L2_The Plasma Membrane 4.pdf

Lecture 2: Plasma Membrane Dr. Safa Almaghrabi MBBS, MBiomedSc, PhD Associate Professor in Clinical Physiology Department Email: [email protected] 1  Learning...

Lecture 2: Plasma Membrane Dr. Safa Almaghrabi MBBS, MBiomedSc, PhD Associate Professor in Clinical Physiology Department Email: [email protected] 1  Learning Objectives 1. List the basic cell structures and functions and illustrate examples of each. 2. Describe the structure and composition of the plasma membrane. 3. list plasma membrane’s main functions. 4. Explain how the distribution of phospholipids and proteins influences the membrane permeability of ions, hydrophilic and hydrophobic compounds. 5. Describe the main functions of the carbohydrate components of the plasma membrane. 6. Describe the structure and functions of the protein components of the plasma membrane. Basic Cell Structures & Functions 3  4 Sherwood L, Human Physiology: From Cells to Systems. 9th edition. 2016  Cell Structures Plasma membrane is a fluid lipid bilayer embedded with proteins Cytoplasm - Organelles (the cell’s “little organs”) ✓ Membranous organelle: Endoplasmic reticulum, golgi complex, lysosomes, peroxisomes, and mitochondria ✓ Nonmembranous organelles: Ribosomes, proteasomes, vaults, and centrioles - Cytoskeleton (a scaffolding of proteins) - Cytosol (a complex, gel-like liquid) Nucleus 5  Cell Functions Plasma membrane Its proteins selectively control the movement of molecules between the ICF and ECF. Endoplasmic reticulum It is primarily a protein- and lipid-producing factory. Golgi complex Modifies, packages, and distributes newly synthesized proteins 6  Mitochondria Act as energy organelles; major site of ATP production Cytoskeleton Maintain cell shapes and coordinate complex cell movements, serving as highways for transport of secretory vesicles within cell. Nucleus Serving as a genetic blueprint during cell replication. Directing protein synthesis 7 8 Plasma Membrane Structure 1. Phospholipids & Cholesterol 2. Membrane carbohydrate 3. Membrane proteins  Plasma Membrane Functions Forms the basic structure of the cell and the outer boundary of every cell and encloses the intracellular contents. Determine the cell’s composition by selectively permitting specific substances to pass between the cell and its environment. It maintains differences in ion concentrations inside and outside the cell, which are important in the membrane’s electrical activity. The plasma membrane participates in the joining of cells to form tissues and organs. It plays a key role in enabling a cell to respond to signals from chemical messengers in the cell’s environment.  1. Phospholipid Bilayer Structures & Functions It forms the basic structure of the membrane. Sherwood L, Human Physiology: From Cells to Systems. 9th edition. 2016 Its hydrophobic interior is a barrier to the passage of water-soluble substances between the ICF and ECF. It is responsible for the fluidity of the membrane. Cholesterol contributes to both the fluidity and the stability of the membrane.  2. Membrane Carbohydrate Structures & Functions Serve as self-identity markers that enable cells to identify and interact with one another. Different cell types have different markers. Involves in tissue growth, which is normally held within certain limits of cell density. Cells do not “trespass” across the boundaries of neighboring tissues—that is, they do not overgrow their own territory. 3. Membrane Proteins Structures & Functions http://classconnection.s3.amazonaws.com/410/flashcards/2392410/jpg/picture21354924380156.jpg  Membrane Proteins Structures & Functions 1. Carrier: transfer across the membrane-specific substances that cannot cross on their own. Uniport Symport Antiport Types of Carrier Proteins 2. Channels: some proteins form water-filled pathways, or channels so water-soluble substances can pass through the membrane. Leak channels Gated channels  Types of Protein Channels Leakage channels https://upload.wikimedia.org/wikipedia/commons/9/93/Blausen_0213_CellularDiffusion.png Gated channels Ligand gated Voltage gated 3. Receptors: sites that recognize and bind with specific extracellular chemical messengers 4. Membrane-bound enzymes: that control specific chemical reactions. 5. Cell adhesion molecules (CAM): protrude from the outer membrane surface and form loops or hooks by which cells grip one another or grasp the connective tissue fibers between cells. 6. Docking-marker Acceptors: located on the inner membrane surface, bind lock-and-key fashion with the docking markers of secretory vesicles. 19 Reference Human Physiology: From Cells to Systems, 9th Edition by Lauralee Sherwood.