identify the main steps in the process of photosynthesis.write a short note about each step
Answers
Explanation:
the cellular level, the photosynthesis process takes place in cell organelles called chloroplasts. These organelles contain a green-coloured pigment called chlorophyll, which is responsible for the characteristic green colouration of the leaves.
As already stated, photosynthesis occurs in the leaves and the specialized cell organelles responsible for this process is called the chloroplast. Structurally, a leaf comprises a petiole, epidermis and a lamina. The lamina is used for absorption of sunlight and carbon dioxide during photosynthesis.
Structure of Chloroplast
Structure of Chloroplast. Note the presence of the thylakoid
“Photosynthesis Steps:”
During the process of photosynthesis, carbon dioxide enters through the stomata, water is absorbed by the root hairs from the soil and is carried to the leaves through the xylem vessels. Chlorophyll absorbs the light energy from the sun to split water molecules into hydrogen and oxygen.
The hydrogen from water molecules and carbon dioxide absorbed from the air are used in the production of glucose. Furthermore, oxygen is liberated out into the atmosphere through the leaves as a waste product.
Glucose is a source of food for plants that provide energy for growth and development, while the rest is stored in the roots, leaves and fruits, for their later use.
Pigments are other fundamental cellular components of photosynthesis. They are the molecules that impart colour and they absorb light at some specific wavelength and reflect back the unabsorbed light. All green plants mainly contain chlorophyll a, chlorophyll b and carotenoids which are present in the thylakoids of chloroplasts. It is primarily used to capture light energy. Chlorophyll-a is the main pigment.
The process of photosynthesis occurs in two stages:
Light-dependent reaction or light reaction
Light independent reaction or dark reaction
Stages of Photosynthesis
Stages of Photosynthesis in Plants depicting the two phases – Light reaction and Dark reaction
Light Reaction of Photosynthesis (or) Light-dependent Reaction
Photosynthesis begins with the light reaction which is carried out only during the day in the presence of sunlight. In plants, the light-dependent reaction takes place in the thylakoid membranes of chloroplasts.
The Grana, membrane-bound sacs like structures present inside the thylakoid functions by gathering light and is called photosystems.
These photosystems have large complexes of pigment and proteins molecules present within the plant cells, which play the primary role during the process of light reactions of photosynthesis.
There are two types of photosystems: photosystem I and photosystem II.
Under the light-dependent reactions, the light energy is converted to ATP and NADPH, which are used in the second phase of photosynthesis.
During the light reactions, ATP and NADPH are generated by two electron-transport chains, water is used and oxygen is produced.
The chemical equation in the light reaction of photosynthesis can be reduced to:
2H2O + 2NADP+ + 3ADP + 3Pi → O2 + 2NADPH + 3ATP
Dark Reaction of Photosynthesis (or) Light-independent Reaction
Dark reaction is also called carbon-fixing reaction.
It is a light-independent process in which sugar molecules are formed from the water and carbon dioxide molecules.
The dark reaction occurs in the stroma of the chloroplast where they utilize the NADPH and ATP products of the light reaction.
Plants capture the carbon dioxide from the atmosphere through stomata and proceed to the Calvin photosynthesis cycle.
In the Calvin cycle, the ATP and NADPH formed during light reaction drive the reaction and convert 6 molecules of carbon dioxide into one sugar molecule or glucose.
The chemical equation for the dark reaction can be reduced to:
3CO2 + 6 NADPH + 5H2O + 9ATP → G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi
* G3P – glyceraldehyde-3-phosphate
Calvin cycle
Calvin photosynthesis Cycle (Dark Reaction)
Explanation:
The process of photosynthesis is commonly written as: 6CO2 + 6H2O → C6H12O6 + 6O2. This means that the reactants, six carbon dioxide molecules and six water molecules, are converted by light energy captured by chlorophyll (implied by the arrow) into a sugar molecule and six oxygen molecules, the products.