Photosynthesis — Science Lesson

Reading Passage

Photosynthesis

Photosynthesis is the process by which plants, algae, and some bacteria convert sunlight into chemical energy stored as glucose. It is one of the most important biological processes on Earth, as it produces the oxygen that most living things breathe and forms the base of nearly every food chain.

The process takes place primarily in the leaves of plants, inside structures called chloroplasts. Chloroplasts contain a green pigment called chlorophyll, which captures the energy from sunlight. Water absorbed through the roots travels up the stem through tube-like structures called xylem and reaches the leaves.

Carbon dioxide enters leaves through tiny pores called stomata. Inside the chloroplasts, sunlight energy is used to combine water and carbon dioxide into glucose (a sugar) and oxygen. The glucose is used by the plant for growth and energy, while oxygen is released into the atmosphere as a byproduct.

Photosynthesis and respiration are complementary processes. Plants use photosynthesis to produce glucose and release oxygen during the day. At night, and in all cells during respiration, glucose is broken back down to release energy, consuming oxygen and releasing carbon dioxide. This cycle maintains the balance of gases in Earth’s atmosphere.

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