answersLogoWhite

0

In simple terms, photosynthesis is the conversion of carbon dioxide (CO2) to carbohydrate (CH2O). To do this two things are needed: energy to drive the reaction and a source of hydrogen.

The light reaction of photosynthesis produces two essential substances: ATP and NADPH. ATP provides the energy for the conversion of CO2 to CH2O, and NADPH provides the hydrogen.

The light reaction depends on groups of chlorophyll molecules, called photosystems, absorbing light energy. The energy is used to eject high energy electrons from the chlorophyll. The energy in the electrons is then used to make ATP and NADPH.

There are two photosystems, called photosystem I (PSI) and photosystem II (PSII), which work in sequence. (PSII comes before PSI in the sequence, but they were discovered and named in the reverse order!).

PSII absorbs light and emits a high energy electron. The energetic electron then passes down a series of molecules, called an electron transport chain (ETC), releasing energy as it goes (you can visualise it as a ball bouncing down a set of stairs, losing energy as it falls). The energy released is used to make the energy carrier compound ATP.

To replace the electrons lost from chlorophyll in PSII water (H2O) is split into hydrogen ions (H+), electrons (e-) and oxygen atoms (O):

H2O = 2H+ + 2e- + O

This is the source of the oxygen released by photosynthesis.

The second photosystem, PSI, also absorbs light and emits a high energy electron from chlorophyll. The energy in this electron is used to drive the synthesis of NADPH from NADP+ ,hydrogen ions (H+) and electrons (e-):

NADP+ + 2H+ + 2e- = NADPH + H+

The hydrogen ions needed for this come from the water which was split by PSII.

The electrons lost from the chlorophyll in PSI are replaced by the electrons ejected from PSII.

The result of all this is that light energy is converted into chemical energy in ATP, water is split to provide the hydrogen needed to make NADPH, and oxygen is released as a waste product.

The ATP and NADPH are then used in the light independent reaction (the Calvin cycle) to concert carbon dioxide into carbohydrate.

User Avatar

Wiki User

14y ago

What else can I help you with?

Related Questions

How is light energy processed in the light reactions of photosynthesis?

through an electron transport chain


Is the chemical reaction of photosynthesis?

6CO2+6H2O+light energy-->C6H12O6+6O2 Chemical reaction of Photosynthesis


What type of chemical reaction is photosynthesis?

The two reactions which occur during photosynthesis are light reaction and dark reaction. Light reaction takes place only in the presence of light. Dark reaction can occur with or without light.


What is light reaction and dark reaction?

Photosynthesis can be divided into two part: light reaction is the first stage of photosynthesis, occurring only in the presence of light, during which energy captured from light drives the production of ATP. dark reaction is the second stage of photosynthesis, not requiring light to occur, and during which energy released from ATP drives the production of organic molecules from carbon dioxide.


What is the function of the light independent reaction of photosynthesis?

To provide ATP and NADPH to drive the next part of photosynthesis, the Calvin Cycle (AKA Dark Reaction, Light Independent Reaction). Light reactions also produce oxygen gas as a byproduct.


A chemical reaction that occurs in plants that changes light energy into chemical energy is?

photosynthesis


How is light energy process in the light reaction of photosynthesis?

through an electron transport chain


What is the name of the process where the light is utilized to produce ATP?

The process is called photosynthesis. In photosynthesis, light energy is used by plants to convert carbon dioxide and water into glucose (energy) and oxygen.


Is exothermic reaction an example of photosynthesis?

An exothermic reaction is a reaction where heat or light energy is released. An example of this type of reaction is burning a candle.


Why is photosynthesis considered an energy conversion reaction?

Photosynthesis converts light energy from the sun into chemical energy stored in glucose molecules. This process involves the conversion of light energy into chemical energy, making it an energy conversion reaction.


Why photosynthesis called endothermic reaction?

Photosynthesis is an endothermic reaction because it takes energy (from sunlight) from the environment to use in the photosynthesis reaction. Without the energy input, the photosynthesis reaction could not occur.


How is ATP produced during the light reaction in photosynthesis?

During the light reaction of photosynthesis, ATP is produced through a process called photophosphorylation. This process involves the conversion of light energy into chemical energy, which is used to add a phosphate group to ADP, forming ATP. This ATP is then used as an energy source for the dark reaction of photosynthesis, where carbon dioxide is converted into glucose.