Lecture on Cells

Introduction to Cells

• Cells are microscopic and cannot be seen with the naked eye.
• Discovered unintentionally by Robert Hooke in 1665 using a microscope to observe cork.
• Term "cells" comes from Latin, meaning "little rooms."
• Anton van Leeuwenhoek further studied cells, observing pond organisms, blood cells, yeasts, and bacteria.

Cell Theory

• Developed from observations post-Hooke's discovery.
• Consists of three core principles:
  1. All organisms are made of one or more cells.
  2. The cell is the basic unit of all living things.
  3. All cells come from existing cells.

Parts of a Cell

• Cell Membrane: Protective layer covering the cell, regulates entry and exit of materials. Contains cytoplasm.
• Genetic Material: DNA is present in all cells, controlling cell activities and passed from parent to offspring. Often housed in a nucleus.
• Organelles: Structures performing various functions within the cell, often membrane-bound.

Types of Cells

Prokaryotic Cells

• Prokaryotes lack a nucleus and membrane-bound organelles.
• Types include:
  • Bacteria:
    • Smallest known cells.
    • No nucleus, circular DNA.
    • Contain a cell wall and sometimes flagella.
  • Archaea:
    • Similar to bacteria but with unique cell wall and membrane compositions.
    • Can live in extreme conditions (hot springs, volcanic vents, salty water).

Eukaryotic Cells

• Have a nucleus and membrane-bound organelles.
• Larger than prokaryotic cells.
• Include both single-celled (e.g., yeast) and multicellular organisms (e.g., plants, animals).

Why Are Cells Small?

• Cells require efficient nutrient intake and waste expulsion.
• Larger cells face challenges as their volume increases faster than surface area, limiting nutrient and waste exchange.
• Surface area limits the size of most cells to ensure survival.

These notes provide a comprehensive overview of cell structure, types, and fundamental biological principles surrounding their existence and functionality.