Module 2: Enzymes Flashcards
What happens in non-competitive inhibition?
Inhibitor binds to enzymes allosteric site which alters the tertiary structure of enzyme and distorts active site
Substrate can no longer bind to active site
Irreversible so enzyme becomes denatured
What happens I competitive inhibition?
Inhibitor competes with substrate to bind to active site of the enzyme
Substrate can’t bind once inhibitor is bound
Most competitive inhibition is reversibles
What is a cofactor?
Non-protein substance that has to be present to ensure enzyme catalysed reaction takes place at an appropriate rate.
e.g. Cl- is a cofactor of amylase
What is a prosthetic group?
Cofactor that is permanently bound to an enzyme
e.g. zn2+ is a prosthetic group in carbonic anhydrase
What is a coenzyme?
Organic, non-protein molecule that binds temporarily to active site to catalyse a reaction
coenzymes are chemically charged during reaction so need to be recycled to their original state
e.g. NADP-coenzyme to photosynthesis
Effect of substrate on enzyme activity
When substrate is added rate of reaction increases
More enzyme-substrate complexes form so more enzyme-product complexes form
Continues until reaction reaches maximum rate
effect of pH on enzyme activity
Above or below the optimum pH slow the rate of reaction because shape of active site is disrupted
If normal pH is restored, hydrogen bonds can reform and active site shape is reformed
Effects of Temperature on enzyme activity
As temperature increases:
- Both molecules have kinetic energy and move faster - increases rate of successful collisions (per second)
- Therefore rate of formation of enzyme-substrate complexes increases so more enzyme-product complexes form up to a certain point
Induced-fit hypothesis
When a substrate fits into an enzymes active site the active site changes shape tp mould around substrate molecule
Change in shape allows reaction to happen at lower activation energy
Lock-and-key hypothesis
Tertiary structure of enzymes active site has a shape complementary to the substrate
Lock is active site, key is substrate
When substrate is bound to active site it becomes enzyme-substrate complex
Role of intracellular and extracellular enzymes
Intracellular
-Catalyse metabolic reactions inside the cell
e.g. catalase breaks down hydrogen peroxide into water and oxygen
Extracellular
- Made inside cell and secreted
-Catalyses metabolic reactions outside cell
e.g. Amylase breaks down starch into maltose
Role of enzymes
Biological catalysts- speed up metabolic reactions in living organisms
Actions affect both structure and function within cell, tissues and organs
