BIO 121 Lecture Notes - Eukaryote, Chromatin, Pinocytosis
1 Oct 2013
School
Department
Course
Professor
Document Summary
Selectively permeable membranes: allow passages of some substances but not others, controls volume and internal composition of cell"s ions and molecules. Osmosis: a type of diffusion, h2o molecules pass through a selectively permeable membrane, from higher effective h2o concentration, to lower effective h2o concentration. Osmotic pressure: determined by concentration of solutes, cells regulate internal osmotic pressure, to prevent shrinking or bursting. Key concept: diffusion is passive - does not require the cell to expend metabolic energy, active transport requires direct expenditure of energy. Active transport: cell uses metabolic energy, to move ions or molecules, across a membrane, against a concentration gradient, example: sodium-potassium pump, uses atp to pump sodium ions out and potassium ions in. Bulk transport: compare transport mechanism of exocytosis and endocytosis. Exocytosis: materials exit cell, membrane surface are increases. Endocytosis: materials enter cell, membrane surface area decreases, three types of endocytosis, phagocytosis - eating, white blood cells engulf bacteria from a cut, pinocytosis - drinking, receptor-mediated endocytosis.
