Chapter 6 - Principals of biology

energy

Capacity to do work and bring about change; occurs in a variety of forms.

kinetic energy

Energy associated with motion.

potential energy

Stored energy in a potentially usable form, as a result of location or spatial arrangement.

chemical energy

Energy associated with the interaction of atoms in a molecule.

mechanical energy

A type of kinetic energy associated with the position, or motion (such as walking or running), of an object.

laws of thermodynamics

Two laws explaining energy and its relationships and exchanges. The first, also called the "law of conservation," says that energy cannot be created or destroyed but can only be changed from one form to another. The second says that energy cannot be changed from one form to another without a loss of usable energy.

entropy

Measure of disorder or randomness in a system.

metabolism

The sum of the chemical reactions that occur in a cell.

reactant

Substance that participates in a reaction.

product

Substance that forms as a result of a reaction

catabolism

Metabolic process that breaks down large molecules into smaller ones; catabolic metabolism.

anabolism

Chemical reaction in which smaller molecules (monomers) are combined to form larger molecules (polymers); anabolic metabolism.

free energy

Energy in a system that is capable of performing work.

exergonic reactions

Chemical reaction that releases energy; opposite of endergonic reaction.

endergonic reaction

Chemical reaction that requires an input of energy; opposite of exergonic reaction.

adenosine triphosphate (ATP)

Nucleotide with three phosphate groups. The breakdown of ATP into ADP + Ⓟ makes energy available for energy-requiring processes in cells.

adenosine diphosphate (ADP)

Nucleotide with two phosphate groups that can accept another phosphate group and become ATP.

coupled reactions

Reactions that occur simultaneously; one is an exergonic reaction that releases energy, and the other is an endergonic reaction that requires an input of energy in order to occur.

metabolic pathway

Series of linked reactions, beginning with a particular reactant and terminating with an end product.

enzyme

Organic catalyst, usually a protein, that speeds a reaction in cells due to its particular shape.

ribozymes

RNA molecule that functions as an enzyme that can catalyze chemical reactions

energy of activation

Energy that must be added in order for molecules to react with one another.

active site

Region of an enzyme where the substrate binds and where the chemical reaction occurs.

induced fit model

Change in the shape of an enzyme's active site that enhances the fit between the active site and its substrate(s).

denatured

Loss of a protein's or enzyme's normal shape so that it no longer functions; usually caused by a less than optimal pH and temperature.

enzyme inhibition

Means by which cells regulate enzyme activity; may be competitive or noncompetitive inhibition.

cofactor

Nonprotein assistant required by an enzyme in order to function. Many cofactors are metal ions; others are coenzymes.

coenzyme

Nonprotein organic molecule that aids the action of the enzyme to which it is loosely bound.

vitamins

Organic nutrient that is required in small amounts for metabolic functions. Vitamins are often part of coenzymes.

oxidation-reduction reaction

A paired set of chemical reactions in which one molecule gives up electrons (oxidized) while another molecule accepts electrons (reduced); commonly called a redox reaction.

redox reaction

A paired set of chemical reactions in which one molecule gives up electrons (oxidized) while another molecule accepts electrons (reduced); also called an oxidation-reduction reaction.