Enzymes Flashcards
What is an enzyme?
a globular protein that catalyses metabolic reactions
What are two types of enzymes?
intracellular and extracellular
What is an active site?
an active site is the place on the enzyme where the substrate fits
What is an enzyme-substrate complex?
the bonded enzyme and substrate by temporary hydrogen bonds between the R groups of their amino acids
What effect does an enzyme have on activation energy?
lowers the energy needed to start a reaction
What is enzyme specificity?
each enzyme is specific for its complementary substrate
What is the lock-and-key hypothesis?
the shape of the substrate is complementary to the active site of the enzyme, and it fits into the enzyme like a lock in a key
What is the induced fit hypothesis?
the enzyme and substrate are not exactly complementary so the enzyme changes shape slightly to allow the substrate to fit better
How can the progress of a reaction be measured?
the amount of product produced or substrate disappeared, plotted on a graph showing rate of reaction
What factors affect the rate of enzyme-catalysed reactions?
- temperature
- PH
- enzyme concentration
- substrate concentration
- inhibitor concentration
How does temperature affect the rate of reaction?
increasing temperature increases rate of reaction, too high temperature causes bonds to break and the enzyme to denature, slowing rate of reaction
How do PH changes affect the rate of reaction?
a more acidic or basic PH interferes with ionic bonds and causes and enzymes to denature, slowing rate of reaction
How does enzyme concentration affect the rate of reaction?
higher enzyme concentration increases initial rate of reaction
How does substrate concentration affect the rate of reaction?
higher substrate concentration increases initial rate of reaction
How does inhibitor concentration affect the rate of reaction?
higher inhibitor concentration slows rate of reaction
What are competitive reversible inhibitors?
inhibit enzyme activity by fitting into active site
What are non-competitive reversible inhibitors?
inhibit enzyme activity by attaching somewhere else on the enzyme molecule, help with end-product inhibition
What is the affect of immobilising an enzyme in alginate?
enzymes can be reused and do not mix with the product, they are also more tolerant to PH and temperature changes
What is Vmax?
velocity max, the maximum rate of reaction, where all enzymes are saturated with substrate
What is the Michaelis-Menten (Km) constant?
half of Vmax, when half the active sites of enzymes are occupied with substrate, the lower the Km constant, the higher the enzyme affinity
What is initial rate of reaction?
the rate of reaction is always fastest at the beginning, calculated by curve gradient or by reading off the graph
What is denaturation?
when an enzymes loses shape and activity
How do you calculate Vmax from a double-reciprocal plot?
1/Vmax is the point where the line meets the y-axis (where 1/S), from there Vmax is calculated
How do you calculate Km from a double-reciprocal plot?
-1/Km is where the line of the graph intersects the x-axis, from there Km is calculated
What is a double-reciprocal plot?
the inverse of velocity plotted against the inverse of substrate concentration
