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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

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February 7, 2014

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february 7 2014
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
Key Terms
  • What do you think are the definitions of the following words?
    • Hydrophobic
    • Hydrophilic
key terms defined
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
  • The structure of the phospholipid molecule generally consists of two hydrophobic tails and a hydrophilic head.
phosphate head
Phosphate Head
  • Hydrophilic
  • Polar (has a charge)
  • Made of phosphate
two fatty acid tails
Two Fatty Acid Tails
  • Hydrophobic
  • Nonpolar (doesn’t have a charge)
  • Made of fatty acids
structure of the cell membrane
Structure of the Cell Membrane
  • Phospholipids make up the cell membrane of cells.
phospholipid cell membrane activity
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
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
Structure Determines Function
  • The cell membrane structure helps it regulate what can and cannot pass through the phospholipid bilayer
selectively permeable
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
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
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=LKN5sq5dtW4
receptor proteins
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
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
Transport Proteins
  • Allows certain necessary substances that cannot pass through the cell membrane into and out of the cell
transport proteins1
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 proteins2
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
Daily Activities
  • Day 1 – Egg Lab
  • Begin Cell Membrane Model
  • Homework:
    • Cell Membrane Labeling Worksheet
february 7 20141
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
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
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
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
Types of Passive Transport
  • Simple Diffusion
  • Facilitated Diffusion
  • Osmosis
simple diffusion
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
Facilitated Diffusion
  • Substances that cannot pass directly through the membrane are helped to diffuse through the membrane using transport proteins
  • 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
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
Predicting Water Movement
  • The direction the water moves depends on the concentration of the cell’s environment
  • Water moves out of the cell
  • There is more solute outside the cell than inside the cell
  • The cell loses water and shrinks
  • Water moves in
  • There is more solute inside the cell than outside the cell
  • Cell gains water and expands
  • There is the same concentration of water inside the cell and outside the cell
  • Equilibrium is reached
  • Cell stays the same size
daily activities1
Daily Activities
  • Egg Lab Day 2 – Place eggs in various solutions
  • Finish Cell Membrane Model
february 11 2014
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
Active Transport
  • Transport of substances against their concentration gradients
  • Requires energy usually in the form of ATP
use of carrier proteins as pumps
Use of Carrier Proteins as Pumps
  • Carrier proteins require energy to pump substances across their concentration gradient
sodium potassium pump
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
  • 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
  • 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
  • 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
daily activities2
Daily Activities
  • Day 3 – Finish Egg Lab