Biology: membrane structure

• What is the primary function of membranes in cells?

  Defining the outer border of all cells and organelles
• How do membranes manage cellular processes?

  By controlling what enters and exits the cell
• What role do membranes play in cellular communication?

  They receive external signals and initiate cellular responses
• How do membranes contribute to tissue structure?

  By adhering to neighboring cells
• What is the main component of membranes?

  Phospholipids
• How do phospholipids arrange themselves in membranes?

  They arrange themselves in a bilayer
• What are the two major types of membrane proteins?

  Integral and peripheral proteins

  
• What is the function of integral proteins?

  They are completely integrated into the bilayer
• What is the role of peripheral proteins?

  They are located only on either surface of the membrane
• What functions do membrane proteins serve?

  Transporters, receptors, enzymes, binding, and adhesion
• Where are carbohydrates found in relation to membranes?

  On the exterior surface of the membrane
• What are glycoproteins and glycolipids?

  Carbohydrates bound to proteins and lipids, respectively
• What is the function of carbohydrates in membranes?

  Cell-cell recognition and attachment
• What role does cholesterol play in membrane structure?

  It acts as a fluidity buffer
• What does it mean for a membrane to be selectively permeable?

  Some molecules are allowed to pass while others are not
• What is the difference between active and passive transport?

  Active transport requires energy, while passive transport does not
• What is osmosis?

  The diffusion of water across a membrane
• In which direction does water move during osmosis?

  From an area of higher water concentration to one of lower concentration
• What do the terms hypertonic, isotonic, and hypotonic describe?

  The osmolarity of the cell compared to its extracellular fluid
• What is facilitated diffusion?

  Movement of substances down their concentration gradients through integral membrane proteins
• What types of substances typically undergo facilitated diffusion?

  Ions and small polar molecules
• What are channel proteins?

  Proteins that allow size and charge discrimination
• What are carrier proteins?

  Proteins that discriminate based on molecule type
• What is simple diffusion?

  Movement from an area of high concentration to low concentration through the membrane
• When does movement stop during simple diffusion?

  When equilibrium is achieved
• What types of molecules typically undergo simple diffusion?

  Small non-polar molecules like O2 and CO2
• What factors affect diffusion?

  • Distance
  • Surface area/volume ratio
  • Concentration gradient
  • Particle size
  • Temperature
  • Polarity
  • Viscosity/Density
  • Pressure
• What is filtration in the context of membrane transport?

  Movement of water and solutes through a semi-permeable membrane along the pressure gradient
• What is active transport?

  Transport of ions or molecules against their concentration gradient requiring energy

  
• What is primary active transport?

  Movement of an ion or molecule up its concentration gradient using ATP hydrolysis

  
• What is an example of primary active transport?

  The sodium-potassium pump

  
• What is exocytosis?

  Packaging substances into vesicles that fuse with the plasma membrane to release contents

  
• What is endocytosis?

  The process of engulfing substances into the cell
• What is phagocytosis?

  Cellular eating where the cell membrane surrounds and engulfs a particle
• What is pinocytosis?

  Cellular drinking where the cell membrane surrounds a small volume of fluid
• What is receptor-mediated endocytosis?

  Uptake of a specific substance by binding to receptors on the membrane

  
• What are the types of bulk transport?

  • Endocytosis (importing)
  • Exocytosis (exporting)
  • Requires energy
• What is secondary active transport?

  Using an electrochemical gradient created by primary active transport to move a different substance

  
• What substances typically enter the cell via secondary active transport?

  Amino acids and glucose