General Science: The Chemistry in Photosynthesis

Vocabulary practice flashcards covering the chemical equations, structural locations, light-dependent reactions, and Calvin Cycle stages of photosynthesis from Grade 11 General Science.

Photosynthesis (Global Environmental Role)

The vital biological process that acts as the primary entry point for energy into the food web across all trophic levels, regulates the carbon and oxygen cycles to maintain breathable air, and functions as an Earth-regulating carbon sink by absorbing atmospheric $CO_2$.

National Greening Program

A reforestation project promoted by the Department of Environment and Natural Resources (DENR) in the Philippines that relies on photosynthesis in newly planted trees to sequester atmospheric carbon dioxide, produce oxygen, and combat climate change.

Photosynthesis Chemical Equation

The balanced chemical formula: $6CO_2 + 6H_2O + \text{Light} \rightarrow C_6H_{12}O_6 + 6O_2$, in which six carbon dioxide molecules and six water molecules produce one molecule of glucose and six molecules of oxygen gas.

Thylakoids

Stacked, chlorophyll-containing disk structures (arranged in grana) located inside the chloroplast that serve as the site of the light-dependent reactions.

Stroma

The fluid-filled space within the chloroplast that surrounds the thylakoids; it serves as the site of the light-independent Calvin Cycle.

Light-Dependent Reactions

The first phase of photosynthesis occurring in the thylakoid membrane, which converts light energy and water ($H_2O$) into chemical energy carriers (ATP and NADPH) while releasing oxygen ($O_2$) as a byproduct.

Photolysis

The light-driven splitting of water molecules at Photosystem II ($\text{PSII}$) that releases oxygen ($O_2$) and protons ($H^+$) to replace electrons energized and lost by chlorophyll.

Photosynthetic Electron Transport Chain (ETC)

A series of membrane proteins through which high-energy electrons pass, releasing energy used to pump protons ($H^+$) into the thylakoid lumen to create a proton gradient.

Photophosphorylation

The synthesis of ATP from ADP and inorganic phosphate ($P_i$) catalyzed by ATP Synthase as protons ($H^+$) flow down their electrochemical gradient out of the thylakoid lumen.

Adenosine Triphosphate (ATP)

A high-energy chemical carrier molecule generated during the light-dependent reactions that travels to the stroma to provide phosphate groups and energy for the Calvin Cycle.

Nicotinamide Adenine Dinucleotide Phosphate (NADPH)

A reduced coenzyme produced at Photosystem I ($\text{PSI}$) that shuttles high-energy electrons into the stroma to drive the reduction steps of the Calvin Cycle.

Calvin Cycle

The light-independent stage of photosynthesis occurring in the stroma that utilizes ATP and NADPH to fix carbon dioxide ($CO_2$) into carbohydrate precursors.

RuBisCO

The primary carbon-fixing enzyme—arguably the most abundant protein on Earth—that catalyzes the reaction between $CO_2$ and ribulose 1,5-bisphosphate (RuBP).

Carbon Fixation (Calvin Cycle Step 1)

The first step of the Calvin Cycle, in which three molecules of inorganic atmospheric $CO_2$ are enzymatically incorporated into three molecules of ribulose 1,5-bisphosphate (RuBP) by RuBisCO to form 3-phosphoglycerate.

Reduction (Calvin Cycle Step 2)

The Calvin Cycle step where 3-phosphoglycerate is phosphorylated by ATP and subsequently reduced by electrons from NADPH to synthesize glyceraldehyde-3-phosphate (G3P).

Regeneration of RuBP (Calvin Cycle Step 3)

The process in which the majority of G3P molecules are rearranged using ATP to regenerate ribulose 1,5-bisphosphate (RuBP), ensuring the cycle can continuously bind incoming $CO_2$.

Glyceraldehyde-3-phosphate (G3P)

A 3-carbon carbohydrate produced by the Calvin Cycle; two molecules exit every six complete turns to assemble into one molecule of glucose ($C_6H_{12}O_6$) in the cytoplasm.