IB Biology Topic C1.3: Photosynthesis Key Definitions

A graph showing the percentage of light absorbed at each wavelength by a pigment or group of pigments.

A graph showing the rate of photosynthesis at each wavelength of light.

The Calvin Cycle is a biochemical pathway that incorporates CO₂ into organic molecules using energy and electrons from ATP and NADPH.

The process of converting inorganic carbon dioxide (CO₂) into organic molecules.

Chemiosmosis is the movement of protons ($H^+$) across a membrane, driven by a concentration gradient, to power the synthesis of ATP.

Chromatography is a technique used to separate and identify components of a mixture based on their differing affinities for a stationary phase and a mobile phase.

Controlled variables are factors kept constant to ensure that changes in the dependent variable (e.g., photosynthesis rate) are due to the independent variable (e.g., CO2 concentration).

A limiting factor is any abiotic or biotic variable that restricts a species’ growth, reproduction, or distribution if it goes beyond the species’ tolerance range.

Photolysis is the process of using light energy to split water molecules into oxygen, protons, and electrons.

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy from the sun into chemical energy stored in the form of organic compounds like glucose.

Photosynthetic pigments are specialized molecules that absorb light energy and convert it into chemical energy during photosynthesis.

A photosystem is a pigment-protein complex that absorbs light energy and transfers it to a reaction center, where it excites electrons for use in photosynthesis.

Photosystems are complexes of proteins and pigments located in the thylakoid membranes of chloroplasts.

The retention factor ($R_f$) is a ratio that describes how far a pigment travels relative to the solvent front:

Rubisco is an enzyme that catalyzes the fixation of carbon dioxide into organic molecules during photosynthesis.