BIOL212 Ch10

Comprehensive vocabulary flashcards generated from Campbell Biology Chapter 10 notes on photosynthesis.

Photosynthesis

The biological process that converts solar energy into chemical energy within chloroplasts, directly or indirectly nourishing almost the entire living world.

Autotrophs

Organisms that sustain themselves without eating anything derived from other organisms, producing organic molecules from $CO_2$ and other inorganic molecules.

Heterotrophs

Organisms that obtain organic material from other living or dead organisms, functioning as the consumers of the biosphere.

Mesophyll

The interior tissue of a leaf where chloroplasts are mainly concentrated and where most photosynthesis occurs.

Stomata

Microscopic pores on the surface of leaves through which $CO_2$ enters and $O_2$ exits.

Stroma

The dense fluid envelope surrounded by the two outer membranes of a chloroplast.

Thylakoids

Connected membranous sacs inside a chloroplast that compose a third membrane system and contain chlorophyll molecules.

Grana

Stacked columns formed by thylakoid sacs inside the chloroplast.

Light Reactions

The initial stage of photosynthesis in thylakoid membranes that splits $H_2O$, releases $O_2$, reduces $NADP^+$ to $NADPH$, and generates ATP via photophosphorylation.

Calvin Cycle

The second stage of photosynthesis occurring in the stroma that uses ATP and $NADPH$ from light reactions to fix $CO_2$ into sugar molecules.

Carbon Fixation

The initial conversion of inorganic carbon from $CO_2$ into organic molecules within photosynthetic organisms.

Electromagnetic Spectrum

The entire range of electromagnetic radiation, ranging from gamma rays with wavelengths shorter than $1\text{ nm}$ to radio waves longer than $1\text{ km}$.

Photons

Discrete particles of light energy, each containing a fixed quantity of energy inversely proportional to its wavelength.

Chlorophyll a

The main light-capturing pigment in chloroplasts that directly participates in light reactions by absorbing violet-blue and red light.

Carotenoids

Accessory pigments in chloroplasts that absorb violet and blue-green light, broaden the photosynthetic spectrum, and photoprotect tissues from light damage.

Photosystem

A light-capturing unit in thylakoid membranes consisting of a reaction-center complex surrounded by light-harvesting complexes.

Reaction-Center Complex

A protein complex in a photosystem holding a special pair of chlorophyll a molecules and a primary electron acceptor.

Light-Harvesting Complex

An array of pigment molecules bound to proteins that transfers photon energy to the special chlorophyll a pair in the reaction-center complex.

Primary Electron Acceptor

A molecule in the reaction-center complex that accepts photoexcited electrons from chlorophyll a and becomes reduced.

Photosystem II (PS II)

A thylakoid photosystem whose reaction-center chlorophyll a pair is known as $P680$ because it absorbs light best at a wavelength of $680\text{ nm}$.

Photosystem I (PS I)

A thylakoid photosystem whose reaction-center chlorophyll a pair is known as $P700$ because it absorbs light best at a wavelength of $700\text{ nm}$.

Linear Electron Flow

The primary pathway during light reactions that routes electrons through both photosystems (PS II and PS I) to produce ATP and $NADPH$.

Cyclic Electron Flow

An alternative electron pathway using only Photosystem I that generates ATP without producing $NADPH$ or releasing oxygen.

Rubisco

RuBP carboxylase-oxygenase, the primary enzyme in the Calvin cycle that catalyzes the binding of $CO_2$ to ribulose bisphosphate (RuBP).

Glyceraldehyde 3-phosphate (G3P)

A three-carbon sugar produced directly as the net output of the Calvin cycle.

Photorespiration

A metabolic process in plants where rubisco binds $O_2$ instead of $CO_2$, consuming organic fuel and oxygen without producing ATP or sugar.

C3 Plants

Plants that fix carbon initially via rubisco into a three-carbon compound (3-phosphoglycerate).

C4 Plants

Plants that minimize photorespiration by incorporating $CO_2$ into a four-carbon compound in mesophyll cells before exporting it to bundle-sheath cells for the Calvin cycle.

PEP Carboxylase

An enzyme in mesophyll cells of $C_4$ plants that fixes $CO_2$ to phosphoenolpyruvate (PEP) with a higher affinity for $CO_2$ than rubisco.

CAM Plants

Plants utilizing crassulacean acid metabolism that open stomata at night to fix $CO_2$ into organic acids and close them during the day to run the Calvin cycle.