The stages of photosynthesis

Reactions of photosynthesis, where they take place, and their ecological importance.

The stages of photosynthesis

Stomata — these are pores holes in the leaves that are responsible for the exchange of gases between the plant leaves and the atmosphere. Carbon dioxide is absorbed from the atmosphere and oxygen is released. Mesophyll — these are photosynthetic parenchyma cells that are located between the upper and lower epidermis.

These cells contain the chloroplasts. Vascular bundle — these are tissues that form part of the transport system of the plant. Vascular bundles consist of xylem and phloem vessels which transport water, dissolved minerals and food to and from the leaves.

Light-dependent Reactions The first stage of photosynthesis is the light dependent reactions. These reactions take place on the thylakoid membrane inside the chloroplast. These protein complexes contain light harvesting chlorophyll molecules and accessory pigments called antenna complexes.

The photosystems are also equipped with reactions centers RC. These are complexes of proteins and pigments which are responsible for energy conversion. The chlorophyll molecules of PSI absorb light with a peak wavelength of nm and are called P molecules. The light dependent reactions begin in PSII.

A photon of light is absorbed by a P chlorophyll molecule in the light harvesting complex of PSII.

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The energy that is generated from the light is passed from one P chlorophyll molecule to another until it reaches the reaction center RC of PSII.

At the RC is a pair of P chlorophyll molecules. An electron in the chlorophyll molecules becomes excited as a result of a higher level of energy. The excited electron becomes unstable and is released. Another electron is released following the capture of another photon of light by the light harvesting complex and the transfer of energy to the reaction center.

The electrons are transported in a chain of protein complexes and mobile carriers called an electron transport chain ETC. Plastoquinone is the mobile carrier that transports the electrons from the reaction center of PSII to the Cytochrome b6f Complex as shown in the diagram above.

The electrons lost from PSII are replaced by splitting water with light in a process called Photolysis. The hydrogen ions and oxygen are released into the thylakoid lumen.

Oxygen is later released into the atmosphere as a by-product of photosynthesis. This results in a higher concentration of hydrogen ions proton gradient in the lumen. Cytochrome b6f transfers the electrons to Plastocyanin which then transports them to Photosystem I.

The electrons have now arrived at PSI.

The stages of photosynthesis

They again receive energy, but this time from light absorbed by P chlorophyll molecules.2 Stages of Photosynthesis. STUDY. PLAY. Light-dependent reaction-Light is absorbed by the chlorophyll and stored as ATP-Water is broken down to release oxygen gas-H+ ions are stored in a carrier molecule called NADPH.

Light-independent reaction. Photosynthesis represents the biological process by which plants convert light energy into sugar to fuel plant cells. Comprised of two stages, one stage converts the light energy into sugar, and then cellular respiration converts the sugar to Adenosine triphosphate, known as ATP, the fuel for all cellular life.

Photosynthesis - Wikipedia

Photosynthesis represents the biological process by which plants convert light energy into sugar to fuel plant cells. Comprised of two stages, one stage converts the light energy into sugar, and then cellular respiration converts the sugar to Adenosine triphosphate, known as ATP, the fuel for all cellular life.

2 Stages of Photosynthesis. STUDY. PLAY.

Photosynthesis Occurs on Thylakoid Membranes

Light-dependent reaction-Light is absorbed by the chlorophyll and stored as ATP-Water is broken down to release oxygen gas-H+ ions are stored in a carrier molecule called NADPH. Light-independent reaction.

The two stages of photosynthesis: Photosynthesis takes place in two stages: light-dependent reactions and the Calvin cycle (light-independent reactions).

Light-dependent reactions, which take place in the thylakoid membrane, use light energy to make ATP and NADPH.

The two stages of photosynthesis: Photosynthesis takes place in two stages: light-dependent reactions and the Calvin cycle (light-independent reactions). Light-dependent reactions, which take place in the thylakoid membrane, use light energy to make ATP and NADPH.

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