digestion and absorption

• Absorption of amino acids: NA+ removed from cell by NA+, K+ pump, amino acids removed from cell by facilitated diffusion, this maintains a concentration gradient, NA+ and amino acids bind to co-transport protein which carries them across membrane
• tissue fluid forms at the atrial end of capillary, high hydrostatic pressure forces fluid from blood plasma out of capillary, forming tissue fluid
• tissue fluid contains few proteins as most are to large to move out of gaps in capillary walls
• explain how water from tissue fluid is returned to circulatory system

  • plasma remains in the blood, creating a water potential gradient
  • water moves via osmosis and returns to blood by lymphatic system
• what is digestion?

  the hydrolysis of large insoluble molecules into smaller molecules that can be absorbed across membranes
• Explain why oxygen uptake is a measure of metabolic rate in organisms?

  Oxygen is used in respiration, which provides

  energy in the form of ATP
• lipid absorption:

  lipids are hydrolysed into glycerol, fatty acids and monoglycerides

  monoglycerides and fatty acids associate with bile salts and phospholipids to form micelles

  micelles deliver the monoglycerides and fatty acids to the epithelial cell where they diffuse in

  triglycerides reform in the epithelial cell and are packaged with cholesterol and phospholipids to form chylomicrons

  chylomicrons released via exocytosis