Cell Membrane 11/16/10
Cell Membrane Function Importance Controls what enters and exits the cell. Importance By regulating this movement it helps the cell to maintain homeostasis.
Homeostasis Maintaining a constant internal state in a changing environment. All living things respond to their environment Cells maintain homeostasis by limiting the movement of substances across the cell membrane Acts as a gatekeeper
Cell Membrane Structure Phospholipid bilayer Carrier Proteins Hydrophilic heads Hydrophobic tails Carrier Proteins Help transport through membrane
Solutions In solutions, moving molecules fill up a space. Equilibrium is when the concentration of a substance is the same throughout a space. When there is a difference in the concentration of a substance, a concentration gradient exists. This concept will be important when talking about some of the vocabulary.
Movement Across Membranes Two types of transport Passive Transport Requires no energy to occur Active Transport Requires energy to occur Boat Analogy
Types of Passive Transport Diffusion Movement of a substance from high concentration to low concentration Diffusion of water is referred to as osmosis. Facilitated Diffusion Uses carrier proteins to help the substances diffuse through the cell membrane. http://www.zerobio.com/flashmx/transport.swf
Diffusion
Osmosis Predicting the movement of water depends on the concentration of the cell’s environment Solutions can have three different concentrations: Hypertonic: Higher concentration outside the cell. Isotonic: Concentration is the same inside and outside the cell. Hypotonic: Lower concentration outside the cell. http://www.zerobio.com/flashmx/tonicity.swf
Osmosis Practice Saltwater solution What is the solute? What is the solvent? Water is the substance moving through the membrane. Which way will the water move? 98% Saltwater
Osmosis Practice Saltwater solution What is the solute? What is the solvent? Water is the substance moving through the membrane. Which way will the water move? 2% Saltwater
Osmosis Practice Sugarwater solution What is the solute? What is the solvent? Water is the substance moving through the membrane. Which way will the water move? 15% Sugarwater
Active Transport In active transport, substances are being transported against their concentration gradient. Requires energy Molecules move from an area of lower concentration to an area of higher concentration
Active Transport Cell Membrane Pumps Proteins that move molecules through the cell membrane
Active Transport Endocytosis Exocytosis Movement of molecules into the cell through a vesicle Exocytosis Movement of molecules out of the cell through a vesicle