Chapter 5: Photosynthesis - Converting Light Energy to Chemical Energy

Vocabulary flashcards reviewing essential terms, structures, and chemical steps in photosynthesis from Chapter 5.

Photosynthesis

The biological process by which autotrophic organisms convert light energy into chemical energy, synthesizing sugars from $CO_2$ and $H_2O$ while releasing $O_2$ gas as a by-product.

Photosynthetic Autotrophs

Organisms—including plants, kelp, Euglena, and cyanobacteria—that produce their own organic molecules using solar energy, $CO_2$, and $H_2O$.

Mesophyll

The internal tissue layer of a leaf that contains chloroplasts, serving as the primary site of photosynthesis.

Stroma

The viscous fluid enclosed within the inner membrane of a chloroplast, surrounding the thylakoid membranes, where the Calvin cycle takes place.

Thylakoids

Folded membranous sacs inside chloroplasts, stacked into grana, where the light reactions of photosynthesis occur.

Photons

High-speed particles representing discrete packets of solar or electromagnetic energy.

Electromagnetic Spectrum

The full range of radiation wavelengths, extending from short, high-energy gamma rays to long, low-energy radio waves.

Chlorophyll

The primary photosynthetic pigment located in chloroplasts that absorbs specific light wavelengths to excite electrons.

Photosystem

A molecular light-capturing complex in the thylakoid membrane, consisting of antenna pigments, a reaction-center chlorophyll a, and a primary electron acceptor.

Light Reactions

The initial phase of photosynthesis in the thylakoids where absorbed light energy is converted into chemical energy (ATP and NADPH), producing $O_2$ from water splitting.

Calvin Cycle (Carbon Reactions)

The metabolic pathway in the stroma that uses energy from ATP and NADPH to fix $CO_2$ and synthesize organic sugar molecules.

Rubisco

The enzyme that catalyzes carbon fixation by binding a molecule of $CO_2$ to RuBP during the first step of the Calvin cycle.

PGAL (G3P)

A three-carbon sugar intermediate produced in the Calvin cycle; two PGAL molecules join to form one molecule of glucose.

Chemiosmotic Phosphorylation

The synthesis of ATP driven by the flow of protons ($H^+$) down their concentration gradient through ATP synthase across the thylakoid membrane.