Light Dependent and Light Independent Reactions Flashcards

Vocabulary flashcards covering key terms, scientists, locations, phases, and numerical values related to light dependent and light independent photosynthetic reactions.

Light Dependent Reaction

Photosynthetic reactions occurring in the thylakoids of the chloroplast that use sunlight to initiate electron transfer, reducing $NADP^+$ to $NADPH$, splitting water to give off oxygen as a by-product, and forming $ATP$ through phosphorylation.

Hill Reaction

Another name for the light dependent reaction, discovered by Robin Hill in $1937$.

Cyclic Photophosphorylation

A process taking place in the thylakoid membrane that uses Photosystem I and chlorophyll $P700$ to convert $ADP$ to $ATP$ for immediate cellular energy.

Light Independent Reaction

Also referred to as 'dark reactions' or the Calvin Cycle; takes place in the stroma of the chloroplast and uses $ATP$ and $NADPH$ produced in light reactions to fix carbon dioxide ($CO_2$) into glucose.

Calvin-Benson Cycle

Another name for the Calvin Cycle, discovered in $1950$ by Melvin Calvin, James Bassham, and Andrew Benson at the University of California, Berkeley using the radioactive isotope carbon-14.

Carbon Fixation

The first stage of the Calvin Cycle involving the process of incorporating an inorganic carbon molecule, $CO_2$, into organic material.

Rubisco

Also known as RuBP carboxylase, an enzyme that attaches $CO_2$ to ribulose-1,5-bisphosphate (RuBP); it accounts for $25-40\%$ of total plant protein and is believed to be the most abundant protein in the chloroplast and on Earth.

Ribulose bisphosphate (RuBP)

A $5$-carbon sugar molecule that reacts with $CO_2$ during carbon fixation to create a short-lived, unstable $6$-carbon intermediate.

3-Phosphoglycerate (3-PGA)

A $3$-carbon molecule formed when the short-lived $6$-carbon intermediate produced during carbon fixation immediately splits in half.

Reduction Phase

The second stage of the Calvin Cycle where $ATP$ provides energy and $NADPH$ provides high-energy electrons to convert $3\text{-PGA}$ into $1,3\text{-bisphosphoglycerate}$ and then into glyceraldehyde-3-phosphate (G3P).

Glyceraldehyde-3-phosphate (G3P)

A higher-energy $3$-carbon sugar produced during the reduction phase of the Calvin Cycle, which can be used to form glucose and other organic compounds.

Phosphoglyceraldehyde (PGAL)

An alternative name/abbreviation for Glyceraldehyde-3-phosphate (G3P).

Regeneration Phase

The third stage of the Calvin Cycle in which five molecules of G3P undergo complex enzymatic reactions costing $3$ molecules of $ATP$ to reform three molecules of RuBP.

Requirements to Produce One G3P Molecule

The specific input needed by the chloroplast to produce one molecule of G3P: $3$ molecules of $CO_2$, $9$ molecules of $ATP$, and $6$ molecules of $NADPH$.

Glucose Synthesis Requirements

The requirement of six turns of the Calvin Cycle (fixing six $CO_2$ molecules) to produce enough G3P to form one molecule of glucose ($C_6H_{12}O_6$).