# BIO202H5 Lecture Notes - Lecture 2: Molecular Mass, Osmosis, Pressure Gradient

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16 Jan 2017
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## Document Summary

Osmosis = diffusion across a semi-permeable membrane. Diffusion = movement of molecules from an area of high concentration to low concentration. We need to create an environment where oxygen is moving in a favourable direction. Diffusion rate = how fast oxygen can move from one environment to the next. Pump - moving oxygen from external environment to internal environment. Think about diffusion rate through equation on slide. The higher the cross-sectional area of something, the higher the diffusion rate. The shorter the diffusion distance, the higher the diffusion rate. Mole(cid:272)ular (cid:449)eight does(cid:374)"t (cid:272)ha(cid:374)ge (cid:373)u(cid:272)h as (cid:449)ell as solu(cid:271)ilit(cid:455) of gas i(cid:374) fluid. In diagram, diffusion distance = amount of water in beaker. External respiration - getting oxygen into the body. Perfusion - getting oxygen into body via circulatory system: somehow embedding oxygen into body. Last step is mitochondrial respiration where you are trying to get energy from oxygen.