Chapter 5: Life Processes Exercise & In-Text Questions & Answers
1Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
Answer:
In multi-cellular organisms, not all cells are in direct contact with the environment. Simple diffusion is too slow to supply oxygen to all cells, especially those deep inside the body. Hence, specialised respiratory and circulatory systems are required. (Section 5.1)
2What criteria do we use to decide whether something is alive?
Answer:
The presence of life processes such as nutrition, respiration, transportation, and excretion indicates life. Molecular movement is essential for maintaining organised structures, and its absence (as in viruses outside a host) leads to debate about whether something is truly alive. (Section 5.1)
3What are outside raw materials used for by an organism?
Answer:
Outside raw materials (like food, water, oxygen) are used for energy production, growth, repair, and maintenance of body structures. Carbon-based food sources provide energy and building blocks. (Section 5.1)
4What processes would you consider essential for maintaining life?
Answer:
Essential life processes include nutrition, respiration, transportation, and excretion. These processes maintain the ordered structure of living organisms and provide energy for cellular activities. (Section 5.1)
5What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer:
Autotrophic Nutrition
Heterotrophic Nutrition
Organisms prepare their own food using CO₂, water, and sunlight.
Organisms depend on other organisms for food.
Example: Green plants, some bacteria.
Example: Animals, fungi, most bacteria.
Involves photosynthesis.
Involves ingestion, digestion, absorption.
(Section 5.2.1 & 5.2.2)
6Where do plants get each of the raw materials required for photosynthesis?
Answer:
- Carbon dioxide: From air through stomata.
- Water: Absorbed from soil by roots.
- Sunlight: Captured by chlorophyll in chloroplasts.
- Chlorophyll: Present in green parts of the plant. (Section 5.2.1)
7What is the role of the acid in our stomach?
Answer:
Hydrochloric acid (HCl) in the stomach:
- Creates an acidic medium for pepsin to digest proteins.
- Kills bacteria present in food.
- Prevents fermentation. (Section 5.2.4)
8What is the function of digestive enzymes?
Answer:
Digestive enzymes break down complex food molecules (carbohydrates, proteins, fats) into simpler absorbable forms (glucose, amino acids, fatty acids & glycerol). Examples: salivary amylase, pepsin, trypsin, lipase. (Section 5.2.4)
9How is the small intestine designed to absorb digested food?
Answer:
The inner lining of the small intestine has numerous finger-like projections called villi, which:
- Increase surface area for absorption.
- Are richly supplied with blood vessels to transport absorbed nutrients to all body cells. (Section 5.2.4)
10What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Answer:
Air has a much higher concentration of oxygen than water. Therefore, terrestrial organisms can obtain oxygen more efficiently and do not need to breathe as rapidly as aquatic organisms (e.g., fish). (Section 5.3)
11What are the different ways in which glucose is oxidised to provide energy in various organisms?
Answer:
Glucose is first broken down to pyruvate in the cytoplasm. Then:
- Aerobic respiration (with oxygen): In mitochondria → CO₂ + H₂O + large energy (ATP).
- Anaerobic respiration (without oxygen):
• In yeast → ethanol + CO₂ + less energy.
• In muscles → lactic acid + less energy. (Section 5.3, Fig. 5.8)
12How is oxygen and carbon dioxide transported in human beings?
Answer:
- Oxygen: Bound to haemoglobin in red blood cells → transported to tissues.
- Carbon dioxide: Mostly dissolved in plasma as bicarbonate; some bound to haemoglobin. (Section 5.3)
13How are the lungs designed in human beings to maximise the area for exchange of gases?
Answer:
Lungs contain millions of alveoli (balloon-like structures) with:
- Thin walls for easy diffusion.
- Extensive network of blood capillaries.
- Total surface area ~80 m². (Section 5.3, Fig. 5.9)
14What are the components of the transport system in human beings? What are the functions of these components?
15Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Answer:
Mammals and birds are warm-blooded and have high energy needs. Separation ensures highly efficient oxygen supply to tissues for maintaining body temperature and supporting high metabolic rates. (Section 5.4.1)
16What are the components of the transport system in highly organised plants?
Answer:
- Xylem: Transports water and minerals from roots to leaves.
- Phloem: Transports food (sucrose, amino acids) from leaves to storage/growing parts. (Section 5.4.2)
17How are water and minerals transported in plants?
Answer:
Water and minerals are absorbed by roots and transported upward through xylem by:
- Root pressure (minor role, especially at night).
- Transpiration pull (major force during day): Evaporation from leaves creates suction. (Section 5.4.2)
18How is food transported in plants?
Answer:
Food (mainly sucrose) is transported via phloem in both upward and downward directions. This process, called translocation, uses energy (ATP) to create osmotic pressure that moves sap to areas of lower pressure (e.g., roots, fruits, buds). (Section 5.4.2)
19Describe the structure and functioning of nephrons.
Answer:
Each nephron consists of:
- Bowman’s capsule: Cup-shaped end surrounding a cluster of capillaries (glomerulus).
- Tubular part: Long coiled tube where selective reabsorption occurs. Function:
1. Filtration of blood in glomerulus → filtrate (water, glucose, amino acids, urea, salts).
2. Reabsorption of useful substances (glucose, amino acids, water) in tubule.
3. Urine (containing urea, excess salts, water) passes to collecting duct → ureter. (Section 5.5.1, Fig. 5.14)
20What are the methods used by plants to get rid of excretory products?
Answer:
Plants excrete by:
- Storing wastes in cell vacuoles.
- Depositing wastes as resins and gums in old xylem.
- Shedding leaves containing wastes.
- Releasing wastes (e.g., oxygen, CO₂) through stomata or into soil. (Section 5.5.2)
21How is the amount of urine produced regulated?
Answer:
Urine volume depends on:
- Water balance in the body (more water → more urine).
- Amount of dissolved wastes (more waste → more urine).
Kidneys adjust reabsorption of water in nephron tubules accordingly. (Section 5.5.1)
22The kidneys in human beings are a part of the system for
Answer:
(c) excretion. (Exercises)
23The xylem in plants are responsible for
Answer:
(a) transport of water. (Exercises)
24The autotrophic mode of nutrition requires
Answer:
(d) all of the above (carbon dioxide, water, sunlight, chlorophyll). (Exercises)
25The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
26How are fats digested in our bodies? Where does this process take place?
Answer:
Fats are digested in the small intestine.
- Bile salts from liver emulsify large fat globules into smaller droplets.
- Pancreatic lipase breaks down emulsified fats into fatty acids and glycerol. (Section 5.2.4)
27What is the role of saliva in the digestion of food?
Answer:
Saliva:
- Moistens food for easy swallowing.
- Contains salivary amylase which breaks down starch into sugar. (Section 5.2.4, Activity 5.3)
28What are the necessary conditions for autotrophic nutrition and what are its by-products?
Answer: Conditions: CO₂, water, sunlight, chlorophyll. By-products: Oxygen and water.
Equation: 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O (in presence of sunlight & chlorophyll). (Section 5.2.1)
29What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Answer:
Aerobic Respiration
Anaerobic Respiration
Occurs in presence of oxygen.
Occurs in absence of oxygen.
End products: CO₂ + H₂O
End products: Ethanol + CO₂ (yeast) or Lactic acid (muscles)
Releases more energy (36-38 ATP)
Releases less energy (2 ATP)
Organisms using anaerobic respiration: Yeast, Lactobacillus, muscle cells during heavy exercise. (Section 5.3)
30How are the alveoli designed to maximise the exchange of gases?
Answer:
(Same as Q13) Alveoli provide a large surface area (~80 m²), thin walls, and dense capillary network for efficient gas exchange. (Section 5.3)
31What would be the consequences of a deficiency of haemoglobin in our bodies?
Answer:
Haemoglobin carries oxygen. Its deficiency (anaemia) reduces oxygen supply to tissues, causing fatigue, weakness, shortness of breath, and pale skin. (Section 5.3)
32Describe double circulation of blood in human beings. Why is it necessary?
Answer: Double circulation means blood passes through the heart twice per cycle:
1. Pulmonary circulation: Right side → lungs → left side (for oxygenation).
2. Systemic circulation: Left side → body → right side (to deliver oxygen). Necessity: Prevents mixing of oxygenated/deoxygenated blood and ensures high-pressure delivery to body tissues, supporting high metabolic rates in warm-blooded animals. (Section 5.4.1)
33What are the differences between the transport of materials in xylem and phloem?
Answer:
Xylem
Phloem
Transports water and minerals.
Transports food (sucrose, amino acids).
Unidirectional (roots → leaves).
Bidirectional (leaves → roots/fruits/buds).
Driven by transpiration pull & root pressure (physical forces).
Driven by osmotic pressure using ATP (energy-dependent).
(Section 5.4.2)
34Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Answer:
Alveoli
Nephrons
Balloon-like sacs in lungs.
Tubular structures in kidneys.
Site of gas exchange (O₂ in, CO₂ out).
Site of blood filtration and urine formation.
Thin walls with capillary network.
Glomerulus (capillary cluster) + tubule with capillary network.
Passive diffusion based on concentration gradient.