, remaining unchanged for reuse.
What is enzyme specificity?
Each enzyme only catalyses one reaction (or small group) due to the active site’s specific shape and chemistry.
Can enzymes be stereospecific?
Yes, some enzymes only fit one enantiomer.
How does temperature affect enzyme activity?
Rate increases with temperature up to an optimum (~37 °C for humans) and denatures above this.
What is the Q10 effect in enzymatic reactions?
The rate doubles per 10 °C increase until denaturation.
What is the effect of pH on enzyme activity?
Each enzyme has an optimum pH, and deviations can disrupt structure and reduce activity.
What happens to enzyme activity as substrate concentration increases?
Rate rises until saturation (Vₘₐₓ), and more enzymes can raise the maximum rate.
What are competitive inhibitors?
Substrate-like molecules that bind to the active site, reducing enzyme activity.
What are non-competitive inhibitors?
Molecules that bind elsewhere on the enzyme, reducing activity.
How is enzyme activity measured?
By tracking substrate decrease or product increase over time.
What is the formula for the rate of reaction?
Rate of reaction = gradient of concentration vs time graph.
What are endopeptidases?
Enzymes like pepsin, trypsin, and chymotrypsin that break internal peptide bonds in proteins.
What are exopeptidases?
Enzymes like dipeptidases that act at the ends of proteins to release amino acids.
