BIOL 243L Lecture Notes - Lecture 2: Osmotic Pressure, Osmosis, Endocytosis
18 Sep 2016
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Enzyme= a biological catalyst that speeds up a chemical reaction. May require a cofactor to work (vitamins and minerals) Bind to substrate at active site to get a specific product o. This is called an enzyme/substrate complex (induced-fit model) Plasma membrane is semi-permeable: allows some substances to pass through but not others o. The medium on inside and outside of cell are solution, so the particles passing through are solutes. Being semi-permeable allows a difference in solute concentration between the two sides of the membrane-concentration gradient. Passive transport= requires no energy; moves from an area of high concentration to lower concentration (down concentration gradient: simple diffusion: water, oxygen, steroid hormones o. Facilitated diffusion: ions, glucose, and amino acids need a transport protein to cross the membrane: examples: simple diffusion, facilitated diffusion, osmosis, filtration. Active transport= uses energy (atp) to move molecules across a membrane: endocytosis, exocytosis.
