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1. Choose correct option
A. The reactions of the TCA cycle occur in
d. endoplasmic reticulum
B. In eucaryotes the complete oxidation of a molecule of glucose results in the net gain of
a. 2 molecules of ATP
b. 36 molecules of ATP
c. 4 molecules of ATP
d. 38 molecules of ATP
C. The intermediate between glycolysis
and TCA cycle is :
a. 2 molecule of ATP
b. 36 molecule of ATP
c. 4 molecule of ATP
d. 38 molecule of ATP
D. Which step of Kreb’s cycle operates
a. α-ketoglutarate → succinyl CoA.
b. Succinyl CoA → succinate
c. Succinate → fumarate
d. Fumarate → malate
2. Fill in the blanks with suitable words
A. Acetyl CoA is formed from Pyruvic acid
and co-enzyme A.
B. In the prokaryotes 38 molecules of ATP are formed per molecule of
C. Glycolysis takes place in cytoplasm.
D. F1- F0 particles participate in the
synthesis of ATP
E. During glycolysis Two molecules
of NADH+H+ are formed.
3. Answer the following questions
A. When and where does anaerobic respiration occur in man and yeast?
Answer : Anaerobic respiration in yeast also takes place during unavailability of adequate oxygen. It produces ethanol and carbon dioxide during the process which is utilised in the process of bread making and brewing. In both cases, it takes place in the cytoplasm of cells.
B. Why is less energy produced during
anaerobic respiration than in aerobic
Answer : Much less energy is released during anaerobic respiration than during aerobic respiration. This is because the breakdown of glucose is incomplete. Anaerobic respirationproduces an oxygen debt. This is the amount of oxygen needed to oxidise lactic acid to carbon dioxide and water.
C. Where is the respiration electron
transport system located in a cell?
Answer :The respiratory electron transport system is located in the inner membrane layer of the mitochondria.
D. Which compound is the terminal electron acceptor in aerobic respiration?
Answer : Oxygen is the terminal electron acceptor in aerobic respiration.
E. What is RQ.? What is its value for fats?
Answer : Ratio of volume of CO2
released to the volume of O2 consumed in respiration is called the respiratory quotient (RQ) or respiratory ratio. It depends on the type of respiratory
substrate. Mostly for fats, RQ is about 0.7
F. What are respiratory substrates? Name the most common respiratory substrate.
Answer : Fats , protein and carbohydrates are ths respiratory subtrate.
G. Write explanatory notes on :
Glycolysis involves the breakdown of glucose molecule into two pyruvic acid molecules. Hence known as glycolysis. This is a common step in anaerobic as well as aerobic
respiration. It occurs in cytoplasm of cell. It is completed in two phases as preparatory phase and pay-off phase. Overall process of glycolysis is completed through ten steps. First five steps constitute the preparatory phase through which glucose is phosphorylated twice at the cost of two ATP molecules.
Glycolysis is only source of energy production in erythrocytes, renal medulla, brain and sperm. Some plant tissues which are modified to store starch (like potato) mainly depend upon glycolysis for energy production
ii. Fermentation by yeast
Answer : Anaerobic respiration is the cellular respiration that does not involve the oxygen at all. It is also called as fermentation. It is completed through steps like glycolysis and conversion of glycolytic product to any suitable product like lactic acid, ethanol, etc.
In yeasts, fermentation results in the production of ethanol and carbon dioxide – which can be used in food processing: Bread – Carbon dioxide causes dough to rise (leavening), the ethanol evaporates during baking.
iii. Electron transport chain
Answer : Wherever the NADH2 (NADH+H+) and FADH2 are produced during glycolysis,
connecting link reaction and Krebs cycle, they are oxidised with the help of various electron carriers and enzymes.
These carriers and enzymes are
arranged on inner mitochondrial membrane in the form of various complexes as complex I, II, III, VI and V. NADH+H+ is oxidised by NADH dehydrogenase (complex I) and
it’s electrons are transferred to ubiquinone
(coenzyme Q CoQ) present on inner membrane of mitochondria. Reduced ubiquinone is called as ubiqunol.
FADH2 is oxidised by complex II
(Succinate dehydrogenase) and these electrons are also transferred to CoQ. During oxidation of NADH+H+ and FADH2, electrons and protons are released but only electrons are carried forward whereas protons are released into outer chamber of mitochondria.
H. How are glycolysis, TCA cycle and electron transport chain linked? Explain.
Answer : Aerobic respiration occurs in main four steps, namely glycolysis, link reaction, Krebs (TCA) cycle and electron transport chain (ETC).
Glycolosis: It is partial oxidation of glucose to form two molecules of pyruvate, two NADH, and two ATP. Glycolysis occurs in the cytoplasm.
Link Reaction: After entering mitochondria, pyruvate undergoes oxidative decarboxylation to form acetyl Co-A and NADH. CO2 is released.2 is released.
Krebs Cycle: Acetyl Co-A reacts with oxaloacetate. The product, citrate, undergoes two oxidative decarboxylations and two dehydrogenations. Oxaloacetate is regenerated. The byproducts are 3 NADH, 1 FADH22, 1 ATP or GTP and 2CO2
Krebs Cycle occurs inside mitochondria.
Terminal Oxidation: NADH and FADH are oxidized. The energy liberated during oxidation is used in the synthesis of ATP and ADP and inorganic phosphate. Hydrogen is ultimately oxidized by oxygen to form water. Terminal oxidation takes place over the inner membrane of mitochondria.
I. How would you demonstrate that
yeast can respire both aerobically and
Answer : Yeast can respire both aerobically and anaerobically. It produces ethanol when it respires anaerobically. Hence, respiration of yeast can be demonstrated by the product produced. Yeast produces water and carbon dioxide aerobically and anaerobically, it produces ethanol.
J. What is the advantage of step wise energy release in respiration?
Answer : The respiratory substrates enter and withdraw from pathway on necessity. ATP gets utilized wherever required and enzymatic rates are generally controlled. Thus, the step-wise release of energy makes the system more efficient in extracting and storing energy.
K. Explain ETS.
Answer : ETS or electron transport system is located in the inner mitochondrial membrane. It helps in releasing and utilizing the energy stored in NADH2
and FADH2. NADH2 which is formed during glycolysis and citric acid cycle, gets oxidized by NADH dehydrogenase (complex I). The electrons so generated get transferred to ubiquinone through FMN. In a similar manner, FADH2(complex II) generated during citric acid cycle gets transferred to ubiquinone. The electrons from ubiquinone are received by cytochrome bc1 (complex III) and further get transferred to cytochrome c. The cytochrome c acts as a mobile carrier between complex III and cytochrome c oxidase complex, containing cytochrome a and a3, along with copper centres (complex IV).
During the transfer of electrons from each complex, the process is accompanied by the production of ATP from ADP and inorganic phosphate by the action ATP synthase (complex V). The amount of ATP produced depends on the molecule, which has been oxidized. 3 ATP molecules are produced by the oxidation of one molecule of NADH. One molecule of FADH2, on oxidation, gives 2 ATP molecules.
L. Discuss. “The respiratory pathway is an amphibolic pathway”.
Answer : The respiratory pathway is an amphibolic pathway as it involves both anabolism and catabolism. It is catabolic pathway as, during this process, various complex molecules are broken down into the simpler molecule to obtain energy. … Similarly, during synthesis of proteins, respiratory substrate amino acid is withdrawn.
M. Why is Krebs cycle reffered as
Answer : Through we describe
the aerobic respiration as catabolic (oxidative) pathway; it is not entirely correct; especially in case of Krebs cycle. Various reactions of Krebs cycle are mainly responsible for step-wise oxidation of acetyl part of acetyl CoA leading to release of energy and CO2. However, as per
need, acetyl CoA or some other intermediates like α-ketoglutarate, oxaloacetate are used as precursors for synthesis of fatty acids, glutamic acid and aspartic acid respectively. Hence, Krebs cycle can be correctly refered to as a
‘Amphibolic pathway’ i.e. involving catabolism as well as anabolism.
N. Which of the following step of aerobic
respiration would be omitted when fatty
acids are used as respiratory substrate?
b. Krebs cycle
c. Electron transfer chain reaction
d. Terminal oxidation.
Answer : ————
A. Photosynthesis and Respiration.
Answer : Respiration Occurs in all living organisms. Photosynthesis Occurs only in all green plants, algae, and in some bacteria.
Respiration is The entire process occurs in Mitochondria. Photosynthesis is The entire process occurs in Chloroplasts.
In respiration Glucose and oxygen are the reactants of this process. In photosynthesis Carbon dioxide, water, and light energy are the reactants of this process.
In respiration Carbon dioxide, water, and energy (ATP) are the by-products. In photosynthesis Glucose, oxygen, and water are the by-products.
Respiration Undergoes Catabolic Process.
Photosynthesis Undergoes Anabolic Process.
In Respiration Oxygen is taken in and carbon dioxide is liberated out. In photosynthesis Producing food and capturing energy.
In respiration this process, food particles are broken down to release energy. In photosynthesis this process, food is synthesis by capturing the energy.
B. Aerobic and Anaerobic respiration.
Answer : In aerobic Oxygen is present when this form of respiration takes place. In Anaerobic Oxygen is absent when this form of respiration takes place.
In aerobic Gases are exchanged in this form of respiration. In anaerobic Gases are not exchanged in this form of respiration.
Aerobic It can be found in the cytoplasm and the mitochondria. Anaerobic It can be found only in the cytoplasm.
In aerobic Glucose breaks down into carbon dioxide and water. In anaerobic Glucose breaks down into ethyl alcohol, carbon dioxide, and energy.
In aerobic All higher organisms such as mammals have this type of respiration. In anaerobic. Lower organisms such as bacteria and yeast use this type.
5. Differentiate between
A. Respiration and combustion
- Respiration is the process of oxidation of food material. Combustion is the process of burning of sugar to form carbon dioxide and water.
- Respiration It does not require any external heat. Combustion External heat is required to burn the sugar.
- In respiration Energy is released in several stages throughout the process. In combustion Energy is released only once.
- The energy released is in the form of ATP. The energy released is in the form of heat.
B. Glycolysis and Krebs cycle
Answer : Glycolysis is the first step involved in the process of respiration and occurs in the cytoplasm of the cell. While Krebs Cycle is the second process of respiration which occurs in the mitochondria of the cell. Both are the process involved in respiration with the aim of fulfilling the energy requirement of the body.
Glycolysis is also known as EMP (Embden-Meyerhof-Parnas Pathway or Cytoplasmic pathway) starts with the breakdown of glucose into pyruvate; Krebs cycle is also known as TCA (tricarboxylic acid) cycle. Mitochondrial respiration starts oxidizing pyruvate into CO2.
In glycolysis Total number of ATP produced is 8 and in Krebs cycle, total ATP is 24.
The site of occurrence of glycolysis is inside the cytoplasm; Krebs cycle occurs inside the mitochondria (cytosol in prokaryotes).
In Glycolysis 2 ATP molecules are consumed for the phosphorylation while Kreb cycle there is no consumption of ATP.
Glycolysis can occur in the presence of oxygen i.e aerobic or in absence of oxygen i.e.anaerobic; Krebs cycle occurs aerobically.
C. Aerobic respiration and fermentation
1. In aerobic respiration Oxygen is used for deriving energy. Fermentation occurs in the absence of oxygen.
2. Aerobic respiration occurs in the cytoplasm and mitochondria. While fermentation occurs in the cytoplasm.
3. Aerobic respirations End products are carbon dioxide and water. End products of fermentation are ethyl alcohol and carbon dioxide.
4. Complete oxidation of the respiratory substrate takes place. In fermentation Incomplete oxidation of the respiratory substrate takes place
5. In aerobic respiration total 38ATP molecules are produced during aerobic respiration. In fermentation Only 2 ATP molecules are produced.