Connecting photosynthesis and respiration

≈ 48 min

Connecting photosynthesis and respiration

Photosynthesis and aerobic respiration are linked through matter but have opposite overall energy directions. Photosynthesis uses light energy to build glucose from carbon dioxide and water; respiration transfers energy from glucose to ATP and returns carbon dioxide and water. The processes do not simply cancel inside one leaf at one moment: their rates change with light, temperature, water and cellular demand.

Work it through

At night, a plant has no light for photosynthesis but its cells still respire. Carbon dioxide may be released overall. In daylight, a well-watered leaf may photosynthesise faster than it respires, so it takes in carbon dioxide overall.

Mastery target

Predict net gas exchange in a stated condition and explain it using relative process rates.

Which process transfers light energy into glucose?

Photosynthesis

Cellular respiration

Diffusion only

Digestion

Name the key biological term from Connecting photosynthesis and respiration: enter the term that best fits the explanation and visual model.

A sealed plant is kept in darkness for several hours. What is the likely net gas change?

Oxygen decreases and carbon dioxide increases.

Oxygen increases because photosynthesis speeds up.

Both gases disappear.

Glucose enters from sunlight.

Which statement corrects a common misunderstanding in Connecting photosynthesis and respiration?

Correct: Oxygen released by a plant is not proof that the plant is not respiring; both processes may occur together.

A single observation is enough to prove every biological claim.

Scientific terms are interchangeable whenever they sound similar.

A process always has exactly the same result in every environment.