The Cell Membrane - Gateway to the Cell The Plasma Membrane 3/25/2017 G. Podgorski, Biol. 1010

Functions of Cell Membrane The Plasma Membrane 3/25/2017 Functions of Cell Membrane Protective barrier Regulate transport in & out of cell (selectively permeable) Allow cell recognition Provide anchoring sites for filaments of cytoskeleton G. Podgorski, Biol. 1010

Homeostasis Balanced internal condition of cells The Plasma Membrane 3/25/2017 Homeostasis Balanced internal condition of cells Also called equilibrium Maintained by cell membrane controlling what enters & leaves the cell G. Podgorski, Biol. 1010

Structure of the Cell Membrane The Plasma Membrane 3/25/2017 Structure of the Cell Membrane G. Podgorski, Biol. 1010

Cell Membrane Hydrophobic molecules pass easily; hydrophilic DO NOT The Plasma Membrane 3/25/2017 Polar heads are hydrophilic “water loving” Nonpolar tails are hydrophobic “water fearing” Makes membrane “Selective” in what crosses Hydrophobic molecules pass easily; hydrophilic DO NOT G. Podgorski, Biol. 1010

Types of Transport Across Cell Membranes The Plasma Membrane 3/25/2017 Types of Transport Across Cell Membranes G. Podgorski, Biol. 1010

2 types of Transport Does not require energy. Active Transport Passive Transport Does not require energy. Move particles from an area of high concentration to an area of low concentration Examples: osmosis and diffusion Requires Energy Moves particles from an area of low concentration to an area of high concentration Examples:endocytosis and exocytosis

The Plasma Membrane 3/25/2017 Diffusion Movement of particles from an area of high concentration to an area of low concentration G. Podgorski, Biol. 1010

Diffusion through a Membrane The Plasma Membrane 3/25/2017 Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW) G. Podgorski, Biol. 1010

Facilitated Diffusion The Plasma Membrane 3/25/2017 Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins. copyright cmassengale G. Podgorski, Biol. 1010

Diffusion across a membrane Semipermeable membrane The Plasma Membrane 3/25/2017 Osmosis Diffusion across a membrane Diffusion of water across a membrane Moves from HIGH water potential to LOW water potential Semipermeable membrane G. Podgorski, Biol. 1010

Active Transport Examples Exocytosis- moving large things out Endocytosis- Moving large things in Pinocytosis- Drinking of the cell Phagocytosis- Eating of the cell

The Plasma Membrane 3/25/2017 Pinocytosis -Takes in dissolved molecules as a vesicle. “Cell Drinking” G. Podgorski, Biol. 1010

Endocytosis – Phagocytosis The Plasma Membrane 3/25/2017 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 3/25/2017 G. Podgorski, Biol. 1010

The Plasma Membrane 3/25/2017 Phagocytosis - Capture of a Yeast Cell by Membrane Extensions of an Immune System Cell G. Podgorski, Biol. 1010

The Plasma Membrane 3/25/2017 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

Exocytosis- moving things out. The Plasma Membrane Moving the “Big Stuff” 3/25/2017 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

Isotonic Solution- concentration inside and outside are equal The Plasma Membrane 3/25/2017 Isotonic Solution- concentration inside and outside are equal 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 3/25/2017 Hypotonic Solution- concentration of solution is lower than concentration of cell 10% NaCL 90% H2O CELL 20% NaCL 80% H2O What is the direction of water movement? G. Podgorski, Biol. 1010

The Plasma Membrane 3/25/2017 Hypertonic Solution- concentration of solution is higher than concentration of cell 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 3/25/2017 G. Podgorski, Biol. 1010

NO NET MOVEMENT OF H2O (equal amounts entering & leaving) The Plasma Membrane 3/25/2017 Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) G. Podgorski, Biol. 1010

Osmosis in Red Blood Cells The Plasma Membrane 3/25/2017 Osmosis in Red Blood Cells Isotonic Hypertonic Hypotonic G. Podgorski, Biol. 1010

isotonic hypotonic hypertonic hypertonic isotonic hypotonic The Plasma Membrane 3/25/2017 isotonic hypotonic hypertonic hypertonic isotonic hypotonic G. Podgorski, Biol. 1010

Transport Across the Membrane The Plasma Membrane Transport Across the Membrane 3/25/2017 G. Podgorski, Biol. 1010

Facilitated diffusion The Plasma Membrane 3/25/2017 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

Active Transport Requires energy or ATP The Plasma Membrane 3/25/2017 Active Transport Requires energy or ATP Moves materials from LOW to HIGH concentration AGAINST concentration gradient G. Podgorski, Biol. 1010