Photosynthesis and the Calvin Cycle

Comprehensive vocabulary flashcards covering the mechanisms, stages, carrier molecules, enzymes, and adaptations of photosynthesis and the Calvin Cycle.

Photosynthesis

The process by which plants generate oxygen and energy in the form of sugar using carbon dioxide, water, and sunlight, represented by $CO_2 + H_2O + \text{LIGHT} \rightarrow (CH_2O) + O_2$.

Triose Phosphate

The true main product of photosynthesis, contrary to the common misconception that it is glucose.

Light-Dependent Reaction

The phase of photosynthesis occurring in the thylakoid membrane that directly utilizes light to oxidize water and produce $ATP$ and $NADPH$.

Pheophytin

The primary electron acceptor that receives electrons from the P680 reaction center of Photosystem II (PII).

Plastoquinone

A mobile electron carrier that transfers electrons from Qa and Qb to the Cytochrome complex (Cytb6f).

Plastocyanin

A mobile electron carrier that transfers electrons from the Cytochrome complex (Cytb6f) to replenish the oxidized P700 reaction center of Photosystem I (PI).

Chemiosmosis Phosphorylation

The process in the light-dependent reaction where hydrogen ions driven into the thylakoid lumen move down their proton gradient back to the stroma through $ATP$ synthase to produce $ATP$.

Calvin Cycle

The biosynthetic phase of photosynthesis occurring in the stroma wherein sugar is formed from carbon dioxide across three phases: carbon fixation, reduction, and regeneration of RuBP.

RuBisCO

The enzyme in the stroma that fixes carbon dioxide to RuBP during carbon fixation, but can also act as an oxygenase under high oxygen conditions.

2-carboxy-3-ketoarabinitol 1,5-bisphosphate

The unstable intermediate molecule formed when carbon dioxide is fixed to RuBP by RuBisCO before it splits into two molecules of 3-phosphoglycerate.

3-phosphoglycerate

The first stable product of the Calvin cycle, consisting of two $3$-carbon molecules formed by the splitting of 2-carboxy-3-ketoarabinitol 1,5-bisphosphate.

Phosphoglycerate Kinase

The enzyme that phosphorylates 3-phosphoglycerate using phosphate from $ATP$ to convert it into 1,3-bisphosphoglycerate while releasing $2$ $ADP$.

Glyceraldehyde 3-phosphate Dehydrogenase

The enzyme that reduces 1,3-bisphosphoglycerate using $NADPH$ to produce glyceraldehyde 3-phosphate (triose phosphate) while releasing $2$ $NADP^+$.

Photorespiration

An energy-requiring process occurring when closed stomata cause oxygen to build up, leading the RuBisCO enzyme to act as an oxygenase rather than a carboxylase and release carbon dioxide.

C4 and CAM Pathways

Carbon-concentrating mechanisms ($CO_2$ fixation pathways) evolved by plants in tropical and arid environments to increase RuBisCO binding with $CO_2$ instead of oxygen, preventing photorespiration.