What is photosynthesis ?
The process in which carbon dioxide and water react with each other in the presence of sunlight and form six carbon compound gulocse is called photosynthesis. This is an anabolic process because simple molecules combine with each other to form complex one.
Difference between anabolism and catabolism ?
The process in which small molecules combine to form larger ones is called anabolism. For example photosynthesis.
The process in which larger molecules broken down into simpler ones is called catabolism. For example respiration is a catabolic process.
There are two types of reactions takes place in photosynthesis :
1 :
light reaction
2:
Dark reaction
Light reaction :
Light reaction is a type of photosynthesis reaction that takes place in the presence of light and chlorophyll.light reaction takes place in the stroma of thylakoid membrane. It is also called photophosphorylation.
Types of light reactions :
1 : Cyclic photophosphorylation
2 : Non - cyclic photophosphorylation
Non cyclic photophosphorylation :
It is also called Z - Scheme. During the non cyclic photophosphorylation light falls on the photosystem || . Chlorophyll molecules are present on photosystem|| which released electrons as they are excited by light energy. These electrons moves towards the electron transport chain where the carrier proteins are present that carries the electrons. The water molecules in the photosystem are also break they release electrons that fills the whole of chlorophyll that have been created as their electrons jumped towards the carrier proteins.
Why it is called Z - scheme ?
The reason is that the whole process of light reactions in the form of Z as shown above this is why it is called Z - scheme.
The protons that released during the break down of water move against their potential gradient from higher concentration to lower concentration and moves through a membrane channels where ADP and pi are converted into ATP with the Help of enzyme ATP synthase. This is called chemiosmosis .
The photons of light also falls at photosystem| and the whole process is repeated. Here carrier proteins carries electrons where NADP and H converted into NADPH.
Non cyclic photophosphorylation :
It is same process like cyclic photophosphorylation but a difference is that the electrons from the photosystem | are expelled back towards photosystem|| but in non Cyclic photophosphorylation electrons area not expelled back.
Carbon cycle :
It is also called malvin calvin cycle . There are three steps of carbon cycle.
First step is carbon fixation
Second step is reduction
Third step is regeneration
Carbon fixation :
In this step five carbon molecules RuBP combines with three molecules of carbon dioxide and form three molecules of sixth carbon compounds called phosphoglycerate.
Reduction Phase :
In this phase six carbon compounds reduced in to three carbon compounds called glyceraldehyde.
Regeneration phase :
In this phase three carbon compounds of glyceraldehyde is converted into five carbon compound called RuBP.
Why it is called dark reaction :
The reason is that it takes place in the absence of light and uses the end product of light reactions to form glucose which is the food of plants.
A helpful information about photosynthesis occurrence :
Photosynthesis occurs in leaves . Where in leaves in mesophyll cells. Where in mesophyll cells . In the chloroplast. Where in chloroplast. In the thylakoid membrane. Where in thylakoid membrane. Reaction center are present on the thylakoid membrane on which chlorophyll are present that are exposed towards the sunlight.