Biology: Photosynthesis and Light-Dependent Reactions

Vocabulary flashcards covering light-dependent and light-independent reactions of photosynthesis, photosystems, photolysis, and photophosphorylation.

Action spectrum

A spectrum showing the rate of photosynthesis, which matches with the absorption spectrum of chlorophyll a, but not perfectly due to accessory pigments.

Light-dependent reactions

Reactions requiring light energy (photons) that occur in the thylakoid membrane of chloroplasts, where water is split into oxygen gas ($\text{O}_2$) and $\text{H}^+$, generating ATP and NADPH.

Light-independent reactions (Dark Reaction)

Reactions taking place in the stroma of the chloroplast that use ATP and NADPH produced in the light reactions to convert $\text{CO}_2$ into glucose ($\text{C}_6\text{H}_{12}\text{O}_6$).

Overview of Chloroplast Reaction Sites

Diagram illustrating light reactions occurring in thylakoids to produce ATP, NADPH, and oxygen gas ($\text{O}_2$), which feed into dark reactions in the stroma to form glucose ($\text{C}_6\text{H}_{12}\text{O}_6$).

ATP

Adenosine triphosphate, a chemical energy compound synthesized via $\text{ADP} + \text{P}_i + \text{Energy} \rightleftharpoons \text{ATP}$.

NADP / NADP+

Nicotinamide adenine dinucleotide phosphate in its oxidized state, reduced during light reactions via $\text{NADP}^+ + 2e^- + 2\text{H}^+ \rightleftharpoons \text{NADPH}$.

NADPH

Nicotinamide adenine dinucleotide phosphate in its reduced state, generated as a chemical energy compound during light-dependent reactions.

Photosystem

A light-harvesting complex located in the thylakoid membrane consisting of a cluster of pigment molecules, containing a reaction center and antenna complexes.

Photosystem Structure

A complex embedded in the thylakoid membrane comprising a primary pigment reaction center (PS1 and PS2) and accessory pigments.

Photosystem I (PSI / P700)

A photosystem with an absorption peak at $700\,\text{nm}$, working simultaneously with Photosystem II to harvest light energy.

Photosystem II (PSII / P680)

A photosystem with an absorption peak at $680\,\text{nm}$, involved in light harvesting and initiating electron transport in photophosphorylation.

Photolysis

The process by which light energy splits water molecules into hydrogen ions ($\text{H}^+$), oxygen ($\text{O}_2$), and electrons ($e^-$).

Photophosphorylation

The process by which ATP is synthesized using light energy to combine inorganic phosphate ($\text{P}_i$) with ADP.

Non-cyclic Photophosphorylation Diagram

A pathway in which electrons move from PS2 (680) through electron carriers to synthesize ATP, then to PS1 (700) and a secondary electron acceptor to reduce $\text{NADP}^+$ to NADPH, using electrons from water splitting.