Photosynthesis: Using Light to Make Food

This set of vocabulary flashcards covers the fundamental concepts of photosynthesis, including the anatomical structures of chloroplasts, the properties of light, the mechanisms of light-dependent and light-independent reactions, and the specific chemical requirements for glucose production.

Photosynthesis

Process by which plants, some protists and some prokaryotes transform light energy from the sun into chemical energy, creating bonds within sugar molecules.

Anabolic Pathway

The metabolic classification of photosynthesis, which builds complex molecules like glucose from simpler ones.

Chloroplasts

Organelles with a double-membrane envelope where photosynthesis takes place in plants.

Stroma

The fluid-filled space within the chloroplast surrounding the thylakoids.

Thylakoids

Interconnected membranous sacs suspended in the stroma where chlorophyll molecules are built into the membranes to capture light energy.

Grana

Concentrated stacks of thylakoids within the chloroplast.

Electromagnetic radiation

A type of energy, such as sunlight, that moves through space in waves.

Photons

Organized packets of energy; photons traveling at the same wavelength carry the same amount of energy.

Wavelength

The distance between the crests of successive waves; the shorter this distance, the higher the energy level packed in the photons.

Electromagnetic spectrum

The entire range of wavelengths and all types of electromagnetic radiation, from less than one $nm$ to more than one $km$.

Pigments

Organic molecules that selectively absorb light of specific wavelengths within the visible light spectrum.

Chlorophyll a

The most common photosynthetic pigment in plants and protists; it absorbs violet, red, and orange light and appears green.

Accessory pigments

Pigments such as chlorophyll b and carotenoids that harvest light wavelengths not absorbed by chlorophyll a to extend the range that drives photosynthesis.

Engelmann’s Experiment

Demonstrated that photosynthesis is driven best by particular wavelengths of visible light, specifically blue and red light.

Photosystem

A cluster of a few hundred pigment molecules (including chlorophylls a and b and carotenoids) that functions as a light-gathering antenna and a reaction center.

Reaction Center

A part of a photosystem consisting of a pair of special Chlorophyll a molecules and a primary electron acceptor.

Light-dependent reactions

The first stage of photosynthesis occurring in the thylakoid membrane, which produces Oxygen, $ATP$, and $NADPH$.

ATP Synthase

An enzyme that uses the flow of hydrogen ions to phosphorylate $ADP$, forming $ATP$ in the stroma.

NADP+

The final electron acceptor in the light-dependent reactions (non-cyclic pathway) of photosynthesis.

Calvin–Benson Cycle

Also known as the light-independent reactions; it functions like a sugar factory in the stroma to construct $G3P$ using carbon from $CO_2$, energy from $ATP$, and electrons from $NADPH$.

Glyceraldehyde 3-phosphate (G3P)

The energy-rich sugar molecule produced by the Calvin cycle that serves as the raw material to make glucose.

Carbon fixation

The process in which carbon from an inorganic source (such as $CO_2$) is incorporated into an organic molecule.

Rubisco

The most abundant enzyme (protein) on Earth, responsible for carbon fixation in the Calvin-Benson cycle.

Stomata

Tiny gateways for gases that allow $CO_2$ to enter and $O_2$ to exit photosynthetic tissues; they close to conserve water on hot, dry days.

Glucose Synthesis Requirements

To synthesize one glucose molecule ($C_6H_{12}O_6$), the Calvin cycle requires $6 CO_2$, $18 ATP$, and $12 NADPH$.