Bioenergetics BISE Rawalpindi 9 class Notes

Board of Intermediate and Secondary Education Rawalpindi biology notes Class 9th Pdf Download mcqs, shrot logn questions answer.

Short Questios Bioenergetics bio bise rawlapindi

Why is it said that all life forms are dependent on photosynthesis?

Photosynthesis is the process by which plant utilizes the sunlight and oxygen to produce carbohydrates and eventually are the main source of energy for humans and all the consumers on earth. Humans and other animals are heterotrophic and cannot make their own food and must rely ultimately on the glucose produced by plants. Moreover, the oxygen humans and other animals breathe is the oxygen released during photosynthesis.

In what ways the respiratory energy is used in the body of organisms?

    Respiration is an anabolic process, during which C-H bonds (glucose) is broken down and this energy is utilized in making ATP which is the energy currency of the cell. ATP is the main energy source used in the majority of the cellular functions as a synthesis of macromolecules  (DNA, RNA, and protein), movement, transmission of nerve impulses, active transport, exocytosis, and endocytosis.

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What structures and phenomena are involved in the intake of carbon dioxide and water by plants?

What is the importance of anaerobic respiration?

Importance of anaerobic respiration:

• Source of energy for anaerobic organisms like bacteria, yeast, and all prokaryotes.
• Source of energy for aerobic organisms in short supply of O₂. When the oxygen supply cannot keep pace with the energy demand, anaerobic respiration supplies the energy continuously by the breakdown of glucose to lactic acid.
• Source of many products (ethanol, cheese, and lactic acid etc) during alcoholic and lactic acid fermentation.

Mcqs on Bioenergetics 9th Class

i) In which of the following steps of respiration, CO₂ is produced?

• A. Glycolysis 
• B. Krebs cycle
• C. Electron transport chain  
• D. All of these

ii) Oxygen takes part in aerobic respiration in;

• A. Glycolysis  
• B. Link step between glycolysis and Krebs cycle
• C. Krebs cycle  
• D. Electron transport chain

iii) When a plant was kept in darkness for many days its leaves turned yellow. Why?

• A. Leaves could not get oxygen and so there was no photosynthesis
• B. Leaves could not get light and so there was no respiration
• C. Leaves could not get oxygen and so there was no respiration
• D. Leaves could not get light and so there was no photosynthesis

iv) From which bonds of ATP molecule energy is taken?

• A. P-P bonds
• B. C-H bonds 
• C. C-N bonds
• D. C-O bonds

v) In which component of the leaf cells, chlorophyll is present?

• A. Stroma
• B. Thylakoids
• C. Plasma membrane
• D. Cytoplasm

vi) Which of these can enter into Krebs cycle?

• A. Glucose 
• B. Pyruvic acid
• C. Citric acid
• D. Acetyl Co-A

vii) When we work hard we suffer from muscle fatigue because of muscle cells;

• A. Carry out aerobic respiration at faster rate and so are tired
• B. Carry out anaerobic respiration and so accumulate more C0₂
• C. Carry out anaerobic respiration and so accumulate lactic acid
• D. Carry out aerobic respiration and so accumulate lactic acid

viii) How many molecules of CO₂ are produced when Krebs cycle operates one

• A. 01
• B. 02
• C. 03
• D. 06

ix) In which of the following metabolic processes, oxidation as well as reduction of molecules occur?

• A. Photosynthesis 
• B. Respiration 
• C. Both  
• D. None of these

x) Chlorophyll pigment absorbs maximum light in wavelengths of;

• A. Green and blue  
• B. Green and red 
• C. Green only
• D. Red and blue

11. Which of the following is a chemical link between catabolism and anabolism?

A. AMP
B. ADP
C. ATP
D. All of these

 12. Photosynthesis is a process in which ________ compounds of carbon (CO2) and hydrogen (H2O) are reduced to carbohydrate like (glucose) using light energy.

A. Organic
B. Energy-rich
C. Energy-poor
D. Reduced

13. The point at which there is no net exchange of gases between leaves and atmosphere is known as

A. Neutral point
B. Compensation point
C. Parallel point
D. Competitive point

14. Net yield of H2O in Photosynthesis is

A. 1 molecule
B. 6 molecules
C. 3 molecules
D. 0 molecule

15. Of the following which one is not an energy releasing process?

A. Glycolysis
B. Respiration
C. Photosynthesis
D. Kreb’s cycle

16. The organisms able to use sunlight directly as a source of energy are

A. Plants
B. Animals
C. Omnivores
D. Fungi

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Understanding The Concepts

Q.1) How would you define bioenergetics while relating it to the oxidation-reduction reactions in living systems?

Answer:
Bioenergetics:
 “Bioenergetics is the study of energy relationships and energy transformations in living organisms.”
Bioenergetics and the role of ATP:
    Organisms obtain energy by metabolizing the food they eat or prepare. The food contains potential energy in its bonds. When these bonds are broken down, a large amount of kinetic energy is usually released. Some of this energy is stored in the form of potential energy in the bonds of ATP molecules while the rest escapes as heat. The potential energy stored in ATP is again transformed into kinetic energy to carry out life activities.
Life processes and constant use of energy:
    Life processes in organisms involve a constant flow of energy. This energy flow comprises the acquisition, transformation and use of energy for various life processes like growth, movement, reproduction etc.
Bioenergetics and its relation with Oxidation-Reduction reactions:
    For all life processes, oxidation-reduction reactions are the direct source of energy. Oxidation-reduction reactions involve the exchange of electrons between atoms.
Definition:
  “An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron.”
Oxidation:
  Oxidation is the loss of electrons.
Reduction:
  A reduction is the gain of electrons.
Role of electrons in bioenergetics:
    Electrons can be an energy source. It depends upon their location and arrangement in atoms.
For example:
   When they are present in oxygen, they make a stable association with oxygen atoms and are not a good energy source. But if electrons are dragged away from oxygen and attach to some other atom e.g. carbon or hydrogen, they make an unstable association. They try to move back to oxygen and when this happens, energy is released.
Role of redox reactions:
    In living organisms, redox reactions involve the loss and gain of hydrogen atoms. A hydrogen atom contains one proton and one electron, which means when a molecule loses a hydrogen atom, it actually loses an electron, and similarly when a molecule gains a hydrogen atom, it actually gains an electron.

Q.2) Interpret that ATP is the chief energy currency of all cells.

Answer:
ATP (Adenosine Triphosphate):
“Adenosine triphosphate (ATP) is a complex organic chemical that provides energy to drive many processes in living cells.”
Discovery of ATP molecule:
ATP was discovered by Karl Lohmann, in 1929 and it was proposed to be the main energy transfer molecule in the cell by the Nobel Prize winner, Fritz Lipmann in 1941.
ATP: Cell’s Energy Currency:
The major energy currency of all cells is a nucleotide called adenosine triphosphate (ATP).
 ATP is the main energy source for the majority of cellular functions like the synthesis of macromolecules (DNA, RNA, and Proteins) movement, transmission of nerve impulses, active transport, exocytosis, and endocytosis etc.
The ability of ATP to store and release energy is due to its molecular structure.
Structure of ATP:
 Each ATP molecule has three subunits:

• Adenine; A double ringed nitrogenous base.
• A Ribose; A five-carbon sugar
• Three phosphate groups in a linear chain

ATP; High energy bond:
The covalent bond connecting two phosphates is indicated by the tilde (~) and it is a high-energy bond. The energy in this bond is released as it breaks and inorganic phosphate (Pi) gets separated from ATP.
Energy released by breaking of one phosphate bond:
    The breaking of one phosphate bond releases about 7.3 kcal energy per molecule as follows:
                    ATP+H₂O →ADP+ Pi+ Energy (7.3 kcal/mole)
The energy from ATP is sufficient to drive most of the cell’s energy-requiring reactions. In common energy reactions, only the outermost of the two high-energy bonds break. When this happens, ATP becomes ADP (adenosine diphosphate) and one pi is released. In some cases, ADP is further broken down to AMP (adenosine monophosphate) and P as follows:
                    ADP+H₂O →AMP +Pi + energy (7.3 kcal/mole)
Recycling of ADP:
Cells constantly recycle ADP by recombining it with Pi to form ATP. The synthesis of ATP from ADP and P requires the expenditure of 7.3 kcal energy/mole. This energy is obtained from the oxidation of food. ATP is generated by energy-releasing processes and is broken down by energy consuming processes. In this way, ATP transfers energy between metabolic reactions.

Q.3) What is the role of chlorophyll and light in photosynthesis?

Answer:
Role of light in photosynthesis:
    Sunlight energy is absorbed by chlorophyll. It is then converted into chemical energy, which drives the photosynthetic process. Not all the light falling on the leaves is absorbed. Only about one percent of the light falling on leaf surface is absorbed, the rest is reflected or transmitted.
  The light rays of different wavelengths are not only differently absorbed by photosynthetic pigments but are also differently effective in photosynthesis. The blue and red light carry out more photosynthesis.
Function of chlorophyll:
    When chlorophyll absorbs light, its electrons are excited and they leave chlorophyll molecule. The excited electrons are passed through an electron transport chain and their energy is captured for the formation of ATP and for reducing NADP to NADPH.
Role of chlorophyll in photosynthesis:
    The photosynthetic pigments are organized in the form of clusters, called photosystems, in thylakoid membranes of chloroplasts.
    Chlorophyll-a is the main photosynthetic pigment. Others are called accessory pigments and include chlorophyll-b and carotenoids.
    Chlorophylls absorb mainly blue and red lights. Some wavelengths not absorbed by chlorophyll-a are very effectively absorbed by accessory pigments and vice versa.

Q.4) Describe the processes involved in photosynthesis?

Answer:
Photosynthesis:
   “Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.”
Mechanism of photosynthesis:
    Photosynthesis occurs in two phases.
1- Light Reactions:
     “During the light reaction, light energy is captured and is used to make high energy molecules (ATP and NADPH).”
Site of light reaction:
  The light reactions, take place on the thylakoid membranes of chloroplasts.
Steps of light reaction:
  The summary of the events of light reactions is as follows:

• When chlorophyll molecules absorb light, their energy level increases and their electrons are emitted.
• Electrons are passed to an electron transport chain to produce ATP.
• Light also breaks the water molecule (photolysis) and oxygen is released. The hydrogen atoms of water give electrons to chlorophyll and become ions.
• The electrons of chlorophyll, after the production of ATP, and the hydrogen ions of water are used for the reduction of NADP⁺ into NADPH.

2- Dark Reactions:
      “During the second phase, carbon dioxide is reduced to make glucose. The energy in the form of ATP is utilized in this process and produce ATP in the bonds of glucose. Since these reactions do not use light directly, they are known as dark reactions.”
A site of Dark reaction:
  The dark reactions take place in the stroma of chloroplasts.
Steps of Dark reaction:
  The summary of the events of dark reaction, also known as the Calvin cycle is as follows;

• CO₂ molecules are combined with 5-carbon compounds to form temporary 6-carbon compounds, each of which splits into two 3-carbon compounds.
• The 3-carbon compounds are reduced to 3-carbon carbohydrates by using ATP and hydrogen from NADPH. The 3-carbon carbohydrates are used to manufacture glucose.
• The 3-carbon carbohydrates are also used to regenerate the original 5-carbon compounds. This step also utilizes ATP.

Q.5) State how the varying light intensity, carbon dioxide concentration and temperature affect the rate of photosynthesis?

Answer:
1- Effect of varying light intensity:
    The rate of photosynthesis varies with light intensity. It decreases as the light intensity decreases and increases as the light intensity increases. However, at a much higher light intensity, the rate of photosynthesis becomes constant.
2- Effect of varying temperature:
     The rate of photosynthesis decreases with a decrease in temperature. It increases as the temperature is increased over a limited range. But if the light intensity is low, increasing the temperature has little influence on the rate of photosynthesis.
3- Effect of varying carbon dioxide concentration:
       As carbon dioxide concentration rises, the rate of photosynthesis goes on increasing until limited by other factors. The initial enzyme of dark reactions, which combines carbon dioxide with 5-carbon compound has a binding affinity for both carbon dioxide and oxygen. When the concentration of carbon dioxide is high, it will bind oxygen instead of carbon dioxide and there would be no photosynthesis. Increase in carbon dioxide beyond a threshold level causes closure of stomata and it decreases the rate of photosynthesis.

Q.6) Outline the mechanism of respiration while defining glycolysis, Krebs oxidation-reduction electron transport chain.

Answer:
Respiration:
  “Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products.”
Steps of aerobic respiration:
  The process of respiration involves a complex series of reactions.
   Aerobic respiration is a continuous process, but for convenience, it is divided into three main stages which are;
1- Glycolysis:
      Glycolysis occurs in cytoplasm and oxygen is not involved in this stage. That is why it occurs in both types of respiration i.e. aerobic and anaerobic. In glycolysis, glucose (6C) molecule is broken into two molecules of pyruvic acid (3C).
2- Krebs cycle:
      In the Krebs cycle, the pyruvic acid molecules are completely oxidized, along with the formation of ATP, NADH, and FADH₂. Before entering in Krebs cycle, pyruvic acid is changed into a 2-carbon compound called acetyl-CoA.
3- Electron transport chain:
       Electron transport chain is the final step of cellular respiration. It is the transfer of electron on an electron transport chain. In this step, NADH, and FADH₂ release electrons and hydrogen ions. These electrons are taken up by a series of electron carriers. When electrons move through the series of electron carriers they lose energy, which is used to synthesize ATP. At the end of the chain, electrons and hydrogen ions combine with molecular oxygen and form water.

Q.7) Draw a comparison of aerobic and anaerobic respiration.

Answer:

Q.8) How will you compare respiration with photosynthesis?

Answer: 

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