Question
Describe the main chemical changes which occur during photosynthesis in:
Light reaction
Light reaction
✓
Answer
The light reaction occurs in two main steps:
(1) Activation of chlorophyll - On exposure to light energy, chlorophyll becomes activated by absorbing photons.
(2) Splitting of water - The absorbed energy is used in splitting the water molecule into hydrogen and oxygen, releasing energy. This reaction is known as photolysis of water.
$2 H _2 O \xrightarrow{\text { energy of } 4 \text { photons }} 4 H ^{+}+4 e ^{-}+ O _2$
The fate of $H ^{+}, e ^{-}$and $( O )$ component are as follows:
The hydrogen ions $\left( H ^{+}\right)$obtained from above are picked up by a compound NADP (Nicotinamide adenine dinucleotide phosphate) to form NADPH.
$NADP ^{+}+ e ^{-}+ H ^{+} \xrightarrow{\text { enzyme }} NADPH$
The oxygen $( O )$ component is given out as molecular oxygen $\left( O _2\right)$.
$'2"O" -> "O"_2'$
The electrons ( $e ^{-}$) are used in converting ADP into energy rich ATP by adding one inorganic phosphate group $P _{ i }$.
$"ADP" + "P" -> "ATP"`$
This process is called photophosphorylation.
(1) Activation of chlorophyll - On exposure to light energy, chlorophyll becomes activated by absorbing photons.
(2) Splitting of water - The absorbed energy is used in splitting the water molecule into hydrogen and oxygen, releasing energy. This reaction is known as photolysis of water.
$2 H _2 O \xrightarrow{\text { energy of } 4 \text { photons }} 4 H ^{+}+4 e ^{-}+ O _2$
The fate of $H ^{+}, e ^{-}$and $( O )$ component are as follows:
The hydrogen ions $\left( H ^{+}\right)$obtained from above are picked up by a compound NADP (Nicotinamide adenine dinucleotide phosphate) to form NADPH.
$NADP ^{+}+ e ^{-}+ H ^{+} \xrightarrow{\text { enzyme }} NADPH$
The oxygen $( O )$ component is given out as molecular oxygen $\left( O _2\right)$.
$'2"O" -> "O"_2'$
The electrons ( $e ^{-}$) are used in converting ADP into energy rich ATP by adding one inorganic phosphate group $P _{ i }$.
$"ADP" + "P" -> "ATP"`$
This process is called photophosphorylation.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
Given below is the outline of the male reproductive system. Name the parts labelled 1 to 8 and state their functions. Also name the corresponding structure of part (4) in the female reproductive system.
Name and describe very briefly the stages in the development of human embryo.
Study the diagram given below and answer the questions that follow :
(a) Name the process being studied in the above experiment.
(b) Explain the process mentioned in (a) above
(c) Why is oil placed over water?
(d) What do we observe with regard to the level of water when this set up is placed in (1) bright sunlight (2) humid conditions (3) windy day?
(e) Mention any three adaptations found in plants to foster the process mentioned in (a) above
(a) Name the process being studied in the above experiment.
(b) Explain the process mentioned in (a) above
(c) Why is oil placed over water?
(d) What do we observe with regard to the level of water when this set up is placed in (1) bright sunlight (2) humid conditions (3) windy day?
(e) Mention any three adaptations found in plants to foster the process mentioned in (a) above
Label the lettered parts of the given figure and answer the following questions:
(i) What does this diagram represent?
(ii) What is the importance of'd'?
(iii) What are the 'staining' properties of 'b' and 'c'?
(iv) Who gave the term used for this structure today?
(v) What is a?
(vi) Is 'e' present in all chromosomes?
(i) What does this diagram represent?
(ii) What is the importance of'd'?
(iii) What are the 'staining' properties of 'b' and 'c'?
(iv) Who gave the term used for this structure today?
(v) What is a?
(vi) Is 'e' present in all chromosomes?
Discuss in detail the process of ozone depletion.
The figure below represents the internal structure of a mammalian heart and the associated blood vessels.
(i) (a) Name each of the structures labeled 1, 2, 3, 4, 5, 6, 7 and 8.
(b) State the function of each of the structures 5, 6, 7, and 8.
(ii) (a) State the function of the heart as an entire organ.
(b) Why are the walls of the left ventricle more muscular than the right?
(i) (a) Name each of the structures labeled 1, 2, 3, 4, 5, 6, 7 and 8.
(b) State the function of each of the structures 5, 6, 7, and 8.
(ii) (a) State the function of the heart as an entire organ.
(b) Why are the walls of the left ventricle more muscular than the right?
Why Neanderthal man and modern man belong to two distinct species?
What is the importance of photosynthesis in the life of the following:
Animals
Differentiate between guttation and bleeding in plants.
| Column 1 | Column 2 | ||
| 1 | SPM | a | Release of methane |
| 2 | Ozone hole | b | Add to greenhouse effect |
| 3 | Melting of polar ice | c | Affects oxygen transport by blood |
| 4 | Acid rain | d | Rise in sea level |
| 5 | Green house effect | e | Bronchitis & inflammation of the lungs |
| 6 | Melting of permafrost | f | Erosion of buildings |
| 7 | Carbon monoxide | g | Chlorofluorocarbons |