Question

what is the overall equation for photosynthesis?
what is the purpose of photosynthesis? why do plants do it?
examine the diagram above. answer the questions:

1. what happens to water when it enters the light - dependent reaction? what happens to the hydrogen (of the water molecule)? what happens to the oxygen (in the water molecule)?
2. where do all the atoms that make up glucose ($c_6h_{12}o_6$) come from? how do you know?

a. carbon comes from
b. oxygen comes from
c. hydrogen come from
summarize the process of photosynthesis

stage of photosynthesis	where does it take place?	what happens (in a nutshell)?
stage 2:

Explanation:

Overall Equation for Photosynthesis

The overall chemical equation for photosynthesis is:
$$6\ce{CO_2} + 6\ce{H_2O} + \text{Light Energy} \xrightarrow{\text{Chlorophyll}} \ce{C_6H_{12}O_6} + 6\ce{O_2}$$

Purpose of Photosynthesis

Plants perform photosynthesis to produce glucose (a carbohydrate), which serves as a source of chemical energy (stored in its bonds) and as a building block for other organic molecules (like cellulose, starch, proteins, etc.). The energy from glucose powers the plant’s metabolic processes (e.g., growth, repair, reproduction).

Question 1: Water in Light - Dependent Reactions

• What happens to water? In the light - dependent reactions (occurring in the thylakoid membranes), water ($\ce{H_2O}$) is split (photolysis).
• What happens to hydrogen? The hydrogen atoms (and their electrons) from water are used to reduce $\text{NADP}^+$ to $\text{NADPH}$ (a carrier of reducing power) and also help generate ATP (via the electron transport chain and chemiosmosis).
• What happens to oxygen? The oxygen atoms from water are released as molecular oxygen ($\ce{O_2}$) into the atmosphere (this is the oxygen we breathe).

Question 2: Atoms in Glucose

a. Carbon: Comes from carbon dioxide ($\ce{CO_2}$). The light - independent reactions (Calvin cycle) use $\ce{CO_2}$ as the source of carbon to build glucose.
b. Oxygen: Comes from carbon dioxide ($\ce{CO_2}$) (and some from water, but most of the oxygen in glucose is from $\ce{CO_2}$; the oxygen from water is released as $\ce{O_2}$).
c. Hydrogen: Comes from water ($\ce{H_2O}$). The hydrogen from split water is used to reduce $\text{NADP}^+$ to $\text{NADPH}$, and this $\text{NADPH}$ then provides the hydrogen (and electrons) needed to build glucose in the Calvin cycle.

Summarize Photosynthesis (Table)

Stage of Photosynthesis	Where does it take place?	What happens (in a nutshell)?
Stage 2: Light - Independent Reactions (Calvin Cycle)	Stroma (inside chloroplasts)	$\ce{CO_2}$ is fixed (incorporated into organic molecules). Using ATP (energy) and $\text{NADPH}$ (reducing power) from the light - dependent reactions, glucose ($\ce{C_6H_{12}O_6}$) is synthesized.

Answer:

Overall Equation for Photosynthesis

The overall chemical equation for photosynthesis is:
$$6\ce{CO_2} + 6\ce{H_2O} + \text{Light Energy} \xrightarrow{\text{Chlorophyll}} \ce{C_6H_{12}O_6} + 6\ce{O_2}$$

Purpose of Photosynthesis

Plants perform photosynthesis to produce glucose (a carbohydrate), which serves as a source of chemical energy (stored in its bonds) and as a building block for other organic molecules (like cellulose, starch, proteins, etc.). The energy from glucose powers the plant’s metabolic processes (e.g., growth, repair, reproduction).

Question 1: Water in Light - Dependent Reactions

• What happens to water? In the light - dependent reactions (occurring in the thylakoid membranes), water ($\ce{H_2O}$) is split (photolysis).
• What happens to hydrogen? The hydrogen atoms (and their electrons) from water are used to reduce $\text{NADP}^+$ to $\text{NADPH}$ (a carrier of reducing power) and also help generate ATP (via the electron transport chain and chemiosmosis).
• What happens to oxygen? The oxygen atoms from water are released as molecular oxygen ($\ce{O_2}$) into the atmosphere (this is the oxygen we breathe).

Question 2: Atoms in Glucose

a. Carbon: Comes from carbon dioxide ($\ce{CO_2}$). The light - independent reactions (Calvin cycle) use $\ce{CO_2}$ as the source of carbon to build glucose.
b. Oxygen: Comes from carbon dioxide ($\ce{CO_2}$) (and some from water, but most of the oxygen in glucose is from $\ce{CO_2}$; the oxygen from water is released as $\ce{O_2}$).
c. Hydrogen: Comes from water ($\ce{H_2O}$). The hydrogen from split water is used to reduce $\text{NADP}^+$ to $\text{NADPH}$, and this $\text{NADPH}$ then provides the hydrogen (and electrons) needed to build glucose in the Calvin cycle.

Summarize Photosynthesis (Table)

Stage of Photosynthesis	Where does it take place?	What happens (in a nutshell)?
Stage 2: Light - Independent Reactions (Calvin Cycle)	Stroma (inside chloroplasts)	$\ce{CO_2}$ is fixed (incorporated into organic molecules). Using ATP (energy) and $\text{NADPH}$ (reducing power) from the light - dependent reactions, glucose ($\ce{C_6H_{12}O_6}$) is synthesized.