PNB 2250 Lecture Notes - Lecture 4: Oxidative Phosphorylation, Photosynthesis, Thermal Mass
9 Sep 2016
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Movement of oxygen as gas, or dissolved in water, past animal tissues: increases the speed at which gas exchange occurs. Diffusion is slow over large distances & faster over smaller distances. Respiration has a fundamental impact on animal design: aquatic, terrestrial. Simple diffusion: gases/molecules moving across a barrier, from high concentration to low concentration (oxygen gradient) An animal must expose tissues to either water or the atmosphere to gain oxygen and lose carbon dioxide: tissue must be thin & large. Respiratory organs must be large and the skin must be thin in order to partake in diffusion. Takes 250 milliseconds for oxygen to saturate blood as it passes through lungs in humans: affected by the presence of water. Lungs are covered with mucus (water) to prevent desiccation. Choices: external skin or another structure (must be very thin, internal specialized organ or organs for respiration, selection factor. Occupied environment (water or air: changes the physical movement of gases.
