First Lecture of Biology: Fundamental Unit of Life

Introduction

• The bodies of all living beings are made up of cells.
• The cell is the main factor in all bodily functions.
• Discovery of the cell: Robert Hooke first discovered the cell.

Important Scientists

• Robert Hooke (1665): First discovered the cell.
• Antonie van Leeuwenhoek (1674): First observed living cells.
• Robert Brown (1831): Discovered the nucleus.
• Matthias Schleiden and Theodor Schwann: Founders of cell theory.
• Rudolf Virchow: “Omnis cellula e cellula” - New cells come from pre-existing cells.

Cell: Structural and Functional Unit

• The body of all living beings is made up of cells, whether the organisms are small or large.
• All processes of our body are carried out by the cell: movement, respiration, nutrition.

Organization of Cells

1. Single Cell: The smallest unit.
2. Tissue: Group of similar cells.
3. Organ: Group of different tissues.
4. Organ System: Group of various organs.
5. Organism: Group of multiple organ systems.

Diversity of Cells

• Variation in size, number, and shape.
• Number:
  • Unicellular: Single-celled organisms (Amoeba, Bacteria).
  • Multicellular: Multi-celled organisms (Humans, Plants).
• Shape: Round, oval, rod-shaped, spindle-shaped, etc.
• Size:
  • Smallest Mycoplasma.
  • Largest Ostrich egg cell.

Cell Structure

• Plasma Membrane: Selectively permeable, made of lipids and proteins.
• Cell Wall: Found in plants, bacteria, made of cellulose.
• Nucleus: Control center, double membrane, contains DNA and RNA.
• Cytoplasm: Jelly-like substance with floating organelles.
• Cell Organelles:
  • Mitochondria: Energy production, ATP synthesis, double membrane.
  • Golgi Body: Protein synthesis, modification, and packaging.
  • Endoplasmic Reticulum (ER): Two types - Rough (protein synthesis), Smooth (lipid synthesis).
  • Lysosomes: Internal digestion, cell's suicide bag.
  • Ribosomes: Protein synthesis.
  • Plastids: Found in plant cells, chloroplast (green), chromoplast (colored), leucoplast (storage).
  • Vacuoles: Storage tanks.
  • Centrioles: Help in cell division.

Cell Division

• Mitosis: Equivalent division, two new cells, chromosome number remains the same.
• Meiosis: Half division, four new cells, chromosome number halves. Useful in the formation of sperm and eggs.

Review and Assignment

• Explain the necessity of the cell and its various functions in terms of different organs.
• Differences between osmosis and diffusion.
• Structural differences of various types of cells.
• Practice given questions.

🪴 That was today's lecture, stay safe and see you in the next class!