BIOS 3500 Lecture 2: The Plasma Membrane PDF

BIOS 3500 Lecture 2 The Plasma Membrane Book Chapter 3 Objectives Last lecture – Course syllabus and Introduction to Physiology. Today’s lecture - Plasma membrane structure and function. Readings: Pages 57-79  The Plasma Membrane Description Functions Functions of...

BIOS 3500 Lecture 2 The Plasma Membrane Book Chapter 3 Objectives Last lecture – Course syllabus and Introduction to Physiology. Today’s lecture - Plasma membrane structure and function. Readings: Pages 57-79  The Plasma Membrane Description Functions Functions of the Plasma Membrane Serves as a mechanical barrier Is selective and only allows specific substances across the membrane Maintains differences in ion concentrations between the interior and exterior sides of the membrane Plays a key role in the ability of the cell to respond to changes in the cell’s environment  Components of Plasma Membrane Lipid Bilayer Proteins Cholesterol Carbohydrates  Characteristics of the Lipid bilayer in Plasma Membrane Phospholipids Hydrophilic/ Hydrophobic Fluidity Fluid mosaic model Fluid Mosaic Model of the Plasma Membrane CAM Proteins found in the plasma membrane Channels Carrier Molecules Receptors Docking Marker Acceptors Membrane Bound Enzymes CAM (cell adhesion molecules) CAM Leak Channels Three types of protein channels that open and close Voltage-gated channels Agonist-gated channels Mechanically-gated channels Agonist-gated channel: Also known as: Ligand-gated channel Neurotransmitter- gated channel Chemically-gated channel Image showing docking markers and receptors Carrier molecules Cell adhesion molecules holding cells together Fluid Mosaic Model of the Plasma Membrane  Organization of cells into groups are at least partially due to the carbohydrate chains on the membrane surface. Once arranged into groups, cells are held together by: Cell adhesion molecules Extracellular matrix - 3 types of proteins (collagen, elastin, fibronectin) - function Specialized cell junctions - 3 types (desmosomes, tight junctions, gap junctions)  Membrane Transport Properties Forces Passive Active  4 Passive Forces Diffusion down concentration gradient Electrical gradient Osmosis Facilitated diffusion  Fick's law of diffusion Magnitude of concentration gradient Permeability of membrane to substance Surface area of membrane Molecular weight of substance Distance through which diffusion must take place Movement of particles is also dependent on their electrical charge Osmosis  What does this potential water movement mean for a cell??? Cells usually don’t experience any net gain or shrinkage of volume because the concentration on nonpenetrating solutes in the ECF is very carefully regulated by the kidneys Tonicity (the osmotic effect that a solution. has on the volume of a cell)  Facilitated Diffusion Carrier-mediated transport No ATP is needed to move molecules across the membrane Movement will always be from a high concentration to a low concentration Transport of glucose (example) Facilitated Diffusion  Active Transport ATP is needed Primary and Secondary Active Transport  Oxidative Phosphorylation 2 ATPs are generated as a result of Kreb’s cycle in the matrix of the mitochondria FADH and NADH2 resulting from the Kreb’s cycle enter the electron transport chain in the mitochondria cristae to create another 32 molecules of ATP A total of 36 molecules of ATP from each glucose molecule 2 from glycolysis 2 from Kreb’s cycle 32 from electron transport chain  Active Transport Na/K ATPase Pump Primary Active Transport: establishes sodium concentration from lumen to cell Secondary Active Transport: maintains sodium concentration gradient to allow simultaneous movement of sodium and glucose from lumen to cell Facilitated Diffusion: Glucose moves passively out of cell into blood  Vesicular Transport Endocytosis Exocytosis Extracellular fluid Intracellular fluid