Photosynthesis and Respiration
- Biology
- Ages 11–14 · Grades 6–8
What you’ll find out
- Photosynthesis uses light energy to rearrange carbon dioxide and water into glucose and oxygen.
- Cellular respiration releases energy from glucose using oxygen, producing carbon dioxide and water.
- Plants both photosynthesise and respire; the two processes form a cycle of matter and energy.
No sign-up and no real names. In the lesson you check your understanding as you read, and practise until it sticks.
Photosynthesis: storing the Sun’s energy
Plants make their own food through photosynthesis, which takes place in the chloroplasts of their leaf cells. The plant absorbs carbon dioxide from the air through tiny pores and water from the soil through its roots. Chlorophyll captures energy from sunlight, and the plant uses it to rearrange carbon dioxide and water into glucose, a sugar. Oxygen is released as a by-product. In this way, energy from sunlight is stored as chemical energy in the glucose. Almost all food on Earth depends on this process.
Respiration: releasing the energy
Every living cell needs energy for growth, movement and repair, and it gets that energy through respiration. In the mitochondria, glucose reacts with oxygen, releasing the chemical energy stored in the glucose, along with carbon dioxide and water as waste products. Animals get glucose from their food, while plants use the glucose they made themselves. Plants respire all the time, day and night. Respiration is essentially photosynthesis in reverse, so the two processes form a cycle.
Curriculum links: NGSS MS-LS1-6 · NGSS MS-LS1-7 · England KS3: Material cycles and energy · Cambridge Lower Secondary Stages 7–9: Biology · NCERT Science, Classes 6–8