Selina Concise Solutions for ICSE Class 6 Biology Chapter 5 Respiratory System

Synopsis -

- The energy released during respiration is stored as chemical energy in the form of ATP - adenosine tri-phosphate.
- Aerobic respiration -
C₆H₁₂O₆+ 6O₂ → 6CO₂ + 6H₂O + 38 ATP
Anaerobic respiration -
C₆H₁₂O₆ → C₂ H₅+ O₂ + 2 ATP
- During vigorous exercise, the cells respire anaerobically and form lactic acid which accumulate in the muscle cells causing fatigue and pain.
- The respiration in humans occur in three phases:
1. Breathing
2. Gaseous Transport
3. Cellular respiration
- The oxygen inhaled in combines with haemoglobin present in the red blood cells forming an unstable compound called oxyhaemoglobin.
- The nasal chamber has got hairy lining to prevent dust particles from reaching the lungs. The lining also has mucous to trap germs and dust.
- The common passage for the food and air is the pharynx.
- Trachea is also called the wind pipe.
- The voice box or the Adam's apple is the larynx which contains ligamentous folds called vocal cords.
- Incomplete closure of epiglottis during swallowing causes coughing.
- The trachea is formed of incomplete C-shaped cartilaginous rings which keep them permanently distended.
- The lungs are protected outside by the two membranes called outer and inner pleura.
- Left lung is slightly smaller than the right lung.
- Left lung has two lobes while the right lung has three lobes.
- Component: O₂ | inspired air: 21% | expired air: 16%
- Component: CO₂ | inspired air: 0.03% | expired air: 4%
- Component: O₂ | inspired air: 79% | expired air: 79%
- Water vapors | inspired air: low | expired air: high
- Breathing is an involuntary act.
- Even after maximum forced expiration, some air is left in the lungs called residual volume.
- In normal adults, the breathing rate is 12-18/minute while a newborn breathes at about 60 breaths per minute.
- Asphyxiation is a condition in which blood becomes venous by the accumulation of excess carbon dioxide and the oxygen supply is diminished.
- The gas composition in artificial respiration is 95% oxygen, 5% carbon-di-oxide.
- Snoring: Vibration of soft palate during breathing when mouth is kept open while sleeping.
- Sneezing: It is a protective mechanism through which a foreign irritant particle is thrown out of the lungs suddenly and forcefully.
- Hiccups: Jerky incomplete inspiration due to blockage of the respiratory tract.
This summary covers the vital components and mechanics of how our bodies process air to create energy. It highlights the differences between breathing as a physical act and cellular respiration as a chemical one.
Teacher's Tip: Remember that ATP is like a rechargeable battery for your cells, storing energy until it is needed.
Exam Tip: For full marks, always specify the number of ATP molecules produced in aerobic (38) versus anaerobic (2) respiration.

Review Questions

Multiple Choice Questions

Question 1: Put a tick (✓) against the most appropriate alternative in the following statements.

Question (i): In humans, taken in of the air through nostrils into the nasal cavity is called
(a) Inhalation
(b) Exhalation
(b) Cellular respiration
(d) Internal respiration

Answer: (a) Inhalation
Inhalation is the active phase of breathing where the diaphragm contracts to pull air into the body. This process ensures that fresh oxygen reaches the lungs for gas exchange.
Teacher's Tip: Think of "In" for Inhalation meaning air goes into the body.
Exam Tip: Do not confuse inhalation with respiration; inhalation is just the first physical step of the whole process.

Question (ii): The front opening of the wind pipe is guarded by -
(a) Glottis
(b) Exoglottis
(c) Epiglottis
(d) Trachea

Answer: (c) Epiglottis
The epiglottis acts as a flap that covers the entrance to the trachea during swallowing. This vital mechanism prevents food and liquid from entering the lungs and causing choking.
Teacher's Tip: Imagine the epiglottis as a traffic signal that directs food to the stomach and air to the lungs.
Exam Tip: Always describe the epiglottis as a "flap-like structure" to get precise marks in anatomy descriptions.

Question (iii): The process during which food is oxidised and energy is released is called
(a) Cellular respiration
(b) Excretion
(c) Digestion
(d) Transpiration

Answer: (a) Cellular respiration
Cellular respiration is a series of chemical reactions that break down glucose molecules in the presence of oxygen. This biological "burning" releases the energy required for every living cell to function.
Teacher's Tip: Respiration is like a factory producing power (ATP), while digestion is just getting the raw materials (food) ready.
Exam Tip: For a complete answer, mention that this process takes place in the mitochondria of the cell.

Short Answer Questions

Question 1: Answer briefly the following:
1. Why do our body cells require oxygen ?
Answer: Body cells require oxygen for the break down of glucose and release energy for carrying out various life functions.

Oxygen acts as a chemical catalyst that allows the mitochondria to extract the maximum amount of energy from nutrients. Without a constant supply of oxygen, cells would quickly run out of the power needed to keep the heart beating and the brain thinking.
Teacher's Tip: Think of oxygen as the "spark" needed to start the energy fire in your cells.
Exam Tip: Use the term "oxidation of glucose" to sound more scientific and score higher marks.

Question 2: What is the difference between breathing and respiration?
Answer: Breathing is a simple physical process of drawing in air through the nostrils and expelling it out. Respiration is a chemical process which involves the breakdown of food and release energy.

Breathing is the mechanical movement of the chest and lungs that moves air in and out. Respiration is the complex biochemical reaction occurring inside individual cells to produce ATP.
Teacher's Tip: Breathing happens in the lungs (Physical); Respiration happens in the cells (Chemical).
Exam Tip: Create a small table with "Physical" vs "Chemical" headings to clearly show the difference.

Question 3: Name the by-product formed during the oxidation of food.
Answer: The by-products formed are 1. carbon-di-oxide, 2. water.

These substances are the waste materials produced when glucose is completely broken down for energy. Carbon dioxide is removed through the lungs during exhalation, while water is either used by the body or excreted.
Teacher's Tip: Just like a car produces exhaust fumes, your cells produce CO₂ as their "exhaust."
Exam Tip: Always list both by-products to provide a complete scientific answer.

Question 4: Name the agency which transports oxygen to all parts of the body.
Answer: Blood .

The blood uses a specialized protein called haemoglobin inside red blood cells to grab onto oxygen molecules. This circulatory system acts as a delivery highway that reaches every single cell in the human body.
Teacher's Tip: Think of Red Blood Cells as tiny "Oxygen Trucks" driving through your veins.
Exam Tip: If the question asks for the specific substance in the blood, mention "Haemoglobin."

Question 5: What is the role of epiglottis during swallowing ?
Answer: Epiglottis closes the wind pipe at the time of swallowing.

By covering the glottis (the opening of the trachea), the epiglottis ensures that food moves only into the esophagus. This automatic reflex is essential for preventing respiratory distress and lung infections caused by inhaled particles.
Teacher's Tip: This is why you should never talk while eating; it confuses the epiglottis!
Exam Tip: Use the word "prevents" when describing the function to clearly state its protective role.

Question 2: Describe in brief the function of ribs and diaphragm in breathing.
Answer: 1. Ribs muscles-During inhalation, the ribs muscles contract and push the ribs upward and outward. During exhalation these relax and cause the ribs to return to original position. 2. Diaphragm: During inhalation it becomes flattened while during exhalation it relaxes and moves up and back into convex (dome) shape.

These muscle movements change the volume of the chest cavity, which in turn changes the air pressure inside the lungs. This pressure difference is what forces air to flow in and out of the body automatically.
Teacher's Tip: Imagine the chest cavity as a bellows; expanding it pulls air in, and squeezing it pushes air out.
Exam Tip: Clearly state that the diaphragm "flattens" during inhalation and becomes "dome-shaped" during exhalation.

Question 3: Name the gas which is expelled out during expiration. Where is it originally produced in our body ?
Answer: The gas which is expelled during expiration is carbon-di-oxide. It is produced as a result of oxidation of glucose in the tissues. (Cellular respiration)

Carbon dioxide is a metabolic waste product that would be toxic if left to accumulate in the bloodstream. It is generated during the final stages of energy production within the mitochondria of our tissue cells.
Teacher's Tip: CO₂ is the "gas waste" of the life process.
Exam Tip: Specify "Cellular Respiration" as the process of production to show advanced understanding.

Question 4: Name the following:
1. Respiratory process in which oxygen is not utilized.
Answer: Cellular respiration (Anaerobic)
2. Respiratory process in which oxygen is utilized.
Answer: Gaseous transport
3. The microscopic air-sacs of the lungs.
Answer: Alveoli
4. The two membranes which protect the lungs.
Answer: Outer pleura, inner pleura

These specific terms describe the anatomy and functional phases of the human respiratory system. The alveoli are particularly important as they are the site where oxygen actually enters the blood.
Teacher's Tip: Alveoli look like "bunches of grapes" at the end of the air tubes.
Exam Tip: Spelling is crucial for terms like "Alveoli" and "Pleura" to get full marks.

Long Answer Questions:

Question 1: Why is a respiratory system necessary ?
Answer: Respiratory system is very important for the body. Respiration in human beings is divided into two distinct parts. The first part involves taking in oxygen from the air or what we commonly call breathing. The respiratory system is responsible for breathing in and out of air, and exchange of gases. The main parts of the respiratory system consist of the nostrils, trachea or wind pipe and lungs. The blood, then, transports the oxygen to the individual cell where it is used for the chemical process of respiration. This is known as cellular respiration.The second part involves taking out carbon dioxide, which is a waste product of cellular function.

Every living cell requires energy to perform its duties, such as repair, growth, and movement. The respiratory system provides the oxygen necessary for energy production and safely removes the gaseous waste generated by cells.
Teacher's Tip: The respiratory system is the body's "Air Logistics Department," managing imports (Oxygen) and exports CO₂.
Exam Tip: Mention both "oxygen intake" and "carbon dioxide removal" to provide a complete explanation of necessity.

Question 2: What factors are most likely to affect the breathing rate ?
Answer: Breathing is a necessary function for human beings. It supplies oxygen for a process called cellular respiration, which is how cells manufacture the energy they need for their life functions. There are lots of things that can affect the rate of breathing in humans and they are:
1. Exercise is one of those things, particularly aerobic exercise. Aerobic exercise is any exercise that causes the person to breathe more, such as running jogging, playing basketball, football, running track, or playing soccer.
2. Even Breathing rate also changes while the person is sleeping, sitting at rest or even after climbing the stairs.
3. Another factor that can influence breathing rate is allergic reactions to stimuli from the environment, such as pollen. This can inflame the passageways leading to the lungs, making them smaller, requiring more air.
4. Smoking is a habit that can influence the development of lung cancer, which in turn influences the rate a person breathes.
5. Nervous conditions and reactions to stimuli also influence the breathing rate, such as the fumed "fight or flight" syndrome.

Our breathing rate is dynamic and changes based on the body's immediate demand for oxygen. When we are active or stressed, our brain signals the respiratory muscles to work faster to keep up with the increased energy usage.
Teacher's Tip: Your breathing rate is like an "Energy Meter" that goes up when the body works harder.
Exam Tip: List at least three distinct factors (like exercise, emotions, and health) to ensure a high score.

Question 3: What happens to the energy liberated during respiration?
Answer: The energy liberated during respiration is utilised for carrying out various life processes. Some of the energy liberated during the breakdown of the glucose molecule, is in the form of heat, but a large part of it is converted into chemical energy called Adenosine Triphosphate (ATP). Any activity inside the cell is carried out by the energy released by these ATP molecules.

ATP acts as a universal currency for energy that the cell can "spend" whenever it needs to perform work. The heat produced during this process also helps warm-blooded animals like humans maintain a constant internal body temperature.
Teacher's Tip: Energy from food is converted into "ATP coins" that cells use to pay for their work.
Exam Tip: Use the full form of ATP (Adenosine Triphosphate) to demonstrate thorough knowledge.

Question 4: What do you understand by inhalation and exhalation ? How are they different from each other ?
Answer: The physical process, by which the air containing oxygen is drawn into the lungs and air containing carbon dioxide is forced out from lungs is called breathing. Breathing involves two steps, inhalation (inspiration) and exhalation (expiration).
Inhalation (Inspiration)
1. Ribs move upwards and outwards.
2. Diaphragm is pushed downwards and flattens.
3. Volume of chest cavity increases.
4. Lungs expand, air pressure becomes low.
5. Atmospheric air at higher pressure rushes into the lungs
Exhalation (Expiration)
1. Ribs move downwards and inward.
2. Diaphragm moves upwards and becomes dome shaped.
3. Volume of chest cavity decreases.
4. Lung size reduces, air pressure becomes high.
5. Air rushes out of lungs as atmospheric air pressure is lower.

Inhalation is an active process requiring muscle contraction, while exhalation is typically a passive process as muscles relax. The rhythmic alternating between these two phases ensures a continuous supply of fresh air to the respiratory surface.
Teacher's Tip: Remember: Inhalation = "Flat Diaphragm," Exhalation = "Dome Diaphragm."
Exam Tip: Draw a comparison table with points like "Rib Movement," "Diaphragm Shape," and "Chest Volume" for clarity.

Question 5: What do you understand by the term respiratory diseases ? Name any three common respiratory diseases.
Answer: Any of the diseases and disorders that affect human respiration are called Respiratory diseases. Diseases of the respiratory system may affect any of the structures and organs that have to do with breathing, including the nasal cavities, the pharynx (or throat), the larynx, the trachea (or windpipe), the bronchi and bronchioles, the tissues of the lungs, and the respiratory muscles of the chest cage.
1. Bronchitis - It is a respiratory infection in which the lining of the bronchi becomes inflamed. As this irritated membrane begins to swell, it narrows or shuts off the bronchial passages, resulting in breathlessness and coughing spells.
2. Asthma - It is a chronic disease that also causes inflammation and swelling in the airways. But this happens periodically. During an asthmatic attack, a patient experiences tightness in the chest, shortness of breath and wheezing. This condition improves considerably with medication.
3. Pneumonia - It is a respiratory infection caused by a bacteria. This bacteria enters the air sacs, multiplies there and the air sacs may get filled with fluid. This disease causes chest pain, chills and high fever.

Respiratory diseases can be caused by infections, environmental pollutants, or genetic factors. They often result in difficulty breathing because they interfere with the clear passage of air or the exchange of gases in the lungs.
Teacher's Tip: "Itis" at the end of a word (like Bronchitis) usually means inflammation or swelling.
Exam Tip: For each disease, mention one specific symptom (like "wheezing" for Asthma) to make your description more accurate.

Question 6: State the cause and treatment for the following diseases: 1. Tuberculosis, 2. Pneumonia, 3. Bronchitis
Answer: 1. Tuberculosis - Cause: Caused by bacteria that can spread by air, dust or sputum. Treatment: BCG vaccine, antibiotic - Streptomycin. 2. Pneumonia - Cause: Mainly caused by bacteria inhaled through air or by contact. Treatment: Antibiotics-Penicillin. 3. Bronchitis - Cause: This respiratory infection is mainly caused by a virus. Air pollution and smoking can also cause bronchitis. Treatment: Drinking plenty of fluids, following a well balanced diet, frequent hand washing and adequate rest can prevent and improve bronchitis.

Understanding the causes of these diseases helps in preventing their spread through good hygiene and vaccination. While bacteria can be treated with specific antibiotics, viral infections like bronchitis primarily require supportive care and rest.
Teacher's Tip: Antibiotics kill $bacteria$, but they don't work against $viruses$!
Exam Tip: Mention "BCG vaccine" specifically for Tuberculosis as it is a key prevention fact.

ADDITIONAL QUESTIONS

A. Fill in the blanks.
1. The respiration is of two types aerobic and anaerobic.
2. In human beings, exchange of gases takes place in lungs.
3. Bronchi divide into smaller tubes called bronchioles.
4. Haemoglobin is present in the red blood cells and helps in the transport of oxygen.
5. Diaphragm is a muscular membrane present below the lungs.
6. Malpighian body consists of Bowman's capsule and glomerulus.
7. Sweat serves to excrete excess of water urea and salts.

Answer: (As provided in bold above)
These terms identify the core structural and functional components of the respiratory and excretory systems. Knowing these names is essential for understanding how our body maintains its internal balance.
Teacher's Tip: Notice that bronchioles are the smaller "branches" that come off the larger "bronchi" trunks.
Exam Tip: Pay attention to the spelling of "Glomerulus" as it is a complex word frequently used in biology.

B. Write true or false for each statement. Rewrite the false statements correctly.

1. Respiration and breathing are two different processes.
Answer: True.

2. Breathing is a chemical process.
Answer: False. Respiration is a chemical process.

3. The oxidation of food to release energy and water is called breathing.
Answer: False. The oxidation of food to release energy and water is called Respiration.

4. The exchange of gases through the skin is called cutaneous respiration.
Answer: True.

5. The trachea branches into two tubes called bronchioles.
Answer: False. The trachea branches into two tubes called bronchi.

6. The microscopic air sacs present in the lungs are called bronchi.
Answer: False. The microscopic air sacs present in the lungs are called alveolar sacs.

Many terms in respiration sound similar, so it is important to distinguish between mechanical acts like breathing and metabolic ones like respiration. Correctly identifying the branching levels of the air tubes ensures you understand the lung's architecture.
Teacher's Tip: Remember the order: Trachea $\rightarrow$ Bronchi $\rightarrow$ Bronchioles $\rightarrow$ Alveoli.
Exam Tip: If a statement is false, you must rewrite the whole correct sentence to get full credit.

Question 7: The walls of alveoli are richly supplied with veins.
Answer: False. The walls of alveoli are richly supplied with blood capillaries.

Question 8: The mature roots and woody stems of certain trees have openings called lenticels.
Answer: True.

Capillaries are the only blood vessels thin enough to allow gases to diffuse across their walls into the lungs. Lenticels perform a similar function for woody plants, allowing air to reach the living tissues inside the trunk.
Teacher's Tip: Lenticels are like "breathing pores" for the bark of a tree.
Exam Tip: Associate "capillaries" with "gas exchange" every time you see a question about alveoli.

C. Arrange the following organs in the correct order to show the path of air.

1. trachea, nose, bronchioles, bronchi, larynx, alveoli, pharynx, lungs
Answer: nose, pharynx, larynx, trachea, bronchi, lungs, bronchioles, alveoli.

Air travels through a single continuous path that filters, warms, and moistens it before it reaches the exchange surface. This sequence follows the air from the external environment deep into the microscopic parts of the lungs.
Teacher's Tip: Use the "N-P-L-T" mnemonic: Nose, Pharynx, Larynx, Trachea.
Exam Tip: Use arrows between the names to show the direction of flow clearly.

D. Differentiate between

Question 1: Aerobic respiration and Anaerobic respiration.
Answer:
Aerobic Respiration
1. It takes place in the presence of oxygen.
2. Complete oxidation of food takes place.
3. 38 molecules of ATP are produced by oxidation of one gram mole of glucose.
4.CO₂ and H₂O are the end products.
Anaerobic Respiration
1. It takes place in the absence of oxygen.
2. Incomplete oxidation of food takes place.
3. 2 molecules of ATP are produced by oxidation of gram mole of glucose.
4. Ethyl alcohol C₂H₅OH and CO₂ are the end products.

Aerobic respiration is highly efficient and common in most complex organisms, providing a large amount of energy. Anaerobic respiration is a "back-up" or simpler method used by yeast or hard-working muscles, though it produces far less power.
Teacher's Tip: Aerobic is "with air," Anaerobic is "without air."
Exam Tip: Mentioning the specific number of ATP (38 vs 2) is the best way to contrast their efficiency.

Question 2: bronchi and alveoli.
Answer:
Bronchi
1. The two branching tube of trachea are called bronchi.
2. There are two bronchi
3. The walls of bronchi are not richly supplied with blood capillaries.
Alveoli
1. The out growths of microscopic air sacs are called alveoli.
2. There are millions of alveolar sacs.
3. The walls of the alveoli are richly supplied with blood capillaries.

Bronchi serve as the main highways for air entering each lung. Alveoli are the tiny "stations" at the end of the line where oxygen actually jumps into the blood and carbon dioxide jumps out.
Teacher's Tip: Bronchi are "conductors" (moving air), Alveoli are "exchangers" (swapping gases).
Exam Tip: Point out that exchange *only* happens in the alveoli, not in the bronchi.

Question 3: Breathing and Respiration.
Answer:
Breathing
1. It is a physical process.
2. Air containing oxygen is taken into the lungs and air loaded with carbondioxide is given out.
3. Lungs are mainly involved.
Respiration
1. It is a catabolic process
2. Oxygen taken in is used in oxidizing glucose and energy is released.
3. Occurs in tissues and cells of the body.

Breathing provides the raw materials (gases) while respiration performs the chemical work (energy release). You can breathe without respiring properly if your cells are damaged, but you cannot respire without breathing in the oxygen first.
Teacher's Tip: Breathing is what you *feel* your chest doing; Respiration is what your cells *do* with the air.
Exam Tip: Always use the word "catabolic" for respiration to describe the breaking down of molecules.

Question 4: Bowman's capsule and alveolus.
Answer:
Bowman's capsule
1. It is a part of kidney i.e. a excretory unit.
2. It is cup shaped structure at the end of nephron.
3. It helps in filtration of blood
Alveolus
1. It is a part of using i.e. a respiratory unit.
2. It is the outgrowth of air sacs (alveolar sacs).
3. It helps in exchange of gases (CO₂ and O₂).

These two structures are both microscopic functional units that interact with the blood. While the Bowman's capsule cleans the blood by filtering out liquid wastes, the Alveolus cleans the blood by removing carbon dioxide and adding oxygen.
Teacher's Tip: Both are "blood cleaners," but one handles liquid (Kidney) and one handles gas (Lung).
Exam Tip: Identify which system (excretory vs respiratory) each belongs to as the first point of difference.

E. Find the odd one out. Give reasons for your choice.

1. ureter, kidney, urinary bladder, lung, urethra
Answer: lung, because all others are organs of excretory system and it is a respiratory organ.

2. skin, heart, lung, liver, kidney
Answer: Heart because it helps to pump blood in our body and the rests help in excretion.

3. tannin, urine, latex, resin
Answer: urine, because it is excretory product of animals and rests are excretory products of plants.

Categorizing organs by their systems or products helps clarify their primary biological roles. For example, urine is a mammalian waste, whereas tannins and resins are defensive or metabolic wastes produced by plants.
Teacher's Tip: Look at the "job" each item does to find the one that doesn't match.
Exam Tip: Always provide the "why" to get full marks on "Odd One Out" questions.

F. Write short answers.

Question 1: Define respiration.
Answer: The process of conversion of glucose molecules in food into energy rich molecules, carbondioxide and water with the help of oxygen is known as respiration.

Respiration is the essential biochemical process that powers all life on Earth. It is the method by which organisms unlock the solar energy stored in food by plants.
Teacher's Tip: Respiration = Food + Oxygen $\rightarrow$ Energy + Waste.
Exam Tip: Include "energy rich molecules" (ATP) in your definition for a more technical answer.

Question 2: What is the full form of ATP ?
Answer: ATP is the energy currency of cell its full form is Adenosine Triphosphate.

ATP is a high-energy molecule that can be quickly broken down to release power for cellular work. It is called the "currency" because the cell "spends" it to perform any task, like muscle contraction.
Teacher's Tip: Think of ATP as "ready-to-use" cash for your cells.
Exam Tip: Check your spelling carefully: A-D-E-N-O-S-I-N-E Triphosphate.

Question 3: Define cutaneous respiration ?
Answer: The exchange of gases through moist skin and blood capillaries underneath is called cutaneous respiration.

This type of breathing is common in animals like frogs and earthworms that have very thin, wet skin. Because their skin is moist, oxygen can dissolve in the water and pass directly into the blood vessels just beneath the surface.
Teacher's Tip: "Cutaneous" always refers to the skin.
Exam Tip: Mention that the skin must be "moist" for this process to work.

Question 4: What is the role of diaphragm in respiration in human beings ?
Answer: Diaphragm moves up and down and helps in the exchange of air between the atmosphere and lung.

The diaphragm is a large sheet of muscle that acts as the floor of the chest cavity. Its rhythmic movement creates the vacuum needed to suck air into the lungs and the pressure needed to push it out.
Teacher's Tip: Without the diaphragm, your lungs couldn't move air on their own!
Exam Tip: Specify that the diaphragm "contracts" to move down and "relaxes" to move up.

G. Answer in detail.

Question 1: How is the process of respiration different from breathing ?
Answer:
Respiration
1. It is a complex bio-chemical process which involves enzymes.
2. It involves oxidation of glucose in to CO₂, water and energy.
3. Energy is released and stored in the form of ATP.
4. It takes place inside the cell.
Breathing
1. It is a mechanical process without the involvement of enzymes.
2. It involves only the exchange of oxygen and CO₂.
3. No energy is released.
4. It takes place outside the cell.

Breathing is simply the logistical system that brings gases to the doorstep of the cell. Respiration is the actual "industrial process" that happens inside the cell factory to produce the energy needed for life.
Teacher's Tip: Breathing is the "In and Out," Respiration is the "Energy Producer."
Exam Tip: Highlighting "Energy Release" as the key difference will always earn you marks.

Question 2: Explain the process of Cellular Respiration.
Answer: Cellular Respiration is a biochemical process which involves the oxidation of glucose to release energy, carbondioxide and water are released as by - products. It involves a series of chemical reactions controlled by different enzymes. The energy released in the process is stored in the form of energy rich substance called ATP (Adenosine triphosphate). The ATP molecules are stored in the cells and later on can be broken down to release energy for various metabolic activities. The entire process takes place partially in the cytoplasm and partially in the mitochondria of our body cells. The process of conversion of glucose molecules in food in to energy rich molecules, CO₂ and water with the help of oxygen is known as respiration.

This process is the microscopic engine of life, transforming the chemical energy of food into a form that biological structures can actually use. It is a slow, multi-step process that ensures energy is released carefully and used efficiently without damaging the cell.
Teacher's Tip: Mitochondria are the main "power plants" where most of this happens.
Exam Tip: Be sure to mention both "cytoplasm" and "mitochondria" as the locations for cellular respiration.

Question 3: How is aerobic respiration different from anaerobic respiration ?
Answer:
Aerobic respiration
1. It occurs in the presence of oxygen
2. It occurs inside the mitochondria.
3. Complete oxidation of food takes place.
4. The end products are CO₂ and water.
5. 38 ATP molecules are produced by oxidation of one gram mole of glucose.
Anaerobic respiration
1. It occurs in the absence of oxygen.
2. It occurs outside the mitochondria.
3. In complete oxidation of food takes place.
4. Ethyl alcohol or lactic acid are the end products.
5. 2 ATP molecules are produced by oxidation of one gram mole of glucose.

Aerobic respiration is the standard mode for animals because it provides nearly 20 times more energy than anaerobic respiration. Anaerobic respiration is useful only for quick bursts of speed or in environments where oxygen is completely missing, like in the mud of a swamp.
Teacher's Tip: Think of Aerobic as a long-distance runner and Anaerobic as a short-distance sprinter.
Exam Tip: Mentioning end products like "lactic acid" for humans or "alcohol" for yeast is very important for a complete answer.

Question 4: What happens to Oxygen after it enters the lungs?
Answer: Each lung contains millions of alveoli. The walls of the alveoli are richly supplied with blood capillaries. The air which reaches the alveoli after passing through trachea, bronchi, bronchioles is rich in oxygen and contains very little CO₂ . The blood capillaries of the alveoli contain blood that has more carbon dioxide and little oxygen. The oxygen diffuses from the thin walls of the capillaries in to the blood and combines with hemoglobin in the red blood cells of blood thereby forming oxyhaemoglobin. Hemoglobin is a type of protein which contains iron. The blood carries oxygen to all the cells of the body. In the cells a series of chemical reactions, CO₂ , water and energy are released. The carbondioxide released combines with the hemoglobin to form carbominohaemoglobin. Then the blood rich in carbominohaemoglobin leaves the cells and reaches the alveoli where CO₂ gas is released and is exhaled out through the nose.

Oxygen's journey in the body is a beautiful dance of chemistry and physics, moving from the lungs to the blood via simple diffusion. This constant exchange ensures that cells are always fueled and that metabolic waste is continuously scrubbed from the system.
Teacher's Tip: Oxyhaemoglobin is like an "Oxygen passenger" sitting on a "Haemoglobin bus."
Exam Tip: Use the term "diffusion" to describe how oxygen moves across the thin alveolar walls.

Question 5: Why is it better to breathe through your nose than your mouth?
Answer: It is better to breathe through our nose than our mouth because our nasal cavity is lined by hair. The air we breathe in contains fine dust particles. These particles get trapped in the hair in the nasal cavity and are thereby prevented from reaching the lungs. The inside of the nose is also covered by a sticky fluid called mucus. Dust and germs stick to the mucus and thus, the air taken in is cleaned. The air is also warmed up by blood vessels present in the nasal cavity.

The nose acts as a built-in air conditioner and filter for the respiratory system. Mouth breathing bypasses these defenses, allowing cold, dirty air to enter directly into the delicate lung tissues.
Teacher's Tip: Your nose is the body's natural "Air Purifier" and "Heater."
Exam Tip: Mention three specific reasons: filtration (hair), trapping germs (mucus), and warming (blood vessels) for full marks.