Chapter 5: Introduction to Energy Transfer

Vocabulary flashcards covering bioenergetics, laws of thermodynamics, energy categories, cellular respiration, enzyme classifications, and chemical reactions.

Bioenergetics

The flow and energy exchange within a living system.

First Law of Thermodynamics

The physical law stating that energy can neither be created nor destroyed but transforms from one form to another without being depleted during the transfer process.

Potential Energy

Energy that relates to the structure or position of a system.

Kinetic Energy

Energy of motion accompanied by the release of heat.

Biosynthesis

The process where bound energy in one substance directly transfers to other substances to increase their potential energy, joining activated atoms of carbon, hydrogen, oxygen, and nitrogen.

Endergonic Reaction

Chemical reactions that store or absorb energy ('uphill' processes), resulting in an increase in free energy for biologic work.

Exergonic Reaction

Any physical or chemical process that releases energy to its surroundings ('downhill' process) with a decrease in free energy.

Second Law of Thermodynamics

The physical law stating that potential energy tends to degrade to kinetic energy of motion with a lower capacity for work.

Entropy

The tendency of potential energy to degrade to kinetic energy with a lower capacity for work.

Six Energy Categories

The six primary forms of energy consisting of chemical, mechanical, heat, light, electrical, and nuclear energy.

Photosynthesis

An endergonic process in which plants trap radiant solar energy to synthesize glucose from carbon dioxide and water, with oxygen as a by-product.

Cellular Respiration

An exergonic process in which stored energy in plants is transferred in the form of ATP for muscle contraction and cellular biosynthesis.

Forms of Biologic Work

The three categories of biologic work in humans: chemical work (cellular biosynthesis), mechanical work (muscle contraction), and transport work (transfer of substances among cells).

Enzymes

Protein catalysts that accelerate chemical reactions without being consumed or changed in the reaction.

Activation Energy

The initial energy input required to initiate a chemical reaction.

Coenzymes

Nonprotein organic substances that facilitate enzyme action by binding a substrate to its specific enzyme.

Oxidoreductases

A class of enzymes that catalyze reactions involving the gain or loss of electrons, such as lactate dehydrogenase.

Transferases

A class of enzymes that catalyze the transfer of a molecular group from one molecule to another, such as hexokinase.

Hydrolases

A class of enzymes that use water to split complex molecules, such as lipase.

Lyases

A class of enzymes that break or form chemical bonds without water, such as carbonic anhydrase.

Isomerases

A class of enzymes that catalyze the structural rearrangement of a molecule, such as phosphoglycerate mutase.

Ligases

A class of enzymes that join or 'glue' molecules together using energy, such as pyruvate carboxylase.

Turnover Number

The number of moles of substrate that react to form a product per mole of enzyme per unit time.

Factors Affecting Enzyme Activity

Environmental factors including reaction temperature and reaction pH that alter enzyme kinetics and turnover rate.

Active Site

The specific region on an enzyme that joins in a 'perfect fit' with a substrate to perform a catalytic reaction.

Noncompetitive Enzyme Inhibitors

Inhibitors that bind to an enzyme at a site other than the active site, altering the enzyme's structure and catalytic activity.

Hydrolysis

A process that digests or degrades complex carbohydrate, lipid, and protein molecules into simpler forms by adding $H^+$ and $OH^+$ to split chemical bonds.

Condensation

An anabolic process in which structural components of nutrients bind together to form more complex molecules and compounds.

Oxidation

Reactions that transfer oxygen or hydrogen atoms, or result in the loss of electrons with a net gain in valence.

Reduction

Any chemical process in which atoms in an element gain electrons or hydrogen atoms, resulting in a net decrease in valence.