Photosynthesis: Energy from Sunlight

This set of vocabulary flashcards covers the fundamental concepts, structures, and chemical pathways involved in photosynthesis as described in the lecture notes.

Photosynthesis

The process by which energy from sunlight is captured and used to convert $CO_2$ to more complex carbon compounds.

Autotrophs

"Self-feeders" such as plants, algae, and cyanobacteria that carry out photosynthesis.

Heterotrophs

"Other-feeders" such as animals, fungi, and most bacteria that must consume other organisms to obtain food.

Stomata

Pores on the leaf surface through which $CO_2$ enters and $O_2$ and $H_2O$ exit.

Light reaction

The pathway of photosynthesis that converts light energy into chemical energy in the form of $ATP$ and $NADPH$.

Carbon-fixation reaction

The pathway of photosynthesis that uses $ATP$, $NADPH$, and $CO_2$ to produce carbohydrates; also known as the light-independent reaction.

Photons

Particles of light that behave as discrete packets of energy.

Pigments

Molecules that absorb specific wavelengths in the visible range of the electromagnetic spectrum.

Absorption spectrum

A graph showing how much of each wavelength of light a specific pigment absorbs.

Chlorophyll

A pigment that absorbs blue and red light and scatters or reflects green light.

Accessory pigments

Pigments that absorb light wavelengths that chlorophyll a and b cannot absorb, providing an advantage for light capture.

Thylakoids

Inner membranes of the chloroplast where light-dependent reactions occur and $H^+$ ions accumulate.

Stroma

The semi-fluid interior of the chloroplast where light-independent reactions like the Calvin cycle take place.

Antenna systems

Also called light-harvesting complexes, these are arrangements of pigment molecules that surround a reaction center in a photosystem.

Photosystem

A cluster of 200–300 pigment molecules located in the thylakoid membranes that functions to absorb light energy and excite electrons.

ATP synthase

A transport protein in the thylakoid membrane that joins $ADP$ to $P_i$ using the energy from an $H^+$ concentration gradient.

Calvin cycle

The $CO_2$ fixation pathway occurring in the stroma, also known as the Calvin-Benson Cycle.

Rubisco

Short for ribulose bisphosphate carboxylase/oxygenase, it is the enzyme that catalyzes the binding of $CO_2$ to $RuBP$.

RuBP

Ribulose bisphosphate, a 5-C compound that combines with $CO_2$ at the start of the Calvin cycle.

3PG

A 3-carbon molecule (also called PGA) formed when the initial 6-C compound in the Calvin cycle breaks down.

PGAL

A high-energy molecule formed in the Calvin cycle using fuel from $ATP$ and $NADPH$; two of these molecules combine to form one glucose.