Question

short answer question
explain the two main parts of photosynthesis and what happens during each part. why are both parts essential for the process to be successful?
write your response below:

Explanation:

Photosynthesis has two main parts: the light - dependent reactions and the light - independent reactions (Calvin cycle).

• Light - dependent reactions:
• Occur in the thylakoid membranes.
• Chlorophyll absorbs light energy.
• Water is split (\(H_2O

ightarrow 2H^{+}+\frac{1}{2}O_2 + 2e^{-}\)), releasing \(O_2\) as a by - product.

• \(ADP + Pi+\text{energy}

ightarrow ATP\) (photophosphorylation) and \(NADP^{+}+H^{+}+2e^{-}
ightarrow NADPH\) (reduction of \(NADP^{+}\))

• Light - independent reactions (Calvin cycle):
• Occur in the stroma.
• \(CO_2\) is fixed (\(CO_2 + C_5

ightarrow 2C_3\) using the enzyme RuBisCO).

• \(ATP\) provides energy and \(NADPH\) provides reducing power (\(2C_3

ightarrow C_6H_{12}O_6 + C_5\)) for the synthesis of glucose (\(C_6H_{12}O_6\)).

Both parts are essential:

• The light - dependent reactions provide \(ATP\) (energy currency) and \(NADPH\) (reducing agent) which are required for the Calvin cycle.
• The Calvin cycle uses the products of the light - dependent reactions to fix \(CO_2\) and produce glucose, which is the end - product of photosynthesis. Without the light - dependent reactions, the Calvin cycle would lack the necessary energy and reducing power. Without the Calvin cycle, the energy and reducing power from the light - dependent reactions would not be used to produce organic compounds.

Answer:

The two main parts of photosynthesis are the light - dependent reactions (in thylakoid membranes: light absorption, water splitting, \(ATP\) and \(NADPH\) production) and the light - independent reactions (Calvin cycle in stroma: \(CO_2\) fixation, glucose synthesis). They are essential as light - dependent reactions supply \(ATP\) and \(NADPH\) for the Calvin cycle, and the Calvin cycle uses these to make glucose.