Case Study Questions Class 11 Biology Chapter 14 Respiration in Plants
CBSE Class 11 Case Study Questions Biology Respiration in Plants. Important Case Study Questions for Class 11 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Respiration in Plants.
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CBSE Case Study Questions Class 11 Biology Respiration in Plants
CASE 1
The TCA cycle starts with the condensation of acetyl group with oxaloacetic acid (OAA) and water to yield citric acid(Before participating in the TCA cycle pyruvic acid enters the mitochondrion. Here it is decarboxylated and the remaining 2-carbon fragment is combined with a molecule of coenzyme A to form acetyl-CoA. This reaction is an oxidative decarboxylation process and produces H+ ions and electrons along with carbon dioxide). The reaction is catalysed by the enzyme citrate synthase and a molecule of CoA is released. Citrate is then isomerised to isocitrate. It is followed by two successive steps of decarboxylation, leading to the formation of α-ketoglutaric acidand then succinyl-CoA. In the remaining steps of citric acid cycle, succinyl-CoA is oxidised to OAA allowing the cycle to continue. During the conversion of succinyl-CoA to succinic acid a molecule of GTP is synthesised. This is a substrate level phosphorylation. In a coupled reaction GTP is converted to GDP with the simultaneous synthesis of ATP from ADP. Also there are three points in the cycle where NAD+ is reduced to NADH + H+ and one point where FAD+ is reduced to FADH2. The continued oxidation of acetyl CoA via the TCA cycle requires the continued replenishment of oxaloacetic acid, the first member of the cycle. In addition it also requires regeneration of NAD+ and FAD+ from NADH and FADH2 respectively.
We have till now seen that glucose has been broken down to release CO2 and eight molecules of NADH + H+ ; two of FADH2 have been synthesised besides just two molecules of ATP in TCA cycle.
Pyruvic Acid produced by glycolysis undergoes aerobic oxidation in the mitochondrial matrix through the TCA cycle. This cycle serves a common oxidative pathway for carbohydrates fats and proteins.
1.) ____________ is the end product of glycolysis, which undergoes aerobic oxidation in citric acid cycle.
a) Acetyl-CoA
b) Pyruvate
c) Malic acid
d) Oxalic acid
2.) When Acetyl-CoA is condensed with oxaloacetic acid, it leads to the formation of ______
a) Citric Acid
b) Succinic Acid
c) Malic Acid
d) Oxalic Acid
3.) Why Krebs cycle is also referred as Citric Acid Cycle?
4.) Name the cycle provides common oxidative pathway for various respiratory substrate, such as carbohydrates fats and proteins.
5.) Explain how Acetyl-CoA molecules are formed?
Answer key
1) c
2.) c
3.) Krebs cycle is also referred to as the Citric Acid Cycle. Citric acid is the first product formed in the cycle.
4.) Citric acid cycle provides common oxidative pathway for various respiratory substrate, such as carbohydrates fats and proteins. This cycle is also known as Tricarboxylic acid cycle and Krebs cycle.
5.) Before entering the TCA cycle pyruvic acid enters the mitochondrion. Here pyruvic acid is decarboxylated and the remaining 2-carbon fragment is combined with a molecule of coenzyme A to form acetyl-CoA.
CASE 2
The scheme of glycolysis was given by Gustav Embden, Otto Meyerhof, and J. Parnas, and is often referred to as the EMP pathway. In anaerobic organisms, it is the only process in respiration. Glycolysis occurs in the cytoplasm of the cell and is present in all living organisms.It is completed in two phases as preparatory phase and pay-off phase. In this process, glucose undergoes partial oxidation to form two molecules of pyruvic acid. In plants, this glucose is derived from sucrose, which is the end product of photosynthesis, or from storagecarbohydrates. Sucrose is converted into glucose and fructose by the enzyme, invertase, and these two monosaccharides readily enter the glycolytic pathway. Glucose and fructose are phosphorylated to give rise to glucose-6- phosphate by the activity of the enzyme hexokinase. This phosphorylated form of glucose then isomerises to produce fructose-6- phosphate. Subsequent steps of metabolism of glucose and fructose are same. The various steps of glycolysis are depicted in Figure. In glycolysis, a chain of ten reactions, under the control of different enzymes, takes place to produce pyruvate from glucose.
ATP is utilised at two steps: first in the conversion of glucose into glucose 6-phosphate and second in the conversion of fructose 6-phosphate to fructose 1, 6-bisphosphate. The fructose 1, 6-bisphosphate is split into dihydroxyacetone phosphate and 3-phosphoglyceraldehyde (PGAL). We find that there is one step where NADH + H+ is formed from NAD+ ; this is when 3-phosphoglyceraldehyde (PGAL) is converted to 1, 3-bisphosphoglycerate (BPGA). Two redox-equivalents are removed (in the form of two hydrogen atoms) from PGAL and transferred to a molecule of NAD+ . PGAL is oxidised and with inorganic phosphate to get converted into BPGA. The conversion of BPGA to 3-phosphoglyceric acid (PGA), is also an energy yielding process; this energy is trapped by the formation of ATP. Another ATP is synthesised during the conversion of PEP to pyruvic acid.
Pyruvic acid is then the key product of glycolysis. What is the metabolic fate of pyruvate? This depends on the cellular need.There are three major ways in which different cells handle pyruvic acid produced by glycolysis. These are lactic acid fermentation, alcoholic fermentation and aerobic respiration. Fermentation takes place under anaerobic conditions in many prokaryotes and unicellular eukaryotes. For the complete oxidation of glucose to CO2 and H2O, however, organisms adopt Krebs’ cycle which is also called as aerobic respiration. This requires O2 supply.
1.) ________________ is the end product of preparatory phase in glycolysis.
a) Fructose 1, 6-bisphosphate
b) Glyceraldehyde-3-phosphate
c) Fructose 1, 6-diphosphate
d) Glyceraldehyde-3-phosulphate
2.) ________________ is the end product of payoff phase in glycolysis.
a) Fructose 1, 6-bisphosphate
b) Glyceraldehyde-3-phosphate
c) 1, 3-bisphosphoglycerate
d) Pyruvate
3) Give the number of ATP molecules are used in preparatory phase of glycolysis
4.) Name the common step which occurs in respiration in presence of oxygen and in absence of oxygen.
5.) Write the chemical equation for first phase of glycolysis.
Answer key
1) b
2) d
3) In preparatory phase of glycolysis two ATP molecules are used to produce two molecules of glyceraldehyde-3- phosphate from glucose.
4) Glycolysis is the common step which occurs in respiration in presence of oxygen and in absence of oxygen.
5) chemical equation for first phase of glycolysis:
CASE 3
In fermentation, say by yeast, the incomplete oxidation of glucose is achieved under anaerobic conditions by sets of reactions where pyruvic acid is converted to CO2 and ethanol. The enzymes, pyruvic acid decarboxylase and alcohol dehydrogenase catalyse these reactions. Other organisms like some bacteria produce lactic acid from pyruvic acid. In animal cells also, like muscles during exercise, when oxygen is inadequate for cellular respiration pyruvic acid is reduced to lactic acid by lactate dehydrogenase. The reducing agent is NADH+H+ which is reoxidised to NAD+ in both the processes. In both lactic acid and alcohol fermentation not much energy is released; less than seven per cent of the energy in glucose is released and not all of it is trapped as high energy bonds of ATP. Also, the processes are hazardous – either acid or alcohol is produced. Yeasts poison themselves to death when the concentration of alcohol reaches about 13 per cent.
In eukaryotes these steps take place within the mitochondria and this requires O2. Aerobic respiration is the process that leads to a complete oxidation of organic substances in the presence of oxygen, and releases CO2, water and a large amount of energy present in the substrate. This type of respiration is most common in higher organisms.
1.) Under ______________________ condition incomplete oxidation of respiratory substrate take place.
a) Aerobic
b) Anaerobic
c) Aerobic and anaerobic
d) None of the above
2.) In fermentation process,
a) pyruvic acid is converted to O2 and ethanol
b) pyruvic acid is converted to CO2 and ethylene
c) pyruvic acid is converted to CO2 and ethanol
d) pyruvic acid is converted to CO2 and ethephon
3.) Name the enzyme which facilitate the reactions where pyruvic acid is converted to CO2 and ethanol.
4.) Name the process which leads to a complete oxidation of organic substances in presence of oxygen.
5.) What resulted in animal, when oxygen is inadequate for cellular respiration during muscular exertion?
Answer key
1.) b
2.) c
3.) Pyruvic acid decarboxylase and Alcohol dehydrogenase catalyse the reactions where pyruvic acid is converted to CO2 and ethanol.
4.) Aerobic respiration is the process that leads to a complete oxidation of organic substances in the presence of oxygen and releases carbon dioxide, water and a large amount of energy present in the organic substance.
5.) In animal cells during muscular exertion like exercise, when oxygen is inadequate for cellular respiration pyruvic acid is reduced to lactic acid by lactate dehydrogenase.
CASE 4
1.) Identify the correct statement
Statement 1 – During aerobic respiration, O2 is consumed and O2 is released
Statement 2 – During aerobic respiration, O2 is consumed and CO2 is released
Statement 3 – During aerobic respiration, CO2 is consumed and O2 is released
Statement 4 – During aerobic respiration, CO2 is consumed and CO2 is released
a.) Only 1
b) Only 3
c) Both 1 & 2
d) None of the above
2.) In case of aerobic respiration oxygen is _____________
a) Consumed
b) Evolved
c) Released
d) All of the above
3.) How respiratory ratio or respiratory quotient are calculated in case of aerobic respiration.
4.) Give reason – why respiration is referred as oxidative reaction?
5.) Name the respiratory substrate in which equal amounts of CO2 and O2 are evolved and consumed.
Answer key
1) b
2) a
3) Respiratory quotient (RQ) or Respiratory ratio is nothing but the ratio of the volume of CO2 evolved to the volume of O2 consumed in respiration. It can be calculated by the formula given below,
RQ = Volume CO2 evolved/Volume of O2 consumed
4.) Respiration is referred as the oxidation reaction because it involves the breakdown of respiratory substrate in the presence of oxygen to release carbon dioxide water and a large amount of energy. This use of oxygen to produce energy from substrate is called as the oxidation reaction.
5.) Carbohydrate is the respiratory substrate in which equal amounts of CO2 and O2 are evolved and consumed.
CASE 5
Photosynthesis, of course, takes place within the chloroplasts (in the eukaryotes), whereas the breakdown of complex molecules to yield energy takes place in the cytoplasm and in the mitochondria (also only in eukaryotes).In prokaryotic cells Respiration occurs in the cytosol and around the plasma membrane. The breaking of the C-C bonds of complex compounds through oxidation within the cells, leading to release of considerable amount of energy is called respiration. The compounds that are oxidised during this process are known as respiratory substrates. Usually carbohydrates are oxidised to release energy, but proteins, fats and even organic acids can be used as respiratory substances in some plants, under certain conditions. During oxidation within a cell, all the energy contained in respiratory substrates is not released free into the cell, or in a single step. It is released in a series of slow step-wise reactions controlled by enzymes, and it is trapped as chemical energy in the form of ATP. Hence, it is important to understand that the energy released by oxidation in respiration is not (or rather cannot be) used directly but is used to synthesise ATP, which is broken down whenever (and wherever) energy needs to be utilised. Hence, ATP acts as the energy currency of the cell. This energy trapped in ATP is utilised in various energy-requiring processes of the organisms, and the carbon skeleton produced during respiration is used as precursors for biosynthesis of other molecules in the cell.
In eukaryotes these steps take place within the mitochondria and this requires O2. Aerobic respiration is a type of cellular respiration that takes place in the presence of oxygen to produce energy. It is a continuous process that takes place within the cells of animals and plants. This process can be explained with the help of the chemical equation;
Glucose (C6H12O6) + Oxygen (6O2) → Carbon dioxide (6CO2) + Water (6H2O) + Energy (ATP)
This type of respiration is most common in higher organisms. Respiration is a catabolic process wherein complex organic substrate is oxidized to simple components to generate biological energy. Cellular respiration occurs in two different ways as aerobic and anaerobic respiration.
1.) Respiration is _________________
a) Constructive process
b) Energy trapping process
c) Energy releasing process
d) Energy storing process
2.) Respiration is _________________
a) Catabolic process
b) Anabolic process
c) Endergonic process
d) Energy trapping
3.) Name the site of respiration in eukaryotes.
4.) Define aerobic respiration.
5.) Give the balanced chemical equation for Respiration take place in presence of oxygen?
Answer key
1.) c
2.) a
3.) Respiration occurs in the cytosol and around the plasma membrane in prokaryotic cells. In eukaryotic cells, respiration takes place in the mitochondria,
4.) Aerobic respiration is a type of cellular respiration that takes place in the presence of oxygen to produce energy.
5.) Balanced chemical equation for Cellular Respiration –
Glucose (C6H12O6) + Oxygen (6O2) → Carbon dioxide (6CO2) + Water (6H2O) + Energy (ATP)