Enzyme notes AP biology

Catalyst

chemical agent that speeds up a reaction without being consumed by the reaction

enzyme

catalytic protein

example of a enzyme catalyzed reaction

hydrolysis of sucrose by the enzyme sucrase

every chemical reaction between molecules involves bond ____ and bond _____

breaking, forming

The initial energy needed to start a chemical reaction is called _______ or ______

free energy of activation, activation energy (Ea)

how do enzymes catalyze reactions

lower the free energy barrier

Do enzymes affect the change in free energy

no, they just speed up reactions

The reactant that an enzyme acts on is called the enzymes ____

substrate

The enzyme binds to its substrate, forming an _____

enzyme-substrate complex

The ______ is the region on the enzyme where the substrate binds

active site

______ of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction

Induced fit

In an enzymatic reaction, the ____ binds to the active site of the enzyme

substrate

how can the active site lower a activation energy barrier

orienting substrates correctly, straining substrate bonds, providing a favorable microenvironment

The more ____ molecules available, the more frequently they access the _____

substrate, active sites of enzyme molecules

If there are so many substrate molecules that all enzymes have their active sites engaged, the enzyme is _____

saturated

How can the rate of reaction be increased if an enzyme is saturated

add more enzymes

How can an enzymes activity be affected

temperature and ph, chemicals that influence the enzyme

Do enzymes have optimal temperatures and pH levels

yes, they favor the most active shape for the enzyme molecule

Up to a point, the rate of a enzymatic reaction ____ with ____ temperature

increases, increasing

Above a point in increasing temperature, rate of reaction ______

drops sharply

Why does rate of reaction drop at a certain temperature

thermal agitation of enzymes disrupts hydrogen bonds, ionic bonds, and other weak interactions that stabilize the shape of the enzyme

Loss of shape =

denaturization

Cofactors

nonprotein enzyme helpers (bind to the enzyme in order to function)

Cofactors may be ____ or _____

inorganic, organic

examples of cofactors

copper, zinc, enzyme

what is a organic cofactor called

coenzyme

what do coenzymes do

binds to active site and changes chemically during the reaction, adds or removes chemical groups from a substrate.

coenzymes include

vitamins

Competitive inhibitors

bind to the active site of an enzyme, competing with the substrate (can be overcome by adding more substrate)

Noncompetitive inhibitors

bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

examples of inhibitors

toxins, poisons, pesticides, antibiotics

Enzymes are ___ encoded by ____

proteins, genes

changes (mutations) in genes lead to changes in _____ of an enzyme

amino acid composition

Altered amino acids in enzymes may alter their _______

substrate specificity

Under new environmental conditions a ___ form of an enzyme might be favored

novel

How does a cell tightly regulate metabolic pathways

switching on or off the genes that encode specific enzymes or by regulating the activity of enzymes

Allosteric regulation

inhibit or stimulate an enzyme’s activity

Allosteric regulation occurs when a regulatory molecule ____ to a protein _____ and ____ the proteins function at ____

binds, at one site, affects, another site

The binding of an activator stabilizes the ____ form of the enzyme

active

The binding of an inhibitor stabilizes the ____ form of the enzyme

inactive

Cooperativity

allosteric regulation that can amplify enzyme activity

Binding of one substrate molecule to an active site makes binding of additional substrate molecules ____

more likely

Why is cooperativity allosteric

binding by a substrate to one active site affects catalysis in a different active site

Feedback inhibition

the end product of a metabolic pathway shuts down the pathway

Feedback inhibition prevents a cell from wasting chemical resources by ________

synthesizing more product than is needed

In eukaryotic cells, some enzymes reside in specific ____

organelles