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Tuesday, 21 April 2015

FSc Notes Biology Part 1 Chapter 11 Bioenergetics

         FSc Notes Biology Part 1 Chapter 11 Bioenergetics

Q 1. What is thylakoid?
Ans. In photosynthetic organisms, chloroplasts have vesicles a wall of which bears photosynthetic pigments, called thylakoid. They vary in form and arrangement in different groups of organisms.

Q 2. What is the function of stomata?
Ans. Stomata are pores present in the epidermis of plants in large numbers, particularly in leaves, through which gaseous exchange takes place.

Q 3. Define bioenergetics.
Ans. The study of energy transfer in living beings is called bioenergetics.

Q 4. Give approximate estimate of chloroplasts in a green leaf.
Ans. The number of chloroplasts is about half a million per square millimeter of the leaf surface.

Q 5. What does the absorption spectrum of a pigment mean?
Ans. A graph showing the absorption of light of different wavelength by a pigment is called its absorption spectrum.

Q 6. How does light affect opening and closing of stomata?
Ans. The stomata open in light and close in darkness.

Q 7. Where does Krebs cycle take place in the cell?
Ans. The Krebs cycle takes place in the mitochondria of the cell.

Q 8. What is the net production of ATP during glycolysis?
Ans. The net production of ATP during glycolysis is two molecules of ATP.

Q 9. What is FAD abbreviation for?
Ans. Fad is abbreviation for flavin adenine dinucleotide.

Q 10. Name two solvents of chlorophyll?
Ans. The solvents of chlorophyll are carbon tetrachloride and alcohol.

Q 11. Write down the first step in Krebs cycle?
Ans.  The first step in the Krebs cycle is the union of acetyl CoA with oxaloacetate to form citrate.

Q 12. Give definition of glycolysis.
Ans. Glycolysis is the conversion of glucose by means of enzymes and co-enzymes till the formation of pyruvic acid.

Q 13. What does a photo system of photosynthesis cell consist of?
Ans. A photo system consists of a light gathering antenna complex and a reaction center.

Q 14. How much of the total photosynthesis take place in water and on land?
Ans. Of the total photo synthesis 90 % takes place in water and 10 % on land.

Q 15. What is the source of energy used on earth?
Ans.  Almost all the energy used on earth comes directly from the sun.

Q 16. Write down the summarized equation for photosynthesis.
Ans.                                     Light
         6CO2  +  12H2O -------------->   C6H12O6  +  6O2  +  6H2O
Q 17. What is the source of oxygen released during photosynthesis in plants?
Ans. The source of oxygen released during photosynthesis in plants is the water.

Q 18. Write down molecular formula of chlorophyll's 'a' and 'b'.
Ans.  Chlorophyll 'a' C55H72O5N4Mg
          Chlorophyll 'b'C55H70O6N4Mg

Q 19. What are the end products of light reactions?
Ans. These are ATP and NADPH.

Q 20. What are the different kinds of chlorophyll and where are these found?
Ans. Chlorophyll a,b,c and d are found in eukaryotic photosynthetic plants and algae while the other found in photosynthetic bacteria are known as bacteria chlorophylls.

Q 21. What is the approximate number of chloroplasts in each mesophyll cell of the leaf?
Ans. It is about 20 to 1000 per mesophyll cell.

Q 22. Which wavelength of the light spectrum are least absorbed by the chlorophyll?
Ans. Green and yellow wavelength are least absorbed by the chlorophylls.

Q 23. What are the colors of chlorophylls 'a' and 'b'?
Ans. The colors of chlorophyll 'a' is blue-green while that of chlorophyll 'b' is yellow-green.

Q 24. What is the role of accessory pigments in light absorption?
Ans. The accessory pigments absorb light and transfer the energy to chlorophyll "a" which then initiates the light reactions.

Q 25. Who obtained first action spectrum and when?
Ans. A German biologist T.W. Engelmam obtained first action spectrum in 1883 using spirogyra.

Q 26. What is Z.scheme in photosynthesis?
Ans. The path of electrons through the photo systems during non-cyclic photo-phosphorylation is known as Z-scheme from its shape.

Q 27. What is chemiosmosis in photosynthesis?
Ans. The synthesis of ATP by obtaining the energy through electrons of the electron transport chain is called chemiosmosis.

Q 28. Who and when was awarded Nobel Prize for his work on dark reactions in photosynthesis?
Ans. Melvin Calvin was awarded Nobel Prize in 1961 for his work on dark reactions on photosynthesis.

Q 29. Name the chain of acids which are formed in a cycle, starting from the citrate, during the Krebs cycle of respiration.
Ans. The chain is from citrate to a-ketoglutorate to succinate to fumarate to malate and finally to oxaloacetate.

Q 30. Define grana.
Ans. In chloroplasts group of disc-shaped, flattened vesicles stacked like coins in a pile, vesicle membranes bearing photosynthetic pigments are called grana. They are most highly developed in chloroplasts of higher plants.

Q 31. Compare which medium, water or air is better for oxygen?
Ans.  Feature                  Water                           Air
         Oxygen contents      10 ml O2 / liter               200 ml O2 / liter
         Rate of diffusion       less                                More (8000 times water)
         Viscosity                  More (50 times)             Less
          Density                   More (8000 times)         Less
          Ventilation               Difficult                          Easy

Q 32. Compare different phases of breathing?
Ans.  Feature               Inspiration                          Expiration
         Other name           Inhalation                             Exhalation
         Basic Mechanism  Passive expansion of lungs    Passive contraction of lungs
         Definition              Taking in of air                     Removal of air from lungs outside body
         Diaphragm            Contracts, moves down       Relaxes, moves up, become more
                                      becomes less dome-like      dome-like 
         Rib Muscles          Contract                              Relax
         Rib cage             Moves upward and forward    Moves downward and inward
         Volume of thorax   Increases                              Decreases
         Pressure on lungs   Decreases                            Increases
         Air moves              Into lungs                             Out of lungs

Q 33. Write down the differences between photorespiration and Calvin cycle.
Ans.   Photorespiration                                     Calvin Cycle
           Oxygen is fixed                                       Carbon dioxide is fixed
          Carbon dioxide is produced                    Oxygen is produced
          Oxygenase is involved                             Carboxylase is involved
          It retards growth                                     It promotes growth

Q 34. Describe respiratory disorders briefly.
Ans.  Disease: Respiratory distress syndrome
Feature: Syndrome of premature infants with gestation period less than 7 months
Cause: Decreased surfactant production
Symptom: No gaseous exchange
Disease: Cancer
Feature: Malignant tumor of lung cancer
Cause: Smoking
Disease: Tuberculosis
Feature: Pulmonary tuberculosis, contagious
Cause: Mycobacterium tuberculosis, poor people, malnutrition, poor living conditions
Symptom: Cough, fever
Disease: Asthma
Feature: Allergic reaction of respiratory tract
Cause: Pollen, spores, humidity, pollution
Symptom: Severe paroxysm of difficult breathing followed by a period of complete relief with recurrent attacks
Disease: Emphysema
Feature: Breakdown of alveoli
Cause: Smoke
Symptom: Smoker's cough. decrease in absorptive area, breathlessness, increased airway resistance

Q 35. How much carbon dioxide is present in venous and arterial blood?
Ans. Arterial blood contains about 50 ml of carbon dioxide per 100 ml of blood while venous blood contains about 54 ml.

Q 36. How does air always remain in the lungs of human beings?
Ans. About 1.5 liter air always remain in the lungs of human beings.

Q 37. What are the products which are produced during photorespiration?
Ans. Glycolate, glycine, serine.

Q 38. How much a water medium is denser than air medium for exchange of respiratory gases?
Ans. Water medium is 8000 times denser than air medium for exchange of respiratory gases.

Q 39. Write difference between Aerobic and Anaerobic respiration.
Ans.  Aerobic Respiration                             Anaerobic Respiration
          Free O2 is required                             Reaction occurs in the absence of free O2
          Glucose is completely oxidized            Some intermediate components are formed due to
          into CO2 and H2O                             incomplete oxidation e.g., lactic acid and alcohol
          Relatively larger amount of energy        Small amount of energy is formed (2 ATP)
          (38 ATP) is released
          In addition to glycolysis, Krebs           Only glycolysis occurs
          cycle and ETC also occur

Q 40. List four features of lead which show that it is able to carry out photosynthesis effectively.
Ans. Feature                                          Significance
        Flatness of lamina                            Maximum light absorption
        Thickness of lamina                         Deep penetration of light and efficient, rapid interval diffusion
                                                              of gases (CO2, O2) throughout the leaf
        Supported on petiole and green       Exposure to sunlight and air
        mosaic
        Cuticle                                            Reduce loss of water by transpiration
        Mesophyll tissue; with chloroplasts,  The photosynthetic tissue
        more in palisade than in spongy:
        Palisade mesophyll                          Characteristic arrangement chloroplast can orient themselves
                                                               according to incident light. Also act as screen against intense
                                                               light. Main photosynthetic tissue
        Spongy mesophyll                           Loose arrangement of cells and air spaces absorption and rapid
                                                              diffusion of CO2 to mesophyll cells; photosynthetic tissue.

Q 41. How does light affect opening of stomata?
Ans. Guard cells are the only photosynthesizing cells of lower epidermis. So in the presence of light, photosynthesis starts and water is used. More water moves into guard cells form surroundings cells, they become turgid, and the inner thick walls bend outwards at the center, thus they produce an opening or pore. It would happen when osmotic potential of guard cells becomes less then that of surrounding epidermal cells. It means light is the driving force for opening of stomata.

Q 42. What causes the variation of osmotic potential in the guard cells?
Ans. Photosynthesis causes the variations of osmotic potential in the guard cells, by use and disuse of water. If photosynthesis is going on, water is being used causing an increase in osmotic potential and movement of water into guard cells. On the other hand when there is no photosynthesis, there will be no use of water so it accumulates in guard cells, thus decreasing osmotic potential and water may move out of the guard cells.

Q 43. Compare cyclic and non-cyclic phosphorylation.
Ans.  Non-Cyclic                                             Cyclic
         Electrons are not reused                           Electrons are reused
         It involves both PS I and II                       It involves only PS I
         It is long circuit                                         It is short circuit
         It is normal process                                  It occurs when ATP are less and NADPH more.
         It generates both ATP and NADPH          It generates only ATP
         Oxygen is released                                    Oxygen is not released

Q 44. Write down the differences between light and dark reaction.
Ans.  Light Reaction                                        Dark Reaction
         Occur in grana of chloroplast                  Occurs in matrix of chloroplast
         Light is required                                      Light is not required
         O2, ATP and NADPH2 are the               In Calvin cyclic, ATP and NADPH2
         end products                                          used to prepare carbohydrates

Q 45. Compare Haemoglobin with Myoglobin?
Ans. Hemoglobin                                            Myoglobin
        It is found in blood                                  It is found in muscles
        It transfers oxygen from lungs to blood     It transfers oxygen from hemoglobin to
        and then to tissues                                   aerobic respiring muscle cells
        It cannot store oxygen                              It can store oxygen
        It consists of four polypeptide chains        It consists of one polypeptide chain
        associated with an iron containing             associated with an iron containing ring
        ring structure                                            structure

Q 46. Define organismic and cellular respiration.
Ans. Organismic Respiration: It is also known as breathing or ventilation during which moist surface absorbs oxygen from the surrounding and carbon dioxide is removed. Organismic respiration in fact provides the basis of cellular respiration.
Cellular Respiration: The cellular respiration is directly involved in the production of energy, necessary for all living activities. Cellular respiration is the process by which cell utilizes oxygen, produce carbon dioxide, extracts and conserves the energy from food molecules in biologically useful form such as ATP. Cellular respiration in cells consists of three steps i.e., glycolysis, Krebs cycle and electron transport chain.The glycolysis takes place in the cytoplasm while other two steps are carried out in the mitochondria.

Q 47. Why are the carotenoids usually not obvious in the leaves? They can be seen in the leaves before leaf fall. Why?
Ans. The carotenoids are usually not obvious in the leaves as their yellowish color is covered by dark green color of chlorophyll. But just before leaf fall, the chlorophyll is destroyed and carotenoids can be seen.

Q 48. How is the formation of Vitamin A linked with eating of carrot?
Ans. Carrots contain carotenoids which are the precursors of vitamin A. This is why the formation of vitamin A is linked with eating of carrot.

Q 49. Explain the roles of the following in aerobic respiration: (a) NAD and FAD (b) Oxygen.
Ans.  NAD and FAD are the co-enzymes which help enzymes to carry out the reactions during aerobic respiration, whereas oxygen accepts the H atoms and make water in the last step of respiratory chain.

Q 50. Sum up how much energy (as ATP) is made available to cell from a single glucose molecule by the operation of glycolysis, the formation of acetyl CoA the citric acid cycle, and the electron transport chain.
Ans. For each glucose molecule that is completely broken down to CO2 and H2O molecules by the sequential actions of glycolysis, the Krebs cycle, and respiratory electron transport, 38 ATP molecules can be formed. 2 ATP molecules are obtained during glycolysis, 2 during Krebs cycle and 34 during respiratory chain.

Q 51. Trace the fate of hydrogen atoms removed from glucose during glycolysis when oxygen is present in muscle; compare this to the fate of hydrogen atoms removed from glucose when the amount of the available oxygen is insufficient to support aerobic respiration.
Ans. When oxygen is present in muscle cells, the hydrogen atoms removed from glucose during glycolysis are carried to respiratory chain but in the absence of oxygen they are used in alcoholic or lactic acid fermentation.

Q 52. What is the difference between an action spectrum and absorption spectrum?
Ans. Action Spectrum: Different wavelengths are not only differently absorbed by photosynthetic pigments but are also differently effective in photosynthesis. Plot showing relative effectiveness of different wavelengths of light in arriving photosynthesis is called action spectrum of photosynthesis.
Absorption Spectrum: A graph plotting absorption of light of different wavelength by a pigment is called absorption spectrum of the pigment. The peaks represent the light that is absorbed by the pigment, while the valleys represent the light that is reflected or transmitted.

Q 53. What is the net production of ATP during glycolysis?
Ans. 10 ATP are produced but 2 ATP are used in the beginning so there is a net gain of 8 ATP molecules.

Q 54. What is the main difference between photo-phosphorylation and oxidative phosphorylation?
Ans. Synthesis of ATP in the presence of light is called photo-phosphorylation while synthesis of ATP int the presence of oxygen is called oxidative phosphorylation.

Q 55. What is the location of ETC and chemiosmosis in photosynthesis and cellular respiration?
Ans. Thylakoid membranes in photosynthesis, and mitochondrial membranes in cellular respiration.

Q 56. How did the evolution of photosynthesis affect the metabolic pathway?
Ans. With the emergence of photosynthesis on earth, molecular oxygen began to accumulate slowly in the atmosphere. The presence of free oxygen made possible the evolution of respiration. Respiration releases great deal of energy, and some of this energy is used in the formation of adenosine triphosphate (ATP) molecules. ATP is a kind of chemical link between catabolism and anabolism.

Q 57. How does absorption spectrum of chlorophyll a differ from that of chlorophyll b?
Ans. The molecular formula fro chlorophyll a and b are:
               Chlorophyll A C55H72O5N4Mg
               Chlorophyll B C55H70O6N4Mg
Due to this slight difference in their structure, the two chlorophylls show slightly different absorption spectra and hence different colors. Some wave length not absorbed by chlorophyll a are very effectively absorbed by chlorophyll b and vice-versa. Such differences in structure of different pigments increase the range of wavelength of the light absorbed. Chlorophyll a is blue-green while chlorophyll b is yellow-green.

Q 58. Write difference between Chlorophyll a and Chlorophyll b.
Ans. Difference                        Chlorophyll A                    Chlorophyll B
        Molecular formula           C55H72O5N4Mg                   C55H70O6N4Mg
        Functional group              -CH3                                   -CHO
        Occurrence                       All photosynthetic                In association with
                                                  organism except                  chlorophyll a in all green
                                                  photosynthetic bacteria         plants and green algae
        Forms                               Differ slightly in their red       No such different forms
                                                 absorbing peaks e.g.,
                                                 670,680,690,700 nm
        Color                                Blue-green                             Yellow-green

Written By: Asad Hussain

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