CBSE Class X Science Chapter 5 Life Processes Questions and Answers

NCERT Chapter 5: Life Processes — Questions and Answers

In-Text Questions: Page 81 (Section 5.1)

Q1. Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?

In multi-cellular organisms like humans, all the cells are not in direct contact with the surrounding environment. Therefore, simple diffusion cannot meet the oxygen requirements of all the cells. Instead, specialised tissues and a transportation system are required to transport oxygen to all parts of the body.

Q2. What criteria do we use to decide whether something is alive?

We use various forms of movement as criteria to decide whether something is alive. This includes visible movements such as walking, running, or growth-related movements in plants, as well as invisible molecular movements happening inside cells to maintain and repair living structures.

Q3. What are outside raw materials used for by an organism?

Outside raw materials are used by organisms for:

• Providing energy required to maintain life processes.
• Growth, development, and building up body structures (such as carbon-based food molecules).
• Synthesising proteins and other necessary compounds.
• Oxidising food sources to generate uniform cellular energy, which requires oxygen sourced from outside.

Q4. What processes would you consider essential for maintaining life?

The processes essential for maintaining life are:

• Nutrition: Transfer of an energy source (food) from outside to inside the body.
• Respiration: Process of acquiring oxygen from outside to break down food sources for cellular energy needs.
• Transportation: System for carrying food, oxygen, and materials from one place to another in the body.
• Excretion: Removal of harmful waste by-products formed during metabolic chemical reactions.

In-Text Questions: Page 87 (Section 5.2)

Figure 5.1: Cross-section of a leaf

Figure 5.2: Variegated leaf (a) before and (b) after starch test

Figure 5.3: (a) Open and (b) closed stomatal pore

Figure 5.4: Experimental set-up (a) with potassium hydroxide (b) without potassium hydroxide

Figure 5.5: Nutrition in Amoeba

Figure 5.6: Human alimentary canal

Q1. What are the differences between autotrophic nutrition and heterotrophic nutrition?

Autotrophic Nutrition	Heterotrophic Nutrition
Organisms use simple inorganic substances like carbon dioxide and water obtained from the environment.	Organisms utilize complex organic substances prepared by autotrophs.
External energy sources like sunlight and chlorophyll are required to synthesize food (photosynthesis).	Food is broken down into simpler substances using biocatalysts called enzymes.
Occurs in green plants and some bacteria.	Occurs in animals, fungi, and parasites.

Q2. Where do plants get each of the raw materials required for photosynthesis?

Plants obtain raw materials from the following sources:

• Carbon dioxide ($CO_2$): Taken from the atmosphere through tiny pores on leaves called stomata.
• Water ($H_2O$): Absorbed from the soil by the roots of terrestrial plants.
• Sunlight: Absorbed by chlorophyll present inside cell organelles called chloroplasts.
• Minerals (Nitrogen, Phosphorus, Iron, Magnesium): Taken up from the soil by the roots.

Q3. What is the role of the acid in our stomach?

Hydrochloric acid ($HCl$) in the stomach serves the following roles:

• Creates an acidic medium required for the protein-digesting enzyme, pepsin, to become active and function.
• Kills germs and bacteria that enter the stomach along with food.

Q4. What is the function of digestive enzymes?

Digestive enzymes act as biological catalysts. Their function is to break down complex food substances into smaller, simpler, and soluble molecules so that they can be absorbed into the walls of the alimentary canal and utilized by the body cells. Examples include salivary amylase (breaks down starch), pepsin and trypsin (digest proteins), and lipase (breaks down emulsified fats).

Q5. How is the small intestine designed to absorb digested food?

The inner lining of the small intestine has numerous finger-like projections called villi. The villi increase the surface area available for absorption. They are richly supplied with blood vessels that carry the absorbed food to every cell of the body.

In-Text Questions: Page 91 (Section 5.3)

Figure 5.7: (a) Air being passed into lime water with a pichkari/syringe, (b) air being exhaled into lime water

Figure 5.8: Break-down of glucose by various pathways

Figure 5.9: Human respiratory system

Q1. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?

Terrestrial organisms take in oxygen from the atmosphere, where the concentration of oxygen is fairly high. Aquatic organisms must use oxygen dissolved in water, which is present in very low amounts compared to the air. Thus, terrestrial organisms do not need to breathe as rapidly as aquatic organisms to meet their oxygen requirements.

Q2. What are the different ways in which glucose is oxidised to provide energy in various organisms?

Glucose (a 6-carbon molecule) is first broken down in the cytoplasm of cells into a 3-carbon molecule called pyruvate. Pyruvate is then broken down in three different pathways depending on oxygen availability:

• In the Absence of Oxygen (Anaerobic respiration in Yeast): Pyruvate is converted into ethanol, carbon dioxide, and energy.
• In Lack of Oxygen (In human muscle cells during sudden activity): Pyruvate is converted into lactic acid (3-carbon molecule) and energy, which causes muscle cramps.
• In Presence of Oxygen (Aerobic respiration in Mitochondria): Pyruvate is broken down into carbon dioxide, water, and a large amount of energy.

Q3. How is oxygen and carbon dioxide transported in human beings?

Oxygen Transport: Oxygen in the alveolar air is taken up by red blood corpuscles (RBCs). It binds with the respiratory pigment called haemoglobin, which has a very high affinity for oxygen, and is transported to all tissues.

Carbon Dioxide Transport: Carbon dioxide is more soluble in water than oxygen. Hence, it is mostly transported in dissolved form in the liquid medium of blood called plasma from tissues back to the lungs.

Q4. How are the lungs designed in human beings to maximise the area for exchange of gases?

Inside the lungs, the respiratory passage branches into smaller and smaller tubes (bronchi and bronchioles) that terminate in tiny balloon-like structures called alveoli. The alveoli present a very large surface area (about $80\text{ m}^2$) for gas exchange. Additionally, the thin walls of alveoli are covered by an extensive network of delicate blood vessels to facilitate efficient diffusion of gases.

In-Text Questions: Page 96 (Section 5.4)

Figure 5.10: Schematic sectional view of the human heart

Figure 5.11: Schematic representation of transport and exchange of oxygen and carbon dioxide

Figure 5.12: Movement of water during transpiration in a tree

Q1. What are the components of the transport system in human beings? What are the functions of these components?

The primary components of the human transport system are:

• Heart: A muscular pumping organ that pumps oxygenated blood to body organs and receives deoxygenated blood to send to the lungs.
• Blood: A fluid connective tissue consisting of:
  • Plasma: Transports food, carbon dioxide, nitrogenous wastes, and dissolved salts.
  • Red Blood Cells (RBCs): Carry oxygen via haemoglobin.
  • Platelets: Plug leaks and clot blood at sites of injury.
• Blood Vessels:
  • Arteries: Carry blood away from the heart under high pressure to various organs.
  • Veins: Collect blood from body organs back to the heart; contain valves to prevent backflow.
  • Capillaries: Ultra-thin (one-cell thick) vessels where exchange of materials between blood and tissue cells occurs.
• Lymph (Tissue Fluid): Drains excess fluid from extracellular spaces back into blood and carries digested and absorbed fat from the intestine.

Q2. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

Mammals and birds are warm-blooded animals that constantly use energy to maintain a constant body temperature. Separating oxygenated and deoxygenated blood prevents them from mixing and provides a highly efficient supply of oxygen to the body to produce the high amount of energy required.

Q3. What are the components of the transport system in highly organised plants?

The transport system in highly organized plants consists of vascular tissues divided into two independent conducting networks:

• Xylem: Consists of vessels and tracheids that transport water and dissolved minerals from the roots upwards to all parts.
• Phloem: Consists of sieve tubes and companion cells that transport photosynthetic products (sugars), amino acids, and other substances from leaves to storage and growing organs.

Q4. How are water and minerals transported in plants?

Water and minerals are transported through the xylem tissue as follows:

• Root Pressure: Root cells actively absorb ions from the soil, creating a concentration gradient that forces water into the root xylem, pushing a column of water steadily upwards.
• Transpiration Pull: Evaporation of water vapour through leaf stomata (transpiration) creates a suction pull that draws water continuously from the root xylem to the uppermost leaves during the day.

Q5. How is food transported in plants?

Food is transported through phloem tissue by a process called translocation:

• Nutrients like sucrose are loaded into phloem tissue using energy from ATP.
• This increases osmotic pressure inside the phloem, causing water to move into it.
• The resulting high pressure moves materials inside the phloem to plant tissues having lower osmotic pressure according to the plant's needs (in both upward and downward directions).

In-Text Questions: Page 98 (Section 5.5)

Figure 5.13: Excretory system in human beings

Figure 5.14: Structure of a nephron

Q1. Describe the structure and functioning of nephrons.

Structure of Nephron:

Nephrons are basic filtration units present in large numbers inside each kidney. Each nephron consists of a cup-shaped top called Bowman's capsule enclosing a bundle of fine blood capillaries called the glomerulus. The Bowman's capsule extends into a long coiled tubular part surrounded by blood capillaries, which finally connects to a common collecting duct.

Functioning of Nephron:

• Filtration: Blood under pressure passes through the glomerulus, where liquid waste, glucose, amino acids, salts, and water are filtered into Bowman's capsule as initial filtrate.
• Selective Reabsorption: As filtrate flows through the tubular part, essential substances like glucose, amino acids, required salts, and major amounts of water are reabsorbed back into surrounding blood capillaries.
• Urine Formation: The remaining fluid containing urea, uric acids, and excess water forms urine, which flows into the collecting duct, ureter, and bladder.

Q2. What are the methods used by plants to get rid of excretory products?

Plants use the following methods for excretion:

• Gaseous waste products like oxygen (from photosynthesis) and carbon dioxide (from respiration) are released through leaf stomata.
• Excess water is eliminated as water vapour via transpiration.
• Cellular waste products are stored inside large cell vacuoles.
• Wastes stored in old leaves are shed off when leaves fall.
• Resins and gums are stored as wastes in old xylem tissues.
• Some waste materials are excreted directly into the surrounding soil through roots.

Q3. How is the amount of urine produced regulated?

The amount of urine produced is regulated by selective reabsorption of water in the nephron tubules. The amount of water reabsorbed depends on:

• How much excess water is present in the body.
• How much dissolved waste (like urea and salts) needs to be excreted.

End-of-Chapter Exercises (Pages 99–100)

Q1. The kidneys in human beings are a part of the system for
(a) nutrition.
(b) respiration.
(c) excretion.
(d) transportation.

Answer: (c) excretion.

Q2. The xylem in plants are responsible for
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.

Answer: (a) transport of water.

Q3. The autotrophic mode of nutrition requires
(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.

Answer: (d) all of the above.

Q4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.

Answer: (b) mitochondria.

Q5. How are fats digested in our bodies? Where does this process take place?

Location: Digestion of fats takes place in the small intestine.

Process:

1. Fats enter the small intestine in the form of large globules, making it difficult for enzymes to act on them.
2. Bile salts secreted by the liver break large fat globules down into smaller globules (emulsification), increasing enzyme efficiency.
3. Pancreatic lipase secreted by the pancreas digests these emulsified fats.
4. Finally, intestinal enzymes present in intestinal juice convert fats into fatty acids and glycerol.

Q6. What is the role of saliva in the digestion of food?

Saliva plays two major roles in digestion:

• It wets and moistens crushed food to make its passage through the smooth esophagus easy.
• It contains an enzyme called salivary amylase that breaks down complex starch molecules into simple sugars.

Q7. What are the necessary conditions for autotrophic nutrition and what are its by-products?

Necessary conditions:

• Presence of chlorophyll
• Availability of sunlight
• Supply of carbon dioxide
• Supply of water

By-products: Oxygen ($O_2$) and Water ($H_2O$).

Q8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

Aerobic Respiration	Anaerobic Respiration
Takes place in the presence of oxygen.	Takes place in the absence of oxygen.
Occurs in the cytoplasm and mitochondria.	Occurs only in the cytoplasm.
Glucose breaks down completely into $CO_2$ and $H_2O$.	Glucose breaks down incompletely into ethanol and $CO_2$ (or lactic acid).
Releases a large amount of energy.	Releases a relatively small amount of energy.

Organisms using anaerobic respiration: Yeast and certain anaerobic bacteria.

Q9. How are the alveoli designed to maximise the exchange of gases?

Alveoli are designed to maximize gas exchange through the following features:

• They are numerous balloon-like structures providing a vast surface area (about $80\text{ m}^2$).
• Their walls are extremely thin to enable fast diffusion of gases.
• Their walls contain an extensive, dense network of capillary blood vessels to transport oxygen and carbon dioxide efficiently.

Q10. What would be the consequences of a deficiency of haemoglobin in our bodies?

Haemoglobin is the respiratory pigment responsible for carrying oxygen from the lungs to body tissues. A deficiency of haemoglobin lowers the oxygen-carrying capacity of blood. As a result, cells receive less oxygen for cellular respiration, leading to less energy production. This condition causes anemia, fatigue, weakness, and shortness of breath.

Q11. Describe double circulation of blood in human beings. Why is it necessary?

Description: In human double circulation, blood passes through the heart twice during each complete cycle across the body. It comprises two pathways:

• Pulmonary Circulation: Deoxygenated blood from the right ventricle is pumped to the lungs for oxygenation and returns as oxygenated blood to the left atrium.
• Systemic Circulation: Oxygenated blood from the left ventricle is pumped to all body tissues and organs, returning as deoxygenated blood to the right atrium.

Why it is necessary: It prevents mixing of oxygenated and deoxygenated blood, ensuring an efficient supply of high-oxygen blood to meet the high energy demands of warm-blooded human beings for temperature regulation.

Q12. What are the differences between the transport of materials in xylem and phloem?

Transport in Xylem	Transport in Phloem
Transports water and dissolved mineral salts from soil.	Transports photosynthetic products (sugars), amino acids, and nutrients.
Movement occurs in a unidirectional (upward) direction only.	Movement occurs in bidirectional (both upward and downward) directions.
Mainly driven by physical forces like root pressure and transpiration pull.	Driven active process utilizing cellular energy in the form of ATP.

Q13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Feature	Alveoli (Lungs)	Nephrons (Kidneys)
Structure	Tiny, thin-walled, balloon-like air sacs surrounded by blood capillaries.	Long tubular structures with a cup-like Bowman's capsule surrounding a capillary cluster (glomerulus).
Functioning	Exchange gases ($O_2$ and $CO_2$) across thin membranes by passive diffusion.	Filters blood to remove nitrogenous metabolic wastes (urea/uric acid) via filtration and selective reabsorption.
End Product	Exhaled air containing high carbon dioxide.	Liquid urine containing urea, uric acid, extra salts, and water.