Photosynthesis and Cellular Respiration Vocabulary

Vocabulary flashcards covering key terms and concepts in photosynthesis, including chloroplast structures, redox reactions, light-dependent reactions, and the Calvin cycle.

Autotroph

An organism that can produce its own food.

Photoautotroph

An organism that uses light energy to power the synthesis of food, such as plants, algae, and certain bacteria.

Heterotroph

An organism that must obtain energy and carbon by consuming other organisms, such as animals, fungi, some protists, and some prokaryotes.

Chloroplast

An organelle in all autotrophic eukaryotes where photosynthesis takes place, bounded by a double membrane.

Thylakoid

A stacked, disc-shaped membrane structure within a chloroplast that contains embedded chlorophyll pigments.

Granum

A stack of thylakoids inside a chloroplast.

Stroma

The fluid-filled space surrounding the granum inside a chloroplast where the Calvin cycle takes place.

Chlorophyll

The primary photosynthetic pigment embedded in the thylakoid membrane that absorbs light energy and gives plants their green color.

Light-dependent reactions

The first stage of photosynthesis taking place on the thylakoid membrane, converting light energy into chemical energy as ATP and NADPH while releasing oxygen.

Calvin cycle

The second stage of photosynthesis occurring in the stroma, using ATP and NADPH from the light-dependent reactions to convert inorganic carbon dioxide into organic sugars.

Oxidation

A chemical reaction that removes an electron or electrons from an atom in a molecule.

Reduction

A chemical reaction involving the addition of an electron or electrons to an atom in a molecule.

Hydride ion ($\text{H}^-$)

An ion containing two electrons and one proton, transferred to $\text{NADP}^+$ to reduce it into NADPH.

Visible light

The range of light wavelengths from $400\,\text{nm}$ to $700\,\text{nm}$ absorbed by pigments in human retinas and photosynthetic organisms.

Carotenoids

A large group of pigments residing in the thylakoid membrane that absorb excess light energy and dissipate it safely as heat.

Absorption spectrum

The specific pattern of wavelengths of visible light absorbed by a particular pigment.

Photosystem

A multiprotein complex in chloroplasts where the absorption of light energy by chlorophyll electrons takes place.

Antenna proteins

Proteins bound to chlorophyll molecules that surround a reaction center and transfer light energy within the light-harvesting complex.

Reaction center

The structure within a photosystem containing a pair of special chlorophyll molecules that give up an electron when excited by absorbed light energy.

Photosystem II (PSII)

The photosystem that extracts low-energy electrons from water, delivers high-energy electrons to an electron transport chain, and captures energy used to produce ATP.

Photosystem I (PSI)

The photosystem that re-energizes electrons using light energy and transfers high-energy electrons to $\text{NADP}^+$ to form NADPH.

ATP synthase

A membrane protein generator driven by the exergonic movement of hydrogen ions diffusing down their electrochemical gradient to catalyze the formation of ATP from ADP and phosphate.

Chemiosmosis

The process that uses the pushing power of a hydrogen ion ($\text{H}^+$) gradient to power the synthesis of ATP.

Ribulose bisphosphate (RuBP)

A five-carbon molecule with two attached phosphates that binds with carbon dioxide during the fixation stage of the Calvin cycle.

Rubisco

Ribulose bisphosphate carboxylase; the enzyme that catalyzes the attachment of a $\text{CO}_2$ molecule to an RuBP molecule.

Phosphoglycerate (PGA)

A three-carbon molecule with one phosphate, produced when the six-carbon intermediate formed during carbon fixation splits.

Phosphoglyceraldehyde (PGAL)

A three-carbon molecule produced in the Calvin cycle by converting PGA using ATP and NADPH, which can exit the cycle to form glucose.

Cellular respiration

The process by which living organisms break down molecules, usually carbohydrates, to acquire energy for producing ATP.