AP Biology - Enzymes

Metabolism

the totality of an organism's chemical reactions

Metabolic Pathway

begins with a specific molecule which is then altered through a series of defined steps to create a product

Metabolism manages _________ _________ resources of the cell

material and energy

catabolic pathways

release energy by breaking down complex molecules into simpler compounds

anabolic pathways

consume energy to build complex molecules from simpler ones

Example of anabolic pathway

synthesis of protein from amino acids

example of catabolic pathway

Cellular respiration, the breakdown of glucose in the presence of oxygen

Energy

The ability to do work or cause change

Kinetic energy

energy of motion

Potential energy

stored energy

Chemical energy

A form of potential energy that is stored in chemical bonds between atoms

Glucose is _______ in chemical energy

high

Thermodynamics

study of the flow and transformation of energy in the universe

first law of thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed

second law of thermodynamics

Every energy transfer or transformation increases the entropy of the universe.

Entropy

A measure of disorder or randomness.

spontaneous process

a process that can occur without an input of energy

Free energy

energy that is available to do work

Equilibrium

A state of balance

When a reaction proceeds towards equilibrium, the free energy of the mixture of reactants and products ___________

decreases

Exergonic

Chemical reactions that release energy

Endergonic

A chemical reaction that requires the input of energy in order to proceed

Why is a living cell not in equilibrium?

there is a constant flow of materials in and out of the cell. This keeps the metabolic pathways from ever reaching equilibrium.

Enzymes are:

- Proteins

- Can be reused

- Function based on shape

- Serve as a catalyst

Reactions go ______

back and fourth. They can be reversed

Induced Fit

The change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by entry of the substrate

What elements are important to enzymes?

Zinc, Iron, Copper, and Manganese

Cofactors

Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely with the substrate during catalysis

Coenzymes

organic cofactors

Inhibition in a chemical reaction

slows down chemical reactions

Competitive inhibition

Inhibitor that bonds to the active site so that the substrate may not bond

Substrate

reactant of an enzyme-catalyzed reaction

noncompetitive inhibitor

A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate.

allosteric inhibition

the mechanism for inhibiting enzyme action in which a regulatory molecule binds to a second site (not the active site) and initiates a conformation change in the active site, preventing binding with the substrate

Activation energy

Energy needed to get a reaction started

Proteins, DNA, and other complex molecules are rich in _______ ________

free energy

High temperature

denatures enzymes

Instead of heat, what do organisms use to speed up their reactions?

catalysts

How does an enzyme catalyze a reaction?

by lowering the energy of activation of a reaction

enzyme-substrate complex

A temporary complex formed when an enzyme binds to its substrate molecule(s)

Active site

The part of an enzyme or antibody where the chemical reaction occurs

What factors effect enzyme activity?

pH and temperature

What determines the rate of a reaction?

The energy of activation (Ea)

Allosteric Regulation

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site

cooperactivity

a form of allosteric regulation that can amplify enzyme activity

Enzyme-inhibiting agents

act on an enzymes active site

feedback inhibition

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway