BIO 10 CHAP 1 Gaseous Exchange

Multiple Choice Questions & Fill in the Blanks

Official textbook exercise solutions and complete evaluation keys.

A. Multiple Choice Questions

i) The biological functions which perform gaseous exchange:

(a) Photosynthesis(b) Respiration (c) Both a and b ✓(d) Growth

ii) Plants do exchange of gases through:

(a) Roots(b) Stomata ✓ (c) Stem(d) All of these

iii) Each stoma is formed by:

(a) one guard cell(b) two guards cells ✓ (c) three guard cells(d) four guard cells

iv) Respiratory surface possesses following property:

(a) thin and wet(b) permeable (c) very large(d) all of these ✓

v) Inspiration involves:

(a) Contraction of intercostal muscles(b) contraction of diaphragm (c) Inward movement of ribs(d) Both a and b ✓

vi) Larynx is located on:

(a) Lungs(b) Trachea ✓ (c) Bronchus(d) Bronchiole

vii) The respiratory surface of human is:

(a) Nostril(b) Bronchiole (c) Alveoli ✓(d) Trachea

viii) Increase in rate of breathing is due to the following:

(a) increase CO₂ in blood ✓(b) Increase O₂ in blood (c) decrease CO₂ in blood(d) decrease O₂ in blood

ix) Which of the following disorder is associated with degeneration of alveoli?

(a) Bronchitis(b) Lung cancer (c) Asthma(d) Emphysema ✓

x) Which of the following disorder is associated with inflammation of air passage ways?

(a) Bronchitis ✓(b) Lung cancer (c) Asthma(d) Emphysema

B. Fill In The Blanks

1. Respiration and photosynthesis require exchange of gases.
2. Respiration takes place in all living organisms.
3. Photosynthesis occurs in green parts of plants.
4. During respiration, oxygen is used and carbon dioxide is given out.
5. In photosynthesis, carbon dioxide is used and oxygen is given out.
6. In terrestrial plants, most of the exchange of gases occurs through minute openings, stomata.
7. The animals use either their body surface, or some internal surface for the exchange of gases.
8. Respiratory surface must be thin, wet, permeable and large in relation to the volume of organism.
9. The respiratory surface of man is alveoli present in lungs.
10. Both lungs have millions of alveoli.
11. Air passage ways lead the atmospheric air to alveoli.
12. Air pollution causes number of respiratory problems.
13. Clean air is essential for better respiratory health.

Short Conceptual Questions Answers

Precise solutions optimized for textbook review and marking indicators.

i

Why do stomata generally open during day-time?

Ans: Stomata control gas exchange in the leaf. Each stoma is surrounded by two guard cells. Stomata open or close depending on how turgid these guard cells are. In the light, during the process of Photosynthesis, guard cells accumulate solutes and absorb water by osmosis, becoming turgid, which causes the stoma to open. In the dark, guard cells lose water, become flaccid, and the stoma closes.

ii

Which parts of the plant intake CO₂ and give out O₂, and vice versa during day-time?

Ans: Plants take in CO₂ and give out O₂ during photosynthesis in the day-time. This occurs mainly in the green parts, specifically the leaves. Conversely, cellular respiration occurs continuously day and night, consuming O₂ and releasing CO₂. Exchange of gases during respiration utilizes roots, stems, and lenticels alongside stomata.

iii

Why must we breathe through nostrils rather than the oral cavity?

Ans: The entire passage of nasal sacs is lined with mucous-secreting ciliated cells and hairs. These trap and remove dust, pollutants, and germs while warming and moistening the incoming air. The oral cavity lacks these filtration mechanisms, leaving air uncleaned and drying out the mouth.

iv

Why do we breathe deeply during or immediately after exercise?

Ans: Physical exercise rapidly increases oxygen consumption by muscle tissues, generating elevated carbon dioxide levels in the blood, which triggers the brain's respiratory center to increase breathing rates. If exertion persists, muscles perform anaerobic respiration, producing lactic acid. Chemical breakdown of accumulated lactic acid creates an oxygen debt, which is resolved through deep, rapid breathing.

v

What is "oxygen debt"?

Ans: During intense exercise, muscle cells break down glucose anaerobically without enough oxygen, producing lactic acid instead of carbon dioxide. Clearing lactic acid later requires extra oxygen. This baseline volume deficit is termed oxygen debt and is repaid via post-exercise deep breathing.

vi

How is asthma characterized?

Ans: Asthma is an inflammatory condition affecting lung airways. It is characterized by shortness of breath, chest tightness, wheezing sounds during expiration, and coughing. It is typically an allergic response triggered by pollen, dust, smoke, animal fur, or feathers that constricts the bronchioles.

vii

Name five animals which use their body surface for gaseous exchange.

Ans: The animals are: 1) Flatworms, 2) Earthworms, 3) Leeches, 4) Sabella (Marine Worms), and 5) Tapeworms.

Core Conceptual Differences Table

Feature	Gaseous Exchange	Breathing	Respiration
Mechanism	Passive physical movement of gases via diffusion.	Mechanical framework of inhalation and exhalation.	Intracellular biochemical breakdown of glucose.
Site	Stomata/Lenticels (plants), Alveoli (humans).	Lungs and respiratory tracts.	Living cells and mitochondria.
Energy	No energy produced or used.	No energy produced; consumes muscular energy.	Produces energy stored as ATP packets.
Enzymes	Enzymes are not directly involved.	No enzyme regulation used.	Highly regulated by metabolic enzymes.

Feature	Inspiration (Inhalation)	Expiration (Exhalation)
Definition	Intake of atmospheric air into lungs.	Expulsion of metabolic air out of lungs.
Diaphragm	Contracts and flattens down.	Relaxes and returns to a dome shape.
Muscles	External intercostals contract.	Internal intercostals contract.
Rib Cage	Moves forward and upward.	Drops downward and inward.
Pressure	Intra-alveolar pressure drops below atmospheric level.	Intra-alveolar pressure rises above atmospheric level.

Long Comprehensive Extensive Questions

Detailed architectural notes, structural descriptions, and pathological insights.

i) Discuss the Human Respiratory System and its Structural Layout

The human respiratory system is an efficient, specialized framework built for gaseous exchange. It is divided into the air passage ways and the lungs:

• Nose & Nasal Cavity: Air enters through external nostrils into nasal sacs. This passage is lined with blood capillaries that warm incoming air, while mucous-secreting ciliated epithelium traps dust and pathogens.
• Pharynx: A muscular passage extending behind the cavities that routes air from the internal nostrils down toward the larynx.
• Larynx (Voice Box): A cartilaginous structure containing fibrous bands called vocal cords that vibrate to produce sound. Its opening, the glottis, is protected by a flap called the epiglottis to prevent food from entering the windpipe.
• Trachea (Windpipe): A 12 cm tubular passage kept open by C-shaped cartilaginous rings that prevent structural collapse during pressure changes.
• Bronchi & Bronchioles: The trachea divides into right and left bronchi. Inside the lungs, these branch into smaller secondary tubes, subdividing into fine muscle-walled structures called bronchioles.
• Alveoli: The functional unit of exchange. These are grape-like clusters of microscopic, single-layered air sacs wrapped in a rich network of pulmonary capillaries. Their ultra-thin walls (1/1000 mm) optimize passive gas diffusion.

ii) Why is Smoking Dangerous? Clinical Pathology of Respiratory Disorders

Cigarette smoke contains over 4,000 chemicals, including more than 69 validated carcinogens. Burning tobacco creates compound toxins that break down cell structures:

• Nicotine: A highly addictive chemical that hardens arterial walls, damages nerve tissues, and increases blood clot risks.
• Tar: Collects in lung tissues, paralyzing and destroying cilia. It triggers excess mucous production, causing "smoker's cough," and directly causes lung cancer.
• Carbon Monoxide: Binds irreversibly to blood hemoglobin, displacing oxygen molecules and causing systemic tissue hypoxia.
• Emphysema: A progressive disorder caused by smoke toxins where alveolar walls tear and break down. This reduces the total surface area available for gas exchange, leaving patients permanently short of breath.

Feature	Photosynthesis	Cellular Respiration
Metabolic Class	Anabolic (building up molecules).	Catabolic (breaking down molecules).
Energy Target	Requires input of light energy.	Releases chemical energy as ATP.
Gas Inputs/Outputs	Consumes CO₂, releases O₂.	Consumes O₂, releases CO₂.
Cellular Site	Chloroplasts (green plant parts).	Cytoplasm and Mitochondria (all cells).

Experimental Laboratory Practical Activities

Step-by-step procedures, observation logs, and critical thinking keys.

Experiment 1: Proving CO₂ Exhalation via Respiration

Principle: Carbon dioxide reacts with calcium hydroxide (lime water) to form an insoluble precipitate of calcium carbonate, turning the liquid milky.

Procedure: Setup two test tubes containing clear lime water. Use a syringe to pump atmospheric air into Tube A. Use a straw to gently blow exhaled breath into Tube B.

Observations Matrix:

• Tube A (Atmospheric Air): Lime water remains clear and unchanged.
• Tube B (Exhaled Air): Lime water rapidly turns cloudy and milky.

Conclusion: Exhaled air contains a significantly higher concentration of carbon dioxide than ambient atmospheric air, confirming CO₂ is a byproduct of respiration.

Experiment 2: Gas Exchange Tracking via Hydrogencarbonate Indicator

Theory: Hydrogencarbonate indicator is sensitive to pH shifts caused by CO₂ levels. High CO₂ levels turn it yellow, baseline atmospheric levels keep it red, and low levels turn it purple.

Tube Setup	Conditions	Final Indicator Color	Biological Cause
Tube 1 (Leaf Only)	Open Light exposure	Purple / Magenta	Photosynthesis rate exceeds respiration; CO₂ drops.
Tube 2 (Leaf Only)	Wrapped in Foil (Dark)	Yellow	Only respiration occurs; CO₂ accumulates.
Tube 3 (Control)	No Leaf / Light exposure	Red	CO₂ levels remain at baseline atmospheric levels.