Lecture Notes: Mechanisms of Transport in the Bloodstream

Key Concepts

• Facilitated diffusion
  • Movement from high to low concentration gradient
  • No energy required
  • Utilizes a transport protein
• Primary Active Transport
  • Movement against the concentration gradient
  • Requires energy (ATP)
  • Uses a pump to move ions/molecules
• Secondary Active Transport
  • Utilizes energy from one molecule moving down its gradient to move another molecule against its gradient
  • Involves proteins (antiporters and symporters)
    • Antiporter: Move molecules in opposite directions
    • Symporter: Move molecules in the same direction
• Pinocytosis
  • Form of endocytosis
  • Known as "cell drinking"
  • Brings in water droplets and dissolved solutes

Glucose Transport

• Importance
  • Glucose is valuable and must be reabsorbed into the blood
• Transport Process
  • Limited by the number of binding sites on transporters
  • Transport Maximum
    • The maximum number of glucose molecules that can be moved
    • Excess glucose results in glucosuria (a sign of diabetes)

Water Transport

• Osmosis
  • Main method for water movement
• Obligatory Water Reabsorption
  • Water follows salt (where salt goes, water follows)
  • Dictated by fluid and electrolyte balance
• Facultative Water Reabsorption
  • Involves principal cells
  • Regulated by ADH (antidiuretic hormone)
  • Inserts aquaporins (water transport proteins)

Summary

• Various methods exist for molecules and ions to move in and out of the bloodstream, including facilitated diffusion, active transport, and endocytosis.
• Understanding these mechanisms is important, particularly how they relate to glucose and water reabsorption in the kidneys.

Note: Review the concepts of antiporters and symporters to ensure a solid understanding of secondary active transport. Also, consider the implications of glucose transport maximums in conditions like diabetes.

Next Steps:

• Five-minute break before continuing the lecture.