Vocabulary

adenosine diphosphate (ADP)

the reduced form of the biological unit of energy, ATP; ADP has one less phosphate group than ATP

bundle-sheath cell

the cell in which the Calvin cycle takes place in C4 plants around the veins of the leaves

C3 plant

plant that undergoes the typical metabolic pathways that fix carbon into three-carbon molecules

C4 plant

plant that uses an alternate metabolic pathway in which carbon is fixed into four-carbon molecules

CAM plant

plant that uses an alternate metabolic pathway in which carbon is fixed into organic acids at night and passed on to the Calvin cycle during the day

chemiosmosis

the movement of ions across a semipermeable membrane down their electrochemical gradient, which results in a charge that can be used as a source of energy

chlorophyll

a green pigment used in photosynthesis

chloroplast

a membrane-bound organelle found in plants and some other organisms that captures energy from light and converts it into chemical energy

cytochrome complex

an enzyme in the thylakoid membrane that forms part of the electron transport chain that moves electrons from photosystem II to photosystem I

glucose

the six-carbon sugar that is the product of reactions following the Calvin cycle

glyceraldehyde 3-phosphate (G3P)

a three-carbon molecule formed in the Calvin cycle that is a precursor to glucose

granum (plural: grana)

stacked thylakoid sacs where the light reactions of photosynthesis takes place

mesophyll cell

the cell in a leaf that contain chloroplasts, where photosynthesis takes place, or where carbon fixation occurs in C4 plants

NADP+

the oxidized form of NADPH, which is used as an electron carrier in the Calvin cycle

NADPH

the reduced form of NADP+ that serves as an electron carrier in the Calvin cycle; the H at the end denotes that the molecule contains an extra hydrogen atom as compared to NADP+

oxaloacetate

the product of the carbon-fixation reaction in C4 photosynthesis

PEP carboxylase

the enzyme that catalyzes carbon fixation in C4 photosynthesis

phosphoenolpyruvate (PEP)

the molecule to which CO2 is added in C4 photosynthesis

photoautotroph

an organism that makes its own food using light energy

photorespiration

the uptake of O2 and release of CO2 driven by light, which consumes energy and decreases the output from photosynthesis

photosynthesis

the process by which autotrophs convert light energy into chemical energy that is stored in organic compounds, such as sugars

photosystem I

the second light-capturing complex found in the thylakoid membrane of a chloroplast that converts light energy into chemical energy

photosystem II

the first light-capturing complex found in the thylakoid membrane of a chloroplast that converts light energy into chemical energy

plasmodesma (plural, plasmodesmata)

small channel between mesophyll cells and bundle-sheath cells through which molecules pass between carbon fixation in the mesophyll cells and the Calvin cycle in the bundle-sheath cells; this channel extends through the cell wall of a plant cell and directly connects the cytoplasm of adjacent plant cells

pyruvate

the molecule that is produced after CO2 is passed on to the Calvin cycle in C4 photosynthesis, which regenerates PEP

ribulose bisphosphate (RuBP)

a five-carbon sugar to which the enzyme rubisco adds one carbon, during carbon fixation, to form a six-carbon sugar that is energetically unstable

rubisco

the enzyme that adds one carbon to a five-carbon sugar called ribulose bisphosphate (RuBP) during carbon fixation

stoma (plural, stomata)

small opening mostly found on the undersides of leaves that allows for gas exchange between the plant and the external environment

stroma

a fluid inside chloroplasts that contains bundles of membrane-bound sacs called thylakoids

thylakoid

a membrane-bound sac inside the stroma that may be stacked into columns, called grana, in which light reactions of photosynthesis take place; the space within each thylakoid sac is called lumen