Plant Carbon Fixation

Vocabulary flashcards covering key terms related to carbon fixation in plants, including C3, C4, and CAM pathways.

G3P

A 3-carbon molecule that is the product of the Calvin cycle; it can be used to synthesize larger sugars like glucose.

Calvin Cycle

A metabolic pathway in the stroma of the chloroplast where CO2 is fixed, reduced, and converted into G3P, using ATP and NADPH.

RuBP

Ribulose-1,5-bisphosphate; a 5-carbon molecule that is the initial CO2 acceptor in the Calvin cycle.

Rubisco

The enzyme that catalyzes the first major step of carbon fixation in the Calvin cycle.

Photorespiration

A process in C3 plants where rubisco binds to O2 instead of CO2, resulting in a decrease in carbohydrate production.

C4 Plants

Plants that minimize photorespiration by using PEP carboxylase to initially fix CO2 into a 4-carbon compound in mesophyll cells before transferring it to bundle-sheath cells for the Calvin cycle.

CAM Plants

Plants that open their stomata at night to fix CO2 into organic acids, which are stored until daylight when they are released to the Calvin cycle.

Stomata

Pores on the surface of leaves that allow for gas exchange (CO2 uptake and O2 release) and transpiration.

PEP Carboxylase

An enzyme in C4 plants that adds CO2 to phosphoenolpyruvate (PEP), forming oxaloacetate (OAA).

OAA (Oxaloacetate)

A 4-carbon molecule formed in C4 plants by PEP carboxylase, which is later converted to malate.

Malate

A 4-carbon molecule that transfers CO2 from mesophyll cells to bundle-sheath cells in C4 plants.

Plasmodesmata

Cell-cell connections that allow malate to diffuse from the mesophyll cells into bundle-sheath cells.

Crassulacean Acid Metabolism (CAM)

A carbon fixation pathway used by some plants in dry conditions where CO2 is stored as organic acids during the night and released for the Calvin cycle during the day.

Bundle-Sheath Cells

A layer of cells in C4 plants where the Calvin cycle occurs, isolated from atmospheric oxygen.

Mesophyll Cells

Cells in the interior of a leaf where carbon fixation initially occurs in C4 and CAM plants.

Transpiration

The process by which plants lose water vapor through stomata.

Sucrose

A disaccharide (table sugar) formed from glucose and fructose, used to transport carbohydrates to other cells of the plant.

Starch

A polymer of glucose molecules used for long-term energy storage in plants.

Carbon Fixation

The initial incorporation of CO2 into organic compounds.

Photorespiration Optimum Temperature

30°C - 47°C. Hot, dry, bright days produce the conditions that encourage photorespiration