Photosynthesis and Calvin Cycle

Chloroplasts

Organelles in eukaryotic cells where photosynthesis occurs, evolved via endosymbiosis of a photosynthetic bacterium.

Photosystem

A complex within chloroplasts composed of a light-harvesting complex and a reaction center, responsible for converting light energy into excited electrons.

Light-harvesting complex

Part of a photosystem containing proteins and pigments that absorb light energy and transfer it to the reaction center.

Reaction center

A part of a photosystem with a pigment that can release an electron when excited by light energy.

Oxygenic photosynthesis

Photosynthesis process where water (H2O) is split to replace electrons in the reaction center, producing oxygen as a byproduct.

Anoxygenic photosynthesis

Photosynthesis process that uses other electron donors (like H2S) and does not produce oxygen.

Calvin-Benson cycle

The light-independent reactions of photosynthesis, occurring in the stroma of chloroplasts, responsible for CO2 fixation into carbohydrates.

RuBisCO

An enzyme catalyzing the fixation of CO2 in the Calvin cycle, considered the most abundant enzyme on Earth.

Noncyclic photophosphorylation

A process in which both ATP and NADPH are produced using both photosystems I and II in the light-dependent reactions.

Cyclic photophosphorylation

A process where ATP is produced using only photosystem I, typically when the cell requires more ATP than NADPH.

Electron Transport System (ETS)

Chain of proteins that transfer electrons from the reaction center, similar to that in cellular respiration, generating ATP.

Chemiosmosis

Process of synthesizing ATP as protons flow through ATP synthase across the membrane.

Photophosphorylation

Production of ATP using light energy during the light-dependent reactions of photosynthesis.

Z-scheme

The model describing the flow of electrons through the two photosystems during noncyclic photophosphorylation.

Thylakoids

Membranous structures within chloroplasts that are stacked into grana, where the light-dependent reactions of photosynthesis occur.

Photosynthetic pigments

Molecules such as chlorophyll that absorb light energy needed for photosynthesis.

Photosynthesis

The process by which light energy is transformed into chemical energy in the form of glucose.

Photoautotroph

Organisms that harness light energy to synthesise organic compounds from inorganic carbon.

Rubisco

The enzyme that catalyzes the addition of carbon from carbon dioxide to ribulose-1,5-bisphosphate (RuBP) in the Calvin cycle.

Calvin Cycle

The series of biochemical reactions that take place in the stroma of chloroplasts; synthesizes carbohydrates from CO2 using ATP and NADPH.

Light dependent reactions

Photosynthetic reactions that capture light energy to generate ATP and NADPH, occurring in the thylakoid membranes.

Light-independent reactions

Reactions of photosynthesis that do not require light, using ATP and NADPH to convert CO2 to sugar in the Calvin cycle.

Carboxylation

The stage in the Calvin cycle where carbon dioxide is added to RuBP, catalyzed by Rubisco.

Reduction phase

A part of the Calvin cycle where 3-Phosphoglycerate is converted into triose phosphate, involving ATP and NADPH.

Regeneration of RuBP

The final stage of the Calvin cycle, where some triose phosphate is used to regenerate RuBP, allowing the cycle to continue.

3-Phosphoglycerate (3-PGA)

An intermediate product in the Calvin cycle, containing 3 carbon atoms and a phosphate group.

Triose phosphate

The final product of the Calvin cycle that can be utilized to form glucose or other carbohydrates.

NADPH

A reducing agent that provides electrons and protons during the reduction phase of the Calvin cycle.

ATP

A nucleotide that serves as the primary energy carrier in cells, used in various cellular functions including photosynthesis.

Redox reactions

Chemical reactions involving the transfer of electrons, with reduction involving gain and oxidation involving loss of electrons.

1,3-Biphosphoglycerate (1,3-BPG)

An intermediate product in the Calvin cycle formed from 3-PGA, which stores energy before being converted into triose phosphate.

Photosynthesis

The process by which light energy is transformed into chemical energy in the form of glucose.

Photoautotroph

Organisms that harness light energy to synthesise organic compounds from inorganic carbon.

Rubisco

The enzyme that catalyzes the addition of carbon from carbon dioxide to ribulose-1,5-bisphosphate (RuBP) in the Calvin cycle.

Calvin Cycle

The series of biochemical reactions that take place in the stroma of chloroplasts; synthesizes carbohydrates from CO2 using ATP and NADPH.

Light dependent reactions

Photosynthetic reactions that capture light energy to generate ATP and NADPH, occurring in the thylakoid membranes.

Light-independent reactions

Reactions of photosynthesis that do not require light, using ATP and NADPH to convert CO2 to sugar in the Calvin cycle.

Carboxylation

The stage in the Calvin cycle where carbon dioxide is added to RuBP, catalyzed by Rubisco.

Reduction phase

A part of the Calvin cycle where 3-Phosphoglycerate is converted into triose phosphate, involving ATP and NADPH.

Regeneration of RuBP

The final stage of the Calvin cycle, where some triose phosphate is used to regenerate RuBP, allowing the cycle to continue.

3-Phosphoglycerate (3-PGA)

An intermediate product in the Calvin cycle, containing 3 carbon atoms and a phosphate group.

Triose phosphate

The final product of the Calvin cycle that can be utilized to form glucose or other carbohydrates.

NADPH

A reducing agent that provides electrons and protons during the reduction phase of the Calvin cycle.

ATP

A nucleotide that serves as the primary energy carrier in cells, used in various cellular functions including photosynthesis.

Redox reactions

Chemical reactions involving the transfer of electrons, with reduction involving gain and oxidation involving loss of electrons.

1,3-Biphosphoglycerate (1,3-BPG)

An intermediate product in the Calvin cycle formed from 3-PGA, which stores energy before being converted into triose phosphate.