Homeostasis Balanced internal condition of cells The Plasma Membrane 4/19/2017 Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by plasma membrane controlling what enters & leaves the cell G. Podgorski, Biol. 1010

Cell Membrane Hydrophobic molecules pass easily; hydrophilic DO NOT The Plasma Membrane Cell Membrane 4/19/2017 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

The Plasma Membrane 4/19/2017 Solubility Materials that are soluble in lipids can pass through the cell membrane easily G. Podgorski, Biol. 1010

Semipermeable Membrane The Plasma Membrane Semipermeable Membrane 4/19/2017 Small molecules and larger hydrophobic molecules move through easily. e.g. O2, CO2, H2O G. Podgorski, Biol. 1010

Semipermeable Membrane The Plasma Membrane Semipermeable Membrane 4/19/2017 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 4/19/2017 Types of Transport Across Cell Membranes G. Podgorski, Biol. 1010

Simple Diffusion Requires NO energy The Plasma Membrane 4/19/2017 Simple Diffusion Requires NO energy Molecules move from area of HIGH to LOW concentration G. Podgorski, Biol. 1010

The Plasma Membrane 4/19/2017 DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY G. Podgorski, Biol. 1010

Diffusion of Liquids The Plasma Membrane 4/19/2017 G. Podgorski, Biol. 1010

Diffusion through a Membrane The Plasma Membrane 4/19/2017 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 4/19/2017 Osmosis 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 G. Podgorski, Biol. 1010

Diffusion of H2O Across A Membrane The Plasma Membrane 4/19/2017 Diffusion of H2O Across A Membrane High H2O potential Low solute concentration Low H2O potential High solute concentration G. Podgorski, Biol. 1010

Aquaporins Water Channels Protein pores used during OSMOSIS The Plasma Membrane 4/19/2017 Aquaporins Water Channels Protein pores used during OSMOSIS WATER MOLECULES G. Podgorski, Biol. 1010

Cell in Isotonic Solution The Plasma Membrane 4/19/2017 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 _______________. G. Podgorski, Biol. 1010

Cell in Hypotonic Solution The Plasma Membrane 4/19/2017 Cell in Hypotonic Solution 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? G. Podgorski, Biol. 1010

Cell in Hypertonic Solution The Plasma Membrane 4/19/2017 Cell in Hypertonic Solution 15% NaCL 85% H2O ENVIRONMENT CELL 5% NaCL 95% H2O What is the direction of water movement? G. Podgorski, Biol. 1010

Cells in Solutions The Plasma Membrane 4/19/2017 G. Podgorski, Biol. 1010

NO NET MOVEMENT OF H2O (equal amounts entering & leaving) The Plasma Membrane 4/19/2017 Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) CYTOLYSIS PLASMOLYSIS G. Podgorski, Biol. 1010

Cytolysis & Plasmolysis The Plasma Membrane 4/19/2017 Cytolysis & Plasmolysis Cytolysis Plasmolysis G. Podgorski, Biol. 1010

Osmosis in Red Blood Cells The Plasma Membrane 4/19/2017 Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic G. Podgorski, Biol. 1010

isotonic hypotonic hypertonic hypertonic isotonic hypotonic The Plasma Membrane 4/19/2017 isotonic hypotonic hypertonic hypertonic isotonic hypotonic G. Podgorski, Biol. 1010

Three Forms of Transport Across the Membrane The Plasma Membrane Three Forms of Transport Across the Membrane 4/19/2017 G. Podgorski, Biol. 1010

Passive Transport Simple Diffusion Doesn’t require energy The Plasma Membrane 4/19/2017 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. G. Podgorski, Biol. 1010

Facilitated diffusion The Plasma Membrane 4/19/2017 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. G. Podgorski, Biol. 1010

Proteins Are Critical to Membrane Function The Plasma Membrane 4/19/2017 Proteins Are Critical to Membrane Function G. Podgorski, Biol. 1010

Types of Transport Proteins The Plasma Membrane 4/19/2017 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 G. Podgorski, Biol. 1010

Facilitated Diffusion The Plasma Membrane 4/19/2017 Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins. G. Podgorski, Biol. 1010

Facilitated Diffusion The Plasma Membrane 4/19/2017 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. G. Podgorski, Biol. 1010

The Plasma Membrane 4/19/2017 Carrier Proteins Other carrier proteins change shape to move materials across the cell membrane G. Podgorski, Biol. 1010

Active Transport Requires energy or ATP The Plasma Membrane 4/19/2017 Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient G. Podgorski, Biol. 1010

The Plasma Membrane 4/19/2017 Active transport Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. Called Na+-K+ Pump G. Podgorski, Biol. 1010

Sodium-Potassium Pump The Plasma Membrane 4/19/2017 Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential G. Podgorski, Biol. 1010

Exocytosis- moving things out. The Plasma Membrane Moving the “Big Stuff” 4/19/2017 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. G. Podgorski, Biol. 1010

The Plasma Membrane Exocytosis 4/19/2017 Exocytic vesicle immediately after fusion with plasma membrane. G. Podgorski, Biol. 1010

The Plasma Membrane Moving the “Big Stuff” 4/19/2017 Large molecules move materials into the cell by one of three forms of endocytosis. G. Podgorski, Biol. 1010

Pinocytosis Most common form of endocytosis. The Plasma Membrane Pinocytosis 4/19/2017 Most common form of endocytosis. Takes in dissolved molecules as a vesicle. G. Podgorski, Biol. 1010

Pinocytosis Cell forms an invagination The Plasma Membrane 4/19/2017 Pinocytosis Cell forms an invagination Materials dissolve in water to be brought into cell Called “Cell Drinking” G. Podgorski, Biol. 1010

Example of Pinocytosis The Plasma Membrane Example of Pinocytosis 4/19/2017 mature transport vesicle pinocytic vesicles forming Transport across a capillary cell (blue). G. Podgorski, Biol. 1010

Receptor-Mediated Endocytosis The Plasma Membrane 4/19/2017 Receptor-Mediated Endocytosis Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc. G. Podgorski, Biol. 1010

Receptor-Mediated Endocytosis The Plasma Membrane Receptor-Mediated Endocytosis 4/19/2017 G. Podgorski, Biol. 1010

Endocytosis – Phagocytosis The Plasma Membrane 4/19/2017 Endocytosis – Phagocytosis Used to engulf large particles such as food, bacteria, etc. into vesicles Called “Cell Eating” G. Podgorski, Biol. 1010

Phagocytosis About to Occur The Plasma Membrane Phagocytosis About to Occur 4/19/2017 G. Podgorski, Biol. 1010

The Plasma Membrane 4/19/2017 Phagocytosis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue) G. Podgorski, Biol. 1010

The Plasma Membrane 4/19/2017 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

The Plasma Membrane 4/19/2017 G. Podgorski, Biol. 1010