Body Fluids & Membrane Transport

• What are the two main components of total body water?

  Intracellular fluid and extracellular fluid
• What is an example of transcellular fluid?

  Cerebrospinal fluid
• What is the function of the plasma membrane?

  Regulation of the intracellular environment
• Why is the plasma membrane described as selectively permeable?

  It allows certain substances to pass through
• What provides permeability in the plasma membrane?

  Transport proteins such as channels and pumps
• What are the two types of membrane transport?

  Passive and active transport
• What is a facilitator or uniport carrier?

  A type of transport protein
• What is the role of transport proteins in cells?

  Uptake of nutrients and export of waste
• What ions are found in high concentration inside the cell?

  K+ ions
• What ions are found in high concentration outside the cell?

  Na+ and Cl- ions
• What generates a membrane potential?

  Asymmetric distribution of K+ ions
• What is the membrane potential of a cell primarily due to?

  K+ ion channel activity
• How does water distribution occur in cells?

  Through osmosis to equal osmotic pressures
• What is the role of capillary endothelium?

  Regulating interstitial fluid
• What is the composition of interstitial fluid (ISF)?

  Small ions and organic solutes, proteins
• What determines water distribution in the body?

  Hydrostatic and osmotic forces
• What is the protective function of epithelia?

  Covering internal and external surfaces
• What are the two types of membranes in epithelial cells?

  Apical and basolateral membranes
• What is the function of tight junctions in epithelial cells?

  Selectively allowing substances in and out
• What are the functions of transport proteins in the plasma membrane?

  • Uptake of nutrients and substrates
  • Export of waste products (urea, lactate, H+)
  • Regulation of intracellular ions
  • Regulation of pH
  • Regulation of cell volume
• What is the distribution of water and solutes across the plasma membrane?

  • Inside: High K+ ions
  • Outside: High Na+ and Cl- ions
• What are the roles of hydrostatic and osmotic forces in water distribution?

  • Hydrostatic forces push water
  • Osmotic forces pull water
• What are the protective and barrier functions of epithelia?

  • Protects internal and external surfaces
  • Acts as a barrier for absorption and secretion