The Plasma Membrane - Gateway to the Cell 11/19/2018 The Plasma Membrane - Gateway to the Cell G. Podgorski, Biol. 1010

Cell Membrane Helps Maintain Homeostasis The Plasma Membrane 11/19/2018 Cell Membrane Helps Maintain Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by cell membrane controlling what enters & leaves the cell G. Podgorski, Biol. 1010

Semipermeable Membrane The Plasma Membrane Semipermeable Membrane 11/19/2018 Ions, molecules larger than water like glucose, and large molecules such as proteins do not move through the membrane on their own. Small molecules (O2, CO2, H2O) move through easily (diffusion/osmosis) G. Podgorski, Biol. 1010

Functions of Plasma Membrane The Plasma Membrane 11/19/2018 Functions of Plasma Membrane Protective barrier Regulate transport in & out of cell (selectively permeable) Allow cell recognition Receptor proteins function in cell communication Contains the cytoplasm (fluid in cell) Provide a binding site for enzymes G. Podgorski, Biol. 1010

Structure of the Cell Membrane The Plasma Membrane 11/19/2018 Structure of the Cell Membrane G. Podgorski, Biol. 1010

Phospholipids Make up the cell membrane The Plasma Membrane 11/19/2018 Phospholipids Make up the cell membrane 2 lipid chains are nonpolar hydrophobic Phosphate Head is polar hydrophilic G. Podgorski, Biol. 1010

The Plasma Membrane 11/19/2018 FLUID MOSAIC MODEL FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above. G. Podgorski, Biol. 1010

Types of Transport Across Cell Membranes The Plasma Membrane 11/19/2018 Types of Transport Across Cell Membranes G. Podgorski, Biol. 1010

Experiment Put cornstarch & water baggie into large beaker containing water and iodine NOTE: When Iodine mixes with starch it turns purple Measure life saver. Width and height write measurement on note sheet Place lifesaver into small beaker of water

Simple Diffusion Molecules move from area of HIGH to LOW concentration The Plasma Membrane 11/19/2018 Simple Diffusion Molecules move from area of HIGH to LOW concentration Fill a plastic baggie with 1 teaspoon of corn starch and 30 ml water. Fill a 200 ml beaker halfway with water ad add 40 drops of iodine G. Podgorski, Biol. 1010

DIFFUSION Diffusion is a PASSIVE process Trying to reach EQUILIBRIUM The Plasma Membrane 11/19/2018 DIFFUSION Diffusion is a PASSIVE process no energy is used to make the molecules move. Trying to reach EQUILIBRIUM Same amount of particles inside as outside G. Podgorski, Biol. 1010

Diffusion through a Membrane The Plasma Membrane 11/19/2018 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW) G. Podgorski, Biol. 1010

Two types of diffusion Facilitated Diffusion Simple Diffusion The Plasma Membrane 11/19/2018 Two types of diffusion Facilitated Diffusion Simple Diffusion G. Podgorski, Biol. 1010

Doesn’t require energy Moves high to low concentration The Plasma Membrane 11/19/2018 Simple Diffusion Doesn’t require energy Moves high to low concentration Example: Oxygen diffusing into a cell and carbon dioxide diffusing out. G. Podgorski, Biol. 1010

Facilitated diffusion The Plasma Membrane 11/19/2018 Facilitated diffusion Doesn’t require energy Uses channel proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell. G. Podgorski, Biol. 1010

Write a Hypothesis Create a data table Starting color Ending color Beaker Baggie Based on your observation which substance moved? How did you determine this? Did this process require energy?

Diffusion across a membrane Semipermeable membrane Osmosis The Plasma Membrane 11/19/2018 Diffusion across a membrane Diffusion of water across a membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute) Semipermeable membrane Measure the diameter and the height of the gummy lifesaver. Fill a 100ml beaker half filled with water and place the gummy lifesaver in the beaker. G. Podgorski, Biol. 1010

Osmosis H2O Across A Membrane The Plasma Membrane 11/19/2018 Osmosis H2O Across A Membrane High H2O potential Low solute concentration Low H2O potential High solute concentration G. Podgorski, Biol. 1010

Cell in Isotonic Solution Equal salt inside and outside the cell The Plasma Membrane 11/19/2018 Cell in Isotonic Solution Equal salt inside and outside the cell 10% NaCL 90% H2O ENVIRONMENT CELL NO NET MOVEMENT 10% NaCL 90% H2O What is the direction of water movement? equilibrium The cell is at _______________. G. Podgorski, Biol. 1010

The Plasma Membrane 11/19/2018 Cell in Hypotonic Solution Less salt outside the cell than inside the cell 10% NaCL 90% H2O CELL 60% NaCL 40% H2O What is the direction of water movement? G. Podgorski, Biol. 1010

The Plasma Membrane 11/19/2018 Cell in Hypertonic Solution more salt outside the cell than inside the cell 20% NaCL 80% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? G. Podgorski, Biol. 1010

NO NET MOVEMENT OF H2O (equal amounts entering & leaving) The Plasma Membrane 11/19/2018 Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) CYTOLYSIS PLASMOLYSIS G. Podgorski, Biol. 1010

Osmosis in Red Blood Cells The Plasma Membrane 11/19/2018 Osmosis in Red Blood Cells Hypotonic Cytolysis Hypertonic Plasmolysis Isotonic Equilibrium G. Podgorski, Biol. 1010

Write a Hypothesis Create a data table Before water After water Diameter Describe what happened to the diameter of your lifesaver? Describe what happened to the texture of the life saver after soaking? Is the water in the beaker hypertonic, hypotonic, or isotonic?

ACTIVE TRANSPORT The Plasma Membrane 11/19/2018 G. Podgorski, Biol. 1010

Active Transport Requires energy or ATP The Plasma Membrane 11/19/2018 Active Transport Requires energy or ATP Moves materials from Low to High concentration EXAMPLE: Sodium/Potassium pump Pumping Na+ out & K+ in against strong concentration gradients. G. Podgorski, Biol. 1010

The Plasma Membrane 11/19/2018 Transport Proteins Some carrier proteins change shape to move materials across the cell membrane G. Podgorski, Biol. 1010

Materials: Plastic grocery bag, a piece of string, a pair of scissors and two small pieces of candy. The grocery bag represents the cell membrane. Pretend the membrane is completely sealed. Problem: Get the candy into the bag without using the opening of the bag

Moving the “Big Stuff” Exocytosis - moving things out. The Plasma Membrane 11/19/2018 Moving the “Big Stuff” Exocytosis - moving things out. Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. This is how many hormones are secreted. G. Podgorski, Biol. 1010

The Plasma Membrane 11/19/2018 Exocytosis Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Outside the Cell G. Podgorski, Biol. 1010

Intake particles suspended in water The Plasma Membrane 11/19/2018 Moving the “Big Stuff” Large molecules move materials into the cell by one of two forms of endocytosis. Phagocytosis Pinocytosis Intake particles suspended in water Intake solid material G. Podgorski, Biol. 1010

The Plasma Membrane 11/19/2018 G. Podgorski, Biol. 1010