Chapter 20: Calvin Cycle & other Dark Reactions of Photosynthesis

Rubisco

Enzyme that catalyzes the fixation of CO2 in the Calvin-Benson Cycle (bind to O2, leading to photorespiration)

Ribulose-1,5-bisphosphate Carboxylase

Enzyme activity where Rubisco adds CO₂ to ribulose-1,5-bisphosphate, initiating the Calvin-Benson cycle (produces 2 molecules of 3-phosphoglycerate)

Ribulose-1,5-bisphosphate Oxygenase

Enzyme activity where Rubisco adds O₂ to ribulose-1,5-bisphosphate, resulting in photorespiration

Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase

Full name of Rubisco

Calvin-Benson Cycle

Series of biochemical reactions that converts CO2 into organic compounds in plants, taking place in the stroma of chloroplasts

Photorespiration

Metabolic pathway where oxygen competes w/ CO2 for fixation by Rubisco, leading to the production of 2-phosphoglycolate, a waste product.

C3 Plants

Plants that use the Calvin-Benson Cycle directly to fix CO2, producing 3C molecules (3-phosphoglycerate)

C4 Plants

Plants that initially fix CO2 into a 4C compound (oxaloacetate or malate) before it enters the Calvin-Benson Cycle

Hatch-Slack Pathway

Pathway used by C4 Plants to transport CO2 to bundle sheath cells where Rubisco can efficiently fix it, minimizing photorespiration

Crassulacean Acid Metabolism

Photosynthetic adaptation in some plants where CO2 is fixed at night into organic acids, which are later used in the day for photosynthesis.

Pentose Phosphate Pathway

Metabolic Pathway parallel to glycolysis that generates NADPH & Ribose-5-Phosphate for biosynthesis

Hexose Monophosphate Shunt

Another name for the Pentose Phosphate Pathway

Phosphopentose Isomerase

An enzyme that converts ribulose-5-phosphate to ribose-5-phosphate in the non-oxidative phase of the Pentose Phosphate Pathway.

Transaldolase

An enzyme in the non-oxidative phase of the Pentose Phosphate Pathway that transfers a 3C unit between sugar molecules

Transketolase

An enzyme that transfers a 2C unit between sugar molecules in the non-oxidative phase of the Pentose Phosphate Pathway

Ribulose-5-Phosphate

A 5C sugar phosphate that is an intermediate in the Pentose Phosphate Pathway

Ribose-5-Phosphate

5C sugar that is essential for the synthesis of nucleotides and nucleic acids.

NADPH

Nicotinamide adenine dinucleotide phosphate, a coenzyme that provides reducing power for anabolic reactions.

Glucose-6-Phosphate Dehydrogenase Deficiency

Genetic condition in which the enzyme glucose-6-phosphate dehydrogenase is deficient, impairing the Pentose Phosphate Pathway & reducing NADPH production

Malaria

A parasitic disease caused by Plasmodium species, transmitted through the bite of infected mosquitoes.

Glutathione

A tripeptide (glutamine-cysteine-glycine) that acts as an antioxidant in cells, protecting them from oxidative damage.