Energy, Chemical Reactions, and Cellular Respiration

Flashcards covering the fundamentals of biological energy, types of chemical reactions, enzyme kinetics, and the stages of cellular respiration based on lecture materials.

Potential energy

Stored energy or energy of position.

Kinetic energy

Energy of motion.

Chemical energy

A form of potential energy stored in a molecule’s chemical bonds; the most important form of energy in the human body.

Triglycerides

Molecules used for long-term energy storage in adipose tissue.

Electrical energy

A form of kinetic energy involving the movement of charged particles, such as 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

Kinetic energy resulting from molecule compression caused by a vibrating object.

First law of thermodynamics

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

Second law of thermodynamics

The principle stating 그that 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 ($AB \rightarrow A + B$).

Catabolism

The collective term for all decomposition reactions in the body.

Synthesis reaction

A reaction occurring when two or more structures combine to form a larger structure ($A + B \rightarrow AB$).

Anabolism

The collective term for all synthesis reactions in the body.

Exchange reaction

A reaction where atoms, molecules, ions, or electrons are exchanged between two chemical structures ($AB + C \rightarrow A + BC$).

Exergonic reactions

Chemical reactions where reactants have more energy in their bonds than products, resulting in a net release of energy.

Endergonic reactions

Chemical reactions where reactants have less energy in their bonds than products, requiring an energy supply and resulting in a net increase in potential energy.

ATP cycling

The continuous formation and breakdown of ATP, where energy released from exergonic reactions is used to form ATP from ADP and phosphate.

Irreversible reaction

A reaction characterized by a net loss of reactants and a net gain in products.

Reversible reaction

A reaction where reactants become products and products become reactants at an equal rate, resulting in no net change in concentration (equilibrium).

Activation energy ($E_a$)

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

Enzymes

Globular protein catalysts that accelerate physiologic activities by decreasing the activation energy of cellular reactions.

Active site

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

Induced fit model

A mechanism of enzyme action where the enzyme changes shape slightly when the substrate enters the active site to create a closer fit.

Metabolic pathway

A series of enzymes where the product of one enzyme becomes the substrate of the next enzyme.

Multienzyme complex

A group of physically attached enzymes that work in a sequence of reactions, such as pyruvate dehydrogenase.

Negative feedback

A regulatory process where the product of a metabolic pathway acts as an allosteric inhibitor to turn off an enzyme early in the pathway.

Cellular respiration

An exergonic multistep metabolic pathway where organic molecules are oxidized and disassembled by enzymes to release energy for ATP production.

Glucose oxidation

The step-by-step breakdown of glucose ($C_6H_{12}O_6$) into carbon dioxide ($CO_2$) and water ($H_2O$) with the release of energy.

Cytosol

The semifluid cell contents where glycolysis occurs.

Mitochondria

Small cellular organelles where the intermediate stage, citric acid cycle, and electron transport system take place.

Glycolysis

The first stage of glucose oxidation occurring in the cytosol; it does not require oxygen and produces a net of $2\,ATP$ and $2\,NADH$, with pyruvate as the final product.

Intermediate stage

The aerobic stage where pyruvate is converted to acetyl CoA by pyruvate dehydrogenase, releasing $CO_2$ and forming $NADH$.

Citric acid cycle

A cyclic metabolic pathway in the mitochondrial matrix that produces $2\,CO_2$, $1\,ATP$, $3\,NADH$, and $1\,FADH_2$ per turn.

Electron transport system

A system in the mitochondrial cristae that transfers electrons from $NADH$ and $FADH_2$ to $O_2$ to establish a proton gradient used for ATP synthesis.

Oxidative phosphorylation

The process of forming ATP using energy released from the electron transport system, producing approximately $34\,ATP$ per glucose molecule.