• Air enters through nostrils.
• Fine hairs and mucus filter dust particles.
• Air passes through:
  • Nostrils → Throat → Lungs.
• Cartilage rings in the trachea prevent collapse of air passage.

8. Alveoli

• Lungs contain millions of alveoli.
• Alveoli are balloon-like structures.
• Provide large surface area for gas exchange.
• Surrounded by a network of blood capillaries.

9. Breathing Mechanism

Inhalation

• Ribs move upward and outward.
• Diaphragm flattens.
• Chest cavity expands.
• Air enters lungs.

Exhalation

• Ribs move downward.
• Diaphragm becomes dome-shaped.
• Chest cavity decreases.
• Air is expelled.

10. Exchange of Gases in Alveoli

• Oxygen diffuses from alveoli into blood.
• Carbon dioxide diffuses from blood into alveoli.
• Residual air always remains in lungs for continuous gas exchange.

11. Transport of Oxygen

• Large animals cannot rely only on diffusion.
• Haemoglobin transports oxygen.
• Present in Red Blood Cells (RBCs).
• Has high affinity for oxygen.

12. Transport of Carbon Dioxide

• Carbon dioxide is more soluble in water than oxygen.
• Most CO₂ is transported in dissolved form in blood.

1. Breakdown of Glucose

• Food is used by cells to release energy.
• First step of respiration:
  • Glucose (6-carbon compound) → Pyruvate (3-carbon compound)
  • Occurs in the cytoplasm.

2. Fate of Pyruvate

(A) Aerobic Respiration (Presence of Oxygen)

• Occurs in mitochondria.
• Pyruvate → Carbon dioxide + Water + Large amount of energy.
• More energy is released than in anaerobic respiration.

(B) Anaerobic Respiration in Yeast

• Occurs in absence of oxygen.
• Pyruvate → Ethanol + Carbon dioxide + Energy.
• Process is called fermentation.

(C) Anaerobic Respiration in Muscles

• Occurs during oxygen deficiency.
• Pyruvate → Lactic acid + Energy.
• Accumulation of lactic acid causes muscle cramps.

3. Gas Exchange in Plants

• Takes place through stomata.
• Large intercellular spaces help diffusion of gases.
• Exchange occurs by diffusion.

At Night

• Photosynthesis stops.
• CO₂ release is the major activity.

During Day

• CO₂ produced in respiration is used in photosynthesis.
• Oxygen release becomes the major event.

4. Respiration in Animals

• Animals have specialized organs for gas exchange.
• Oxygen is taken in and carbon dioxide is removed.

5. Aquatic Animals

• Use oxygen dissolved in water.
• Dissolved oxygen is much less than atmospheric oxygen.
• Therefore, breathing rate is faster.
• Fishes take water through mouth and pass it over gills.

6. Terrestrial Animals

• Use atmospheric oxygen.
• Respiratory surfaces:
  • Have large surface area.
  • Are thin and delicate.
  • Are kept inside the body for protection.
• Air passages carry air to respiratory surfaces.

After sucrose is digested into glucose and fructose in the small intestine:

1. Absorption into blood: Glucose is absorbed through the villi of the small intestine into the bloodstream.
2. Transport to cells: Blood carries glucose to all body cells.
3. Entry into cells: Glucose enters cells through the cell membrane using specific transport proteins (glucose transporters).
4. Reaches the cytoplasm: Once it crosses the cell membrane, glucose is present in the cytoplasm (cytosol) of the cell.
5. Glycolysis begins: In the cytoplasm, glucose is broken down to pyruvate during glycolysis.

Flow Chart

Sucrose → Glucose + Fructose (small intestine) → Blood → Body cells → Cytoplasm → Glycolysis → Pyruvate

For NEET, remember:

• Digestion of sucrose: Small intestine
• Absorption of glucose: Intestinal villi
• Site of glycolysis: Cytoplasm
• Site of aerobic respiration after glycolysis: Mitochondria

Sucrose is converted into glucose and fructose in the small intestine.

Process:

• Sucrose (table sugar) is a disaccharide.
• It cannot be absorbed directly into the blood.
• The enzyme Sucrase (also called invertase), present in the intestinal juice of the small intestine, breaks:Sucrose → Glucose + Fructose
• The resulting glucose and fructose are then absorbed through the intestinal villi into the bloodstream.

Quick Facts (NEET/CBSE)

• Enzyme: Sucrase
• Site of digestion: Small intestine (brush border of intestinal epithelial cells)
• Products formed: Glucose + Fructose

1

2.

3.

4.

4.

5.

6  7, 8

9.

1 – a

2- c

3. b

4. a

5.b

6. b

7.b

8.b

9.b

1. The functional megaspore enlarges and develops into the embryo sac.
2. The nucleus of the functional megaspore undergoes mitotic division to form 2 nuclei.
3. These two nuclei move to opposite poles, forming the 2-nucleate embryo sac.
4. The nuclei divide again mitotically to form the 4-nucleate stage.
5. A third mitotic division produces the 8-nucleate stage.
6. These divisions are free-nuclear divisions, meaning:
   • Nuclear division occurs.
   • Cell wall formation does not occur immediately.
7. After the 8-nucleate stage, cell walls are formed, organizing the embryo sac.
8. Out of the 8 nuclei:
   • 6 nuclei are enclosed by cell walls to form cells.
   • 2 nuclei remain free in the central cell as polar nuclei.

Arrangement of Cells in Mature Embryo Sac

Micropylar End (Egg Apparatus)

9. Three cells are present at the micropylar end, called the egg apparatus:
   • 1 Egg cell
   • 2 Synergids
10. Synergids possess filiform apparatus (finger-like wall thickenings) which:
    • Guide the pollen tube into the embryo sac.
    • Help in nutrient transfer.

Chalazal End

11. Three cells are present at the chalazal end called antipodal cells.

Central Cell

12. The large central cell contains two polar nuclei.

Mature Embryo Sac Summary

• Total nuclei = 8
• Total cells = 7
  • 1 Egg cell
  • 2 Synergids
  • 3 Antipodal cells
  • 1 Central cell (with 2 polar nuclei)

Concave Mirror: All Possible Image Formations

Object Position	Image Position	Nature of Image	Size
At infinity	At F	Real, inverted	Highly diminished (point-sized)
Beyond C	Between C and F	Real, inverted	Diminished
At C	At C	Real, inverted	Same size
Between C and F	Beyond C	Real, inverted	Enlarged
At F	At infinity	Real, inverted	Highly enlarged
Between F and P	Behind mirror	Virtual, erect	Enlarged

Key:

• P = Pole
• F = Principal Focus
• C = Centre of Curvature

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Convex Mirror: All Possible Image Formations

Object Position	Image Position	Nature of Image	Size
At infinity	At F (behind mirror)	Virtual, erect	Highly diminished
Anywhere in front of mirror	Between P and F (behind mirror)	Virtual, erect	Diminished

Quick NEET/JEE Points

1. Concave mirror can form both real and virtual images.
2. Convex mirror always forms virtual, erect, and diminished images.
3. Real images are inverted and can be obtained on a screen.
4. Virtual images cannot be obtained on a screen.
5. Convex mirrors are used as rear-view mirrors because they provide a wider field of view.

Health and Disease – Important Points

Meaning of Health

• Earlier, health was considered a balance of certain “humors” in the body.
• Ancient Greek physician Hippocrates and the Indian Ayurveda system supported this idea.
• People believed that excess “black bile” caused fever and hot personality.

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Scientific Development of Health Concept

• William Harvey discovered blood circulation using experimental methods.
• Thermometer studies showed that people with “black bile” had normal body temperature.
• This disproved the old “good humor” theory.

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Modern Definition of Health

Health is a state of:

1. Physical well-being
2. Mental well-being
3. Social well-being

Health does not mean only absence of disease or physical fitness.

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Importance of Good Health

• Increases working efficiency
• Improves productivity
• Brings economic prosperity
• Increases life span (longevity)
• Reduces infant mortality
• Reduces maternal mortality

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Ways to Maintain Good Health

• Balanced diet
• Personal hygiene
• Regular exercise
• Practice of yoga
• Awareness about diseases
• Vaccination (immunisation)
• Proper disposal of wastes
• Control of disease vectors
• Clean food and water

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Disease

• When one or more organs or body systems do not function properly, disease occurs.
• Disease is identified by various signs and symptoms.

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Types of Diseases

1. Infectious Diseases

• Spread from one person to another.
• Caused by pathogens.
• Common examples:
  • Cold
  • Flu
  • AIDS

2. Non-infectious Diseases

• Do not spread from person to person.
• Examples:
  • Cancer
  • Diabetes

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Harmful Effects of Drug and Alcohol Abuse

• Damage physical and mental health
• Reduce body efficiency
• Affect nervous system and organs

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Factors Affecting Health

Health is affected by:

(i) Genetic Disorders

• Defects inherited from parents
• Disorders present from birth

(ii) Infections

• Diseases caused by microorganisms

(iii) Lifestyle

• Food and water intake
• Rest and exercise
• Personal habits

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Role of Mind and Immune System

• Mind influences the nervous system and endocrine system.
• These systems affect the immune system.
• A healthy mental state helps maintain good health.