1.9. MAQUINARIA DE OBRA
1.9.1. Maquinaria en general
a) Light:- Light intensity needed for stomatal opening is low the stomata open in light but close in dark. In CAM plants, stomata open in dark & closed during daytime.
b) Temperature:- If temperature is increased, then the stomata open but when there is decrease in temperature the stomata close.
c) Availability of water:- The stomata are closed due to water stress or moisture deficit.
d) Concentration of CO2 :- If there is an increase in CO2 concentration inside the
leaf the stomatal openings are closed even in light. When CO2 is used up by
plant in photosynthesis the stomata open.
10. Transpiration is a phenomenon naturally occurring in plants through which water is lost from plants in the form of water vapours through their aerial parts. It is useful to plants because
i) It helps in movement of xylem sap.
ii) It causes cooling of leaf surface & thereby protects leaf from heat injury by intense sunlight
Transpiration is affected by 3 environmental factors:-
a) humidity:- water is lost slowly in the atmosphere, if the humidity is high or increased.
b) temperature:- the rate of transpiration is doubled with rise in temperature by 10.c
c) wind speed:- high wind speed or a dry breeze greatly increases the transpiration
CBSE TEST PAPER-01
CLASS - XI BIOLOGY (Mineral Nutrition)
1. Name a soil bacteria which is capable of converting ammonia to nitrates. [1]
2. Which macronutrient is essential for synthesis of auxin. [1]
3. What do you mean by “chlorosis”? [1]
4. A farmer adds azotobacter culture to the soil before sowing maize. How does it increase the yield of maize?
[2]
5. Name the pigment found in root nodules of legumes. What is its function? [2]
6. What is hydroponics? Mention its uses? [2]
7. What do you understand by “Donnan Equilibrium? [3]
8. What are essential mineral elements? [3]
9. Describe the process of development of root nodules in leguminous plant. Name the oxygen scavenger molecule present in root nodules?
CBSE TEST PAPER-01
CLASS - XI BIOLOGY (Mineral Nutrition)
[ANSWERS]
Ans 01. Nitrosomonas. Ans 02. Zinc
Ans 03. Lack of development of chlorophyll in the leaves.
Ans 04. Azotobacter provides nitrogen fixing bacteria which converts free nitrogen into nitrous and nitrites. It increases soil fertility. So it increases yield of maize.
Ans 05. Root nodules of leguminons plants contain pigment leghaemglobin. Its function is to protect nitrogenase from oxygen. Hence called ‘oxygen scavenger’.
Ans 06. Hydroponics is the cultivation of plants in the nutrient solution by placing their rooted part in nutrient solution. By hydroponics or water culture experiment, essentiality of an element for plant growth can be determined by exceeding a particular element in culture solution and by observing the symptoms caused by its deficiency.
Ans 07. This theory explains that the passive accumulation of ion that are fixed on non- diffusible, against an ecp gradient. A membrane that separates a cell from the external medium and allows exchange of some ions and not the other. On the inner side of this membrane are anions (fixed & non-diffusible). The membrane becomes impermeable to these anions. In such condition (for equilibrium) mobile cations are needed to balance the negative charges of the anions. According to it Donnan equilibrium is reached, if the product of anions and cations is the internal solution becomes equal to the product of anions and cations in the external solution.
[Ci+] [Ai-] = [Co+] [Ao-]
Where Ci+ = cations inside
Ai- = Anions in side
Co+ = Cations outside
Ao- = Anions outside.
Ans 08. Mineral elements found in soil which may enter plants through the roots. More than 60 elements of 105 discovered so far occur in different plants. Some
accumulate selenium but some others gold. Some plants growing near nuclear test sites takes up radioactive strontium.
Ans 09. Formation of root nodules in a leguminous plant:
1) When a root hair of a leguminous plant comes in contact with Rhizobium, the root hair becomes curled or deformed, due to chemicals secreted by bacterium.
2) At the site of curling or deformation, the bacteria invade the root and multiply within the root hair.
3) Some of the bacteria enlarge to become membrane – bound structures known as bacteroids, which help in spreading infection.
4) An infection thread made of plasma membrane is formed by the host that separates the infected cell from rest of the tissue.
5) Cell division is stimulated in the infected tissue and more bacteria enter the newly formed cells.
Leghaemoglobin (Lb) is the oxygen scavenger found in root nodules of legume plants.
CBSE TEST PAPER-02
CLASS - XI BIOLOGY (Mineral Nutrition)
1. Name any two elements having toxic effect on protoplasm? [1]
2. What is hydroponics? [1]
3. Give the function of enzyme nitrate reductase. [1]
4. What is balanced nutrient solution? [2]
5. What is nitrification? Name any two nitrifying bacteria in soil? [2]
6. In what form is magnesium absorbed by plants from the soil. Given two functions of magnesium in plants & its deficiency symptoms.
[2]
7. Differentiate between active & passive absorption. [3]
8. List the criteria for essentiality of elements as nutrient in plants. [3]
CBSE TEST PAPER-02
CLASS - XI BIOLOGY (Mineral Nutrition)
[ANSWERS]
Ans 01. Lead, mercury and arsenic.
Ans 02. Plant growth in nutrient rich liquid culture medium. Ans 03. It reduces nitrate ions to ammonia.
Ans 04. Balanced nutrient solution or balanced salt solution is prepared by dissolving definite proportions of salts in distilled water needed for normal plant growth. The plants growing in these solutions survive munch longer as they get all essential as well as the trace elements from medium.
Ans 05. Nitrification is the process of conversion of ammonia into nitrites. It involves two steps:-
(i) Ammonium ions are oxidized into nitrates by the bacteria like Nitrosomonas and Nitrosococcus.
(ii) Nitrites are converted into nitrates by the bacteria like Nitrobacter. Ans 06. Magnesium is absorbed by the plants from the soil in the form of divalent Mg2+.
Functions –
1) Synthesis of DNA and RNA.
2) It activates enzymes in respiration and photosynthesis. Deficiency symptoms –
1) Chlorosis between the leaf veins. 2) Premature leaf abscission. Ans 07.
Active Absorption Passive Absorption
1. Absorption of minerals is against the concentration gradient.
Absorption of minerals is along the concentration gradient by simple diffusion.
2. Energy is utilized for absorption. Energy is not utilized for absorption
3. It is fast. It is slow.
4. It is unidirectional. It may be bidirectional. 5. It is a biochemical process. It is a physical process.
Ans 08. Criteria for essentiality of element are fallowing-
1) The element must be absolutely essential for supporting normal growth and reproduction.
2) The requirement are need of the element must be specific and not replaceable by another element.
3) An element should be directly involved in the metabolism of the plant. Ans 09. Some important functions of mineral elements are –
(1) Maintenance of the osmotic pressure in the plant cells – The mineral salts and organic compounds of the cell sap produce necessary osmotic pressure.
(2) Constituents of the plant body – Elements form constitution of the plant body. For ex – Carbon, Hydrogen and oxygen are essential constituents of carbohydrates. Hence, called framework elements. Nitrogen, sulphur and phosphorous are required for synthesis of proteins. Magnesium is important constituent of chlorophyll.
(3) Influence on the PH of the cell sap – They also influence the PH of the cell sap.
(4) They influence the permeability of cytoplasmic membrane – They increase or decrease the permeability of the plasma membrane.
(5) They take part in enzymatic reactions – some elements work as activators while the others works as inhibitors in various enzymatic reactions.
(6) They have balancing functions reactions – some of the minerals balance the effects of the other.
CBSE TEST PAPER-03
CLASS - XI BIOLOGY (Mineral Nutrition)
1. Name essential components of biomolecules. [1]
2. Name the enzyme that can reduce nitrogen to ammonia. [1]
3. What are micronutrients? [1]
4. List the four broad groups of essential elements. [2]
5. How is hydroponics useful? [2]
6. What is mineral nutrition? Name one essential element that is a component of energy – related chemical compounds.
[2]
7. Describe the process of nitrogen fixation in plants. Mention the site where this process actually occur is such plants.
[3]
8. Differentiate between apoplast and symplast. [3]
CBSE TEST PAPER-03
CLASS - XI BIOLOGY (Mineral Nutrition)
[ANSWERS]
Ans 01. C, H, O and N.
Ans 02. Nitrogenase enzyme.
Ans 03. Elements which are required by the plants in very small or trace quantities are termed as micronutrients for eg; zinc copper, etc.
Ans 04.
Type Examples and its Role
1. Components of bimolecules C,H,O,N is a component of nucleic acids and proteins.
2. Components of energy related chemical compounds.
Mg. P. P is a constituent of ATP molecule.
3. Activate or Inhibit enzymes. Mg2+, Zn2+, Mo. Mo is activator of
nitrogenase in N2 metabolism.
4. Alter osmotic potential of a cell. Potassium. It is a essential. In opening of closing of stomata leaves.
Ans 05. Hydroponics is essential to know the following- (i) Essentiality of mineral element.
(ii) Deficiency symptom due to non – availability of specific nutrient. (iii) Toxicity to plant if element is present is excess.
(iv) Role of essential elements is metabolism of a plant.
Ans 06. Plants require mineral nutrients for their growth and development which do not occur in the plant body in Free State. The utilization of there elements by the plants for its growth and development is called mineral nutrition. Mg in chlorophyll is essential component of energy-related chemical compound. Ans 07. Nitrogen fixation occurs in nodules in legume plants is gram and arhar. They act
as sites for it. The legume plants like pea, gram show symbiosis or mutualism with bacterium, Rhizobium leguminasauram. Nitrogen fixation occurs with the help of enzymes nitrogenase & leghaemoglobin. Leghaemoglobin act as O2
scavenges and nitrogenase catalyse the conversion of N2 into NH3
Ans 08.
Apoplast (outer space) Symplast (Inner space)
1. It includes cell wall and intercellular space.
It includes the cytoplasm and vacuole of the cell.
2. Uptake of ions into space is a passive process and involves no expenditure of energy.
Uptake of ions is an active process and involves expenditure of energy.
3. Initially, the ions are taken up quickly into outer space into medium.
Uptake of ions occurs slowly from the outer space.
Ans 09.
Micronutrient Role in plants life
1. Boron (B) Pectin formation in cell wall, Translocation of sugar, Absorption of water.
2. Molybdenum (Mo) Reduction of nitrates constituent of nitrate reductases. Activation for photophosphorylation. 3. Manganese (Mn) Nitrogen metabolism, chlorophyll synthesis,
Activation of enzymes.
4. Copper (Ca) Component of enzymes. Component of plastocyanin. 5. Chloride (Cl) Transfer of electron.
CBSE TEST PAPER-01
CLASS - XI BIOLOGY (Photosynthesis in higher plants)
1. Expand NADP. [1]
2. Name one plant that carries out photosynthesis at night? [1]
3. Name the cell – organelles involved in photorespiration. [1]
4. What is red Drop? [2]
5. What are the enzymes that catalyze the dark reaction of carbon fixation located?
[2]
6. What are the two main functions of pigments other than chlorophyll in green leaves?
[2]
7. Explain -There is no oxygen evolution in bacterial photosynthesis. [3] 8. What is the advantage of using chlorella rather than a higher plant? [3] 9. (a) suggest some habitats or natural circumstances in which
(i) Light intensity (ii) CO2 concentration
(iii) temperature might be limiting factors in photosynthesis.
(b) In C4 plants which type of chloroplast is specialized for light reactions and
which for dark reactions?
(c) Why is it an advantage that bundle sheath chloroplast lack grana?
CBSE TEST PAPER-01
CLASS - XI BIOLOGY (Photosynthesis in higher plants)
[ANSWERS]
Ans 01. Nicotinamide adenine dinucleotide phosphate.
Ans 02. Opuntia, chenopodium.
Ans 03. Mitcohondria, chloroplast and peroxisomes.
Ans 04. It is the occasional fall in photosynthetic yield beyond red region of spectrum. This is also called Emerson effect.
Ans 05. The stroma contains enzymes which are capable of utilizing ATP and NADPH2 to
produce carbohydrate during dark reaction. The carbon fixation occurs in the stroma by a series of enzymes catalysed steps which are located outside the thylakoids.
Ans 06. (i) To absorb light energy and transfer it to chlorophyll for photosynthesis. (ii) To protect the chlorophyll molecule from photo oxidation.
Ans 07. In bacterial photosynthesis, the raw material for the supply of proton is H2S than
H2O Thus, these is production of S than O2 during splitting in light reaction.
2H2S → 2HS + + 2H+
HS + HS → H2S + S
Ans 08. Photosynthesis in chlorella and higher plants is biochemically similar but chlorella was used by Melvin Calvin (1954) due to following reasons –
(i) Chlorella culture is a chloroplast culture as a large volume of every cell is occupied by a single chloroplast.
(iii) Cells are very quickly exposed to radioactive carbondioxcide and are quickly killed; thus handling chlorella for experiments is easier.
Ans 09. (a) Some situations are –
(i) In a shaded community; dawn and twilight in a warm climate.
(ii) Carbon dioxide is normally limiting, but it may be more so in a crowded stand of plants under sunny, warm conditions.
(iii) On a bright day winter.
(b) Mesophyll chloroplast for light reaction. Bundle sheath chloroplast for dark reaction.
(c) Oxygen production is related to grana and oxygen would compete with CO2 for RuBP carboxylase and stimulate photorespiration. Grana occupy
a large area of the chloroplast. In their absence in the bundle sheath there is more stroma, and so more RuBP carboxylase and more storage space for starch.
CBSE TEST PAPER-02
CLASS - XI BIOLOGY (Photosynthesis in higher plants)
1. Why photosynthesis important? [1]
2. Define photosynthesis? [1]
3. What is the site for photosynthesis in Opuntia? [1]
4. Differentiate between respiration and photorespiration. [2]
5. Explain the role of water in photosynthesis. [2]
6. What is the law of limiting factor? [2]
7. What is the advantage of having more than one pigment molecule in a photo centre?
[3]
8. Why are C4 plant preferred in the tropical region? [3]
CBSE TEST PAPER-02
CLASS - XI BIOLOGY (Photosynthesis in higher plants)
[ANSWERS]
Ans 01. (a) Primary source of all food on earth.
(b) O2 is released by green plants into the atmosphere.
Ans 02. Photosynthesis is an anabolic endergonic as well as oxidation reduction process in which green plants manufacture food by raw materials in sunlight.
Ans 03. Stem Ans 04.
Respiration Photorespiration
1. It occurs in all plants (C3 and C4) It occurs in C3 plants only.
2. Glucose is the substrate of this reaction.
Glycolate is the substrate which is connected into Glycine, NH3 and CO2 in
peroxisomes. Ans 05 (i) It is a reactant in light reaction.
(ii) Water stress causes closure of stomata. (iii) It reduces the availability of CO2
(iv) Reduces surface area of leaves.
Ans 06. This law states that “if a chemical process is affected by more than one factor which is nearest to its minimal value; then the rate will be determined by the factor which is nearest to its minimal value; it is the factor that directly affects process if its quantity is changed”.
Ans 07. Light reaction depends upon the amount of solar energy trapped by the pigment. Energy trapped by a single pigment molecule is not enough to start the initial reaction which may occur in light. Hence, a number of pigment molecules provide protection to the chlorophyll molecule against photo oxidation.
Ans 08. C4 plants utilize 30 ATP’s to produce one molecule of glucose favoured in tropical
region. In these plants photorespiration is the mechanism not to lose the photosynthetic carbon. In the process of photorespiration RuBP is catabolised to a 3-carbon atom compound instead of combining with CO2. More than 50% CO2
fixed by photosynthesis is lost in photorespiration. Photorespiration acts to undo the work of photosynthesis as no energy rich compound is produced during this
process. Thus C4 plants are better photosynthesizes than C3 plants and C4
pathway is of adaptive advantage in tropical region and thus these plants are preferred.
Ans 09. Chemiosmotic hypothesis explained the mechanism of ATP synthesis in chloroplast. In photosynthesis, ATP synthesis is linked to development of proton gradient across a membrane. These are membrane of thylakoids. The proton accumulation is towards the inside of the membrane (in the lumen).
The processes which occur during activation of electrons and their transport to determine the steps that causes a proton gradient to develop. ATP synthesis is linked to development of proton gradient.
CBSE TEST PAPER-03
CLASS - XI BIOLOGY (Photosynthesis in higher plants)
1. Explain chlorophyll is an essential photosynthetic pigment? [1]
2. What is the end product of light reaction? [1]
3. Give examples of photosynthetic micro – organisms which also fixes atmospheric nitrogen?
[1]
4. Compare between chlorophyll ‘a’ and chlorophyll ‘b’? [2]
5. What is kranz anatomy? [2]
6. Give advantages of C4 cycle over C3 Cycle. [2]
7. Distinguish between photo system – I and Photo system – II [3]
8. How does temperature affect photosynthesis? [3]
9. Explain the process of bio-synthetic phase of photosynthesis occurring in chloroplast.
CBSE TEST PAPER-03
CLASS - XI BIOLOGY (Photosynthesis in higher plants)
[ANSWERS]
Ans 01. Chlorophyll – b and other pigments of a reaction centre or photosystem absorb solar energy and transfer it to chlorophyll–a. Ultimately it is chlorophyll–a that initiates photosynthesis process.
Ans 02. ATP, NADPH2 and O2
Ans 03. Anabaena, Nostoc. Ans 04.
Chlorophyll a Chlorophyll b
1. Chlorophyll a has methyl group at the 3rd carbon position of II
pyrrole ring of porphyrin head.
It has an aldhyde group at the 3rd
carbon position of II pyrrole ring or porphyrin head.
2. It shows maximum absorption at 429 nm (blue) and 660 nm (red) wavelength.
It shaves maximum absorption at 453 nm (blue) and 642 nm (red) wavelengths.
3. It is highly soluble in petroleum, ether.
It is highly soluble in methyl alcohol. 4. It is blue – green in colors. It is yellow green in colors.
Ans 05. Kranz Anatomy – The anatomy in which, the vein of the leaf is surrounded by the bundle sheath containing a member of chloroplasts, having a bull form cells in upper epidermis is known as “Kranz anatomy”.
Ans 06. (i) C4 cycle is more efficient than C3 cycle.
(ii) The photorespiration is lacking in C4 plants.
(iii) C4 cycle can use CO2 at very low concentrations in comparison to C3
plants.
(iv) C4 cycle operates in plants adapted to high integrity of light, high
temperature and low water availability, C3 cycle cannot operate under
Ans 07.
Photosystem – I Photosystem – II
1. It is the cluster of pigment molecules which absorb light wavelengths at or below 700nm.
It is the cluster of pigment molecules which absorb light wavelength at or below 680nm.
2. The light absorbed by any pigment molecule of the cluster is transferred to P700, which is the reaction centre.
The light absorbed by any pigment molecule of the cluster is transferred to P680 which is the reaction centre. 3. It has a high ratio of chlorophyll – a
to chlorophyll – b.
It contains relatively more chlorophyll – b than chlorophyll – a.
Ans 08. The dark reactions are temperature controlled. The C4 plants respond to higher
temperatures, C4 plants exhibit high rate of photosynthesis. C3 have much low
temperature optimum. Tropical plants have higher temperature for photosynthesis.
Ans 09. Biosynthetic phase (Dark Reaction) : The process by which carbon – dioxide is reduced to carbohydrates is known as carbon fixation in plants. The fixation of carbon takes place in the stroma of chloroplasts, by a series of enzyme – catalyzed reactions.
C3 pathway: It is known as Calvin cycle. The path of carbon in the dark reaction
was traced by Melvin Calvin through a technique called autoradiography, using 14C, hence this pathway is called Calvin cycle.
Calvin cycle consist of three phases:
(i) Carboxylation (ii) Glycolytic reversal (iii) Regeneration of RuBP.
(i) Carboxylation – Six molecules of Ribulose 1, 5 biphoshate react with six molecules of carbon-dioxide to form six molecules of carbon dioxide to form six molecules of a short – lived 6C – compound. The reaction is catalysed by RuBP – carboxylase (Rubisco). The six molecules of the 6C – compound break into 12 molecules of 3-phosphoglyceric acid (PGA), a 3C – compound PGA is the first stable compound in this pathway.
(ii) Reduction – 12 molecules of phosphoglyceric acid are converted into 12 molecules of 1,3 diphosphoglycerate and then reduced to phosphogly acetaldehyde (PGAL) using ATP and NADPH molecules respectively. Two molecules of PGAL are diverted for the synthesis of sugar and then into the