Presentation on theme: "+ February 7, 2014 Objective: To create a model of the cell membrane To explain the structure of the cell membrane Journal: What does it mean to have a."— Presentation transcript:
+ February 7, 2014 Objective: To create a model of the cell membrane To explain the structure of the cell membrane Journal: What does it mean to have a phobia of something? What is an example of a phobia?
+ Key Terms What do you think are the definitions of the following words? Hydrophobic Hydrophilic
+ Key Terms Defined Hydrophobic: Literally means fear of water Molecules that are hydrophobic repel water and try to stay away from water Hydrophilic: Literally means water loving Molecules that are hydrophilic are attracted to water and tend to be found next to water
+ Phospholipids The structure of the phospholipid molecule generally consists of two hydrophobic tails and a hydrophilic head.
+ Phosphate Head Hydrophilic Polar (has a charge) Made of phosphate
+ Two Fatty Acid Tails Hydrophobic Nonpolar (doesn’t have a charge) Made of fatty acids
+ Structure of the Cell Membrane Phospholipids make up the cell membrane of cells.
+ Phospholipid Cell Membrane Activity Both inside and outside the cell contain water, so how do you think phospholipids are arranged to make a cell membrane? Keep in mind that phospholipids contain hydrophilic heads and hydrophobic tails.
+ Cell Membrane Structure Phospholipids form a double layer called a Phospholipid Bilayer with the phosphate groups on the outside and the fatty acid tails in the middle This happens because there is water inside and outside of the cell, so the water loving phosphate end is always by the water
+ Structure Determines Function The cell membrane structure helps it regulate what can and cannot pass through the phospholipid bilayer
+ Selectively Permeable The cell membrane is selectively permeable, meaning that not everything can go across it. Only certain things can get into the cell and only certain things can leave the cell
+ What can pass through the membrane? This allows only small, nonpolar substances to pass directly through the phospholipid bilayer All other substances are repelled by the nonpolar fatty acids, so they cannot go directly through the phospholipid bilayer
+ Other Ways to Pass Through the Phospholipid Bilayer The cell needs to let other things in and out of the cell so it uses membrane proteins to allow specific substances across the membrane at specific times Membrane proteins can be found on top of or within the phospholipid bilayer http://www.youtube.com/watch?v=LKN5sq5d tW4
+ Receptor Proteins Found on the outside of your cells Enable a cell to sense its surroundings by binding substances outside the cell Allows the cell to react to its surroundings
+ Cell-Surface Proteins Similar to a nametag Protein attached to a chain of carbohydrates attached to the cell membrane used to identify each type of cell
+ Transport Proteins Allows certain necessary substances that cannot pass through the cell membrane into and out of the cell
+ Transport Proteins Channel Proteins: Serve as a tunnel through the lipid bilayer that allow SPECIFIC ions, sugars, and amino acids to pass through the membrane Ex: The channel for sodium ions does not allow sugars to pass through
+ Transport Proteins Carrier Proteins: Only transport substances that fit within their binding site through the cell membrane Carrier protein binds to a specific substance on one side of the cell membrane, changes shape and allows the substance out on the other side of the cell membrane
+ Daily Activities Day 1 – Egg Lab Begin Cell Membrane Model Homework: Cell Membrane Labeling Worksheet
+ February 7, 2014 Objectives: To differentiate between osmosis and diffusion To describe how molecules can move down a concentration gradient Journal: What do you think the following words mean? Equal Concentration Diffuse If the Monksville dam broke, what would happen to the water in the Monksville Reservoir?
+ Passive Transport Vocabulary Equilibrium: when there is an equal number of molecules on both sides of the cell membrane Concentration: the amount of a particular substance in a given volume Concentration Gradient: When there is a higher concentration of a substance on one side than the other Diffusion: When a substance moves from an area of higher concentration to an area of lower concentration
+ Types of Transport Passive Transport: does not require energy to move substances across the cell membrane Active Transport: requires energy to move substances across the cell membrane
+ Passive Transport When substances enter or leave the cell by diffusing across the cell membrane down their concentration gradient The direction the substances move depends on the concentration gradient
+ Types of Passive Transport Simple Diffusion Facilitated Diffusion Osmosis
+ Simple Diffusion When small, nonpolar (uncharged) substances pass directly through the phospholipid bilayer from an area of higher concentration to an area of lower concentration Ex: If there is more oxygen outside the cell than inside the cell, it will diffuse across the lipid bilayer and into the cell.
+ Facilitated Diffusion Substances that cannot pass directly through the membrane are helped to diffuse through the membrane using transport proteins
+ Osmosis Facilitated diffusion of water from an area of higher concentration to an area of lower concentration Allows the cell to maintain water balance as their environment changes
+ Water Channels Since water is a polar substance, it does not directly diffuse across the cell membrane So the cell has specific protein channels that only allow water to pass through called aquaporins
+ Predicting Water Movement The direction the water moves depends on the concentration of the cell’s environment
+ Hypertonic Water moves out of the cell There is more solute outside the cell than inside the cell The cell loses water and shrinks
+ Hypotonic Water moves in There is more solute inside the cell than outside the cell Cell gains water and expands
+ Isotonic There is the same concentration of water inside the cell and outside the cell Equilibrium is reached Cell stays the same size
+ Daily Activities Egg Lab Day 2 – Place eggs in various solutions Finish Cell Membrane Model
+ February 11, 2014 Objectives: To differentiate active transport from active transport To describe how active transport moves molecules Journal: How is active different than passive?
+ Active Transport Transport of substances against their concentration gradients Requires energy usually in the form of ATP
+ Use of Carrier Proteins as Pumps Carrier proteins require energy to pump substances across their concentration gradient
+ Sodium-Potassium Pump Sodium ions inside the cell bind to the carrier protein which changes shape and releases sodium ions outside the cell membrane As a result a phosphate group is released from the pump, returning the channel protein to its original shape, and releasing potassium ions inside the cell For every three sodium ions pumped out, two potassium ions are brought inside This prevents sodium from building up inside the cell, which would cause the cell to burst due to osmosis bringing in too much water
+ Vesicles Large substances are too big to cross the membrane in channel proteins so they use vesicles Vesicle membranes are lipid bilayer, so they can bud off from the cell membrane or fuse with it to move large substances in or out of the cell
+ Endocytosis The movement of large substances into a cell using a vesicle The cell membrane forms a pouch around the substance that closes and then pinches off inside the cell Pinocytosis: also known as cellular drinking, engulfing liquid particles Phagocytosis: engulfing solid particles
+ Exocytosis The movement of large substances out of a cell using a vesicle Vesicles inside the cell fuse with the cell membrane and are released outside the cell Used to transport proteins modified by the Golgi apparatus, excrete wastes, or remove bacteria