Cell Structure and Function

Cell Structure and Function

Cell Membrane

• A thin, semi-permeable membrane that surrounds the cell
• Composed of phospholipid bilayer with embedded proteins
• Regulates what enters and leaves the cell
• Maintains cell shape and provides mechanical support

Cell Organelles

• Specialized structures within the cell that perform specific functions
• Examples:
  • Nucleus: contains genetic material (DNA)
  • Mitochondria: generates energy for the cell
  • Endoplasmic Reticulum (ER): involved in protein synthesis and transport
  • Ribosomes: site of protein synthesis
  • Lysosomes: contain digestive enzymes for breaking down waste and foreign substances

Function of Plasma Membrane

• Controls the movement of molecules in and out of the cell
• Regulates the exchange of nutrients, waste, and signaling molecules
• Maintains cell homeostasis and osmotic balance

Diffusion in Cells

• The movement of molecules from an area of higher concentration to an area of lower concentration
• Types of diffusion:
  • Passive diffusion: movement down concentration gradient (e.g., diffusion of oxygen into the cell)
  • Facilitated diffusion: movement down concentration gradient using transport proteins (e.g., glucose uptake)
  • Active transport: movement against concentration gradient using energy (e.g., pumping ions out of the cell)

Composition of Living Organisms

• Living organisms are composed of cells, which are the basic structural and functional units of life
• Cells are made up of:
  • Water (~70%)
  • Organic compounds (carbohydrates, proteins, fats, nucleic acids)
  • Inorganic compounds (salts, minerals)
  • Organelles and other cellular structures