Maharashtra Board Class 11 Biology Important Questions Chapter 13 Respiration and Energy Transfer

Balbharti Maharashtra State Board 11th Biology Important Questions Chapter 13 Respiration and Energy Transfer Important Questions and Answers.

Maharashtra State Board 11th Biology Important Questions Chapter 13 Respiration and Energy Transfer

Question 1.
What is Phosphorylation?
Answer:
It is the formation of ATP, by addition inorganic phosphate to ADP.
ADP + Pi → ATP
Maharashtra Board Class 11 Biology Important Questions Chapter 13 Respiration and Energy Transfer 1

Question 2.
What are the different ways of Phosphorylation?
Answer:
Phosphorylation occurs in three different ways as – photophosphorylation, substrate-level phosphorylation and oxidative phosphorylation.

Question 3.
What is Substrate-level phosphorylation? Where does it occur?
Answer:
Substrate-level phosphorylation is a direct phosphorylation of ADP by transfer of a phosphate group from any suitable substrate. It occurs in cytoplasm of the cells and matrix of mitochondria.

Question 4.
What is oxidative phosphorylation? Mention the site of this reaction.
Answer:
In oxidative phosphorylation ATP is synthesize by using the energy released during the oxidation of substrates like NADH + H⁺ and FADH₂. This occurs on the inner mitochondrial membrane only.

Question 5.
When is ATP hydrolysed?
Answer:
ATP is hydrolysed whenever energy is required for any metabolic reactions.

Question 6.
What is respiration?
Answer:
Respiration is a catabolic process wherein complex organic substrate is oxidized to simple components to generate biological energy, i.e. ATP.

Question 7.
Give an example for anabolic and catabolic process.
Answer:
Anabolic process- Photosynthesis (Biosynthetic process).
Caiabolic process- Respiration (Breakdown process).

Question 8.
Name the following.

The substrate that undergoes oxidation during oxidative phosphorylation
The phosphorylation that occurs only in inner mitochondria! membrane
Two ways of cellular respiration

Answer:

NADH+H⁺ and FADH₂
Oxidative phosphorylation
Anaerobic and aerobic respiration

Question 9.
What is anaerobic respiration?
Answer:
1. Anaerobic respiration is the cellular respiration that does not involve the atmospheric oxygen. It is also called as fermentation.
2. It involves glycolysis where the product of glycolysis i.e. pyruvate is converted to either lactic acid or ethanol.

Question 10.
What is glycolysis? Describe various steps involved in glycolysis.
OR
Describe the process involved in formation of pyruvic acid from glucose molecule.
OR
What is glycolysis? Describe the process of glycolysis with the help of schematic representation.
Answer:
Glycolysis is a process where glucose is broken down into two molecules of pyruvic acid, hence called glycolysis (glucose-breaking). It is common to both aerobic and anaerobic respiration. It occurs in the cytoplasm of the cell. It involves ten steps.
Glycolysis consists of two major phases:
1. Preparatory phase (1-5 steps).
2. Payoff phase (6-10 steps).
1. Preparatory phase:
a. In this phase, glucose is phosphorylated twice by using two ATP molecules and a molecule of fructose 1,6-bisphosphate is formed.
b. It is then cleaved into two molecules of glyceraldehyde-3-phosphate and dihydroxy acetone phosphate. These two molecules are 3-carbon carbohydrates (trioses) and are isomers of each other.
c. Dihydroxy acetone phosphate is isomerised to second molecule of glyceraldehyde-3-phosphate.
d. Therefore, two molecules of glyceraldehyde-3- phosphate are formed.
e. Preparatory phase of glycolysis ends.

2. Payoff phase:
a. In this phase, both molecules of glyceraldehyde-3-phosphate are converted to two molecules of 1,3- bisphoglycerate by oxidation and phosphorylation. Here, the phosphorylation is brought about by inorganic phosphate instead of ATP.
b. Both molecules of 1, 3-bisphosphoglycerate are converted into two molecules of pyruvic acid through series of reactions accompanied with release of energy. This released energy is used to produce ATP (4 molecules) by substrate-level phosphorylation.
Maharashtra Board Class 11 Biology Important Questions Chapter 13 Respiration and Energy Transfer 2

Question 11.
Write down the overall chemical reaction of a process in which glucose in broken down to two molecules of pyruvic acid.
Answer:
Overall reaction of glycolysis:
Glucose + 2 ATP + 2iP + 4 ADP + 2 NAD⁺ → 2 Pyruvate + 2 ADP + 4 ATP + 2 NADH + 2 Ha⁺ + 2 H₂O

Question 12.
Write explanatorv notes on: Glycolysis
Answer:
Glycolysis is a process where glucose is broken down into two molecules of pyruvic acid, hence called glycolysis (glucose-breaking). It is common to both aerobic and anaerobic respiration. It occurs in the cytoplasm of the cell. It involves ten steps.
Glycolysis consists of two major phases:
1. Preparatory phase (1-5 steps).
2. Payoff phase (6-10 steps).
1. Preparatory phase:
a. In this phase, glucose is phosphorylated twice by using two ATP molecules and a molecule of fructose 1,6-bisphosphate is formed.
b. It is then cleaved into two molecules of glyceraldehyde-3-phosphate and dihydroxy acetone phosphate. These two molecules are 3-carbon carbohydrates (trioses) and are isomers of each other.
c. Dihydroxy acetone phosphate is isomerised to second molecule of glyceraldehyde-3-phosphate.
d. Therefore, two molecules of glyceraldehyde-3- phosphate are formed.
e. Preparatory phase of glycolysis ends.

Question 13.
How glycolysis is regulated?
Answer:
Glycolysis is strongly regulated by the complex interplay between ATP consumption, NADH₂ regeneration and regulation of various glycolytic enzymes like hexokinase, PFK-1, pyruvate kinase, etc. Besides, it is also controlled by hormones like glucagon, epinephrine and insulin.

Question 14.
Where does glycolysis take place in a cell?
Answer:
Glycolysis takes place in the cytoplasm of a cell.

Question 15.
What are the products of cleavage in glycolysis?
Answer:
Dihydroxyacetone phosphate (DHAP) and 3-phosphoglyceraldehyde (3-PGAL) are the products of cleavage in glycolysis.

Question 16.
Where does dehydration occur in glycolysis?
Answer:
In glycolysis, dehydration occurs when 2-Phosphoglyceric acid loses a water molecule (dehydration) to form phosphoenol pyruvic acid in presence of the enzyme enolase.

Question 17.
Name the process which is common to both aerobic and anaerobic respiration.
Answer:
Glycolysis is common to both aerobic and anaerobic respiration.

Question 18.
Name the enzymes that catalyse the irreversible reactions.
Answer:
Hexokinase, Phosphoffuctokinase, Phosphoglycerate kinase and Pyruvate kinase are the enzymes that catalyse the irreversible reactions.

Question 19.
Where glycolysis is the only source of energy production?
Answer:
Glycolysis is only source of energy production in erythrocytes, renal medulla, brain and sperm.

Question 20.
Which type of muscle fibres are rich in myoglobin?
Answer:
Red muscles are rich in myoglobin.

Question 21.
Which type of muscle fibre mainly performs anaerobic respiration?
Answer:
White muscle fibres mainly performs anaerobic respiration.

Question 22.
What is lactic acid fermentation?
Answer:
It is a process of anaerobic respiration where the pyruvic acid undergoes reduction by addition of one proton and two electrons donated by NADH+H⁺ to form lactic acid as the product and NAD⁺ as the byproduct of oxidation. Skeletal muscles usually derive energy by this process. It is represented as follows:
Maharashtra Board Class 11 Biology Important Questions Chapter 13 Respiration and Energy Transfer 3

Question 23.
What is the fate of pyruvate in yeast?
Answer:
Yeast shows both aerobic and anaerobic respiration depending upon the presence or absence of oxygen.
1. In absence of oxygen, the pyruvate undergoes anaerobic respiration where it is decarboxylated to acetaldehyde. The acetaldehyde is then reduced by NADH+H to ethanol and carbon dioxide. This type of anaerobic respiration is termed alcoholic fermentation.
2. In the presence of oxygen however, it can respire aerobically to produce C02 and H20.

Question 24.
What is alcoholic fermentation?
Answer:
Alcoholic fermentation is a type of anaerobic respiration where the pyruvate is decarboxylated to acetaldehyde. The acetaldehyde is then reduced by NADH+H+ to ethanol and Carbon dioxide. Since ethanol is produced during the process, it is termed alcoholic fermentation. It is represented as follows:
Maharashtra Board Class 11 Biology Important Questions Chapter 13 Respiration and Energy Transfer 4

Question 25.
Name the process of respiration which does not involve intake of oxygen (0₂) and release of carbon dioxide (C0₂).
Answer:
Lactic acid fermentation is the process of anaerobic respiration which does not involve intake of oxygen (0₂) and release of carbon dioxide (C0₂).

Question 26.
Why yeast stops multiplying in the culture after alcoholic fermentation?
Answer:
After alcoholic fermentation the multiplication of yeast stops because the alcohol formed during the process kills the yeast cells.

Question 27.
What is aerobic respiration?
Answer:

Aerobic respiration occurs in the presence of free molecular oxygen during oxidation of glucose.
In this type of respiration, the glucose is completely oxidized to C0₂ and H₂0 with release of large amount of energy.
It involves glycolysis, acetyl CoA formation (connecting link reaction), Krebs cycle, electron transfer chain reaction and terminal oxidation.

Question 28.
Where does aerobic respiration occur in eukaryotic cell?
Answer:
Aerobic respiration occurs in the mitochondria in eukaryotes.

Question 29.
Explain the conversion of pyruvic acid to acetyl CoA.
OR
Describe the connecting link between glycolysis and Krebs cycle.
Answer:

The conversion of pyruvic acid to acetyl CoA is an oxidative decarboxylation reaction.
It is catalyzed by a multienzyme complex-pyruvate dehydrogenase complex (PDH). This enzyme is present in mitochondria of eukaryotes and cytosol of prokaryotes.
This reaction is called as ‘connecting link’ reaction between glycolysis and Krebs cycle.

Maharashtra Board Class 11 Biology Important Questions Chapter 13 Respiration and Energy Transfer 5

Question 30.
Name the following.
1. Which enzymes converts pyruvic acid to acetyl CoA?
2. Name the coenzyme required by pyruvate dehydrogenase.
Answer:
1. Pyruvate dehydrogenase
2. Thiamin (vitamin Bi)

Question 31.
Why is acetyl Co-A called connecting link between glycolysis and Krebs cycle?
Answer:

The conversion of pyruvic acid to acetyl CoA is an oxidative decarboxylation reaction.
It is catalyzed by a multienzyme complex-pyruvate dehydrogenase complex (PDH). This enzyme is present in mitochondria of eukaryotes and cytosol of prokaryotes.
This reaction is called as ‘connecting link’ reaction between glycolysis and Krebs cycle.

Question 32.
Why vitamin Bi is important for maintaining good health?
Answer:
1. Pyruvate dehydrogenase (PDH) requires thiamin (vitamin Bi) as a co-enzyme. It cannot function in absence of vitamin B₁.
2. Thiamin deficiency causes many disorders such as pyruvic acidosis and lactic acidosis, which are life threatening conditions. Hence, it is required to maintain good health.

Question 33.
Describe Citric acid cycle.
OR
With the help of schematic representation explain Krebs cycle.
Answer:

Krebs cycle or citric acid cycle is the second phase of aerobic respiration which takes place in the matrix of the mitochondria.
The acetyl CoA formed during the link reaction undergoes aerobic oxidation.
This cycle serves a common oxidative pathway for carbohydrates, fats and proteins.
In mitochondria pyruvic acid 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.
During the process NAD⁺ is reduced to NADH+H⁺.
P-oxidation of fatty acids also produces acetyl-CoA as the end product.
Acetyl-CoA from both sources is condensed with oxaloacetic acid to form citric acid. Citric acid is oxidized step-wise by mitochondrial enzymes, releasing carbon dioxide.
Regeneration of oxaloacetic acid occurs to complete the cycle.
There are four steps of oxidation in this cycle, catalyzed by dehydrogenases (oxidoreductases) using NAD⁺ or FAD⁺ as the coenzyme.
The coenzymes are consequently reduced to NADH⁺H⁺ and FADH₂ respectively. These transfer their electrons to the mitochondrial respiratory chain to get reoxidised.
One molecule of GTP (ATP) is also generated for every molecule of citric acid oxidized.

Question 34.
What is the site of Krebs cycle in mitochondria?
Answer:
Krebs cycle takes place in the mitochondrial matrix.

Question 35.
Match the following:

Column I	Column II	Column III
1. Krebs cycle	(a) 1,3-Bisphosphoglycerate → 3-Phosphoglycerate	(p) Pyruvate dehydrogenase
2. Glycolysis	(b) Succinyl CoA → Succinate	(q) NADH dehydrogenase
3. ETS	(c) Pyruvic acid → Acetyl CoA	(r) Two ATP are produced
4. Link reaction	(d) Transfer of electrons from Complex to Ubiquinone	(s) Succinyl CoA – synthetase

Answer:

Column I	Column II	Column III
1. Krebs cycle	(b) Succinyl CoA → Succinate	(s) Succinyl CoA – synthetase
2. Glycolysis	(a) 1,3-Bisphosphoglycerate → 3-Phosphoglycerate	(r) Two ATP are produced
3. ETS	(d) Transfer of electrons from Complex I to Ubiquinone	(q) NADH dehydrogenase
4. Link reaction	(c) Pyruvic acid → Acetyl CoA	(p) Pyruvate dehydrogenase

Question 36.
Explain ETS.
OR
Illustrate the mechanism of electron transport system.
OR
Give an account of ATP generation steps during ETS.
OR
Explain the mechanism of electron transportation system (ETS).
OR
Explain terminal oxidation.
Answer:

NADH₂ and FADH₂ produced during glycolysis, connecting link reaction and Krebs cycle are oxidized 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.
The open end of the glass tube (delivery tube) is dipped into lime water containing in a test tube (Tube B).
Stoppers of both the tubes are fitted tightly to prevent leakage of gases. First test tube is placed in warm water (37° C-38° C) in a beaker.
Lime water gradually turns milky, indicating the evolution of carbon dioxide from the yeast preparation.
Level of the lime water in the delivery tube does not rise, showing that there is no decline in volume of gas in test tube A and consequently no utilization of oxygen by yeast. Preparation is stored for a day or two.
When we open the stopper of tube A we will notice a smell of alcohol indicating the formation of ethanol.
From this activity it may be inferred that yeast respires anaerobically to ferment glucose to ethanol and carbon dioxide.

Question 37.
Explain the significance of electron transport system.
Answer:
Significance of ETS:

Major amount of energy is generated through ETS or terminal oxidation in the form of ATP molecules.
Per glucose molecule 38 ATP molecules are formed, out of which 34 ATP molecules are produced through ETS.
Oxidized coenzymes such as NAD and FAD are regenerated from their reduced forms (NADH+H⁺ and FADH₂) for recycling.
In this process, energy is released in a controlled and stepwise manner to prevent any damage to the cell.
ETS produces water molecules.

Question 38.
What is oxidative phosphorylation?
Answer:
Oxidative phosphorylation: It is a metabolic pathway that uses energy released by the oxidation of substrates to produce ATP.

Oxidative phosphorylation takes place in the mitochondrial membrane.
Many intermediate products during respiration are oxidised and release 2H⁺.
The released hydrogen is trapped by NAD⁺ or FAD⁺.
Electrons pass through electron transport system to produce ATP and metabolic water.

Question 39.
Give the balance sheet of ATP formed in aerobic respiration.
Answer:

Step of Respiration	Consumption	Production				Total	Net benefit
		Substrate level phosphorylation	1 Oxidative Phosphorylation
		Substrate level phosphorylation	NADH⁺ H⁺	FADH₂	Total
Glycolysis	2	4	2 × 3 = 6	___________	6	10	8
Pyruvate → AcetylCoA	_______________	___________	2 × 3 = 6	___________	6	6	6
Krebs cycle	_______________	1 × 2 = 2	6 × 3 = 18	2×2 = 4	22	24	24
Total	2	[6]	30 + 4 = [34]			m	38

Question 40.
With the help of an experiment explain how yeast respires anaerobically.
Answer:
Respiration in yeast can be demonstrated with the help of an experiment.
Anaerobic respiration in yeast:

A pinch of dry baker’s yeast suspended in water containing 10ml of 10% glucose in a test tube (test tube A).
The surface of the liquid is covered with oil to prevent entry of air and the test tube is closed tightly with rubber stopper to prevent leakage.
One end of a short-bent glass tube is inserted through it to reach the air inside the tube.
Other end of the glass tube is connected by a polyethylene or rubber tubing to another bent glass tube fitted into a stopper.
The open end of the glass tube (delivery tube) is dipped into lime water containing in a test tube
(Tube B).
Stoppers of both the tubes are fitted tightly to prevent leakage of gases. First test tube is placed in warm water (37° C-38° C) in a beaker.
Lime water gradually turns milky, indicating the evolution of carbon dioxide from the yeast preparation.
Level of the lime water in the delivery tube does not rise, showing that there is no decline in volume of gas in test tube A and consequently no utilization of oxygen by yeast. Preparation is stored for a day or two.
When we open the stopper of tube A we will notice a smell of alcohol indicating the formation of ethanol.
From this activity it may be inferred that yeast respires anaerobically to ferment glucose to ethanol and carbon dioxide.

Maharashtra Board Class 11 Biology Important Questions Chapter 13 Respiration and Energy Transfer 6

Question 41.
With the help of an experiment explain how germinating seeds respire.
Answer:

Seed coats of a few germinating seeds (peas, beans or gram) are removed and are then put in a test tube filled with mercury.
After closing the test tube with the thumb, it is vertically inverted in a trough of mercury and the thumb is carefully removed.
Being lighter than mercury, the seeds rise to the closed upper end of the test Uibe. No gas is seen at first in the test tube.
As germination proceeds, a gas begins to collect at the top of the mercury in the test tube.
On introducing a pellet of potassium hydroxide into the tube, it rises to the top and absorbs the gas. The mercury again fills the tube.
The potassium hydroxide reacts with carbon dioxide gas to produce potassium carbonate and water.
The gas therefore disappears. Evidently germinating seeds produce carbon dioxide by anaerobic respiration in the absence of oxygen in the mercury column.

[Note: Mercury is toxic chemical. Proper precautions must be taken while performing this experiment ]
[Note: Students can scan the adjacent QR code to get conceptual clarity with the aid of a relevant example.]

Question 42.
Give the significance of respiration.
OR
Write a short note on significance of respiration.
Answer:

Respiration provides energy for biosynthesis of biomolecules.
It is also a source of energy for cell division, growth, repairs and replacement of worn out parts, movements,
locomotion etc.
Various intermediates of Krebs cycle are used as building blocks for synthesis of other complex compounds.
Coupled with photosynthesis, it helps to maintain the balance between C0₂ and O₂ in the atmosphere.
Anaerobic respiration (fermentation) is used in various industries such as dairies, bakeries, distilleries, leather industries, paper industries etc. It is used in the commercial production of alcohol, organic acids, vitamins, antibiotics etc.

Question 43.
Match the following:

Column I	Column II	Column III
1. Krebs cycle	(a) 1,3-Bisphosphoglycerate → 3-Phosphoglycerate	(p) Pyruvate dehydrogenase
2. Glycolysis	(b) Succinyl CoA → Succinate	(q) NADH dehydrogenase
3. ETS	(c) Pyruvic acid → Acetyl CoA	(r) Two ATP are produced
4. Link reaction	(d) Transfer of electrons from Complex I to Ubiquinone	(s) Succinyl CoA – synthetase

Answer:

Column I	Column II	Column III
1. Krebs cycle	(b) Succinyl CoA → Succinate	(s) Succinyl CoA – synthetase
2. Glycolysis	(a) 1,3-Bisphosphoglycerate → 3-Phosphoglycerate	(r) Two ATP are produced
3. ETS	(d) Transfer of electrons from Complex I to Ubiquinone	(q) NADH dehydrogenase
4. Link reaction	(c) Pyruvic acid → Acetyl CoA	(p) Pyruvate dehydrogenase

Question 44.
Apply Your Knowledge

Question 1.
While teaching respiration professor said that oxygen is important for respiration in humans, Rakesh kept thinking, where exactly oxygen is required during cellular respiration? What would be the correct explanation for his doubt?
Answer:
Oxygen is very important for life, we humans cannot survive without oxygen. Glycolysis, link reaction and Krebs cycle do not involve oxygen. In cellular reaction, oxygen is required only during ETS where it acts as an electron acceptor hence leading to terminal oxidation where it gets converted into water called metabolic water.

The process of respiration is very fast and occurs continuously as cell require continuous supply of energy to carry out metabolic activities, thus, we require oxygen for cellular respiration even when we are sleeping.

Question 2.
Sonal while studying ETS had a doubt, why FADH2 yields only 2 ATP’s whereas NADH₂ yields three ATP’s? What would be the correct explanation for her doubt?
Answer:

During ETS, NADH₂ and FADH₂ undergoes oxidation where they are converted to NAD⁺ and FAD⁺ respectively.
During this conversion, hydrogen is removed, which latter forms proton and electron. This electron so formed is passed on to different electron carriers. During this transfer of electron, energy is released which is used in ATP synthesis.
In case of NADH₂, energy is released at three places hence results into formation of 3 ATPs whereas, in case of FADH₂ energy is released at only two places, hence results into formation of only 2 ATPs.
Here, the ATP formation occurs by Chemiosmotic hypothesis.

Question 45.
Quick Review

Various steps involved in glycolysis:

Step(s)	Substrate	Enzyme	End product(s)
Phosphorylation	Glucose + ATP	Hexokinase	Glucose – 6 – Phosphate + ADP
Isomerisation	Glucose – 6-Phosphate	Phosphohexose isomerase	Fructose – 6 – Phosphate
Phosphorylation	Fructose – 6-Phosphate + ATP (Phosphate donor)	Phosphofructokinase	Fructose 1,6-Diphosphate + ADP
Cleavage	Fructose -1, 6-Diphosphate	Aldolase	3 – Phosphoglyceraldehyde + Dihydroxyacetone phosphate
Phosphorylation and Dehydrogenation	3-PGAL + H₃PO₄ + NAD+	Triosephosphate dehydrogenase	1, 3 Diphosphoglyceric acid + NADH + H+
Dephosphorylation	1, 3-DPGA + ADP	Diphosphoglycerate kinase (Mg2)	ATP + 3-Phosphoglyceric acid
Rearrangement	3-PGA	Phosphoglycerate mutase	2-Phosphoglyceric acid
Dehydration	2-PGA	Enolase	Phosphoenol Pyruvic acid + H₂0
Dephosphorylation	Phosphoenol Pyruvic acid +ADP	Pyruvate kinase	Pyruvic acid + ATP

Various steps involved in Krebs cycle:

Step(s)	Substrate	Enzyme	End product(s)
Condensation	Acetyl-CoA+Oxalo- acetic acid + H₂0	Citrate synthase	Citric acid (6C) + Coenzyme- A
Dehydration Hydration	It is again completed in two steps: Citric acid Cis-Aconitic acid + H₂0	Aconitase Aconitase	Cis-Aconitic acid + H₂0 Iso-citric acid(6C)
Oxidative decarboxylation	a. Isocitric acid + NAD⁺	Isocitrate dehydrogenase	Oxalo succinic acid(6C) + NADH + H⁺
Oxidative decarboxylation	b. Oxalosuccinic acid	Isocitrate dehydrogenase	a – ketoglutaric acid(5C) + CO
Oxidative Decarboxylation. (-2H) (-C0₂)	a-Ketoglutaric acid + H₂0 + NAD + Coenzyme A	a-Ketoglutarate dehydrogenase complex	Succinyl-CoA(4C) + NADH + H⁺⁺co₂
Substrate level phosphorylation	Succinyl – Co A + GDP + iP	Succinyl CoA synthetase	Succinic acid (4C) + Coenzyme-A + GTP
Dehydrogenation (-2H)	Succinic acid + FAD (H-acceptor)	Succinate dehydrogenase	Fumaric acid (4C) + FADH2
Hydration(+H20)	Fumaric acid + H₂0	Hydration(+H₂0)	Fumaric acid + H₂0
Dehydrogenation (-2H)	Malic acid + NAD+ (H-acceptor)	Dehydrogenation (-2H)	Malic acid + NAD+ (H-acceptor)

Maharashtra Board Class 11 Biology Important Questions Chapter 13 Respiration and Energy Transfer 7

Question 46.
Exercise

Question 1.
Define phosphorylation.
Answer:
It is the formation of ATP, by addition inorganic phosphate to ADP.
ADP + Pi → ATP

Question 2.
Mention the different ways of phosphorylation.
Answer:
Phosphorylation occurs in three different ways as – photophosphorylation, substrate-level phosphorylation and oxidative phosphorylation.

Question 3.
Define substrate-level phosphorylation.
Answer:
Substrate-level phosphorylation is a direct phosphorylation of ADP by transfer of a phosphate group from any suitable substrate. It occurs in cytoplasm of the cells and matrix of mitochondria.

Question 4.
What is fermentation?
Answer:
1. Anaerobic respiration is the cellular respiration that does not involve the atmospheric oxygen. It is also called as fermentation.
2. It involves glycolysis where the product of glycolysis i.e. pyruvate is converted to either lactic acid or ethanol.

Question 5.
Where does glycolysis occurs?
Answer:
Glycolysis is a process where glucose is broken down into two molecules of pyruvic acid, hence called glycolysis (glucose-breaking). It is common to both aerobic and anaerobic respiration. It occurs in the cytoplasm of the cell. It involves ten steps.
Glycolysis consists of two major phases:
1. Preparatory phase (1-5 steps).
2. Payoff phase (6-10 steps).
1. Preparatory phase:
a. In this phase, glucose is phosphorylated twice by using two ATP molecules and a molecule of fructose 1,6-bisphosphate is formed.
b. It is then cleaved into two molecules of glyceraldehyde-3-phosphate and dihydroxy acetone phosphate. These two molecules are 3-carbon carbohydrates (trioses) and are isomers of each other.
c. Dihydroxy acetone phosphate is isomerised to second molecule of glyceraldehyde-3-phosphate.
d. Therefore, two molecules of glyceraldehyde-3- phosphate are formed.
e. Preparatory phase of glycolysis ends.

Question 6.
What is glycolysis? Explain with the help of schematic representation.
Answer:
Glycolysis is a process where glucose is broken down into two molecules of pyruvic acid, hence called glycolysis (glucose-breaking). It is common to both aerobic and anaerobic respiration. It occurs in the cytoplasm of the cell. It involves ten steps.
Glycolysis consists of two major phases:
1. Preparatory phase (1-5 steps).
2. Payoff phase (6-10 steps).
1. Preparatory phase:
a. In this phase, glucose is phosphorylated twice by using two ATP molecules and a molecule of fructose 1,6-bisphosphate is formed.
b. It is then cleaved into two molecules of glyceraldehyde-3-phosphate and dihydroxy acetone phosphate. These two molecules are 3-carbon carbohydrates (trioses) and are isomers of each other.
c. Dihydroxy acetone phosphate is isomerised to second molecule of glyceraldehyde-3-phosphate.
d. Therefore, two molecules of glyceraldehyde-3- phosphate are formed.
e. Preparatory phase of glycolysis ends.

Question 7.
Define fermentation. What are the different types of fermentation?
Answer:
1. Anaerobic respiration is the cellular respiration that does not involve the atmospheric oxygen. It is also called as fermentation.
2. It involves glycolysis where the product of glycolysis i.e. pyruvate is converted to either lactic acid or ethanol.
It is a process of anaerobic respiration where the pyruvic acid undergoes reduction by addition of one proton and two electrons donated by NADH+H⁺ to form lactic acid as the product and NAD⁺ as the byproduct of oxidation. Skeletal muscles usually derive energy by this process.
Alcoholic fermentation is a type of anaerobic respiration where the pyruvate is decarboxylated to acetaldehyde. The acetaldehyde is then reduced by NADH+H⁺ to ethanol and Carbon dioxide. Since ethanol is produced during the process, it is termed alcoholic fermentation.

Question 8.
Name the products of lactic acid fermentation.
Answer:
It is a process of anaerobic respiration where the pyruvic acid undergoes reduction by addition of one proton and two electrons donated by NADH+H⁺ to form lactic acid as the product and NAD⁺ as the byproduct of oxidation. Skeletal muscles usually derive energy by this process.

Question 9.
Write the chemical reaction of lactic acid fermentation.
Answer:
It is a process of anaerobic respiration where the pyruvic acid undergoes reduction by addition of one proton and two electrons donated by NADH+H⁺ to form lactic acid as the product and NAD⁺ as the byproduct of oxidation. Skeletal muscles usually derive energy by this process.

Question 10.
Explain alcoholic fermentation.
Answer:
Alcoholic fermentation is a type of anaerobic respiration where the pyruvate is decarboxylated to acetaldehyde. The acetaldehyde is then reduced by NADH+H⁺ to ethanol and Carbon dioxide. Since ethanol is produced during the process, it is termed alcoholic fermentation.

Question 11.
Less energy is produced during anaerobic respiration that in aerobic respiration. Justify.
Answer:
Anaerobic respiration produces less energy because:

Incomplete breakdown of respiratory substrate takes place.
Some of the products of anaerobic respiration can be oxidised further to release energy which shows that anaerobic respiration does not liberate the whole energy contained in the respiratory substrate.
NADH₂ does not produce ATP, as electron transport is absent.
Only 2 ATP molecules are generated from one molecule of glucose during anaerobic respiration.

Question 12.
Enlist steps involved in aerobic respiration.
Answer:
It involves glycolysis, acetyl CoA formation (connecting link reaction), Krebs cycle, electron transfer chain reaction and terminal oxidation.

Question 13.
Write the reaction of connecting link between glycolysis and Krebs cycle.
Answer:
This reaction is called as ‘connecting link’ reaction between glycolysis and Krebs cycle.

Question 14.
How glycolysis is regulated?
Answer:
Glycolysis is strongly regulated by the complex interplay between ATP consumption, NADH₂ regeneration and regulation of various glycolytic enzymes like hexokinase, PFK-1, pyruvate kinase, etc. Besides, it is also controlled by hormones like glucagon, epinephrine and insulin.

Question 15.
Write the significance of ETS.
Answer:
Significance of ETS:

Major amount of energy is generated through ETS or terminal oxidation in the form of ATP molecules.
Per glucose molecule 38 ATP molecules are formed, out of which 34 ATP molecules are produced through ETS.
Oxidized coenzymes such as NAD and FAD are regenerated from their reduced forms (NADH+H⁺ and FADH₂) for recycling.
In this process, energy is released in a controlled and stepwise manner to prevent any damage to the cell.
ETS produces water molecules.

Question 16.
Give the schematic representation of glycolysis.
Answer:
Glycolysis is a process where glucose is broken down into two molecules of pyruvic acid, hence called glycolysis (glucose-breaking). It is common to both aerobic and anaerobic respiration. It occurs in the cytoplasm of the cell. It involves ten steps.
Glycolysis consists of two major phases:
1. Preparatory phase (1-5 steps).
2. Payoff phase (6-10 steps).
1. Preparatory phase:
a. In this phase, glucose is phosphorylated twice by using two ATP molecules and a molecule of fructose 1,6-bisphosphate is formed.
b. It is then cleaved into two molecules of glyceraldehyde-3-phosphate and dihydroxy acetone phosphate. These two molecules are 3-carbon carbohydrates (trioses) and are isomers of each other.
c. Dihydroxy acetone phosphate is isomerised to second molecule of glyceraldehyde-3-phosphate.
d. Therefore, two molecules of glyceraldehyde-3- phosphate are formed.
e. Preparatory phase of glycolysis ends.

Question 17.
Describe the formation of Acetyl Co-A in respiration.
Answer:

The conversion of pyruvic acid to acetyl CoA is an oxidative decarboxylation reaction.
It is catalyzed by a multienzyme complex-pyruvate dehydrogenase complex (PDH). This enzyme is present in mitochondria of eukaryotes and cytosol of prokaryotes.
This reaction is called as ‘connecting link’ reaction between glycolysis and Krebs cycle.

Question 18.
Give the schematic representation of the overall view of Krebs cycle.
Answer:

Krebs cycle or citric acid cycle is the second phase of aerobic respiration which takes place in the matrix of the mitochondria.
The acetyl CoA formed during the link reaction undergoes aerobic oxidation.
This cycle serves a common oxidative pathway for carbohydrates, fats and proteins.
In mitochondria pyruvic acid 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. During the process NAD⁺ is reduced to NADH+H⁺.
P-oxidation of fatty acids also produces acetyl-CoA as the end product.
Acetyl-CoA from both sources is condensed with oxaloacetic acid to form citric acid. Citric acid is oxidized step-wise by mitochondrial enzymes, releasing carbon dioxide.
Regeneration of oxaloacetic acid occurs to complete the cycle.
There are four steps of oxidation in this cycle, catalyzed by dehydrogenases (oxidoreductases) using NAD⁺ or FAD⁺ as the coenzyme.
The coenzymes are consequently reduced to NADH+H⁺ and FADH₂ respectively. These transfer their electrons to the mitochondrial respiratory chain to get reoxidised.
One molecule of GTP (ATP) is also generated for every molecule of citric acid oxidized.

Question 19.
Explain why the respiratory pathway is an amphibolic pathway?
Answer:

Respiration is considered as a catabolic process; however, it is not entirely correct in case of Krebs cycle.
Many reactions of Krebs cycle involve oxidation of acetyl CoA to release energy and C0₂.
However, the breakdown of respiratory substrates provides intermediates like a-ketoglutarate, oxaloacetate are used as precursors for synthesis of fatty acids, glutamic acid and aspartic acid respectively.
Thus, as the same respiratory process acts as catabolic as well as anabolic pathway for synthesis of various intermediate metabolic products, it is called amphibolic pathway.

Question 20.
Write a detailed note on the connecting link between glycolysis and Krebs cycle.
Answer:

The conversion of pyruvic acid to acetyl CoA is an oxidative decarboxylation reaction.
It is catalyzed by a multienzyme complex-pyruvate dehydrogenase complex (PDH). This enzyme is present in mitochondria of eukaryotes and cytosol of prokaryotes.
This reaction is called as ‘connecting link’ reaction between glycolysis and Krebs cycle.

Question 21.
Give the diagrammatic representation of ETS.
Answer:

NADH₂ and FADH₂ produced during glycolysis, connecting link reaction and Krebs cycle are oxidized 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 canned forward whereas protons are released into outer chamber of mitochondria (intermembrane space).
Ubiquinol is oxidised by complex-III (Cytochrome bcl complex) and it’s electrons are transferred to cytochrome C.
Cytochrome C is a small, iron-containing protein, loosely associated with inner membrane. It acts as a mobile electron carrier, transferring the electrons between complex III and IV.
Cytochrome C is oxidised by complex IV or cytochrome C oxidase consisting of cytochrome a and a₃. Electrons are transferred by this complex to the molecular oxygen. This is terminal oxidation.
Reduced molecular oxygen reacts with protons to form water molecule called as metabolic water.
Protons necessary for this are channelled from outer chamber of mitochondria into inner chamber by F₀ part of oxysome (complex V) present in inner mitochondrial membrane.
This proton channelling by F₀ is coupled to catalytic site of F₁ which catalyses the synthesis of ATP from ADP and inorganic phosphate. This is oxidative phosphorylation.
As transfer of protons is accompanied with synthesis of ATP, this process is named as ‘Chemiosmosis’ by Peter Mitchell.

Question 22.
Explain the process of terminal oxidation. Give its significance (any two points).
Answer:

NADH₂ and FADH₂ produced during glycolysis, connecting link reaction and Krebs cycle are oxidized 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 canned forward whereas protons are released into outer chamber of mitochondria (intermembrane space).
Ubiquinol is oxidised by complex-III (Cytochrome bcl complex) and it’s electrons are transferred to cytochrome C.
Cytochrome C is a small, iron-containing protein, loosely associated with inner membrane. It acts as a mobile electron carrier, transferring the electrons between complex III and IV.
Cytochrome C is oxidised by complex IV or cytochrome C oxidase consisting of cytochrome a and a₃. Electrons are transferred by this complex to the molecular oxygen. This is terminal oxidation.
Reduced molecular oxygen reacts with protons to form water molecule called as metabolic water.
Protons necessary for this are channelled from outer chamber of mitochondria into inner chamber by F₀ part of oxysome (complex V) present in inner mitochondrial membrane.
This proton channelling by F₀ is coupled to catalytic site of F₁ which catalyses the synthesis of ATP from ADP and inorganic phosphate. This is oxidative phosphorylation.
As transfer of protons is accompanied with synthesis of ATP, this process is named as ‘Chemiosmosis’ by Peter Mitchell.

Question 23.
1. Enlist the main steps involved in aerobic respiration and their place of occurrence.
2. Differentiate between photosynthesis and aerobic respiration.
Answer:
1. Glycolysis takes place in the cytoplasm of a cell.
2. It is catalyzed by a multienzyme complex-pyruvate dehydrogenase complex (PDH). This enzyme is present in mitochondria of eukaryotes and cytosol of prokaryotes.,
3. Krebs cycle or citric acid cycle is the second phase of aerobic respiration which takes place in the matrix of the mitochondria. and These carriers and enzymes are arranged on inner mitochondrial membrane in the form of various complexes as complex I, II, III, VI and V.

Question 24.
1. Give the schematic representation of ETS.
2. Differentiate between respiration and combustion.
Answer:

NADH₂ and FADH₂ produced during glycolysis, connecting link reaction and Krebs cycle are oxidized 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 canned forward whereas protons are released into outer chamber of mitochondria (intermembrane space).
Ubiquinol is oxidised by complex-III (Cytochrome bcl complex) and it’s electrons are transferred to cytochrome C.
Cytochrome C is a small, iron-containing protein, loosely associated with inner membrane. It acts as a mobile electron carrier, transferring the electrons between complex III and IV.
Cytochrome C is oxidised by complex IV or cytochrome C oxidase consisting of cytochrome a and a₃. Electrons are transferred by this complex to the molecular oxygen. This is terminal oxidation.
Reduced molecular oxygen reacts with protons to form water molecule called as metabolic water.
Protons necessary for this are channelled from outer chamber of mitochondria into inner chamber by F₀ part of oxysome (complex V) present in inner mitochondrial membrane.
This proton channelling by F₀ is coupled to catalytic site of F₁ which catalyses the synthesis of ATP from ADP and inorganic phosphate. This is oxidative phosphorylation.
As transfer of protons is accompanied with synthesis of ATP, this process is named as ‘Chemiosmosis’ by Peter Mitchell.

Question 25.
Enlist the different respiratory substrate.
Answer:
Respiratory substrates are the molecules that are oxidized during respiration to release energy which can be used for ATP synthesis. Carbohydrates, fats and proteins are the common respiratory substrate. Glucose is the most common respiratory substrate.

Question 26.
Define R.Q. What is its value for fats?
Answer:
1. Respiratory quotient (R.Q.) or respiratory ratio is the ratio of volume of CO₂ released to the volume of O₂ consumed in respiration.
2. R.Q. = Volume of CO₂ released/Volume of O₂ consumed

Question 27.
Write the significance of respiration.
Answer:

Respiration provides energy for biosynthesis of biomolecules.
It is also a source of energy for cell division, growth, repairs and replacement of worn out parts, movements,
locomotion etc.
Various intermediates of Krebs cycle are used as building blocks for synthesis of other complex compounds.
Coupled with photosynthesis, it helps to maintain the balance between C0₂ and O₂ in the atmosphere.
Anaerobic respiration (fermentation) is used in various industries such as dairies, bakeries, distilleries, leather industries, paper industries etc. It is used in the commercial production of alcohol, organic acids, vitamins, antibiotics etc.

Question 47.
Multiple Choice Questions:

Question 1.
Respiration is regarded as a ________ process.
(A) catabolic
(B) anabolic
(C) reduction
(D) synthetic
Answer:
(A) catabolic

Question 2.
Anaerobic respiration is also called as ________ .
(A) Glycolysis
(B) fermentation
(C) phosphoryaltion
(D) decarboxylation
Answer:
(B) fermentation

Question 3.
The first compound formed in glycolysis is
(A) Glucose-6-phosphate
(B) Glucose-1,6-biphosphate
(C) Fructose-6-phosphate
(D) Pyruvic acid
Answer:
(A) Glucose-6-phosphate

Question 4.
Which of the following compounds in last step of glycolysis gives pyruvic acid?
(A) 3 – phosphoglyceraldehyde
(B) dihydroxy acetone phosphate
(C) phosphoenolpyruvate
(D) 2-phosphoglycerate
Answer:
(C) phosphoenolpyruvate

Question 5.
In glycolysis, dehydration occurs during formation of
(A) 3 – phosphoglyceraldehyde
(B) 2 – phosphoglycerate
(C) phosphoenolpyruvate
(D) dihydroxyacetone phosphate
Answer:
(B) 2 – phosphoglycerate

Question 6.
In which of the following steps dehydrogenation occurs?
(A) Glucose → Glucose 6-phosphate
(B) 3-phophoglcerate → 2-phophoglccratc
(C) phosphoenolpyruvate → pyruvate
(D) 3 – phosphoglyceraldehyde → 1, 3-bisphosphoglycerate
Answer:
(D) 3 – phosphoglyceraldehyde → 1, 3-bisphosphoglycerate

Question 7.
The compound common to both aerobic and anaerobic respiration is
(A) C0₂
(B) pyruvic acid
(C) acetyl CoA
(D) free oxygen
Answer:
(B) pyruvic acid

Question 8.
Which compound is found both in respiration and photosynthesis?
(A) Phosphoglycerate
(B) Phosphoglyceraldehyde
(C) Both (A) and (B)
(D) Succinic acid
Answer:
(C) Both (A) and (B)

Question 9.
Which type of respiration does not release C0₂?
(A) Aerobic respiration
(B) Alcoholic fermentation
(C) Lactic acid fermentation
(D) Krebs cycle
Answer:
(C) Lactic acid fermentation

Question 10.
What is the overall goal of glycolysis, Krebs cycle and electron transport system?
(A) Synthesis of ATP in fermentation reaction
(B) Carbohydrates
(C) Nucleic acids
(D) ATP in small stepwise units
Answer:
(D) ATP in small stepwise units

Question 11.
The intermediate between glycolysis and TCA cycle is:
(A) Lactic acid
(B) Acetaldehyde
(C) Fructose-6-phosphate
(D) Acetyl Co-A
Answer:
(D) Acetyl Co-A

Question 12.
During alcoholic fermentation, decarboxylation of pyruvate gives
(A) acetaldehyde
(B) lactic acid
(C) ethyl alcohol
(D) methyl alcohol
Answer:
(A) acetaldehyde

Question 13.
Where the link reaction occurs in prokaryotes?
(A) cytoplasm
(B) mitochondrial matrix
(C) cell membrane
(D) mitochondrial membrane
Answer:
(A) cytoplasm

Question 14.
In Krebs cycle, dehydration of substrate occurs
(A) once
(B) twice
(C) thrice
(D) four times
Answer:
(A) once

Question 15.
Which of the following steps generate ATP without ETS?
(A) Pyruvic acid → Acetyl Co-A
(B) ∝-ketoglutarate → Succinic acid
(C) Iso-citric acid → Oxalosuccinic acid
(D) Succinyl Co-A → Succinic acid
Answer:
(D) Succinyl Co-A → Succinic acid

Question 16.
In Krebs cycle, the acid which undergoes oxidative decarboxylation is
(A) citric acid
(B) succinic acid
(C) malic acid
(D) ∝-ketoglutaric acid
Answer:
(D) ∝-ketoglutaric acid

Question 17.
During Krebs cycle, fumaric acid gets converted into malic acid by
(A) decarboxylation
(B) dehydrogenation
(C) dehydration
(D) hydration
Answer:
(D) hydration

Question 18.
Krebs cycle is also called TCA cycle because
(A) the first compound formed is citric acid.
(B) it was discovered by Sir Hans Krebs.
(C) organic acids formed have 3 carboxylic acid groups.
(D) acetyl Co-A is formed
Answer:
(C) organic acids formed have 3 carboxylic acid groups.

Question 19.
Which of the following compound is the acceptor of Acetyl Co-A in Krebs cycle?
(A) Oxaloacetic acid
(B) Fumaric acid
(C) Malic acid
(D) Oxalo succinic acid
Answer:
(A) Oxaloacetic acid

Question 20.
Which of the following compounds is formed in Krebs cycle from fumaric acid?
(A) Oxalo acetic acid
(B) Malic acid
(C) ∝-KGA
(D) Citric acid
Answer:
(B) Malic acid

Question 21.
Which of the following step of aerobic respiration would be omitted when fatty acids are used as respiratory substrate?
(A) Glycolysis
(B) Krebs cycle
(C) Electron transfer chain reaction
(D) Terminal oxidation.
Answer:
(A) Glycolysis

Question 22.
During Krebs cycle, decarboxylation occurs _______ time/s.
(A) 1
(B) 2
(C) 3
(D) 4
Answer:
(B) 2

Question 23.
The conversion of malic acid to oxalo acetic acid is catalyzed by
(A) malate reductase
(B) malate thiokinase
(C) fumarase
(D) malate dehydrogenase
Answer:
(D) malate dehydrogenase

Question 24.
Electron carriers of oxidative phosphorylation are present on
(A) outer membrane of mitochondria.
(B) inner membrane of mitochondria.
(C) thylakoid membrane of chloroplast.
(D) matrix of mitochondria.
Answer:
(B) inner membrane of mitochondria.

Question 25.
Which of the following derives maximum energy per molecule of glucose?
(A) Alcoholic fermentation.
(B) Lactic acid fermentation.
(C) Aerobic respiration in unicellular organisms.
(D) Glycolysis in liver cells.
Answer:
(C) Aerobic respiration in unicellular organisms.

Question 26.
The cytochrome which donates de-energised electron to oxygen is
(A) cytochrome-a
(B) cytochrome-b
(C) cytochrome-a₃
(D) cytochrome-c
Answer:
(C) cytochrome-a₃

Question 27.
In terminal oxidation FADH₂ is oxidized by
(A) complex I
(B) complex II
(C) complex III
(D) complex IV
Answer:
(B) complex II

Question 28.
The net gain of energy from a molecule of glucose in the aerobic respiration is
(A) 38
(B) 35
(C) 70
(D) 76
Answer:
(A) 38

Question 29.
Each molecule of NADH₂ through ETS yields
(A) 1 ATP
(B) 2 ATPs
(C) 3 ATPs
(D) 4 ATPs
Answer:
(C) 3 ATPs

Question 30.
One glucose molecule, through ETS yields
(A) 2 ATP molecules
(B) 3 ATP molecules
(C) 34 ATP molecules
(D) 38 ATP molecules
Answer:
(C) 34 ATP molecules

Question 31.
The adenosine triphosphate (ATP) gain during glycolysis, connecting link and Krebs cycle respectively are _______ .
(A) 8, 6,24
(B) 8,24, 6
(C) 24, 8, 6
(D) 6, 8, 24
Answer:
(A) 8, 6,24

Question 32.
The respiratory quotient (R.Q.) of carbohydrate is ________ .
(A) 0.7
(B) 1
(C) 0.9
(D) 0.1
Answer:
(B) 1

Question 33.
R. Q. for proteins is about _______ .
(A) 0.7
(B) 0.8
(C) 0.9
(D) 1.0
Answer:
(C) 0.9

Question 48.
Competitive Corner:

Question 1.
Which of the following statements regarding mitochondria is INCORRECT?
(A) Inner membrane is convoluted with infoldings.
(B) Mitochondrial matrix contains single circular DNA molecule and ribosomes.
(C) Outer membrane is permeable to monomers of carbohydrates, fats and proteins.
(D) Enzymes of electron transport are embedded in outer membrane.
Hint: Enzymes of electron transport are embedded in inner membrane.
Answer:
(D) Enzymes of electron transport are embedded in outer membrane.

Question 2.
Where is the respiratory electron transport system (ETS) located in plants?
(A) Intermembrane space
(B) Mitochondrial matrix
(C) Outer mitochondrial membrane
(D) Inner mitochondrial membrane
Answer:
(D) Inner mitochondrial membrane

Question 3.
In case of anaerobic respiration, the R.Q is _____ .
(A) always less than one
(B) always more than one
(C) always infinity
(D) Variable on the basis of substrate.
Answer:
(C) always infinity

Question 4.
The net gain of ATP molecules during aerobic breakdown of one glucose molecule is _______ .
(A) 40
(B) 38
(C) 36
(D) 30
Answer:
(B) 38

Question 5.
During glycolysis the compounds PGAL and DHAP are formed from fructose 1,6- diphosphate by _______ .
(A) cleavage
(B) isomerisation
(C) phosphorylation
(D) condensation
Answer:
(A) cleavage

Question 6.
Number of oxygen molecules utilized in glycolysis is ________ .
(A) 0
(B) 2
(C) 4
(D) 6
Answer:
(A) 0