Biology - Biochemical Pathways & Enzymes_ch 6

Biochemical Pathways

A chemical reaction in a living cell that proceeds via a series of intermediate compounds (or steps) to the final product.

Noncompetitive inhibitors

A molecule that binds to an enzymeat a site other than the active site; this changes the shape of the enzyme so that the substrate can no longer bind to the active site.

Consider the biochemical pathway below, where A, B, and C are substrates and products and E1 and E2 are the enzymes that catalyze the reactions. If Enzyme 1 (E1) is inactive, which compounds will accumulate?

A only

Coenzyme

A small orgnaic cofactor molecule that plays an important role in enzyme-catalysed process; it may function as a carrier, donor or aceptor of a substance involved in the reaction (e.g. haem, ATP and NAD) and/or it may bind with an enzyme to activate it.

Inhibitor

A substance that binds to an enzyme and decreases its activity.

Competitive Inhibitors

A substance that competes with a substance for an enzyme's active site.

Based on the graph, indicate if statements are true or false. A. B is influenced by temperature B. A is lowered by an enzyme C. B is lowered by an enzyme

A. True B. True C. False

Enzyme Mechanics Which statement about enzymes is TRUE?

An enzyme can couple a nonspontaneous reaction to a spontaneous reaction so that anabolic processes will occur.

endergonic

Any reaction that requires an input of energy, "inward energy"

Consider the biochemical pathway below, where A, B, and C are substrates and products and E1 and E2 are the enzymes that catalyze the reactions. If Enzyme 1 (E1) is inactive, which of the following compounds will become deficient?

B and C

Cofactors

Cofactor Various substances, such as mineral ions and vitamins, that need to be presented in addition to an enzyme to catalyse a certain reaction.

Based on the reaction in the animation, what can you say about the change in free energy of the cleavage of sucrose into glucose and fructose?

It is negative and the reaction is exergonic.

Catabolism

Reactions that harvest energy by breaking down molecules.

L-arabinose is a naturally occurring, non-caloric sweetener that acts as a non-competitive inhibitor of the enzyme sucrase. If L-arabinose is consumed, what will happen to the hydrolysis of sucrose?

Sucrose hydrolysis will be greatly reduced, since L-arabinose binding to sucrase will inactivate the enzyme.

Energy

The capacity to do work.

Consider the biochemical pathway below, where A, B, and C are substrates and products and E1 and E2 are the enzymes that catalyze the reactions. If B is also the substrate of another reaction that is catalyzed by enzyme 3 (E3) to form product D, how does the cell regulate the production of C and D?

The cell uses activators and inhibitors to regulate the activity of enzymes 2 and 3 (E2 and E3).

Anabolism

The chemical reactions that expend energy to build up molecules.

Kinetic Energy

The energy of motion.

Biochemical Pathways 1: Based on the animation, which observation is true?

The product from one reaction served as the substrate for the next reaction.

Metabolism

The total of all chemical reactions carried out by an organism.

Catalysis An enzyme may catalyze a reaction by stressing or destabilizing the bonds of the substrates. This point in the enzymatic reaction is known as the

Transition State

Sucrase uses _______ to cleave sucrose into two monosaccharides.

Water

The enzyme in the animation is most likely catalyzing

an anabolic reaction.

Reduction

an atom or molecule that GAINS an electron is said to be reduced.

Oxidation

an atom or molecule that LOOSES an electron is said to be reduced.

When it binds to sucrose, sucrase

goes through a conformational change.

Heat

is a measure of the random motion of molecules.

Potential energy

is stored energy.

Thermodynamics

is the branch of chemistry concerned with energy changes.

How often can a sucrase molecule be used to hydrolyze sucrose?

many times.

In the human body, sucrase is found

on the microvilli of the small intestine.

Consider the biochemical pathway below, where A, B, and C are substrates and products and E1 and E2 are the enzymes that catalyze the reactions. Enzyme 1 (E1) can use

only A as substrate.

What type of biological molecule are enzymes?

proteins

The component that binds most tightly to the active site of an enzyme is

substrate.

A mutation occurred in the gene that encodes the enzyme sucrase, resulting in a single amino acid substitution in the active site of the enzyme whereby a polar amino acid changed to a nonpolar amino acid. The most likely result of this mutation is

sucrase will not be able to bind sucrose in the active site.

Free energy

the energy available to do work in any system. ∆G