Chapter 03A: Energy, Chemical Reactions, and Cellular Respiration

This flashcard set covers the fundamental concepts of energy, thermodynamic laws, chemical reaction classifications, and the mechanisms and regulation of enzymes based on the Chapter 03A lecture notes.

Potential energy

The energy of position or stored energy.

Kinetic energy

The energy of motion.

Chemical energy

A form of potential energy stored in a molecule’s chemical bonds, which is released when those bonds are broken.

Electrical energy

The movement of charged particles, such as the movement of ions across the plasma membrane of a neuron.

Mechanical energy

Energy exhibited by objects in motion due to an applied force, such as muscle contraction for walking.

Sound energy

The compression of molecules caused by a vibrating object, such as sound waves causing the vibration of the eardrum.

Radiant energy

The energy of electromagnetic waves, such as visible light striking the retina.

Heat

Kinetic energy produced by the movement of atoms, ions, or molecules, which is usually not available to do work and is measured as temperature.

First law of thermodynamics

A law stating that energy can neither be created nor destroyed; it can only change in form.

Second law of thermodynamics

A law stating that when energy is transformed, some energy is lost to heat, and the amount of usable energy decreases.

Metabolism

The collective term for all biochemical reactions in living organisms.

Reactants

Substances present prior to the start of a chemical reaction, written on the left side of a chemical equation.

Products

Substances formed by a chemical reaction, written on the right side of a chemical equation.

Decomposition reaction

A reaction where an initial large molecule is broken down into smaller structures, expressed as $AB \rightarrow A + B$.

Catabolism

The collective term for all decomposition reactions occurring in the body.

Synthesis reaction

A reaction where two or more structures combine to form a larger structure, expressed as $A + B \rightarrow AB$.

Anabolism

The collective term for all synthesis reactions occurring in the body.

Exchange reaction

A reaction in which groups are exchanged between two chemical structures ($AB + C \rightarrow A + BC$), involving both decomposition and synthesis components.

Oxidation

A process in an exchange reaction where a chemical structure loses an electron.

Reduction

A process in an exchange reaction where a chemical structure gains an electron.

Exergonic reactions

Reactions where the reactants have more energy in their chemical bonds than the products, resulting in a net release of energy.

Endergonic reactions

Reactions where the reactants have less energy in their chemical bonds than the products, requiring energy to be supplied for a net increase in potential energy.

ATP cycling

The continuous cycle of forming $ATP$ through endergonic reactions and splitting $ATP$ through exergonic reactions to provide energy for cellular processes.

Activation energy ($E_a$)

The energy required to break existing chemical bonds to initiate a chemical reaction.

Enzymes

Biologically active globular protein catalysts that accelerate chemical reactions by decreasing the required activation energy.

Active site

A unique three-dimensional pocket or structure in an enzyme that permits only a specific substrate to bind.

Induced fit model

The mechanism where an enzyme changes shape slightly when a substrate enters the active site to ensure a closer, stressed fit.

Cofactors

Nonprotein organic or inorganic substances required to ensure an enzyme-catalyzed reaction occurs.

Coenzymes

Organic cofactors, such as vitamins or modified nucleotides.

Kinases

A subclass of transferase enzymes that specifically transfer phosphate groups between chemical structures.

Saturation

The state where the substrate concentration is so high that all available enzyme molecules are engaged in a reaction.

Optimum temperature

The temperature at which human enzymes function most efficiently, usually around $40^{\circ}\text{C}$ ($104^{\circ}\text{F}$).

Optimum pH

The pH range, typically between $6$ and $8$ for most enzymes, where an enzyme maintains its shape and functions best.

Competitive inhibitor

A substance that resembles a substrate and competes for occupation of the enzyme's active site.

Noncompetitive inhibitor

A substance that binds to an allosteric site rather than the active site, inducing a conformational change that turns the enzyme off.