fundamental life of unit

• Properties of a cell:

  • The cell is the smallest living unit of life
  • Not visible to the naked eye
  • Varies in shape within and among organisms
  • Varies in size
  • All living cells exhibit basic properties like respiration, growth, and metabolism
  • Cells originate from pre-existing cells through cell division
• Milestones in Cell Biology:

  • Robert Hooke discovered the cell
  • Leeuwenhoek discovered the microscope
  • Robert Brown discovered the nucleus
  • Purkinje coined the term protoplasm
  • Schleiden and Schwann presented the Cell theory
  • Camillo Golgi first described the Golgi apparatus
• Invention of Microscope:

  • Antony van Leeuwenhoek constructed the first simple microscope using biconvex lenses
  • Robert Hooke invented the compound microscope with concave lenses
  • Modern compound microscopes are modifications of Hooke's design with improved magnification up to 2,000 times
  • Electron microscopes use electronic beams for magnification over 200,000 times
• Cell theory:

  • All plants and animals are composed of cells
  • The cell is the basic unit of life
  • Virchow expanded the theory by suggesting that all cells arise from pre-existing cells
• Classification of Cells based on cellular complexity:

  • Prokaryotic cell:
  • Poorly defined nuclear region with no membrane-bound organelles
  • Unicellular organisms
  • Eukaryotic cell:
  • Well-defined nuclear region with a nuclear membrane and other membrane-bound organelles
  • Usually multicellular organisms
• Structural Organization of a cell:

  • Cell wall:
  • Present in plant, fungal, and some bacterial cells
  • Provides structural strength with cellulose in plants and peptidoglycan in bacteria
  • Plasma membrane or cell membrane:
  • Outermost covering of animal cells and next to the cell wall in plant cells
  • Selectively allows molecules to move in and out of the cell
  • Engulfs or expels substances through endocytosis or exocytosis
  • Cytoplasm:
  • Inner content of the cell membrane containing cytosol, organelles, and inclusions
• • Region for cellular activities, water balance, and maintenance of cell shape
  • Contains cytoskeleton for cell movement and division
• Nucleus:

  • Controls all cellular activities
  • Enclosed by a double nuclear membrane with pores for material transport
  • Contains nucleoplasm, nucleoli, and chromatin
  • Plays a role in cellular reproduction and chemical activities
• Vacuole:

  • Found in both plant and animal cells
  • Provides turgidity and rigidity in plant cells
  • Stores substances and expels waste material in some organisms
• Endoplasmic reticulum:

  • Interconnected network of membranous structures like tubules, vesicles, and cisternae
  • Smooth ER synthesizes fats and lipids, detoxifies drugs, and metabolizes carbohydrates
  • Rough ER transports proteins and is the main site of glycosylation
• Golgi Apparatus:

  • Membrane-bound sac-like structures called cisternae
  • Involved in storage, modification, and packaging of products in vesicles
  • Forms lysosomes
• Lysosome:

  • Acts as the waste disposal system of the cell
  • Contains digestive enzymes to destroy foreign organic material
  • Can digest own cell when lysosomes burst
• Mitochondria:

  • Known as the 'Powerhouse of the cell'
  • Double membrane-bound organelle with its own DNA
  • Involved in cellular respiration and ATP production
• Plastids:

  • Present in plants and absent in animals
  • Types include chromoplasts and leucoplasts
  • Chromoplasts contain color pigments for plant coloration
  • Leucoplasts are colorless and contribute to photosynthesis and plant color