Sep 23 Lecture - Biology 101 Sep 23 Membranes and Transport...

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Biology 101 – Sep 23 Membranes and Transport – Chapter 5 The Fluid-Mosaic Model The fluid part is the lipids. We have phospholipids We also have cholesterol Fig 5-6 Peripheral proteins Integral proteins Carbohydrate chains – glycol proteins Carbohydrates attached to lipids. – glycolipids The cells assess the carbohydrate chains and make decisions on the cells next to them. Membrane proteins - integral membrane proteins - embedded in lipid bilayer - transmembrane proteins -integral proteins that extend completely through membrane - peripheral membrane proteins - at surface of lipid bilayer - bound to exposed integral proteins Everything that goes through the cell passes through the plasma membrane. There are many ways of moving things across membranes and cells. Diffusion - net movement of substance down its concentration gradient - from region of greater concentration - to region of lower concentration - diffusion is passive transport – does not use direct metabolic energy (no ATP etc required) Example – homogenization in water. Simple diffusion - consider diffusion of CO2 across the plasma membrane of one of your cells - what is the concentration of net movement? - what is the source of energy? The gradient of concentration is a form of potential energy.
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Mitochondria are carrying cellular respiraton, so there is higher concentration of CO2 inside than there is inside.
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