Science
Photosynthesis Deep Dive Quiz
Chlorophyll, Calvin cycle, and the most important reaction on Earth — photosynthesis deep dive.
Chlorophyll, Calvin cycle, and the most important reaction on Earth — photosynthesis deep dive.
Rubisco is the most abundant protein on Earth — an estimated 700 million tonnes of it exists at any given time, and it single-handedly fixes around 120 gigatons of carbon from the atmosphere each year. Without this one enzyme powering the Calvin cycle, life as we know it simply would not exist.
Each round presents 10 randomized multiple-choice questions drawn from a pool of 50, so every playthrough is different. You get instant feedback with explanations after each answer, plus a shareable score at the end.
You'll explore both stages of photosynthesis — light-dependent reactions in the thylakoids and the Calvin cycle in the stroma. Learn about the differences between C3, C4, and CAM plants, the history of discovery from Ingenhousz to Melvin Calvin, chlorophyll pigments, and cutting-edge research in artificial photosynthesis.
The Calvin cycle (also called the Calvin-Benson-Bassham cycle) is the light-independent stage of photosynthesis that occurs in the stroma of chloroplasts. Using the enzyme Rubisco, it fixes carbon dioxide into a 3-carbon compound (3-PGA), which is then reduced using ATP and NADPH from the light reactions to produce G3P — the building block for glucose and other organic molecules. It takes 6 turns of the cycle to produce one molecule of glucose.
Chlorophyll is the green pigment in plants that absorbs light energy for photosynthesis. Chlorophyll a is the primary pigment that directly participates in the light reactions, while chlorophyll b is an accessory pigment that absorbs different wavelengths and passes energy to chlorophyll a. Plants appear green because chlorophyll reflects green light wavelengths rather than absorbing them.
C3 plants (like rice and wheat) fix carbon directly via Rubisco but lose efficiency in hot, dry conditions through photorespiration. C4 plants (like corn and sugarcane) first fix CO2 into a 4-carbon compound in mesophyll cells, then shuttle it to bundle sheath cells where the Calvin cycle runs — this concentrates CO2 and minimizes photorespiration. CAM plants (like cacti) open their stomata only at night to collect CO2, storing it as an acid and using it during the day, which dramatically reduces water loss.
Last updated: April 2026