Mechanism of Photosynthesis : There are two major phases are found in Photosynthesis. They are as follows: 1. Light reaction 2. Dark reaction
1) Light Reaction (Photo chemical Phase)
In this reaction light plays the key role. A series of chemical reactions occurs in a very quick succession initiated by light and therefore the phase is technically called the photochemical phase. The light reaction takes place in chlorophyll containing thalakoids called Grana of Chloroplasts . The light reaction occurs in several steps.
Step-I : The chlorophyll on exposure to light energy becomes activated by absorbing
photons. (Photon is the smallest energy of light)
Step-II: The energy is used in splitting the water molecule into its two component ions H2O H+ + OH
The reaction is known as photolysis, which means splitting by light (photo means light, lysis means breaking)
Step-III: The highly reactive ions of water undergoes quick change in two different
directions of OH- and H+ ions as described below OH- ions through a series of steps produce water (H20) and Oxygen (O2). The Water may be used inside the plant but O2 is released into the atmosphere. H+ ions undergo series of changes in dark reaction. ATP and NADPH are formed at the end of the light reaction these are called as assimilatory powers.
2. Dark reaction (Bio synthetic phase)
This reaction in the phase do not require light energy and occur simultaneously with
the light reaction. (time gap between the two being less than even one thousands of a second)
The term dark reaction does not mean that they occur when it is dark at night. It only means that the reactions are not depend on light. H+ Ions produced in photolysis are immediately picked up by special compound NADP to form NADPH. In the dark phase the hydrogen of the NADPH is used to combine it with Co2 by utilizing ATP energy and to ultimately produce glucose (C6H12O6). This synthesis occurs in a number of steps
using certain special intermediate compounds (mainly RUBP Ribulose bi phosphate) and enzymes. Finally the glucose to convert to starch. During photosynthesis several events occur in the chloroplast some of them are :
1. Conversion of light energy to chemical energy
2. Splitting of water molecule
3. Reduction of carbondioxide to carbohydrates
Light is required to initiate several events while several may continue even in the absence of it. That would mean, once light energy has been captured it can help reactions to continue even in the dark. Light dependent events or reactons are called light reactions and it has been found to take place in grana, while the rest are called dark reactions and they occur in the stroma.
Plants are capable of working under a range of situations, from very lighted hot dry conditions to wet, humid dim light conditions and requirement of light and other factors varies from one plant to another.
10th Biology - Photosynthesis and Sun Light - New Syllabus
Sunlight is necessary to form starch: Take a plant with destarched leaves. Remember the process of destraching leaves.
• Cover one of its leaves with black paper on which a design is cut. Fix
the paper on the leaf in such a manner that light does not enter the dark
part.
• Place this plant in the sun.
• After few hours of exposure to bright sunlight, test the leaf which is
covered by black paper for the presence of starch.
• It will be observed that only the parts of the leaf, which could get light
through the cut out design, turns blue-black showing the presence of starch.
Chlorophyll and Photosynthesis
Ingenhousz wanted to find out more about photosynthesis and carried out several other experiments. He proposed that only green plant parts could carry out the process of photosynthesis.
What about plants having colored leaves? How is it that new leaves which look dark red in colour in several plants turn green? Do plants having reddish or yellowish leaves also carry out photosynthesis? Questions like these remained challenges until
scientists could isolate the green coloured substance from plant parts and study its nature.
Establishment of Ingenhousz’s proposition came after several experiments till the mid 20th century when scientists could also locate the site of photosynthesis and even isolate it. Around four decades after Ingenhousz’s proposition scientists could only isolate the green substance to observe its nature and find out whether photosynthesis could be carried out with it. This had become possible in the year 1817 due to the work of two scientists Pelletier and Caventou who obtained an extract of the green
colored substance and named it as chlorophyll means green leaf.
It was also found that the other pigments would aid in the process of photosynthesis by passing on the energy of sunlight trapped by them to chlorophyll.
Where does Photosynthesis take place?
Try to name some parts where you think photosynthesis occurs. Do you think the new reddish leaves of plants also carry out photosynthesis? What could be the role of their colour?
The exact location of the photosynthetic part or a part containing chlorophyll was not known till another 60 decades after Pelletier and Caventou discovered chlorophyll. It was believed to be spread in the cells of green plant parts. In 1883, Julius von Sachs, observed that chlorophyll in plant cells is not spread through the entire cell. It is found in organelles within the cell. Such organelles were named as chloroplasts. These are present in large numbers in the cells (around 40 – 100) of parts like the stomatal guard cells and ground tissues of plants .
• Cover one of its leaves with black paper on which a design is cut. Fix
the paper on the leaf in such a manner that light does not enter the dark
part.
• Place this plant in the sun.
• After few hours of exposure to bright sunlight, test the leaf which is
covered by black paper for the presence of starch.
• It will be observed that only the parts of the leaf, which could get light
through the cut out design, turns blue-black showing the presence of starch.
Chlorophyll and Photosynthesis
Ingenhousz wanted to find out more about photosynthesis and carried out several other experiments. He proposed that only green plant parts could carry out the process of photosynthesis.
What about plants having colored leaves? How is it that new leaves which look dark red in colour in several plants turn green? Do plants having reddish or yellowish leaves also carry out photosynthesis? Questions like these remained challenges until
scientists could isolate the green coloured substance from plant parts and study its nature.
Establishment of Ingenhousz’s proposition came after several experiments till the mid 20th century when scientists could also locate the site of photosynthesis and even isolate it. Around four decades after Ingenhousz’s proposition scientists could only isolate the green substance to observe its nature and find out whether photosynthesis could be carried out with it. This had become possible in the year 1817 due to the work of two scientists Pelletier and Caventou who obtained an extract of the green
colored substance and named it as chlorophyll means green leaf.
It was also found that the other pigments would aid in the process of photosynthesis by passing on the energy of sunlight trapped by them to chlorophyll.
Where does Photosynthesis take place?
Try to name some parts where you think photosynthesis occurs. Do you think the new reddish leaves of plants also carry out photosynthesis? What could be the role of their colour?
The exact location of the photosynthetic part or a part containing chlorophyll was not known till another 60 decades after Pelletier and Caventou discovered chlorophyll. It was believed to be spread in the cells of green plant parts. In 1883, Julius von Sachs, observed that chlorophyll in plant cells is not spread through the entire cell. It is found in organelles within the cell. Such organelles were named as chloroplasts. These are present in large numbers in the cells (around 40 – 100) of parts like the stomatal guard cells and ground tissues of plants .
New Medical Colleges in Andhra Pradesh in 9 Districts in 2014
Here is a good news for the medicine aspirants from Andhra Pradesh. The Government of India is proposed to establish new medical colleges across the country. The districts which do not have any medical college will be given preference.
In Andhra Pradesh, the new medical colleges are likely to come up in at least 9 districts. These are Mahaboobanagar, Nalgonda, Vizianagaram, Eluru, Karimnagar, Medak, Khammam, Tandur (Rangareddy district) and Rajahmundry (East Godavari).
It is also proposed to convert district hospitals as teaching hospitals and research centers. As a whole, about 10000 seats will be increased in MBBS course. The Union health ministry will provide financial assistants to establish these new medical colleges.
In Andhra Pradesh, the new medical colleges are likely to come up in at least 9 districts. These are Mahaboobanagar, Nalgonda, Vizianagaram, Eluru, Karimnagar, Medak, Khammam, Tandur (Rangareddy district) and Rajahmundry (East Godavari).
It is also proposed to convert district hospitals as teaching hospitals and research centers. As a whole, about 10000 seats will be increased in MBBS course. The Union health ministry will provide financial assistants to establish these new medical colleges.
Subscribe to:
Comments (Atom)