Question

which is true for both photosynthesis and cellular respiration?
○ they require oxygen as a reactant.
○ they require organelles.
○ they require light energy from the sun.
○ they require cells to use water.

Explanation:

• Oxygen as a reactant: Photosynthesis produces oxygen (\(6CO_2 + 6H_2O+light

ightarrow C_6H_{12}O_6 + 6O_2\)), while cellular respiration (aerobic) uses oxygen (\(C_6H_{12}O_6+6O_2
ightarrow 6CO_2 + 6H_2O+energy\)). So oxygen is not a reactant for both.

• Require organelles: Some photosynthetic bacteria (like cyanobacteria) do not have chloroplasts (the organelle for photosynthesis in plant cells), and some anaerobic bacteria carry out cellular - like processes without mitochondria (the main organelle for aerobic cellular respiration in eukaryotes).
• Light energy from the Sun: Only photosynthesis requires light energy. Cellular respiration is a process that occurs in the dark (e.g., at night in plants) and breaks down glucose.
• Require cells to use water: In photosynthesis, water is split (\(2H_2O

ightarrow O_2 + 4H^++4e^-\) in the light - dependent reactions). In cellular respiration, water is also involved. For example, in the electron - transport chain, \(O_2 + 4H^++4e^-
ightarrow 2H_2O\), and water is a reactant in some of the hydrolysis reactions in the breakdown of macromolecules that can feed into cellular respiration pathways.

Answer:

They require cells to use water.