In the process of photosynthesis, plants synthesize glucose ([tex]$C _6 H _{12} O _6$[/tex]) by using light energy to convert carbon dioxide ([tex]$CO_2$[/tex]) and water ([tex]$H_2O$[/tex]) into glucose and oxygen ([tex]$O_2$[/tex]). The overall chemical equation for photosynthesis can be simplified as:
[tex]\[ 6CO_2 + 6H_2O + light \ energy \rightarrow C_6H_{12}O_6 + 6O_2 \][/tex]
To form one molecule of glucose ([tex]$C_6 H _{12} O _6$[/tex]), 12 hydrogen atoms are required. These hydrogen atoms are sourced from water ([tex]$H _2 O$[/tex]), which plants absorb through their roots.
In detail:
1. Water molecules are split during the light-dependent reactions of photosynthesis, which take place in the thylakoid membranes of the chloroplasts.
2. This process, known as photolysis, splits water into hydrogen ions ([tex]$H^+$[/tex]), electrons ([tex]$e^-$[/tex]), and oxygen gas ([tex]$O_2$[/tex]).
3. The hydrogen ions are then used in the Calvin cycle (light-independent reactions) to help form glucose by combining with carbon dioxide.
Therefore, the hydrogen ([tex]$H$[/tex]) used in the formation of glucose ([tex]$C_6 H _{12} O _6$[/tex]) comes from water ([tex]$H _2 O$[/tex]).
The correct answer is:
- water
