Fundamental Unit of Life

Introduction

• The first lecture in the series organized by the Class 9th Science Club.
• Designed with the view to make science fun and easy to learn.
• A promise to cover every line of NCERT.
• Today's chapter: Fundamental Unit of Life.

Importance

• Every living thing is made up of cells.
• It is the fundamental unit of life.

What is a cell?

• The basic unit of life.
• The smallest unit of construction of living things.

Cell Division

• Tissues are formed by the aggregation of cells.
• Tissues form organs.
• Organs form organ systems.
• Organ systems form organisms.

Discovery of Cell

• Robert Hooke: 1665, found in the tissue of dead cork.
• Antony van Leeuwenhoek: First to see living cells.
• Robert Brown: Discovered the nucleus.

Cell Theory

• Schleiden and Schwann: All plants and animals are made up of cells.
• Rudolf Virchow: New cells arise from pre-existing cells.
• The three directives of the theory:
  • All living beings are made up of cells.
  • All functions of life are controlled by cells.
  • New cells are formed from other cells.

Cell Size and Type

Unicellular Organism

• A single cell that is a complete organism.
• Example: Bacteria, Protozoa.

Multicellular Organism

• Organisms made up of more than one cell.
• Example: Humans, Plants.

Cell Structure

• Plasma Membrane: The body's guard of the cell.

  • Selective permeable membrane: Allows only certain substances to enter.
  • Active and Passive Transport:
    • Active transport: Requires energy.
    • Passive transport: Occurs without energy, through diffusion and osmosis.

• Cell Wall: Found in plant cells, akin to Z+ Security.

  • Made of cellulose.
  • Provides rigidity and structure.

• Nucleus: The brain of the cell, holds genetic information.

  • DNA and Chromosomes

Other Cell Organelles

• Ribosomes: Protein factory.
• Endoplasmic Reticulum (ER):
  • Rough ER: Protein synthesis
  • Smooth ER: Lipid synthesis
• Golgi Apparatus: Storage, packaging, and transport of products.
• Lysosomes: Decompose the cell's waste products, also known as suicide bags.
• Vacuoles: Storage and resources.
• Mitochondria: The powerhouse of the cell, ATP production.
• Chloroplasts: Found only in plant cells, facilitates photosynthesis.

Cell Division

• Mitosis: One cell divides into two daughter cells, chromosome numbers remain the same.
• Meiosis: One cell divides into four daughter cells, chromosome number is halved.
• Essential for reproduction and growth.

Practical Application

• The discovery and study of cells are the foundation of modern biology.
• Pay special attention to the unique properties of Mitochondria and Chloroplasts.

Key Point: A good understanding of this subject is essential as it forms the basis for all studies in biology.

Note: Ensure a thorough study of the nucleus and mitochondria, as understanding them will make it easier to grasp the subsequent chapters in biology.