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Canada (162,369)
York University (12,903)
KINE 2011 (117)
Gillian Wu (14)
Chapter 3

CHAPTER 3.docx

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Kinesiology & Health Science
Course Code
KINE 2011
Gillian Wu

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- Desmosomes are most abundant in tissues that are subject to considerable stretching (skin) - Tight junctions – firmly bind with each other at points of direct contact to seal passageway o Impermeable and thus prevent materials from passing  Passage must occur through the cells not between them - Gap junction – linked by small connecting tunnels formed by connexons o Connexon is made up of six protein subunits arranged in a hollow tubelike structure o Permit small water soluble particles to pass through o Found mostly in cardiac muslcle and smooth muscle o Serve as a pathway for direct transfer of small signalling molecules - Glucose is an example of a large, poorly lipid soluble particles that must gain entry to the cell - Diffusion – uniform spreading out of molecules because of their random intermingling - Net diffusion – the difference between two opposing movements - Steady state is when molecules from both sides are moving the same amounts - Diffusion is crucial to survival of every cell and important for homeostatic activities FICK’S LAW - Greater the difference in concentration, the faster the rate of net diffusion - During exercise we exhale more CO2 to coincide with the fact that we are creating much more - More permeable the membrane is to a substance, the more rapid the substance can diffuse down its concentration gradient - The larger the surface area available, the greater the rate of diffusion it can accommodate - The greater the distance, the slower the rate of diffusion - Diffusion is efficient only for short distance between cells - Movement of ions is also affected by their electrical charge - Same charges repel each other o Vice versa - A difference in charge between two adjacent area produces an electrical gradient that promotes the movement of ions toward the area of opposite charge o Is a passive transport  Similar to concentration gradient  Only ions that can permeate the membrane can move along gradient  When both an electrical and a concentration (chemical) gradient act simultaneously on a specific ion, the result is an electrochemical gradient OSMOSIS - Water can readily permeate the plasma membrane o Small enough to pass bilayer - Membrane proteins form aquaporins, which are channels used for the passage of water o Water molecules pass thr
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