Unit 1 Lesson 4 - Photosynthesis, Calvin Cycle, CAM table

What are light-dependent reactions?

Series of reactions in the thylakoid membrane that use light energy to split water, release oxygen, and generate ATP and NADPH through photosystems and an electron transport chain.

What is photosystem II?

Protein complex in the thylakoid membrane containing chlorophyll that absorbs light, excites electrons, and initiates the electron transport chain while splitting water via photolysis.

What does photosystem I do?

Protein complex in the thylakoid membrane that receives electrons from the transport chain, re-energizes them with light, and reduces NADP⁺ to NADPH.

What is the function of the electron transport chain?

Series of protein carriers in the thylakoid membrane that pass excited electrons from photosystem II to photosystem I, releasing energy to pump protons and create a gradient.

What is photolysis?

Splitting of water molecules in photosystem II using light energy to release oxygen, protons, and electrons that replenish the reaction center.

What is a proton gradient?

Buildup of H⁺ ions in the thylakoid space created by the electron transport chain, providing the energy for ATP synthesis.

What role does ATP synthase play?

Enzyme complex in the thylakoid membrane that uses the flow of protons down their gradient to phosphorylate ADP into ATP.

Define chemiosmosis.

Process where protons flow through ATP synthase from high to low concentration, driving ATP production in the light-dependent reactions.

What is cyclic electron flow?

Alternative path around photosystem I that generates extra ATP without producing NADPH or oxygen, used to balance energy needs.

What is non-cyclic electron flow?

Main linear path from photosystem II to photosystem I that produces both ATP and NADPH while splitting water and releasing oxygen.

What is Rubisco?

Enzyme that catalyzes the attachment of CO₂ to RuBP in carbon fixation, also capable of binding O₂ in photorespiration.

What does RuBP stand for?

Five-carbon sugar molecule that combines with CO₂ in the Calvin Cycle and is regenerated at the end of each turn.

What is 3-PGA?

Three-carbon compound formed immediately after Rubisco fixes CO₂ onto RuBP, the first stable product in the Calvin Cycle.

What does G3P represent?

Three-carbon sugar produced by reduction of 3-PGA using ATP and NADPH, which can form glucose or regenerate RuBP.

Define carbon fixation.

First phase of the Calvin Cycle where Rubisco incorporates atmospheric CO₂ into an organic molecule (RuBP) to form 3-PGA.

What occurs in the reduction phase of the Calvin Cycle?

Second phase where ATP and NADPH convert 3-PGA into G3P by adding energy and electrons.

What happens during the regeneration phase of the Calvin Cycle?

Third phase where five G3P molecules are rearranged using ATP to reform three RuBP molecules.

What is photorespiration?

Wasteful process where Rubisco binds O₂ instead of CO₂ under hot/dry conditions, consuming energy and releasing fixed carbon without producing sugar.

What characterizes Kranz anatomy?

Specialized leaf structure in C4 plants where mesophyll cells form a wreath around bundle sheath cells containing Rubisco for CO₂ concentration.

What is the function of PEP carboxylase?

Enzyme in mesophyll cells of C4 and CAM plants that fixes CO₂ into a four-carbon acid with high affinity and no oxygenase activity.

Define oxaloacetate.

Four-carbon acid formed first when PEP carboxylase fixes CO₂ in C4 and CAM pathways before conversion to malate.

What is malate?

Four-carbon acid that shuttles CO₂ from mesophyll to bundle sheath in C4 plants or stores it overnight in CAM plants.

What are bundle sheath cells?

Inner cells surrounding vascular tissue in C4 leaves where CO₂ is released and fixed by Rubisco in a high-concentration environment.

What is temporal separation in CAM plants?

Strategy where CO₂ fixation by PEP carboxylase occurs at night and decarboxylation occurs during the day.

What describes spatial separation in C4 plants?

Strategy where initial CO₂ fixation occurs in mesophyll cells and the Calvin Cycle occurs in bundle sheath cells.

What is an absorption spectrum?

Graph showing wavelengths of light absorbed by photosynthetic pigments, with peaks for chlorophyll a in blue and red regions.

What is an action spectrum?

Graph showing the relative rate of photosynthesis at different wavelengths, peaking in blue and red where absorption is highest.