combined

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize foods with the use of chlorophyll.

Visible Spectrum

The range of wavelengths of light that are visible to the human eye, typically from about 380 nm to 750 nm.

Wavelength

The distance between successive crests of a wave, often related to the energy of light.

Photon

A particle representing a quantum of light or other electromagnetic radiation.

Chlorophyll

A green pigment found in plants that is crucial for photosynthesis.

Chloroplast

An organelle found in plant cells that conducts photosynthesis.

Mesophyll

The inner tissue of a leaf, containing many chloroplasts.

Stoma (pl. Stomata)

Small openings on the surface of leaves that allow gas exchange.

Stroma

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

Thylakoid

Membrane-bound structures within chloroplasts that contain chlorophyll and are the site of the light-dependent reactions.

Thylakoid Lumen

The space inside the thylakoid membranes.

Granum (pl. Grana)

Stacked thylakoids within chloroplasts.

Light-dependent Reactions

The first stage of photosynthesis where light energy is converted into chemical energy.

Antenna Complexes

Groups of pigment molecules that capture and funnel light energy to the reaction center.

Reaction Center

The part of the photosystem where absorbed light energy is converted into chemical energy.

Photosystem I (P700)

A photosystem that absorbs light at 700 nm and is involved in the light-dependent reactions.

Photosystem II (P680)

A photosystem that absorbs light at 680 nm and is involved in the light-dependent reactions.

Electron Transport Chain

A series of protein complexes that transfer electrons to generate ATP and NADPH.

Chemiosmosis

The movement of ions across a selectively permeable membrane, generating ATP.

Photophosphorylation

The process of converting ADP to ATP using light energy.

Photolysis

The splitting of water molecules through the energy of light during photosynthesis.

Carbon Fixation Reactions

The part of photosynthesis where carbon dioxide is converted into organic compounds.

Calvin Cycle (C3 Pathway)

The series of biochemical reactions in the stroma of chloroplasts that convert carbon dioxide into glucose.

Photorespiration

A process that occurs when the enzyme rubisco fixes oxygen instead of carbon dioxide, decreasing photosynthetic efficiency.

C4 Pathway

A pathway that allows plants to minimize photorespiration, leading to more efficient use of CO2.

Bundle Sheath Cells

Plant cells that surround the vascular tissue and are involved in the C4 pathway.

CAM Pathway

A carbon fixation pathway that uses temporal separation to efficiently capture CO2 in arid conditions.

ADP/ATP

Energy-carrying molecules; ATP is the energy currency of the cell.

NADP+/NADPH

A coenzyme involved in the transfer of electrons in photosynthesis.

Ribulose Bisphosphate (RuBP)

A 5-carbon sugar that reacts with CO2 in the Calvin cycle.

Rubisco

The enzyme that catalyzes the first step of the Calvin cycle.

Glyceraldehyde-3-Phosphate (G3P)

A three-carbon sugar produced during the Calvin cycle.

PEP Carboxylase

An enzyme that catalyzes the fixation of CO2 in the C4 pathway.

H2O

Water, a reactant in the photosynthetic process.

CO2

Carbon dioxide, a reactant in photosynthesis.

O2

Oxygen, a byproduct of photosynthesis.

Cellular Respiration

A set of metabolic reactions that convert biochemical energy from nutrients into ATP.

Aerobic Respiration

The process of producing cellular energy in the presence of oxygen.

Anaerobic Respiration

The process of producing cellular energy without oxygen.

Redox Reaction

A chemical reaction involving the transfer of electrons between two species.

Oxidation

The process of losing electrons.

Reduction

The process of gaining electrons.

Glycolysis

The first stage of cellular respiration that breaks down glucose into pyruvate.

Substrate-level Phosphorylation

The direct production of ATP from ADP using energy from a coupled reaction.

Citric Acid Cycle (Krebs Cycle)

A series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA.

Electron Transport Chain (ETC)

A series of protein complexes that transfer electrons from electron donors to electron acceptors.

Oxidative Phosphorylation

The metabolic pathway in which the mitochondria synthesize ATP from ADP and inorganic phosphate, driven by the transfer of electrons.

Chemiosmosis

The movement of ions across a selectively permeable membrane, down their electrochemical gradient.

Glucose

A simple sugar that is an important energy source in living organisms.

ADP

A molecule that plays an important role in cellular energy transfer.

ATP

A high-energy molecule that stores and supplies energy for many cellular processes.

NAD+

A coenzyme that functions as an electron carrier in cellular respiration.

NADH

The reduced form of NAD+; carries electrons to the electron transport chain.

Pyruvate

The end product of glycolysis that can be converted into glucose or enter the citric acid cycle.

Coenzyme A (CoA)

A coenzyme that carries acetyl groups in the Krebs cycle.

Acetyl Coenzyme A (Acetyl CoA)

A molecule that participates in the citric acid cycle.

Carbon Dioxide

A waste product of cellular respiration.

Oxaloacetate

A four-carbon molecule that combines with Acetyl CoA to form citrate.

FAD

A coenzyme that is an electron carrier in cellular respiration.

FADH2

The reduced form of FAD; carries electrons to the electron transport chain.

ATP Synthase

An enzyme that creates ATP from ADP and inorganic phosphate during chemiosmosis.