University:
California State University, Northridge
Course:
BIOL 101 | General Biology
Academic year:

2024
Views:

283

Pages:

4
Author:

Skye S.

Chapter 1 : Cellular Biology Introduction to Pathophysiology Osmosis and Osmolality ● Osmosis is the movement of water across a semipermeable membrane from an area of higher water concentration to an area of lower concentration ● For osmosis to occur, the membrane must be more permeable to water than to solutes, and the concentration of solutes on one side of the membrane must be greater than the other side ● Osmolality measures the concentration of molecules per weight of water, while osmolarity measures the concentration of molecules per volume of solution ● The normal osmolality of body fluids ranges from 280 to 294 mOsm/kg, with ICF and ECF osmolalities tending to equalize Osmotic Pressure and Oncotic Pressure ● Osmotic pressure refers to the amount of hydrostatic pressure required to oppose the osmotic movement of water ● Oncotic pressure, or colloid osmotic pressure, is the overall osmotic effect of colloids (e.g., plasma proteins) ● Gibbs-Donnan equilibrium occurs when small, diffusible ions are present with large, nondiffusible, charged particles like plasma proteins, creating an asymmetry in the distribution of small ions Tonicity ● Tonicity describes the effective osmolality of a solution Types of solutions based on tonicity ● Isotonic solution: has the same concentration as body fluids ● Hypotonic solution: has a lower concentration and is more dilute than body fluids ● Hypertonic solution: has a higher concentration than body fluids Importance of tonicity in correcting imbalances ● Tonicity is important when administering replacement solutions to correct water and solute imbalances Active transport of Na+ and K+ ● Active transport system found in virtually all mammalian cells ● Uses ATP to transport Na+ out of the cell and K+ into the cell ● Requires ATPase and magnesium ions ● ATPase induces conformational changes in transporter protein, causing movement of Na+ and K+ ● Results in an electrical potential with the inside of the cell more negative than the outside Summary of major transport systems in mammalian cells ● Glucose: passive transport through protein channels or active transport through symport with Na+ ● Fructose: active transport through symport with Na+ ● Amino acids: transported through specific transporters or coupled channels Amino acid transport ● Active transport with symport with Na+ (except proline) ● Active transport liver-specific amino acids ● Passive transport in small intestine Organic molecule transport ● Active transport with symport with Na+ (cholic acid, deoxycholic acid, taurocholic acid) Organic anion transport ● Antiport with counter-organic anion ATP-ADP transport ● Antiport transport of nucleotides; can be active Inorganic ion transport ● Passive transport of Na+ ● Active antiport with Na+/H+ ● Active transport with Na+/K+ ● Active antiport with Ca++ ● Active H+/K+ transport Water transport ● Passive osmosis NOTE: The known transport systems are listed here; others have been proposed. Most transport systems have been studied in only a few tissues and their sites of activity may be more limited than indicated. ADP, Adenosine diphosphate; ATP, adenosine triphosphate; Ca++, calcium; Cr"HCO3, chloride/bicarbonate; H+, hydrogen; K+, potassium; Na+, sodium.