Cell Membrane Structure and Functions

Cell Membrane

• Structure: Phospholipid bilayer with embedded proteins
• Functions:
  • Regulates what enters and leaves the cell
  • Maintains cell shape
  • Provides mechanical support
  • Acts as a barrier to separate internal and external environments
• Semipermeability: Allows certain substances to pass through while restricting others
• Fluid mosaic model: Describes the dynamic structure of the cell membrane, with proteins and lipids moving freely

Cellular Transport

• Types:
  1. Passive transport: No energy required
     • Diffusion: Movement of molecules from high to low concentration
     • Osmosis: Movement of water molecules from high to low concentration
     • Facilitated diffusion: Assisted transport of molecules through transport proteins
  2. Active transport: Energy required
     • Carrier proteins: Transport molecules against their concentration gradient
     • Pump proteins: Use energy to transport molecules against their concentration gradient
• Transport mechanisms:
  • Simple diffusion: Direct movement of molecules through the membrane
  • Facilitated diffusion: Transport proteins assist molecule movement
  • Vesicle transport: Molecules transported through vesicles

Cell Organelles

• Types:
  1. Membrane-bound organelles:
     • Nucleus: Contains genetic material
     • Mitochondria: Generates energy through cellular respiration
     • Endoplasmic reticulum (ER): Involved in protein synthesis and transport
     • Golgi apparatus: Modifies and packages proteins for transport
     • Lysosomes: Contains digestive enzymes for breaking down waste
  2. Non-membrane-bound organelles:
     • Ribosomes: Site of protein synthesis
     • Cytoskeleton: Provides structural support and shape
     • Centrioles: Involved in cell division and formation of cilia
• Functions:
  • Protein synthesis and transport
  • Energy generation and storage
  • Waste management and recycling
  • Cell signaling and communication
  • **Cell division and growth

Cell Membrane

• Consists of a phospholipid bilayer with embedded proteins
• Regulates the movement of substances in and out of the cell
• Maintains cell shape and provides mechanical support
• Acts as a barrier to separate internal and external environments
• Is semipermeable, allowing certain substances to pass through while restricting others
• Has a dynamic structure, with proteins and lipids moving freely, described by the fluid mosaic model

Cellular Transport

• There are two main types of transport: passive and active
• Passive transport does not require energy
• Diffusion is the movement of molecules from high to low concentration
• Osmosis is the movement of water molecules from high to low concentration
• Facilitated diffusion is the assisted transport of molecules through transport proteins
• Active transport requires energy
• Carrier proteins transport molecules against their concentration gradient
• Pump proteins use energy to transport molecules against their concentration gradient
• Transport mechanisms include simple diffusion, facilitated diffusion, and vesicle transport

Cell Organelles

• There are two main types of organelles: membrane-bound and non-membrane-bound
• Membrane-bound organelles include:
  • Nucleus, which contains genetic material
  • Mitochondria, which generates energy through cellular respiration
  • Endoplasmic reticulum (ER), which is involved in protein synthesis and transport
  • Golgi apparatus, which modifies and packages proteins for transport
  • Lysosomes, which contain digestive enzymes for breaking down waste
• Non-membrane-bound organelles include:
  • Ribosomes, which are the site of protein synthesis
  • Cytoskeleton, which provides structural support and shape
  • Centrioles, which are involved in cell division and formation of cilia
• Organelles perform various functions, including:
  • Protein synthesis and transport
  • Energy generation and storage
  • Waste management and recycling
  • Cell signaling and communication
  • Cell division and growth

Osmosis and Diffusion

• An isotonic solution has the same concentration of solutes as another solution, such as a cell or a reference solution.
• In an isotonic solution, there is no net movement of water into or out of the cell, maintaining its shape and size.
• Examples of isotonic solutions include 0.9% saline solution (used in medical settings) and a 5% glucose solution.

Concentration Gradients

• A concentration gradient is a gradual change in the concentration of a substance from one area to another.
• There are two types of concentration gradients: concentration gradient (decreasing concentration) and reverse concentration gradient (increasing concentration).
• Diffusion occurs from an area of higher concentration to an area of lower concentration, down the concentration gradient.
• The steeper the concentration gradient, the faster the rate of diffusion.
• Concentration gradients are important in biological systems, driving the movement of molecules and ions across cell membranes.