Integrated Science 4th Quarter Reviewer: BIO, CHEM, PHYSICS

• Cell membrane

  Crucial as it acts as the "gatekeeper" of the cell
• Components of the cell membrane

  • Phospholipid bilayer
  • Proteins
  • Carbohydrates
• Phospholipid bilayer


  Consists of hydrophilic heads facing the watery surroundings and hydrophobic tails avoiding water
• Proteins


  Embedded in the phospholipid bilayer aiding in transport across membranes and cellular communication
• Carbohydrates


  Attached to membrane proteins and phospholipids, aiding in cell recognition
• Fluid Mosaic Model


  Describes the cell membrane as a mosaic of phospholipids, proteins, and carbohydrates, with fluidity essential for controlling substance movement
• Types of Passive Transport

  • Diffusion
  • Osmosis
  • Facilitated Diffusion
• Diffusion


  Movement of molecules from high to low concentration
• Examples of diffusion


  • Perfume diffusion
  • Movement of non-polar (oxygen and carbon dioxide) and small polar molecules (water) across the membrane
• Osmosis


  Specialized diffusion focusing on water movement across the membrane
• Types of solutions


  • Isotonic
  • Hypotonic
  • Hypertonic
• Hypotonic solution


  Lower solute concentration, higher water concentration. Causes water to rush into the cell, leading to cell expansion and potential bursting (cytolysis)
• Hypertonic solution


  Higher solute concentration, lower water concentration. Causes water to rush out of the cell, leading to cell contraction shrinkage (plasmolysis)
• Isotonic solution


  Equal concentrations inside and outside the cell. Results in dynamic equilibrium, with no net movement of water molecules
• Facilitated diffusion


  Occurs through transport proteins for molecules unable to pass freely through the membrane. Movement facilitated by concentration gradient, no energy used
• Types of Active Transport

  • Transport Proteins (e.g. sodium-potassium pump)
  • Bulk Transport (Endocytosis and Exocytosis)
• Active transport


  Requires energy as substances move against concentration gradient
• Sodium-potassium pump


  Moves ions against their concentration gradient using ATP energy
• Endocytosis


  Cell membrane folds inward, enclosing material within vesicle. Types include phagocytosis (solid engulfment) and pinocytosis (liquid engulfment)
• Exocytosis


  Vesicle fuses with cell membrane, releasing contents outside the cell. Used by endocrine cells to release hormones
• Cells have a finite range of conditions for survival. Too hot, too cold, too watery, too salty, too acidic or too basic affects cell function
• Selective permeability of cell membranes


  Cell membranes allow certain particles to pass through but not others. Fitted with special protein channels called Aquaporins for water molecules
• Concentration


  A measure of solute per volume of solvent
• Diffusion


  Molecules move from higher to lower concentration areas, eventually reaching equilibrium with equal concentrations on both sides of the membrane (inside and outside the cell)
• Drinking sea water is not advisable, even in extreme circumstances
• Phospholipid bilayer


  Consists of two layers of lipids with polar heads and nonpolar tails
• Simple diffusion


  Small non-polar molecules, such as oxygen and carbon dioxide, can pass through the membrane
• Facilitated diffusion


  Transport proteins within the membrane facilitate the passage of larger or polar molecules, which also occurs without energy input
• Active transport


  Requires energy, often in the form of ATP, to move molecules against their concentration gradient
• ATP can energize transport proteins to force molecules to move against their concentration gradient
• The sodium-potassium pump moves molecules against their concentration gradient using ATP energy
• Endocytosis


  Involves the fusion of substances with the cell membrane to bring them inside the cell, forming vesicles
• Exocytosis


  The process of molecules exiting the cell, which can be used to eliminate waste or to transport important materials, such as large carbohydrates for making plant cell walls
• Cells have tiny pumps that require energy. ATP is used as energy currency for many pumps
• Sodium-potassium pump


  Maintains a resting membrane potential. Cells have a resting potential that is more negative inside than outside. Excitable cells depend on changes in electric potential
• Sodium-potassium pump operation


  Moves 3 sodium ions out for every 2 potassium ions pumped in, creating an electrochemical gradient with more potassium ions inside the cell and more sodium ions outside
• Electrochemical gradient


  Influences cell function, enabling various cellular responses like action potential and other protein transport
• The sodium-potassium pump is a remarkable protein pump that plays a crucial role in maintaining cellular function
• Components of external (physiological) respiration

  • Inhalation
  • Exhalation
  • Gas exchange
• External respiration (breathing)


  The process of moving air in and out of the lungs