WBBSE Class 9 Life Science Solutions Chapter 3.2B Cellular Level Respiration

Detailed explanations in West Bengal Board Class 9 Life Science Book Solutions Chapter 3.2B Cellular Level Respiration offer valuable context and analysis.

WBBSE Class 9 Science Chapter 3.2B Question Answer – Cellular Level Respiration

Very Short Questions and Answers : (1 mark for each question)

Question 1.
Which type of respiratory process generates energy inside the living cell?
Answer:
Internal or cellular respiration generates energy inside the living cell.

Question 2.
What is meant by respiratory substrate?
Answer:
The compounds, which are oxidised during cellular respiration to release energy, are known as respiratory substrates.

Question 3.
In which form does respiratory substrate liberate energy during cellular respiration?
Answer:
During cellular respiration, energy is liberated from respiratory substrate in the form of ATP.

Question 4.
Where do reactions of glycolysis take place during cellular respiration?
Answer:
Reactions of glycolysis take place in the cytoplasm during cellular respiration.

Question 5.
What is meant by glycolysis?
Answer:
The breakdown of glucose by enzymes, releasing energy and pyruvic acid, is called glycolysis.

Question 6.
How many pyruvic acid molecules are formed at the end of glycolysis?
Answer:
Two pyruvic acid molecules are formed at the end of glycolysis.

Question 7.
Where do the reactions of Krebs cycle take place?
Answer:
Reactions of Krebs cycle occur in the mitochondria.

Question 8.
Mention the by-products of Krebs cycle.
Answer:
The by-products of Krebs cycle are CO₂, reduced NAD and FAD (i.e. NADH + H⁺ and FADH₂ respectively).

Question 9.
Which reactions of respiration occur in the inner membrane of mitochondria?
Answer:
The reactions of electron transport system or terminal respiration occur in the inner membrane of mitochondria.

Question 10.
In which phase of aerobic respiration is ATP produced?
Answer:
ATP is produced by ETS (electron transport system) of aerobic respiration.

Question 11.
Mention two organic end-products of anaerobic respiration.
Answer:
Lactic acid and ethyl alcohol are two organic end-products of anaerobic respiration.

Question 12.
Name a type of animal tissue, where anaerobic respiration takes place.
Answer:
Anaerobic respiration occurs in the voluntary muscles of animals.

Question 13.
Which organic compound is formed in muscle cells due to anaerobic respiration?
Answer:
Lactic acid is formed in muscle cells due to anaerobic respiration.

Question 14.
Which organic compound is produced in plant cells due to anaerobic respiration?
Answer:
Ethyl alcohol is produced in plant cells by anaerobic respiration.

Question 15.
Which organic compound is produced by fermentation of milk?
Answer:
Lactic acid is produced by fermentation of milk.

Question 16.
Which organic compound is produced by fermentation of glucose or sucrose in oxygen free condition?
Answer:
Ethyl alcohol is produced by fermentation of glucose or sucrose in oxygen free condition.

Question 17.
Name an enzyme present in yeast, wihch helps in aicoholic fermentation of sugar solution.
Answer:
Enzyme zymase is present in yeast, which helps in alcoholic fermentation of sugar solution.

Question 18.
Which enzyme, present in Lactobacillus, helps in fermentation of milk-sugar?
Answer:
Lactate dehydrogenase is the enzyme, present in Lactobacillus, which helps in fermentation of milk-sugar.

Question 19.
Where does aerobic respiration take place?
Answer:
Aerobic respiration takes place in all organisms living in air, water and soil in contact with free molecular oxygen.

Question 20.
How many high energy bonds are present in ATP?
Answer:
Two high energy bonds are present in ATP.

Question 21.
How much energy is released during hydrolysis of 1 molecule of ATP?
Answer:
During hydrolysis of 1 molecule of ATP, 7.3 kcal energy is released.

Question 22.
Which cell organelies are called ‘energy transducers’?
Answer:
Those cell organelles which convert one form of energy into another, are called ‘energy transducers’.

Question 23.
Name two organelles which act as energy transducers.
Answer:
Two organelles which act as energy transducers are chloroplast and mitochondrion.

Question 24.
Name the scientist who first observed the difference between respiration and combustion.
Answer:
Antoine Lavoisier first observed the difference between respiration and combustion.

Short Questions and Answers : (2 marks for each question)

Question 1.
What is respiration?
Answer:
Respiration is a catabolic process, which involves the intake of oxygen within cells and liberation of kinetic energy by oxidation of food or respiratory substrates, for performing different life activities.

Question 2.
What is meant by cellular respiration?
Answer:
The bio-chemical process by which food or respiratory substrates are oxidised within the cells to liberate kinetic energy in the form of ATP, is known as cellular respiration.

Question 3.
What is meant by aerobic respiration?
Answer:
Aerobic respiration is a type of cellular respiration, where respiratory substrate is oxidised completely in the presence of free oxygen to discharge carbon dioxide and water as by-products and to liberate the total energy from the substrate.

Question 4.
Write down the chemical equation of aerobic respiration.
Answer:
The chemical equation of aerobic respiration is mentioned below.

Question 5.
What is meant by anaerobic respiration?
Answer:
Anaerobic respiration is a type of cellular respiration, where respiratory substrate is incompletely oxidised in absence of free molecular oxygen but by the help of the oxygen of inorganic compounds like \(\mathrm{NO}_3^{-}\) \(\mathrm{SO}_4^{2-}\), \(\mathrm{CO}_3^{2-}\), etc. to release carbon dioxide as by-products and to a little amount of energy from the substrate, along with organic compounds.

Question 6.
In which organisms anaerobic respiration occurs?
Answer:
Anaerobic respiration occurs in some bacteria such as Paracoccus denitrificans, Methanobacterium autotrophicum, Bacillus licheniformis etc., few fungi such as yeast, protozoa, all endoparasitic worms (Taenia, Ascaris, Echinococcus etc.). It also occurs in the seeds and few other cells of plants and voluntary muscle cells of animals.

Question 7.
What is meant by fermentation?
Answer:
Fermentation is a typical anaerobic, enzymedependent process of incomplete oxidation of sugar, which produces different organic compounds (ethyl alcohol, lactic acid, butyric acid etc.) with partial liberation of energy from the respiratory substrate.

Question 8.
Write down the chemical equation of ethyi alcohol fermentation.
Answer:
The chemical equation of ethyl alcohol fermentation is mentioned below.

Question 9.
Write down the chemical equation of lactic acid fermentation.
Answer:
The chemical equation of lactic acid fermentation is as follows-

Question 10.
What is meant by alcoholic fermentation?
Answer:
Alcoholic fermentation is a special type of fermentation, where yeast (Saccharomyces) ferments sugar (glucose, fructose, sucrose etc.) solutions to produce ethyl alcohol with the help of a typical enzyme, zymase. In this process, CO₂ and a little energy are also released.

Question 11.
What is meant by lactic acid fermentation?
Answer:
The fermentation process, where certain bacteria (Lactobacillus) ferment milk-sugar (lactose), to produce lactic acid in absence of O₂, liberating a little amount of energy ( 36 kcal ), called lactic acid fermentation.

Question 12.
What is glycolysis?
Answer:
Glycolysis is an oxygen-independent reaction, where glucose, within the cytoplasm of living cells, is broken into pyruvic acid molecules through a series of enzyme-mediated reactions and in this process produce NADH+H⁺, H₂ O and ATP as by-products.

Question 13.
Why is glycolysis called EMP path?
Answer:
Scientists Embden, Meyerhof and Parnas discovered the reaction pathway of glycolysis. Therefore, after the first letter of the names of these three scientists, glycolysis is known as EMP path.

Question 14.
What is Krebs cycle?
Answer:
Krebs cycle is a cyclic reaction pathway, through which, acetyl Co-A, the decarboxylated end product of pyruvate (produced in glycolysis), is oxidised in steps to produce CO₂ and H₂ O and in this process, NAD and FAD are reduced to NADH+H⁺and FADH₂ respectively. It is named after scientist Hans Krebs.

Question 15.
Why is Krebs cycle known as TCA cycle and citric acid cycle?
Answer:
Citric acid is produced in the first step of Krebs cycle, therefore it is called Citric acid cycle. Citric acid contains three carboxylic groups, therefore, this cycle is also known as tricarboxylic acid cycle or TCA cycle.

Question 16.
What is meant by terminal respiration?
Answer:
Terminal respiration is the last step of aerobic respiration, where NADH+H⁺and FADH₂, produced in giycolysis and Krebs cycle, are oxidised by electron carriers, situated in the inner membrane of mitochondria, and hydrogen is oxidised by the atmospheric oxygen to form water and piroduce ATP.

Question 17.
Mention the four phases involved in aerobic respiration.
Answer:
The four phases involved in aerobic respiration are-

• glycolysis
• oxidation of pyruvate
• kerbs cycle
• terminal respiration.

Question 18.
What is ATP synthases?
Answer:
ATP synthase is a enzyme, present on the inner membrane of mitochondria and helps in the synthesis of ATP.

Question 19.
How does organ-level respiration differs from cellular respiration?
Answer:

Features	Organ level respination	Cellatar respiration
1. Nature of reaction	It is a physical process	It is bio-chemical process
2. Site of respiration	Different respiratory organs are involved	All living cells are involved
3. Occurence of chemical reaction	No chemical reaction occurs	Various chemical reactions occur
4. Steps involved	Inspiration, gaseous exchange and expiration	Glycolysis, Krebs cycle and terminal respiration

Question 20.
Distinguish between glycolysis and Krebs cycle.
Answer:

Features	Glycolysis	Krebs cycle
1. Occurrence	Cytoplasm	Mitochondria
2. Entry-level substrate	Glucose	Acetyl Co-A
3. Reaction path	Straight	Circular
4. End product	Pyruvate, ATP, NADH + H+	CO2, NADH + H+, FADH2 and GTP

Question 21.
Distinguish between combustion and respiration.
Answer:

Features	Combustion	Respiration
1. Nature of reaction	Physico-chemical process	Bio-chemical process
2. Enzymes	No role	Plays essential role
3. Free oxygen	Essential	May occur in absence of oxygen
4. Regulation of oxidation	Very fast and not controlled	Slow and controlled
5. Energy generated	Heat and light energy	Only heat energy

Question 22.
Distinguish between alcoholic fermentation and lactic acid fermentation.
Answer:

Features	Alcoholic fermentation	Lactic acid fermentation
1. Occurence	Occurs in yeast cell	Occurs in voluntary muscles and certain bacterial cells
2. CO2 production	Occurs	Does not occur
3. End-products	Ethyl alcohol	Lactic acid

Long Questions and Answers : (5 marks for each question)

Question 1.
Briefly describe the process of glycolysis with the help of a schematic diagram.
Answer:
Glycolysis
Glycolysis is the primary step of cellular respiration occurring in cytoplasm of all living cells. By this process, glucose is enzymatically broken into two pyruvic acids (3C) through a straight chain reaction path. Each step requires a specific enzyme which acts as biocatalyst.
In this metabolic process, glucose is first converted into glucose 6-phosphate and then to fructose 1, 6-bisphosphate. In this phase, two ATP molecules are consumed. In the next step, this fructose

1, 6-bisphosphate is broken into two 3C compounds-glycerabldehyde 3-phosphate and dihydroxyacetone phosphate. Enzymatically, this dihydroxyacetone phosphate is transformed into glyceraldehyde 3 phosphate. At the final phase, two molecules of glyceraldehyde 3phosphate transforms step-by-step to form two molecules of pyruvic acid. By glycolytic breakdown of one molecule of glucose, four ATP molecules are produced and two are consumed, therefore, two ATP molecules are net gained. In this reaction, two molecules of NADH + H⁺ are also produced.

Question 2.
Briefly describe the reaction process of Krebs cycle with the help of schematic diagram.
Answer:
Krebs cycle

Krebs cycle is the second major phase of aerobic respiration. This reaction occurs in the mitochondria in a cyclic reaction path, where a 6 carbon substrate, citric acid is converted step-by-step into 5 C and 4 C substrates. The entry-level substrate of Krebs cycle is acetyl Co-A, which is produced from pyruvic acid, the end product of glycolysis. In Krebs cycle, acetyl Co-A and oxaloacetic acid combine to form citric acid. This is the initial product of this cycle.

In this process CO₂, is released in steps. The other products are NADH+H⁺, FADH₂ and GTP. This GTP is transformed into ATP directly. The other two products NADH+H⁺ and FADH₂ are oxidised by dissociation of hydrogen through electron transport system.

Question 3.
Mame the enzyme present in the oxysomes of mitochondria. How does terminal respiration occur in a cell of any aerobic organism? 1 + 4
Answer:
Enzyme in oxysome
ATP synthetase enzyme is present in the oxysomes of mitochondria.

Terminal respiration
Terminal respiration is the final phase of aerobic reaction, which involves the production of ATP and H₂ O. This is the energy generating, i.e., ATP producing final phase of cellular respiration. NADH + H⁺ and FADH₂, (reduced hydrogen carriers) which are produced during glycolysis, decarboxylation of pyruvic acid & Krebs cycle, are oxidised in this reaction path. At first, hydrogen atoms are released from NADH + H⁺ and FADH₂. Then each hydrogen atom releases one electron, which is then transported by iron containing electron carriers cytochrome. This process generates huge chemical energy, which finally produces energy-rich ATP molecules. So, this reaction pathway is also known as electron transport system or ETS. The hydrogen atoms, released from NADH+ H⁺ and FADH₂ finally react with O₂ present in the atmosphere to produce H₂ O.

Question 4.
Mention the significance of respiration.
Answer:
Significance of respiration
The significance of respiration are mentioned below.
1. Conversion of energy and ATP production: The potential energy stored in food, is converted into kinetic energy by respiration. This energy is dissipated as heat and some portion of it is stored in ATP within the cells, as chemical energy for future use.

2. Maintenance of O₂-CO₂ balance: During respiration, atmospheric oxygen is consumed and carbon dioxide is released. Whereas, photosynthesis does the opposite. Thus, photosynthesis and respiration jointly maintain the balance of oxygen and carbon dioxide in the environment.

3. Economic importance: Fermentation of flour (starch) by yeast makes cakes and breads puffy. Ethyl alcohol is a fermentation product, which has great economic importance for medicinal purpose and to prepare alcoholic beverages. Cheese, butter, curds are prepared by fermentation of milk. Some vitamins like vit B₁, vit B₁₂, vit C etc. are also produced in the body by bacterial fermentation.

4. Excretion: Various excretory products like ammonia, ketone body, alcohol, water vapour, volatile fatty acids, etc., are given out of the body through respiration.

5. Maintenance of Acid-Base balance: Since CO₂ is liberated during respiration, it helps to maintain acid-base balance in the body.

6. Regulation of temperature: When animals exhale, certain amount of heat is liberated from their bodies, thus regulating the temperature of the body.

7. Light generation: Certain deep-sea animals, like Ctenophorans and insects, like fireflies can generate light. This phenomenon is called bioluminescence. This light is generated from the chemical energy, gained by respiration.

8. Electrical power generation: Some fishes like Torpedo and electric eel can generate huge electrical power within their electric organs to kill preys. Respiration produces this power from chemical energy.

Question 5.
Compare among aerobic respiration, anaerobic respiration and fermentation.
Answer:
Comparison among aerobic respiration, anaerobic respiration and fermentation

Question 6.
Distinguish between photosynthesis and respiration.
Answer:
Differences between photosynthesis and respiration