Photosynthesis & Cellular Respiration Cheat Sheet

A printable reference covering photosynthesis, cellular respiration, ATP, chloroplasts, mitochondria, and chemical equations for grades 10-11.

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Photosynthesis and cellular respiration are the two major energy processes that connect plants, animals, and most ecosystems. This cheat sheet helps students compare where each process happens, what molecules enter and leave, and how energy changes form. Understanding these processes is essential for explaining carbon cycling, oxygen production, food webs, and how cells make usable energy. It also helps students interpret diagrams of chloroplasts, mitochondria, and membrane-based energy transfer. Photosynthesis stores energy by using light to convert carbon dioxide and water into glucose and oxygen. Cellular respiration releases energy by breaking glucose down with oxygen to produce carbon dioxide, water, and ATP. The main formulas are 6CO₂ + 6H₂O + light energy -> C₆H₁₂O₆ + 6O₂ for photosynthesis and C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O + ATP for cellular respiration. The two processes are complementary because the products of one process are often the reactants of the other.

Key Facts

The overall photosynthesis equation is 6CO₂ + 6H₂O + light energy -> C₆H₁₂O₆ + 6O₂.
The overall cellular respiration equation is C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O + ATP.
Photosynthesis occurs in chloroplasts, with light reactions in the thylakoid membranes and the Calvin cycle in the stroma.
Cellular respiration occurs mainly in mitochondria, with glycolysis in the cytoplasm, the Krebs cycle in the matrix, and the electron transport chain on the inner mitochondrial membrane.
Light reactions split water, release O₂, and make ATP and NADPH for the Calvin cycle.
The Calvin cycle uses CO₂, ATP, and NADPH to build sugar molecules such as glucose.
Aerobic respiration usually produces about 30 to 32 ATP per glucose molecule in eukaryotic cells.
Photosynthesis stores energy in glucose, while cellular respiration transfers energy from glucose into ATP that cells can use.

Vocabulary

Photosynthesis: Photosynthesis is the process by which plants, algae, and some bacteria use light energy to make glucose from carbon dioxide and water.
Cellular respiration: Cellular respiration is the process cells use to break down glucose and make ATP, usually using oxygen.
ATP: ATP is the main energy-carrying molecule that cells use to power chemical reactions and cellular work.
Chloroplast: A chloroplast is the organelle in plant and algal cells where photosynthesis occurs.
Mitochondrion: A mitochondrion is the organelle where most ATP is produced during aerobic cellular respiration.
Electron transport chain: The electron transport chain is a series of membrane proteins that move electrons and help produce ATP.

Common Mistakes to Avoid

Saying photosynthesis makes energy is wrong because it converts light energy into chemical energy stored in glucose rather than creating energy from nothing.
Forgetting to balance the equations is wrong because photosynthesis and respiration must follow conservation of matter, so the numbers of C, H, and O atoms must match on both sides.
Mixing up chloroplasts and mitochondria is wrong because chloroplasts carry out photosynthesis, while mitochondria carry out most steps of aerobic respiration.
Thinking plants only do photosynthesis is wrong because plants also perform cellular respiration to make ATP for their cells.
Calling oxygen the energy source in respiration is wrong because glucose is the fuel, while oxygen is the final electron acceptor in aerobic respiration.

Practice Questions

1 Write and balance the overall equation for photosynthesis using CO₂, H₂O, light energy, C₆H₁₂O₆, and O₂.
2 If a plant produces 12 molecules of O₂ during photosynthesis, how many molecules of CO₂ were used?
3 If one glucose molecule produces about 30 ATP during aerobic respiration, about how many ATP could 5 glucose molecules produce?
4 Explain why photosynthesis and cellular respiration are often described as complementary processes.