Extra long-answer questions from Chapter 5: Life Processes of Class 10 CBSE Science, along with their detailed answers. These questions are designed to provide a comprehensive understanding of the chapter's key concepts.
1. Explain the process of photosynthesis in plants. Discuss the factors affecting it and its significance.
Answer:
Photosynthesis is the process by which green plants synthesize glucose from carbon dioxide and water using sunlight and chlorophyll. The overall chemical equation is:
6CO2+6H2O→sunlight, chlorophyllC6H12O6+6O26CO_2 + 6H_2O \righteous{\text{sunlight, chlorophyll}} C_6H_{12}O_6 + 6O_26CO2+6H2Osunlight, chlorophyllC6H12O6+6O2
Stages of Photosynthesis:
Light-Dependent Reactions:
Occur in the thylakoid membranes of chloroplasts where chlorophyll absorbs sunlight, leading to the splitting of water molecules (photolysis) into oxygen, protons, and electrons. Oxygen is released as a
by-product
.
Light-Independent Reactions (Calvin Cycle):
Take place in the stroma of chloroplasts where ATP and NADPH produced in the light-dependent reactions are used to fix carbon dioxide into glucose.
Factors Affecting Photosynthesis:
Light Intensity:
Increased light intensity boosts the rate of photosynthesis up to a certain point.
Carbon Dioxide Concentration:
Higher CO₂ levels can enhance the rate of photosynthesis.
Temperature:
Optimal temperatures (usually between 25°C to 35°C)
favour
enzyme activity involved in photosynthesis.
Water Availability:
Adequate water is essential; water stress can reduce photosynthesis.
Significance of Photosynthesis:
Primary Source of Organic Matter:
Provides the base of the food chain.
Oxygen Production:
Releases oxygen essential for aerobic respiration.
Carbon Dioxide Regulation:
Helps in reducing atmospheric CO₂ levels.
2. Describe the human digestive system, detailing the structure and function of each part involved in the digestion process.
Answer:
The human digestive system comprises the alimentary canal and associated glands, facilitating the breakdown of food into absorbable nutrients.
Main Components:
Mouth:
Mechanical digestion begins with chewing; salivary amylase starts carbohydrate digestion.
Oesophagus
:
Transports food to the stomach via peristalsis.
Stomach:
Secretes gastric juices (HCl and pepsin) to digest proteins; churns food into chyme.
Small Intestine:
Consists of the duodenum, jejunum, and ileum. Enzymes from the pancreas and bile from the liver aid in the digestion of proteins, fats, and carbohydrates. Villi and microvilli increase the surface area for nutrient absorption.
Large Intestine:
Absorbs water and electrolytes; forms and stores
feces
.
Rectum and Anus:
Expel waste from the body.
Accessory Organs:
Salivary Glands:
Produce saliva containing enzymes like amylase.
Liver:
Produces bile for fat emulsification.
Pancreas:
Secretes digestive enzymes and bicarbonate to neutralize stomach acid.
Gallbladder:
Stores and concentrates bile.
3. Discuss the human respiratory system's structure and function. Explain the mechanism of breathing and gas exchange.
Answer:
The human respiratory system facilitates the intake of oxygen and removal of carbon dioxide.
Main Components:
Nose/Nasal Cavity:
Filters, warms, and humidifies incoming air.
Pharynx:
Passageway for air and food.
Larynx:
Contains vocal cords; protects the trachea during swallowing.
Trachea:
Windpipe that filters air; lined with cilia and mucus.
Bronchi and Bronchioles:
Branching airways leading to the lungs.
Lungs:
Contain alveoli where gas exchange occurs.
Diaphragm:
Muscle aiding in breathing by changing thoracic volume.
Mechanism of Breathing:
Inhalation:
Diaphragm contracts (moves down) and intercostal muscles lift the ribcage, increasing thoracic volume and decreasing pressure, drawing air in.
Exhalation:
Diaphragm relaxes (moves up) and intercostal muscles lower the ribcage, decreasing thoracic volume and increasing pressure, pushing air out.
Gas Exchange:
Occurs in the alveoli where oxygen diffuses into the blood, binding to haemoglobin in red blood cells, and carbon dioxide diffuses from the blood into the alveoli to be exhaled.
4. Explain the transportation system in plants, focusing on the processes of transpiration, translocation, and the role of xylem and phloem tissues.
Answer:
Plants have specialized tissues for transporting water, minerals, and nutrients.
Xylem:
Function:
Transports water and dissolved minerals from roots to other parts of the plant.
Mechanism:
Utilizes transpiration pull, root pressure, and capillary action.
Phloem:
Function:
Translocate
organic nutrients (sugars) from leaves to other parts of the plant.
Mechanism:
Operates on pressure-flow hypothesis
5. Describe the role of the nephron in the process of excretion. Explain the three main steps of urine formation.
Answer:
A nephron is the structural and functional unit of the kidney responsible for urine formation. Each kidney contains about 1 million nephrons.
Structure of Nephron:
Glomerulus:
A network of capillaries inside the Bowman’s capsule that filters blood.
Bowman’s Capsule:
A cup-like structure that collects the filtrate.
Tubule:
Includes the
proximal convoluted tubule (PCT)
,
Loop of Henle
, and
distal convoluted tubule (DCT)
, leading to the collecting duct.
Steps of Urine Formation:
Filtration:
Blood enters the glomerulus under high pressure.
Waste products, water, glucose, and salts are filtered into the Bowman’s capsule.
Large proteins and blood cells remain in the blood.
Reabsorption:
Essential substances like glucose, amino acids, and water are
reabsorbed
into the blood from the tubule.
Secretion:
Excess salts, urea, and harmful substances are actively secreted into the tubule, forming
urine
.
Urine passes into the
collecting duct
and moves to the bladder for excretion.
Significance of Nephron:
Helps in maintaining
water balance
(osmoregulation).
Regulates
blood pressure
and
pH
balance.
Removes
toxic metabolic wastes
.
6. Explain how energy is released during respiration. Differentiate between aerobic and anaerobic respiration with examples.
Answer:
Respiration is the biological process of breaking down glucose to release energy in the form of ATP (Adenosine Triphosphate).
Aerobic Respiration:
Occurs in the
presence of oxygen
.
Glucose is completely oxidized
into carbon dioxide and water.
Takes place in the
mitochondria
.
Equation:
C6H12O6+6O2→6CO2+6H2O+38ATPC_6H
_{
12}O_6 + 6O_2 → 6CO_2 + 6H_2O + 38ATPC6H12O6+6O2→6CO2+6H2O+38ATP
Example:
In humans and plants.
Anaerobic Respiration:
Occurs
without oxygen
.
Incomplete breakdown of glucose
, producing less energy.
Takes place in the
cytoplasm
.
Equation (In muscles):
C6H12O6→LacticAcid+2ATPC_6H
_{
12}O_6 → Lactic Acid + 2ATPC6H12O6→LacticAcid+2ATP
Equation (In yeast):
C6H12O6→Alcohol+CO2+2ATPC_6H
_{
12}O_6 → Alcohol + CO_2 + 2ATPC6H12O6→Alcohol+CO2+2ATP
Examples:
Yeast, bacteria, and human muscles under strenuous activity.
Comparison:
|
Feature |
Aerobic Respiration |
Anaerobic Respiration |
|---|---|---|
|
Oxygen |
Present |
Absent |
|
End Products |
CO₂ + H₂O |
Lactic Acid (in humans) or Alcohol + CO₂ (in yeast) |
|
Energy Produced |
38 ATP |
2 ATP |
|
Location |
Mitochondria |
Cytoplasm |
7. What is double circulation in humans? Why is it important? Explain with a diagram.
Answer:
Double circulation means that blood passes twice through the heart in one complete cycle. It ensures separation of oxygenated and deoxygenated blood, allowing efficient oxygen supply to the body.
Two Types of Circulation:
Pulmonary Circulation (Heart → Lungs → Heart):
Deoxygenated blood from the
right ventricle
is pumped to the
lungs
via the
pulmonary artery
.
In the lungs, blood picks up
oxygen
and releases
carbon dioxide
.
Oxygenated blood returns to the
left atrium
via the
pulmonary vein
.
Systemic Circulation (Heart → Body → Heart):
Oxygenated blood from the
left ventricle
is pumped to the
body
via the
aorta
.
Tissues use oxygen and produce CO₂, which is carried back to the
right atrium
via the
vena cava
.
Importance of Double Circulation:
Efficient oxygen supply:
Ensures tissues receive fully oxygenated blood.
Maintains high pressure:
Blood reaches organs quickly.
Prevents mixing of blood:
Oxygenated and deoxygenated blood do not mix, increasing efficiency.
8. Explain the structure and function of human blood. Discuss its components and their roles.
Answer:
Blood is a fluid connective tissue that transports oxygen, nutrients, hormones, and waste products throughout the body.
Components of Blood:
Plasma (55% of blood volume):
A
liquid component
that carries nutrients, hormones, and waste.
Contains
proteins
(albumin, fibrinogen),
salts
, and
enzymes
.
Red Blood Cells (RBCs or Erythrocytes):
Contain
haemoglobin
, which binds to oxygen for transport.
Transport
oxygen
to tissues and remove
CO₂
.
Have a
biconcave shape
for maximum oxygen absorption.
White Blood Cells (WBCs or Leukocytes):
Defend the body against
infections
and
diseases
.
Types:
Neutrophils, Lymphocytes, Monocytes, Eosinophils, and Basophils
.
Platelets (Thrombocytes):
Help in
blood clotting
to prevent excessive bleeding.
Functions of Blood:
Oxygen Transport:
RBCs carry oxygen from lungs to tissues.
Nutrient Transport:
Plasma carries glucose, amino acids, and vitamins.
Waste Removal:
CO₂ and urea are transported to the lungs and kidneys for excretion.
Immunity:
WBCs fight pathogens.
Clotting:
Platelets help prevent bleeding.
9. What is transpiration? Explain its types, factors affecting it, and its significance in plants.
Answer:
Transpiration is the process of water loss in the form of vapor from plant leaves and stems through stomata.
Types of Transpiration:
Stomatal Transpiration:
Through stomata on leaves (most common).
Cuticular Transpiration:
Through the waxy cuticle of leaves.
Lenticular Transpiration:
Through lenticels in woody stems.
Factors Affecting Transpiration:
Temperature:
High temperature increases transpiration.
Humidity:
High humidity reduces transpiration.
Wind Speed:
High wind speed increases transpiration.
Light Intensity:
More light opens stomata, increasing transpiration.
Significance of Transpiration:
Cooling Effect:
Keeps the plant cool.
Water Transport:
Creates a
transpiration pull
that moves water from roots to leaves.
Mineral Transport:
Helps in the movement of dissolved nutrients.
Maintains Water Balance:
Regulates water content in the plant.
10. What is nutrition? Explain the different types of nutrition with examples.
Answer:
Nutrition is the process by which living organisms obtain food and utilize it for energy, growth, and repair.
Types of Nutrition:
Autotrophic Nutrition:
Organisms make their own food using sunlight and simple inorganic substances.
Example: Green plants, algae, some bacteria (via
photosynthesis
).
Equation for Photosynthesis:
6CO2+6H2O→sunlight, chlorophyllC6H12O6+6O26CO_2 + 6H_2O \
righteous
{
\text{sunlight, chlorophyll}} C_6H_{12}O_6 + 6O_26CO2+6H2
Osunlight
, chlorophyllC6H12O6+6O2
Heterotrophic Nutrition:
Organisms depend on other organisms for food.
Examples: Humans, animals, fungi.
Types:
Holozoic (Humans, Amoeba)
– Ingestion, digestion, absorption, assimilation, egestion.
Parasitic (Plasmodium,
Cuscuta
)
– Live on another organism.
Saprotrophic (Fungi, Bacteria)
– Feed on dead organic matter.
11. Explain the process of digestion in humans with a labelled diagram.
Answer:
Digestion is the breakdown of food into simpler substances for absorption.
Steps of Digestion:
Mouth:
Teeth
break food into small pieces.
Salivary glands
secrete
salivary amylase
, which digests starch into maltose.
Oesophagus
:
Peristalsis moves food to the stomach.
Stomach:
Secretes
HCl
(kills microbes, activates pepsin).
Pepsin
digests proteins into peptides.
Small Intestine:
Liver
secretes
bile
, which emulsifies fats.
Pancreas
secretes enzymes:
Amylase
(carbohydrates → maltose),
Trypsin
(proteins → amino acids),
Lipase
(fats → fatty acids + glycerol).
Villi
absorb nutrients into the blood.
Large Intestine:
Absorbs water and minerals.
Waste is excreted through the
rectum and anus
.
12. Describe the human respiratory system. Explain the mechanism of breathing.
Answer:
Respiration is the process of breaking down glucose to release energy (ATP).
Human Respiratory System Components:
Nasal Cavity:
Filters air.
Pharynx & Larynx:
Air passageway.
Trachea:
Carries air to bronchi.
Bronchi & Bronchioles:
Branch into lungs.
Alveoli:
Site of gas exchange.
Mechanism of Breathing:
Inhalation (Inspiration):
Diaphragm contracts
and moves
down
.
Rib cage expands
.
Lung volume increases
, and air enters.
Exhalation (Expiration):
Diaphragm relaxes
and moves
up
.
Rib cage contracts
.
Lung volume decreases
, and air is pushed out.
