Build each reaction molecule by molecule — then test yourself.
🌿 Photosynthesis
Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. It takes place in the chloroplasts of plant cells, using the green pigment chlorophyll to absorb sunlight.
Plants take in carbon dioxide (CO2) through tiny pores called stomata, and absorb water (H2O) through their roots. Using light energy, they rearrange the atoms to produce glucose (C6H12O6) and release oxygen (O2).
6CO2 + 6H2O + light energy → C6H12O6 + 6O2
Challenge
Drag the correct molecules (in the right amounts!) into the reaction zone.
Reaction Zone
Correct! Light energy rearranges the atoms of CO2 and H2O into glucose and oxygen.
Products
Did you know? Photosynthesis produces the oxygen that almost all living organisms need to survive and is the starting point of nearly every food chain on Earth.
Aerobic respiration is the process by which cells break down glucose using oxygen to release energy. This happens in the mitochondria — often called the powerhouses of the cell.
The energy released is stored as ATP, which cells use to power everything from muscle movement to brain activity. The waste products are carbon dioxide and water — the exact reverse of photosynthesis!
Aerobic respiration is very efficient, producing around 38 ATP molecules per glucose.
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (ATP)
Challenge
Drag the correct reactants for aerobic respiration into the reaction zone.
Reaction Zone
Correct! Cells break down glucose with oxygen to release energy, producing CO2 and H2O.
Products
Connection: Aerobic respiration is the reverse of photosynthesis. Plants produce glucose and oxygen; animals (and plants!) consume them and produce CO2 and H2O. A beautiful cycle in nature.
When oxygen is not available, cells can still release energy from glucose through anaerobic respiration — but much less efficiently.
In yeast and some bacteria (fermentation): glucose is broken down into ethanol (C2H5OH) and carbon dioxide. This is used in brewing and baking — the CO2 makes bread rise and beer fizzy!
In animals and muscles: glucose is broken down into lactic acid (C3H6O3). This causes the burning feeling in your muscles during intense exercise.
Both produce only 2 ATP per glucose — far less than the 38 from aerobic respiration.
In yeast: C6H12O6 → 2C2H5OH + 2CO2 + energy (2 ATP)
In animals: C6H12O6 → 2C3H6O3 + energy (2 ATP)
Challenge — Fermentation (Yeast)
Drag the correct reactant for yeast fermentation.
Reaction Zone
Correct! Without oxygen, yeast ferments glucose into ethanol and CO2 — this is how bread and beer are made!
Products
Challenge — Lactic Acid (Animals)
Drag the correct reactant for anaerobic respiration in muscles.
Reaction Zone
Correct! During intense exercise, your muscles produce lactic acid when oxygen runs low. That is the burning feeling!
Products
Comparison: Aerobic respiration produces ~38 ATP per glucose. Anaerobic produces only 2 ATP. That is why you cannot sprint forever — your muscles switch to anaerobic respiration when oxygen runs low, which is far less efficient and builds up lactic acid.