Learning Objectives Students will be able to: Identify three types of passive transport Explain how an equilibrium is established as a result of diffusion. Distinguish between diffusion and osmosis.

copyright cmassengale The Plasma Membrane 9/10/2018 The Plasma Membrane - Gateway to the Cell copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Cell Membrane The cell membrane is flexible and allows a unicellular organism to move copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by plasma (cell) membrane controlling what enters & leaves the cell copyright cmassengale G. Podgorski, Biol. 1010

Functions of Plasma Membrane The Plasma Membrane 9/10/2018 Functions of Plasma Membrane Protective barrier Regulates transport of materials in & out of cell (selectively permeable) Provides anchoring sites for filaments of cytoskeleton copyright cmassengale G. Podgorski, Biol. 1010

Membrane Components Phospholipids Proteins Carbohydrates (glucose) The Plasma Membrane 9/10/2018 Phospholipids Proteins Cholesterol Carbohydrates (glucose) G. Podgorski, Biol. 1010

Cell Membrane Polar heads are hydrophilic “water loving” The Plasma Membrane Cell Membrane 9/10/2018 Polar heads are hydrophilic “water loving” Nonpolar tails are hydrophobic “water fearing” Makes membrane “Selective” in what crosses G. Podgorski, Biol. 1010

The Plasma Membrane Cell Membrane 9/10/2018 The cell membrane is made of 2 layers of phospholipids called the lipid bilayer Hydrophobic molecules pass easily; hydrophilic DO NOT G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Solubility Materials that are soluble in lipids can pass through the cell membrane easily copyright cmassengale G. Podgorski, Biol. 1010

Semipermeable Membrane The Plasma Membrane Semipermeable Membrane 9/10/2018 Small molecules and hydrophobic molecules move through easily. e.g. O2, CO2, Steroid hormones copyright cmassengale G. Podgorski, Biol. 1010

Semipermeable Membrane The Plasma Membrane Semipermeable Membrane 9/10/2018 Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own. G. Podgorski, Biol. 1010

Types of Transport Across Cell Membranes The Plasma Membrane 9/10/2018 Types of Transport Across Cell Membranes copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Simple Diffusion Requires NO energy Molecules move from area of HIGH to LOW concentration copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move. They have a natural KINETIC ENERGY copyright cmassengale G. Podgorski, Biol. 1010

Diffusion through a Membrane The Plasma Membrane 9/10/2018 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW) G. Podgorski, Biol. 1010

Diffusion across a membrane Semipermeable membrane The Plasma Membrane 9/10/2018 Osmosis Diffusion of water across a membrane Movement of water molecules (solute) from an area of LOW solute concentration to an area of HIGH solute concentration. Diffusion across a membrane Semipermeable membrane G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Aquaporins Water Channels Protein pores used during OSMOSIS WATER MOLECULES copyright cmassengale G. Podgorski, Biol. 1010

Cell in Isotonic Solution The Plasma Membrane 9/10/2018 Cell in Isotonic Solution 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 _______________. copyright cmassengale G. Podgorski, Biol. 1010

Cell in Hypotonic Solution The Plasma Membrane 9/10/2018 Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? copyright cmassengale G. Podgorski, Biol. 1010

Cell in Hypertonic Solution The Plasma Membrane 9/10/2018 Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Cells in Solutions copyright cmassengale G. Podgorski, Biol. 1010

NO NET MOVEMENT OF H2O (equal amounts entering & leaving) The Plasma Membrane 9/10/2018 Hypotonic Solution Hypertonic Solution Isotonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) PLASMOLYSIS The contraction of a cell due to loss of water in plants and bacterial cells CYTOLYSIS When cells burst due to water moving into the cell until it bursts G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 https://youtu.be/sdiJtDRJQEc copyright cmassengale G. Podgorski, Biol. 1010

What Happens to Blood Cells? copyright cmassengale

copyright cmassengale The Plasma Membrane 9/10/2018 isotonic hypotonic hypertonic hypertonic isotonic hypotonic copyright cmassengale G. Podgorski, Biol. 1010

Three Forms of Transport Across the Membrane The Plasma Membrane 9/10/2018 G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Passive Transport Simple Diffusion Doesn’t require energy Moves high to low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out. copyright cmassengale G. Podgorski, Biol. 1010

Facilitated diffusion The Plasma Membrane 9/10/2018 Passive Transport Facilitated diffusion Doesn’t require energy Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell. copyright cmassengale G. Podgorski, Biol. 1010

Proteins Are Critical to Membrane Function The Plasma Membrane 9/10/2018 Proteins Are Critical to Membrane Function copyright cmassengale G. Podgorski, Biol. 1010

Types of Transport Proteins The Plasma Membrane 9/10/2018 Types of Transport Proteins Channel proteins are embedded in the cell membrane & have a pore for materials to cross Carrier proteins can change shape to move material from one side of the membrane to the other copyright cmassengale G. Podgorski, Biol. 1010

Facilitated Diffusion The Plasma Membrane 9/10/2018 Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins. copyright cmassengale G. Podgorski, Biol. 1010

Facilitated Diffusion The Plasma Membrane 9/10/2018 Facilitated Diffusion Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer and release them on the opposite side. copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Carrier Proteins Other carrier proteins change shape to move materials across the cell membrane copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+ - K+ Pump copyright cmassengale G. Podgorski, Biol. 1010

Sodium-Potassium Pump The Plasma Membrane 9/10/2018 Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential G. Podgorski, Biol. 1010

Moving the “Big Stuff” Exocytosis- moving things out. The Plasma Membrane Moving the “Big Stuff” 9/10/2018 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 and how nerve cells communicate with one another. copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane Exocytosis 9/10/2018 Exocytic vesicle immediately after fusion with plasma membrane. copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane Moving the “Big Stuff” 9/10/2018 Large molecules move materials into the cell by one of three forms of endocytosis. copyright cmassengale G. Podgorski, Biol. 1010

Pinocytosis Most common form of endocytosis. The Plasma Membrane Pinocytosis 9/10/2018 Most common form of endocytosis. Takes in dissolved molecules as a vesicle. G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Pinocytosis Cell forms an invagination Materials dissolve in water to be brought into cell Called “Cell Drinking” copyright cmassengale G. Podgorski, Biol. 1010

Example of Pinocytosis The Plasma Membrane Example of Pinocytosis 9/10/2018 mature transport vesicle pinocytic vesicles forming Transport across a capillary cell (blue). G. Podgorski, Biol. 1010

Receptor-Mediated Endocytosis The Plasma Membrane 9/10/2018 Receptor-Mediated Endocytosis Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc. G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane Receptor-Mediated Endocytosis 9/10/2018 copyright cmassengale G. Podgorski, Biol. 1010

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Endocytosis – Phagocytosis The Plasma Membrane 9/10/2018 Endocytosis – Phagocytosis Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating” G. Podgorski, Biol. 1010

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copyright cmassengale The Plasma Membrane Phagocytosis About to Occur 9/10/2018 copyright cmassengale G. Podgorski, Biol. 1010

copyright cmassengale The Plasma Membrane 9/10/2018 Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue) copyright cmassengale G. Podgorski, Biol. 1010

The Plasma Membrane 9/10/2018 Exocytosis The opposite of endocytosis is exocytosis. Large molecules that are manufactured in the cell are released through the cell membrane. Inside Cell Cell environment G. Podgorski, Biol. 1010