Cell Structure And Function Cell The Unit Of Life 1

Cell Theory:#

• Given by shelden and schwann and modified by rudolf virchow
• Cell theory is a fundamental concept in biology that states:
  • All living organisms are composed of cells.
  • The cell is the basic unit of life.
  • All cells arise from pre-existing cells through cell division.

Classification of Bacteria Based on Shape:#

• Bacteria can be classified into various shapes:
  • Cocci: Spherical-shaped bacteria.
  • Bacilli: Rod-shaped bacteria.
  • Spirilla: Spiral-shaped bacteria.
  • Vibrio: Curved rod-shaped bacteria.
  • Spirochetes: Spiral-shaped bacteria with a corkscrew-like appearance.

GRAM STAINING:#

• Gram staining is a laboratory technique used to differentiate bacteria into two main groups based on the structure of their cell walls.
• Gram-positive bacteria retain the violet stain and appear purple/blue under a microscope.
• Gram-negative bacteria do not retain the violet stain and appear pink/red under a microscope.

Structure of a Bacterial Cell:**#

• Bacterial cells are typically simpler than eukaryotic cells.
• Key components of a bacterial cell include:
  • Cell wall: Provides structural support.
  • Cell membrane: Regulates transport and surrounds the cytoplasm.
  • Cytoplasm: Contains cellular components.
  • Ribosomes: Site of protein synthesis.
  • DNA: Genetic material usually found in a single, circular chromosome.
  • Plasmids: Small, circular DNA fragments.

Structure of Cell Membrane:#

• Given by Sanger and nicolsan
• The bacterial cell membrane, also known as the plasma membrane, is a phospholipid bilayer.
• It regulates the passage of molecules in and out of the cell.
• Proteins in the membrane play roles in transport, energy production, and cell signaling.

Cell Wall:#

• The bacterial cell wall is a rigid structure located outside the cell membrane.
• It provides shape, support, and protection to the cell.
• In Gram-positive bacteria, the cell wall consists mainly of peptidoglycan.
• In Gram-negative bacteria, the cell wall has a thinner layer of peptidoglycan and an outer lipid membrane.

Centriole:#

• Centrioles are organelles found in animal cells, particularly in the centrosome.
• They are involved in cell division, where they play a role in organizing and separating chromosomes during mitosis and meiosis.
• Centrioles are not present in bacterial cells.