Biological Science Chapter 10: Photosynthesis Flashcards

Vocabulary flashcards covering the key terms, pigments, and reactions of photosynthesis as presented in Chapter 10 of Biological Science, Seventh Edition.

Photosynthesis

The use of sunlight to manufacture carbohydrates, converting light energy into chemical energy.

Autotrophs

Organisms called self-feeders that make their own food from ions and molecules.

Heterotrophs

Organisms called different-feeders that must obtain sugars from other organisms.

Chloroplasts

The specific organelles in which photosynthesis occurs.

Stroma

The fluid-filled space within the chloroplast where the Calvin cycle occurs.

Thylakoids

Flattened, sac-like structures within chloroplasts where light-capturing reactions happen.

Light-capturing reactions

The set of reactions that use light energy and water to produce $O_2$, $NADPH$, and $ATP$.

Calvin cycle

The set of reactions that uses $CO_2$, $NADPH$, and $ATP$ to produce sugars like glucose.

Pigments

Molecules that absorb only certain wavelengths of light and reflect or transmit others.

Chlorophyll

The most common pigment in thylakoids; it reflects green light and is responsible for the green color of plants.

Wavelength

The distance between two wave crests, used to characterize light as a wave.

Photons

Discrete packets of light that represent its particle-like nature.

Electromagnetic radiation

A type of energy that acts both wavelike and particle-like, including visible light.

Carotenoids

Accessory pigments that absorb blue and green light and reflect yellow, orange, and red light.

Chlorophyll Head

A ring structure in a chlorophyll molecule that absorbs light.

Chlorophyll Tail

The part of the chlorophyll molecule that anchors it in the thylakoid membrane.

Xanthophylls

Accessory pigments found in chloroplasts that absorb light and pass energy to chlorophyll.

Antioxidants

The role played by carotenoids when they protect chlorophylls from damage by stabilizing free radicals.

Excited state

A higher energy state an electron enters when a chlorophyll molecule absorbs a photon.

Fluorescence

The release of energy as a combination of heat and light when an excited electron falls back to its ground state.

Photosystems

Protein complexes in the thylakoid membrane composed of $200$ to $300$ chlorophyll and accessory pigment molecules.

Antenna pigments

Pigment molecules that gather light energy and guide it toward a central reaction center.

Reaction center

The location where electromagnetic energy from sunlight is transformed into chemical energy.

Resonance energy transfer

The process where energy released from an electron excites an electron in a nearby pigment.

Pheophytin

An electron acceptor in Photosystem II that receives excited electrons from the reaction center.

Plastoquinone ($PQ$)

A molecule in the electron transport chain that helps pump protons into the thylakoid lumen.

Plastocyanin ($PC$)

A protein that carries electrons from the cytochrome complex to Photosystem I.

Ferredoxin

A protein that transfers electrons to the enzyme that reduces $NADP^+$.

Photophosphorylation

The production of $ATP$ triggered by the electrochemical gradient created by the electron transport chain during photosynthesis.

Z-scheme

A model that explains how Photosystem II and Photosystem I are linked in a linear pathway.

Enhancement effect

The phenomenon where photosynthesis runs at maximum rate when both red and far-red wavelengths are available.

Noncyclic electron flow

The linear pathway of electrons passing from water to $NADP^+$ through Photosystems II and I.

Cyclic electron flow

An alternative electron pathway that leads to $ATP$ production instead of producing $NADPH$.

Waxy cuticles

Structures on leaves that block the passage of $O_2$, $H_2O$, and $CO_2$.

Stomata

Openings in the leaf, controlled by guard cells, through which $CO_2$ enters and $H_2O$ and $O_2$ exit.

Carbon fixation

The addition of carbon atoms from an inorganic compound like $CO_2$ to an organic compound.

Ribulose 1,5-biphosphate ($RuBP$)

The initial five-carbon reactant and $CO_2$ acceptor in the Calvin cycle.

Rubisco

Ribulose-1,5 biphosphate carboxylase/oxygenase; the enzyme that fixes $CO_2$ and is the most abundant enzyme on Earth.

Photorespiration

A process that increases when stomata close and $CO_2$ transport stops, slowing photosynthesis.

$C_4$ pathway

A pathway used by some photosynthetic cells to increase $CO_2$ concentrations and make photosynthesis more efficient.

Crassulacean acid metabolism ($CAM$)

A photosynthetic pathway where carbon fixation occurs at night and the Calvin cycle occurs during the day.

Fixation phase

The first phase of the Calvin cycle where $CO_2$ reacts with $RuBP$ to produce two molecules of $3$-phosphoglycerate.

3-phosphoglycerate ($3PGA$)

The two-carbon molecule produced during the fixation phase of the Calvin cycle.

Reduction phase

The second phase of the Calvin cycle where $3PGA$ is phosphorylated and reduced to form glyceraldehyde-3-phosphate.

Glyceraldehyde-3-phosphate ($G3P$)

The product of the reduction phase used to make glucose or regenerate $RuBP$.

Regeneration phase

The third phase of the Calvin cycle which uses $ATP$ to regenerate $RuBP$ from $G3P$.

Gluconeogenesis

The process by which $G3P$ molecules are used to make glucose and fructose, which combine to form sucrose.

Sucrose

A sugar synthesized in the cytosol of plant cells when glucose and fructose are combined.

Starch

A polymer of glucose produced inside the chloroplast when sucrose is abundant.

Lumen

The interior space of the thylakoid into which protons are pumped to create an electrochemical gradient.