Biology 2601A/B Lecture Notes - Lecture 9: Heme, Lipid Bilayer, Vacuole
10 Jan 2017
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Aerobic metabolism: dependent on the exchange of oxygen (o2) and carbon dioxide (co2) from the environment. Diffusion is too slow to maintain the rates of gas exchange needed to support the metabolism of larger organisms. Blue whale vs. rotifer; 1012 fold range difference in size: diffusion of a small rotifer (0. 1 mg) have a small area for the diffusion to occur, whale has a small surface area relative to its mass/volume. Concentration gradient depends on movement by diffusion alone: cell membrane is only 10nm in thickness, muscle is thicker, longer diffusion times. Bulk flow; convection: most multicellular organisms. Oxygen from sea water cells of organism: sea water circulates out of body cavity by means of bulk flow, eg. Getting o2 out of the external medium and into the cells: often via the circulatory system. Getting co2 out of the cells and into the external medium. Air: 21% o2 as a gas: air breathers have easy access to oxygen.
