Unit 4 – Cellular Energetics Study Guide

Metabolism

All chemical reactions in a cell.

Catabolic

Processes that break down molecules and release energy.

Anabolic

Processes that build molecules and use energy.

Energy

The ability to do work.

Kinetic Energy

Energy of motion.

Chemical Energy

Energy stored in the bonds of molecules.

Thermodynamics

The study of energy transfer.

Law of Conservation of Energy

Energy is not created or destroyed.

Entropy

The disorder of a system.

System

The reaction being studied.

Surroundings

Everything outside the system.

Spontaneous

A reaction that happens naturally without energy input.

Nonspontaneous

A reaction that requires energy input.

Exergonic

Reactions that release energy.

Endergonic

Reactions that require energy.

Equilibrium

A state of no net change in a reaction.

Work

Energy used to move matter or drive reactions.

ATP (Adenosine Triphosphate)

The cell’s main energy molecule.

ADP

Low-energy form of ATP.

ATP Synthase

An enzyme that synthesizes ATP.

Energy Coupling

Using ATP to power endergonic reactions.

Activation Energy

The energy needed to start a reaction.

Substrate

The reactant an enzyme acts on.

Active Site

The region where the substrate binds on an enzyme.

Enzyme-Substrate Complex

A temporary binding state during enzymatic reactions.

Cofactor

An inorganic helper to enzymes, such as Zn or Fe.

Coenzyme

An organic helper to enzymes, such as NAD⁺ or FAD.

Competitive Inhibitor

A molecule that competes for the active site of an enzyme.

Noncompetitive Inhibitor

A molecule that changes the shape of an enzyme.

Allosteric Regulation

Regulation of an enzyme by binding an effector molecule at a site other than the active site.

Feedback Inhibition

A process where the end product of a pathway shuts off the pathway.

Cooperativity

A phenomenon where one substrate binding increases affinity for additional substrates.

Factors affecting enzymes

Temperature, pH, denaturation, and inhibitors.

Cellular Respiration

The process of breaking down glucose to produce ATP.

Aerobic

Processes that require oxygen.

Anaerobic

Processes that do not require oxygen.

Mitochondria

Cellular organelles involved in energy production.

Oxidation

The loss of electrons in a chemical reaction.

Reduction

The gain of electrons in a chemical reaction.

Glycolysis

The first step in cellular respiration occurring in the cytosol.

Pyruvate Oxidation

The transition phase of cellular respiration occurring in the matrix.

Krebs Cycle

Also known as the Citric Acid Cycle, occurs in the mitochondrial matrix.

Electron Transport Chain

A series of complexes that transfer electrons to generate ATP.

Chemiosmosis

The movement of protons across a membrane to generate ATP.

Fermentation

A metabolic process that regenerates NAD⁺ under anaerobic conditions.

Alcoholic Fermentation

Conversion of pyruvate to ethanol and carbon dioxide.

Lactic Acid Fermentation

Conversion of pyruvate to lactate.

Facultative Anaerobes

Organisms that can switch between aerobic and anaerobic processes.

Obligate Anaerobes

Organisms that cannot survive in the presence of oxygen.

Autotroph

An organism that produces its own food.

Heterotroph

An organism that consumes other organisms for food.

Photosynthesis overall equation

6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.

Chloroplast structure

Contains outer membrane, inner membrane, stroma, thylakoids, and grana.

Light Reactions

Photosynthesis processes that convert light energy into chemical energy.

Calvin Cycle

Uses ATP and NADPH to fix CO₂ into organic molecules.

RuBP (Ribulose bisphosphate)

The CO₂ acceptor in the Calvin cycle.

RuBisCO

The main carbon-fixing enzyme in photosynthesis.