unit 3-easy to learn

Cellular energetics

The study of how cells obtain and use energy.

Enzyme

A protein that speeds up a chemical reaction by lowering activation energy.

Substrate

The reactant an enzyme acts on.

Active site

The part of an enzyme where the substrate binds.

Activation energy

The energy needed to start a chemical reaction.

Catalyst

A substance that speeds up a reaction without being used up.

Competitive inhibitor

A molecule that blocks the enzyme’s active site.

Noncompetitive inhibitor

A molecule that binds elsewhere on an enzyme and changes its shape.

Denaturation

The change in a protein’s shape that causes it to lose function.

Optimal temperature

The temperature at which an enzyme works best.

Optimal pH

The pH at which an enzyme works best.

Feedback inhibition

A process in which the final product of a pathway stops an earlier reaction.

ATP

The main energy-carrying molecule in cells.

ADP

A lower-energy molecule formed when ATP loses a phosphate group.

Phosphorylation

The addition of a phosphate group to a molecule.

Exergonic reaction

A reaction that releases free energy.

Endergonic reaction

A reaction that requires an input of free energy.

Free energy

The energy available to do work.

Metabolism

All chemical reactions occurring in an organism.

Coupled reaction

An energy-releasing reaction that powers an energy-requiring reaction.

Cellular respiration

The process that breaks down glucose to produce ATP.

Aerobic respiration

Cellular respiration that uses oxygen.

Glycolysis

The process that splits glucose into two pyruvate molecules.

Pyruvate

The three-carbon product of glycolysis.

Citric acid cycle

A series of reactions that releases carbon dioxide and transfers energy to electron carriers.

Electron transport chain

A series of proteins that transfer electrons and help produce ATP.

Oxidative phosphorylation

ATP production using the electron transport chain and chemiosmosis.

Chemiosmosis

The movement of hydrogen ions down their gradient through ATP synthase to make ATP.

ATP synthase

An enzyme that makes ATP using the flow of hydrogen ions.

Proton gradient

A difference in hydrogen ion concentration across a membrane.

NADH

An electron carrier that delivers high-energy electrons to the electron transport chain.

FADH2

An electron carrier that delivers high-energy electrons to the electron transport chain.

Fermentation

A process that regenerates NAD+ so glycolysis can continue without oxygen.

Lactic acid fermentation

Fermentation that produces lactate.

Alcohol fermentation

Fermentation that produces ethanol and carbon dioxide.

Photosynthesis

The process that uses light energy to make sugars from carbon dioxide and water.

Chloroplast

The organelle where photosynthesis occurs.

Chlorophyll

The pigment that absorbs light energy for photosynthesis.

Light-dependent reactions

Reactions that use light to produce ATP, NADPH, and oxygen.

Thylakoid

A membrane sac in a chloroplast where light-dependent reactions occur.

Stroma

The fluid-filled space inside a chloroplast where the Calvin cycle occurs.

Photolysis

The splitting of water using light energy.

Photosystem

A group of pigments and proteins that captures light energy.

Calvin cycle

Reactions that use carbon dioxide, ATP, and NADPH to build sugar molecules.

Carbon fixation

The process of incorporating carbon dioxide into an organic molecule.

G3P

A three-carbon sugar produced by the Calvin cycle that can be used to build glucose.

NADPH

An electron carrier that provides high-energy electrons for the Calvin cycle.

Autotroph

An organism that makes its own organic molecules.

Heterotroph

An organism that obtains organic molecules by consuming other organisms or organic matter.

Redox reaction

A reaction involving the transfer of electrons.

Oxidation

The loss of electrons.

Reduction

The gain of electrons.

Energy transformation

The conversion of energy from one form to another.