Chapter – 3C : Transpiration | Chapter Solution Class 9

(b) Energy giving

Explanation: Respiration is a catabolic process where glucose and other food molecules are broken down to release energy. This energy is stored in the form of ATP (Adenosine Triphosphate) which powers all biological activities in the cell. Therefore, it is an energy-giving process, not a destructive or building (anabolic) one.

(c) Respiratory organ

Explanation: Respiratory organs like lungs (in humans) or gills (in fish) have moist surfaces and are richly supplied with blood vessels to allow efficient exchange of gases — oxygen is absorbed and carbon dioxide is released. This structural setup is essential for respiration to occur effectively.

(c) Day and night

Explanation: Respiration is a continuous process, unlike photosynthesis. Every living cell needs a constant supply of energy, so respiration takes place both during day and night, irrespective of light availability.

(c) Glucose

Explanation: Among various molecules used in respiration, glucose is the primary and most commonly used substrate. It breaks down through glycolysis, Krebs cycle, and electron transport chain to release maximum energy (ATP).

(c) Breathing

Explanation: The physical process of inhaling oxygen and exhaling carbon dioxide using respiratory organs (like lungs) is called breathing, which supports cellular respiration inside the body.

(a) 38 kcal (But this value is usually for aerobic respiration)

Explanation: In anaerobic respiration, only 2 ATP molecules (≈ 21 kcal) are produced from one glucose molecule due to incomplete breakdown, unlike aerobic respiration which yields 38 ATP (≈ 38 kcal). So the correct answer may reflect a mismatch, but as per standard understanding, anaerobic respiration gives less energy, not 38 kcal.

(c) Fermentation

Explanation: Fermentation is an anaerobic process where glucose is only partially broken down, producing less energy (only 2 ATP) and by-products like ethanol or lactic acid depending on the organism.

Trachea

Explanation: Cockroaches breathe through a network of air tubes called tracheae, which deliver oxygen directly to body tissues without involving blood.

Fish (e.g., Magur, Anabas)

Explanation: Some fish like Magur and Anabas have accessory respiratory organs that help them breathe air when water is insufficient in oxygen. This adaptation helps them survive in shallow or muddy water.

All or External

Explanation: Organs like lungs, gills, and skin in different organisms must be moist and semi-permeable to allow diffusion of gases (O₂ and CO₂) during respiration.

Glucose

Explanation: Glucose is the main carbohydrate used by most cells in the process of respiration to release energy in the form of ATP.

Energy

Explanation: The chemical energy stored in food (mainly glucose) is released during respiration and used to power various functions in the body.

True

Explanation: Glycolysis, the first step of glucose breakdown, occurs in the cytoplasm of cells and does not require oxygen.

True

Explanation: In humans, the lungs are located in the thoracic cavity, one on each side of the heart, and are protected by the rib cage.

True

Explanation: Magur fish has a tubular-shaped accessory organ that helps it breathe atmospheric air, allowing survival in low-oxygen waters.

True

Explanation: Every step of respiration (glycolysis, Krebs cycle, etc.) is enzyme-catalyzed. Enzymes speed up chemical reactions and help control the energy release.

True

Explanation: The Krebs cycle begins when acetyl-CoA combines with oxaloacetic acid to form citric acid, which is why it’s also called the citric acid cycle.

Lenticels

Explanation: Trachea, gill, and lungs are respiratory organs in animals, whereas lenticels are structures found in plants (especially woody stems) that help in gas exchange — not in animal respiration.

Cardiac exercise

Explanation: Glycolysis, Krebs cycle, and terminal respiration are stages of cellular respiration, while cardiac exercise is a physical activity, not a biochemical pathway.

Combustion

Explanation: The first three are biological processes that occur in living organisms for energy release. Combustion is a non-biological, external chemical process of burning substances in presence of oxygen.

To release energy.

Explanation: Respiration breaks down food molecules (like glucose) to release energy in the form of ATP, which is used by the cell for all life processes.

Aerobes.

Explanation: Aerobic organisms, or aerobes, are those that use oxygen to carry out respiration.

Glucose.

Explanation: Glucose is the most commonly used and preferred respiratory substrate for energy production during respiration.

Breathing is the physical act of taking in air (inhalation) and pushing it out (exhalation), allowing gas exchange in the lungs.

In respiratory organs.

Explanation: Breathing occurs in lungs in humans and many animals, or in other respiratory organs like gills or tracheae depending on the organism.

Atmosphere.

Explanation: Terrestrial animals obtain oxygen from the atmosphere through breathing air via lungs or other respiratory structures.

Production of energy (ATP).

Explanation: Mitochondria are called the “powerhouse of the cell” because they produce ATP through aerobic respiration.

38 ATP.

Explanation: In aerobic respiration, 1 molecule of glucose produces a total of 38 molecules of ATP.

Because glucose is only partially broken down.

Explanation: Fermentation is an anaerobic process that does not fully oxidize glucose, so only 2 ATP are produced instead of 38, resulting in less energy release.

Accessory respiratory organs are additional structures that help in breathing when normal respiration is insufficient. In Anabas and Clarias (Magur), arborescent (tree-like) air sacs act as accessory respiratory organs.

In frogs and toads, inspiration occurs by lowering the floor of the buccal cavity and closing the glottis, drawing air in. Expiration happens when the buccal floor rises and the glottis opens, forcing air out through the nostrils.

The thoracic cavity wall is formed by the ribs, intercostal muscles, sternum, and the diaphragm. These structures help in expanding and contracting the chest during breathing.

Lungs communicate with the atmosphere through the trachea and nasal passage. Alveoli are the sites where oxygen enters the blood. Respiration involves oxidation of glucose to release energy in the form of ATP.

Respiratory site: Mitochondria

Respiratory organ cells: Alveolar cells

Respiratory substratum: Glucose

Respiratory enzyme: Cytochrome oxidase

When glucose is burnt with oxygen in a calorimeter, it undergoes complete combustion, releasing a large amount of heat and CO₂. No ATP is produced as enzymes are absent.

Human breathing involves two main processes: inhalation and exhalation, which occur due to the movement of the diaphragm and intercostal muscles.

• Inhalation: The diaphragm contracts and moves downward, while intercostal muscles lift the rib cage. This increases the thoracic volume, reducing pressure, and air enters the lungs.
• Exhalation: The diaphragm relaxes and moves upward, and the rib cage lowers. Thoracic volume decreases, pressure increases, and air is pushed out of the lungs.

This mechanical process ensures continuous gas exchange, supplying oxygen to the body and removing carbon dioxide.

During daytime, green plants perform both photosynthesis and respiration.

• In photosynthesis, plants absorb sunlight, CO₂, and water to produce glucose and release O₂.
• In respiration, glucose is broken down using oxygen to release energy in the form of ATP.

Both processes occur in different organelles — chloroplasts for photosynthesis and mitochondria for respiration. Photosynthesis dominates during the day, producing more O₂ than consumed by respiration.

Respiration is the process by which cells release energy from glucose or other food molecules. It is mainly of two types: aerobic respiration and anaerobic respiration.

• In aerobic respiration, oxygen is used to completely break down glucose into carbon dioxide and water, releasing a large amount of energy (38 ATP). This type of respiration occurs in most plants, animals, and aerobic microorganisms. It takes place in the mitochondria and is the most efficient form of energy production.
• On the other hand, anaerobic respiration occurs in the absence of oxygen. Here, glucose is partially broken down to release a small amount of energy (2 ATP). The by-products are different depending on the organism—ethanol and CO₂ in yeast, or lactic acid in human muscles during heavy activity. Anaerobic respiration is less efficient but useful when oxygen is limited.

Fermentation is an anaerobic process in which organisms, especially microorganisms like yeast and certain bacteria, partially break down glucose or other sugars without using oxygen, producing less energy along with by-products such as alcohol, lactic acid, or gases. This process helps in energy production when oxygen is absent.

There are mainly two types of fermentation:

1. Alcoholic Fermentation – This occurs in yeast and some bacteria, where glucose is converted into ethanol (alcohol) and carbon dioxide, with the release of a small amount of energy (2 ATP). It is used in the production of alcoholic beverages and bread.
2. Lactic Acid Fermentation – This takes place in some bacteria and in human muscle cells under low oxygen conditions. Glucose is converted into lactic acid with the release of energy. It causes muscle fatigue during intense exercise.