Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Cellular activity - Our eclass community
Document related concepts
Transcript
CELL MEMBRANES Biology ATAR Unit 2 Text: Chapter 8 pages 184-206 & TRANSPORT CODE OF CONDUCT Our classroom community ... Our values Our responsibilities Our words, our actions •Be punctual •Bring everything you need to class being prepared •Know your due dates giving your best effort persisting in the face of •Complete all tasks to the best of your ability difficulties •Never give up – mistakes are OK •Participate in group discussions Is about learning Learning matters Learning well means: ● ● ● Treating people well means: Is about people People matter ●showing respect ●being kind ●listening •Be encouraging – no put downs •Help others •Always listen well •Be accepting of differences and work well with your peers •Treat others how you would like to be treated. Keywords Diffusion Osmosis Fluid mosaic model Phospholipid bilayer Hydrophobic Hydrophilic Channel proteins Carrier proteins Carrier mediated transport Facilitated diffusion Active transport Vesicular transport Endocytosis Pinocytosis Phagocytosis Exocytosis Receptor proteins Making connections The cells of all living organisms are surrounded by a cell membrane. Cell membranes are made up of lipid (fat) molecules interspersed with protein and cholesterol molecules. The cell membrane is a dynamic system and responds to changes in the environment. LEARNING OUTCOMES Understand the structure and function of cell membranes Describe and explain the Fluid Mosaic model Describe and explain passive and active transport processes MOVEMENT ACROSS CELL MEMBRANES Movement of molecules across the membrane is either through passive processes or active processes. Active processes require energy because the molecules are being moved from an area of lower concentration to an area of higher concentration CONCENTRATION GRADIENT When the concentration of a substance is different at two places, the substance will diffuse along the concentration gradient until the concentration of the two areas becomes equal. High concentration Low concentration Concentration at A Concentration at B 1 High concentration Low concentration 2 Equilibrium 3 Uniform concentration DIFFUSION Diffusion is the movement of molecules from an area of high concentration to an area of low concentration Diffusion is a passive process and requires no energy input from the cell OSMOSIS Osmosis is a special case of diffusion. It is the diffusion of water through a semi- permeable membrane. Osmotic flow is simply diffusion of a solvent (water) through a membrane impermeable to the solute molecules (eg. salt) Osmosis is a passive process and requires no energy input from the cell DEFINITIONS Concentration gradient The concentration gradient is the difference in concentration of ions in a solution Ions will move along the gradient from the area of high concentration to the area of low concentration Osmotic gradient The osmotic gradient is similar to a concentration gradient but involves the difference in concentration across a semi-permeable membrane Water moves across the membrane along the gradient from the area of high concentration to the area of low concentration REVIEW: DIFFUSION & OSMOSIS OSMOSIS Net water movement from high concentration to low concentration High water concentration (dilute solution) Low water concentration (concentrated solution) Semipermeable membrane THE CELL MEMBRANE The cell membrane is the outer skin of a cell. It surrounds the whole cells and and separates the contents of the cell from the extracellular or interstitial fluid The cell membrane is selectively or differentially permeable – it allows some substances to cross more easily than others. FUNCTION OF THE CELL MEMBRANE A physical barrier: separates the cell from the extracellular fluid The regulation of the passage of materials: the membrane controls the movement of materials into/out of cells Sensitivity: the cell membrane is the first part of the cell affected by any changes in the extracellular fluid Support: cell membrane is attached to microfilaments to give cell support FUID MOSAIC MODEL One model that explains the cell membrane is called the fluid mosiac model The membrane is said to be fluid because the molecules are constantly changing position Its said to be mosiac because it is composed of many kinds of molecules FLUID MOSAIC MODEL The main structure of the membrane is composed phospholipid molecules, which are lipids that contain a phosphate group The phospholipids are arranged in 2 layers called a bilayer FLUID MOSAIC MODEL Each phospholipid molecule has a hydrophilic head (water loving) and a hydrophobic tail (water hating) They are arranged so that their heads are on the outside and tails on the inside FLUID MOSAIC MODEL Embedded in the phospholipid bilayer are cholesterol and protein molecules MEMBRANE PROTEINS Many of the proteins are involved in the movement of substances through the membrane There are 4 types of membrane proteins, each with a different function: Channel proteins 2. Carrier proteins 3. Receptor proteins 4. Cell-identity markers 1. MEMBRANE TRANSPORT: CHANNEL PROTEINS & CARRIER Channel proteins are like open doors They allow certain types of molecules (mostly ions) to flow freely in and out of the cell The cell may be able to close these ‘doors’ when required Channel proteins allow passive diffusion across the membrane (osmosis) PROTEINS Carrier proteins are involved in carrier mediated transport These proteins bind to molecules to be transported and help their passage across the membrane They bind to the molecule, change shape and then release the molecule OSMOSIS: WATER TRANSPORT You would think that water does not cross this membrane easily because of the hydrophobic middle layer. However, considering that ... the concentration of water in water is extremely high AND the surface area to volume ratio (membrane to cell) is also very high ... water does diffuse across the membrane quite well Transport proteins are also involved in water diffusion MEMBRANE TRANSPORT: CHANNEL PROTEINS & CARRIER PROTEINS MEMBRANE TRANSPORT: CARRIER MEDIATED TRANSPORT There are 2 main types of carrier mediated transport Facilitated diffusion is a passive process which substances move along the concentration gradient. The protein changes shape and the molecule is released through the membrane Active transport requires an energy input as the substance is being transported across the membrane against the concentration gradient SIMPLE DIFFUSION & FACILITATED DIFFUSION Diagram created by LadyofHats ACTIVE TRANSPORT (SODIUM PUMP) Diagram created by LadyofHats MEMBRANE TRANSPORT: CARRIER MEDIATED TRANSPORT Carrier proteins are specific - they will only bind to a particular molecule Carriers can become saturated. Once all the available carriers are occupied, any increase in the concentration of molecules cannot increase the rate of movement Carrier activity is regulated by substances ie. hormones MEMBRANE VESICULAR TRANSPORT: TRANSPORT Vesicular transport is the movement of substances across the cell membrane in membranous bags called vesicles MEMBRANE VESICULAR TRANSPORT: TRANSPORT Endocytosis is taking liquids or solids into the cell by vesicular transport Pinocytosis is taking in liquids Phagocytosis is taking in solids Exocytosis is when the contents of a vesicle inside the cell are passed to the outside of the cell ENDOCYTOSIS Diagram created by LadyofHats EXOCYTOSIS Diagram created by LadyofHats MEMBRANE RECEPTORS Membrane receptor proteins are sensitive to certain molecules outside the cell, and when those molecules are present they bind with the receptor protein The receptor and the bound molecule then trigger changes in the cell. MEMBRANE RECEPTORS Receptor proteins are specific. Each type of receptor protein will bind to only one specific molecule. There are a limited number of receptor proteins in the membrane of each cell, so when each receptor is bound to a molecule there can be no further increase in the rate of the cell’s activity MEMBRANE RECEPTORS Different cells have different types and numbers of receptor proteins Receptor proteins also function for communication between cells Receptor proteins are binding sites for hormones
