Biology 2e - Chapter 8: Photosynthesis Flashcards

This set of vocabulary flashcards covers building blocks of photosynthesis, including autotrophs vs. heterotrophs, leaf and chloroplast structures, light energy properties, thylakoid components, the Electron Transport Chain, and the stages of the Calvin Cycle.

Photoautotrophs

Organisms that use sunlight to make food, including plants, algae, and cyanobacteria.

Chemoautotrophs

Organisms, such as thermophilic bacteria, that capture energy from inorganic compounds to make food.

Heterotrophs

Organisms, including animals, fungi, and most bacteria, that rely on organic carbon produced by autotrophs for their energy needs.

Anoxygenic Photosynthesis

A form of photosynthesis that does not generate oxygen, performed by some bacteria.

Stomata

Small pores on the leaf underside through which gas exchange occurs ($CO_2$ enters and $O_2$ exits).

Guard Cells

The specialized cells that surround a stoma (singular) to regulate the opening and closing of the pore.

Thylakoid

Disc-shaped structures within the chloroplast where the light reaction occurs; the membranes contain chlorophyll and other pigments.

Grana

The name given to stacks of thylakoids within the chloroplast.

Stroma

The fluid-filled space within the chloroplast (outside the thylakoids) where the Calvin cycle occurs.

Lumen

The internal space located inside the thylakoid membrane.

Mesophyll

The specialized "middle leaf" cells where high densities of chloroplasts are found.

Electromagnetic Energy

Light energy composed of photon particles that travel as waves; shorter wavelengths carry more energy than longer wavelengths.

Visible Range

The fraction of electromagnetic energy seen by humans and used by plants, ranging from $700-400\,nm$.

Chlorophyll a

A primary pigment consisting of a phytol chain embedded in the membrane and a tetraporhyrin ring that lies flat on the thylakoid surface.

Chlorophyll b

An accessory pigment similar to chlorophyll a, but containing a $-CHO$ group instead of a $-CH_3$ group in a specific position.

$\beta$-carotene

A type of carotenoid pigment that protects photosystems by dissipating excess energy, also responsible for the color of carrots and oranges.

Photosystem II (PSII)

The site of light absorption where electrons are excited and water is split to release oxygen ($O_2$) as a by-product.

Photosystem I (PSI)

The site where light excites an electron from the chlorophyll a pair, which is then passed to the second part of the ETC leading to NADP reductase.

ATP Synthase (ATPase)

An enzyme complex in the thylakoid membrane that uses a $H^+$ gradient (chemiosmosis) to generate ATP from ADP and $P_i$.

Plastocyanin (Pc)

A component of the first electron transport chain that helps transport electrons between the Cytochrome $b_6f$ complex and PSI.

Ferredoxin (Fd)

A molecule that transports electrons from Photosystem I to NADP reductase in the second part of the ETC.

NADP Reductase

The enzyme complex that uses electrons from the second ETC to reduce $NADP^+$ into NADPH.

RuBisCO

Ribulose bis-phosphate carboxylase-oxidase; the enzyme that catalyzes the addition of $CO_2$ to RuBP in the Calvin cycle.

Carbon Fixation

The first stage of the Calvin cycle where $CO_2$ is added to RuBP by RuBisCO to generate two $3$-PGA molecules.

Reduction (Calvin Cycle)

The second stage of the Calvin cycle where ATP and NADPH are used to add electrons to molecules, producing sugar in the form of GA3P.

GA3P (Glyceraldehyde-3-phosphate)

The organic carbon product of the Calvin cycle; three cycles are required to create one molecule, and $2\,GA3P$ molecules are needed to make one glucose.

Photorespiration

The process that occurs when RuBisCO functions as an oxygenase instead of a carboxylase, resulting in no sugar production.

Primary Production Proxies

Methods used to quantify photosynthesis, such as measuring $[^{14}C]\text{-}HCO_3$ uptake, dissolved $O_2$ production, or $[^{18}O]\text{-}H_2O$ water splitting.