Question

why do the biochemical reactions of living things depend on water?
select all that apply
a water can dissolve many substances.
b water must be present for many biochemical reactions to take place.
c water may be a reactant or a product.
d water holds energy needed for many reactions.

Explanation:

• Option a: Water is a universal solvent. Many biochemical substances (like ions, small molecules) dissolve in water, allowing them to move and react in the aqueous environment of cells.
• Option b: Most biochemical reactions (such as hydrolysis reactions) occur in an aqueous medium. The presence of water is essential for the proper orientation and interaction of reactant molecules.
• Option c: Water can participate in biochemical reactions. For example, in photosynthesis (a reactant: \(6CO_2 + 6H_2O

ightarrow C_6H_{12}O_6+6O_2\)) and in cellular respiration (a product: \(C_6H_{12}O_6 + 6O_2
ightarrow6CO_2+6H_2O + ATP\)).

• Option d: Water does not hold the energy needed for reactions. Energy for biochemical reactions is mainly carried by molecules like ATP (adenosine - tri - phosphate).

Answer:

A. Water can dissolve many substances.
B. Water must be present for many biochemical reactions to take place.
C. Water may be a reactant or a product.