Q: Question 1Write the overall summary of the chemical equation of photosynthesis.

6CO2+12H2O→chlorophylllight energyC6H12O6+6H2O+6O2↑6\text{CO}_2 + 12\text{H}_2\text{O} \xrightarrow[\text{chlorophyll}]{\text{light energy}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{H}_2\text{O} + 6\text{O}_2 \uparrow6CO2+12H2Olight energychlorophyllC6H12O6+6H2O+6O2↑

Question 1

Question 2Given below is the figure of an experimental set-up, showing a physiological act of the plants. Study and answer the following questions.(a) What is the objective of this experiment ?(b) Name and define the process shown here.(c) Why do we destarch the leaves before performing the experiment ?(d) How do we destarch the leaves ?(e) What will be the observation when we pour iodine solution over the bleached experimental leaf.(f) Write a well-balanced equation of the above process.

Accepted Answer

(a) The objective of given experiment is to show that sunlight is necessary for photosynthesis.(b) The process shown here is photosynthesis.Photosynthesis is the process by which living plant cells, containing chlorophyll, produce food substances (glucose and starch), from carbon dioxide and water, by using light energy and release oxygen as a by-product.(c) We destarch the leaves before experiment in order to remove the starch from leaves so that occurence of photosynthesis can be detected.(d) To destarch the leaves the plant is kept in dark for 24-48 hours. This stops photosynthesis in the plant. During this time the starch already present in the leaves is translocated to storage organ of the plant fom the leaves.(e) When we pour iodine solution over the bleached experimental leaf the area where starch is present turns blue.(f) The equation for photosynthesis is given below:6CO2+12H2O→chlorophylllight energyC6H12O6+6H2O+6O2↑6	ext{CO}_2 + 12	ext{H}_2	ext{O} \xrightarrow[	ext{chlorophyll}]{	ext{light energy}} 	ext{C}_6	ext{H}_{12}	ext{O}_6 + 6	ext{H}_2	ext{O} + 6	ext{O}_2 \uparrow6CO2​+12H2​Olight energychlorophyll​C6​H12​O6​+6H2​O+6O2​↑

Question 2

Question 4Distinguish between the following pairs on the basis of words indicated in the brackets ( )(a) Light reaction and Dark reaction (end products)(b) Producers and Consumers (organisms)(c) Grass and Grasshopper (mode of nutrition)(d) Stoma and Stroma (structure)

Accepted Answer

(a) Differences between light reaction and dark reaction (end products) —Light ReactionDark ReactionATP and NADPH are the end products of this reaction.Glucose is the main product formed during dark reaction.The water molecule split into hydrogen and oxygen.No splitting of water.(b) Differences between producers and consumers (organisms) —ProducersConsumersThey are autotrophs.They are heterotrophs.They can convert inorganic substances into organic substances.They cannot convert inorganic substances into organic substances.It includes green plants and photosynthetic micro-organisms.It includes herbivores and carnivores.For example — green plantsFor example — Animals(c) Differences between grass and grasshopper (mode of nutrition) —GrassGrasshopperGreen grass being a producer is capable of producing its own food by photosynthesis.Grasshopper is a primary consumer (herbivore) and directly feeds on producers like grass.(d) Differences between stoma and stroma (structure) —StomaStromaA stoma is a microscopic pore surrounded by two specialized guard cells found in the leaves and stems. Its main function is gaseous exchange.Stroma is the colourless ground substance found in the chloroplast. It is the site of the light independent reactions of photosynthesis.

Question 3

Question 5How would you demonstrate that green plants release oxygen when exposed to light?

Accepted Answer

Place some water plants (Elodea or Hydrilla) in a beaker containing pond water and cover them by a short-stemmed funnel.Invert a test-tube full of water over the stem of the funnel. (Ensure that the level of water in the beaker is above the level of stem of the inverted funnel).Place the apparatus in the sun for a few hours. Bubbles of the gas will collect in the test-tube.Test the gas in the test-tube. A glowing splinter bursts into flame which shows the presence of oxygen.

Question 4

Question 6Describe the main chemical changes which occur during photosynthesis inLight reactionDark reaction

Accepted Answer

Light reactionThe light reaction occurs in two main steps:Step 1 — Activation of chlorophyllThe chlorophyll on exposure to light energy becomes activated by absorbing photons.Step 2 — Splitting of WaterThe absorbed energy is used in splitting the water molecule (H2O) into its two components (Hydrogen and Oxygen) and releasing electrons.2H2O⟶energy of 4 photons4H++4e−+O22 H_2O \overset{	ext{energy of 4 photons}}{\longrightarrow} 4H^+ + 4e^- + O_22H2​O⟶energy of 4 photons​4H++4e−+O2​This reaction is known as photolysis of water.End result of the products of photolysisThe hydrogen ions (H+) are picked up by a compound NADP (Nicotinamide adenine dinucleotide phosphate) to form NADPH.NADP++e−+H+⟶enzymeNADPHNADP^+ + e^- + H ^+ \overset{	ext{enzyme}}{\longrightarrow} NADPHNADP++e−+H+⟶enzyme​NADPHThe oxygen (O) component is given out as molecular oxygen (O2).2O⟶O22O \longrightarrow O_22O⟶O2​The electrons (e-) are used in converting ADP (adenosine diphosphate) into energy rich compound ATP (adenosine triphosphate) by adding one phosphate group Pi (inorganic phosphate).ADP+Pi (inorganic phosphate)⟶ATPADP + P_i 	ext{ (inorganic phosphate)} \longrightarrow ATPADP+Pi​ (inorganic phosphate)⟶ATPThis process is called photophosphorylation.Dark reactionThe reactions in this phase do not require light energy and occur simultaneously with the light reaction. The time gap between the light and dark reaction is less than one thousandth of a second. In the dark reaction, ATP and NADPH molecules (produced during light reaction) are used to produce glucose (C6H12O6) from carbon dioxide. Fixation and reduction of carbon dioxide occurs in the stroma of the chloroplast through a series of reactions. The glucose produced is either immediately used up by the cells or stored in the form of starch.Below is the summary of events in Light reaction and Light independent reactions of photosynthesis:

Question 5

Question 1Write the overall summary of the chemical equation of photosynthesis.

Accepted Answer

6CO2+12H2O→chlorophylllight energyC6H12O6+6H2O+6O2↑6	ext{CO}_2 + 12	ext{H}_2	ext{O} \xrightarrow[	ext{chlorophyll}]{	ext{light energy}} 	ext{C}_6	ext{H}_{12}	ext{O}_6 + 6	ext{H}_2	ext{O} + 6	ext{O}_2 \uparrow6CO2​+12H2​Olight energychlorophyll​C6​H12​O6​+6H2​O+6O2​↑

Question 6

Question 7Why is it better to call the dark phase of photosynthesis as "light-independent phase"?

Accepted Answer

The old term 'dark-phase' did not mean that it occurs when it is dark i.e. night. It only means that the reactions are not dependent on light. That is why, it is now better called as "light-independent phase".

Question 7

Question 8Match the terms given in column A with column B:Column AColumn BChlorophyllRemoves/absorbs CO2Methylated spiritTests presence of starchPotassium hydroxideTraps solar energyIodine solutionProduces oxygenWaterBleaches chlorophyll

Accepted Answer

Column AColumn BChlorophyllTraps solar energyMethylated spiritBleaches chlorophyllPotassium hydroxideRemoves/absorbs CO2Iodine solutionTests presence of starchWaterProduces oxygen

Question 8

Question 9Complete the following by filling the blanks 1 to 5 with appropriate words/ terms/ phrases:To test the leaf for starch, the leaf is boiled in water to (1) ............... . It is next boiled in methylated spirit to (2) ............... . The leaf is placed in warm water to soften it. It is then placed in a dish and (3) ............... solution is added. The region, which contains starch, turns (4) ............... and the region, which does not contain starch, turns (5) ............... .

Accepted Answer

To test the leaf for starch, the leaf is boiled in water to (1) kill the cells. It is next boiled in methylated spirit to (2) remove chlorophyll. The leaf is placed in warm water to soften it. It is then placed in a dish and (3) iodine solution is added. The region, which contains starch, turns (4) blue-black and the region, which does not contain starch, turns (5) brown..

Question 9

Question 10Write the exact location of each :(a) Chlorophyll(b) Chloroplast in the parts of a plant(c) Stroma(d) Guard cells(e) Palisade cells

Accepted Answer

(a) Wall of thylakoid.(b) Mesophyll cells of upper and lower epidermis of leaves.(c) Chloroplast.(d) Stomata.(e) Beneath epidermis.

Question 10

Question 3A potted plant with variegated leaves was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours and then placed in bright sunlight for a few hours. Observe the diagram and answer the questions:(a) What aspect of photosynthesis is being tested in the above diagram?(b) Why was the plant placed in the dark before beginning the experiment?(c) Write a balanced chemical equation to represent the process of photosynthesis.(d) What will be the result of starch test when performed on leaf A shown in the diagram?(e) Draw a neat and labelled diagram of a chloroplast.

Accepted Answer

(a) The above experiment is conducted to show that chlorophyll is necessary for photosynthesis.(b) The plant was placed in the dark before beginning the experiment to destarch the leaves.(c) Balanced chemical equation representing the process of photosynthesis is given below:6CO2+12H2O→chlorophylllight energyC6H12O6+6H2O+6O2↑6	ext{CO}_2 + 12	ext{H}_2	ext{O} \xrightarrow[	ext{chlorophyll}]{	ext{light energy}} 	ext{C}_6	ext{H}_{12}	ext{O}_6 + 6	ext{H}_2	ext{O} + 6	ext{O}_2 \uparrow6CO2​+12H2​Olight energychlorophyll​C6​H12​O6​+6H2​O+6O2​↑(d) After the starch test on leaf A, only the green parts of the leaf turn bluish, showing the presence of starch.(e) Below diagram shows Chloroplast with its different parts labelled:

Photosynthesis

Descriptive Type

Progress Check 2

Short Answer Type

Structured Application Skill Type