Lecture 6 - Enzyme Activity

What happens to ΔG when an enzyme is used?

g unchanged

How is the substrate held in the active site?

by weak interactions

What happens to the substrate during catalysis?

converted into product

What happens after products form?

released from the enzyme

What happens to the active site after product release?

available for new substrates

What is induced fit?

substrate binding causes the enzyme to change shape for a close fit

How do most enzyme names end?

ase

What do enzyme names usually describe?

the reaction they catalyze

What does an isomerase do?

catalyzes intramolecular rearrangements

What does a ribonuclease do?

hydrolyzes rna

What does a deoxyribonuclease do?

hydrolyzes dna

What does a polymerase do?

synthesize rna or dna

What are cofactors?

non protein helpers needed by some enzymes

Can cofactors bind permanently or temporarily?

yes, bind permanently or reversibly

What is a prosthetic group?

molecule bound tightly to a protein

What are examples of prosthetic groups?

heme, vitamins, mineral ions

What are coenzymes?

small organic molecules that bind non covalently

What is an example of a coenzyme?

vitamins

How does enzyme concentration affect reaction rate?

increases rate if enough substrate available

What happens when enzymes become saturated with substrate?

all enzyme occupied

How do temperature and pH affect enzymes?

affect enzymes structure and activity

Does every enzyme have the same optimal temperature and pH?

no, each has its own optimum

Why do cells regulate enzyme activity?

control when and where enzymes are active

How can cells control enzyme production?

switching genes encoding enzymes on or off

How can enzymes be regulated after they are made?

inactive precursor activated to an active enzyme

What is cellular localisation?

keeping enzymes in organelles

What is allosteric regulation?

regulatory molecules change enzyme activity by binding away from active site

How do allosteric molecules affect enzymes?

activate or inhibit enzyme activity

What is feedback inhibition?

end product inhibits an enzyme early in the pathway

Why does feedback inhibition occur?

switch the metabolic pathway off when enough product is present