Ch03 Student Part 1 PDF

CHAPTER 3 THE CELLULAR LEVEL OF ORGANIZATION Dr. Jody Ralph NURS 1210 Learning Objectives- Part 1 Name and describe the main parts of a cell. Describe the structure and functions of the plasma membrane. Describe the processes that transport substances acros...

CHAPTER 3 THE CELLULAR LEVEL OF ORGANIZATION Dr. Jody Ralph NURS 1210 Learning Objectives- Part 1 Name and describe the main parts of a cell. Describe the structure and functions of the plasma membrane. Describe the processes that transport substances across the plasma membrane. Compare and contrast mitosis and meiosis. Understand the effects aging has on the cell. Cells Basic, living, structural, and functional units of the body Average adult 100 trillion cells A generalized view of the cell is a composite of many different cells in the body. No single cell includes all of the features seen in the generalized cell. PARTS OF A CELL Structures of a Cell Cell Anatomy Link Parts of a Cell The cell can be subdivided into 3 parts: Plasma (cell) membrane Cytoplasm  Cytosol  Organelles Nucleus  Chromosomes  Genes In what part of a cell would you find most of the intracellular fluid? a) Plasma membrane b) Cytoplasm c) Nucleus d) Mitochondrion e) Centrosome In what part of a cell would you find chromosomes? a) Plasma membrane b) Cytoplasm c) Nucleus d) Microtubules e) Centrosome THE PLASMA MEMBRANE The Plasma Membrane The plasma membrane is a flexible yet sturdy barrier that surrounds and contains the cytoplasm of the cell Membrane Anatomy Link The Plasma Membrane The fluid mosaic model describes the plasma membrane structure. The membrane consists of proteins in a sea of lipids. The lipid bilayer is the basic framework of the plasma membrane and is made up of three types of lipid molecules: phospholipids, cholesterol, and glycolipids. The Lipid Bilayer The bilayer arrangement occurs because the lipids are amphipathic molecules.  They have both polar (charged) and nonpolar (uncharged) parts with the polar “head” of the phospholipid pointing out and the nonpolar “tail” pointing toward the center of the membrane. Nonpolar tails Polar heads Functions of Plasma Membrane Barrier separating inside and outside of the cell Controls substances into and out of the cell Identify the cell to other cells (e.g., immune cells). Participates in intercellular signaling Membrane Proteins Two types of membrane proteins are 1. Integral (also called transmembrane) proteins 2. Peripheral proteins Membrane Proteins Integral proteins extend into or across (transmembrane) the entire lipid bilayer among the fatty acid tails of the phospholipid molecules. Peripheral proteins are found at the inner or outer surface of the membrane and can be stripped away from the membrane without disturbing membrane integrity. Membrane Proteins Integral membrane proteins are amphipathic.  Transmembrane proteins: stretch across the entire bilayer and project on both sides of the membrane.  Many integral proteins are glycoproteins. Glycocalyx: formed by the carbohydrate portions of glycolipids and glycoproteins The combined glycoproteins and glycolipids form the glycocalyx which helps cells recognize one another, adhere to one another, and be protected from digestion by enzymes in the extracellular fluid. Functions of Membrane Proteins Membrane proteins can serve a variety of functions as ion channels, carriers (transporters), receptors, enzymes, linkers, and cell-identity markers The different proteins help determine many of the functions of the cell membrane Functions of Membrane Proteins Membrane Fluidity Membranes are fluid structures because most of the membrane lipids and many of the membrane proteins move easily in the bilayer  Membrane lipids and proteins are mobile in their own half of the bilayer Cholesterol serves to stabilize the membrane and reduce membrane fluidity Membrane Permeability Plasma membranes are selectively permeable  The lipid bilayer is always permeable to small, nonpolar, uncharged molecules  The observed permeability to water is the result of aquaporin channels or proteins imbedded within the plasma membrane that are selective for water molecules  Transmembrane proteins that act as channels or transporters increase the permeability of the membrane  Macromolecules are only able to pass through the plasma membrane by vesicular transport Gradients Across the Plasma Membrane A concentration gradient is the difference in the concentration of a chemical between one side of the plasma membrane and the other  Oxygen and sodium ions are more concentrated outside the cell membrane with carbon dioxide and potassium ions more concentrated inside the cell membrane. Gradients Across the Plasma Membrane The inner surface of the membrane is more negatively charged and the outer surface is more positively charged. This sets up an electrical gradient, also called the membrane potential. Maintaining the concentration and electrical gradients are important to the life of the cell. The combined concentration and electrical gradients are called the electrochemical gradient. Which membrane proteins are involved with the transport of molecules that otherwise would be unable to enter the cell? a) linker proteins b) glycoproteins c) carrier proteins d) peripheral proteins e) receptor proteins Which of the following best describes the basic structure of the plasma membrane of a cell? a) lipid bilayer b) glycocalyx c) phospholipids d) glycoproteins Which of the labeled structures in the image is an example of a peripheral protein? a) structure A b) structure B c) structure C d) structure D e) structure E Which of the labeled structures in the image are examples of integral, transmembrane proteins? a) structures A and B b) structures A and C c) structures B and C d) structures C and D e) structures D and E TRANSPORT ACROSS THE PLASMA MEMBRANE Transport Across the Cell Membrane Processes to move substances across the cell membrane are essential to the life of the cell. Some substances cross the lipid bilayer while others cross through ion channels. Transport processes that move substances across the cell membrane are either active or passive.  Passive processes are driven by concentration gradients  Active processes require cellular energy Transport Across the Plasma Membrane Passive processes  Simple diffusion  Facilitated diffusion  Osmosis Active processes  Primary and Secondary transport  Vesicular transport Transport Across the Plasma Membrane Passive Transport: Diffusion Diffusion is the random mixing of particles that occurs in a solution as a result of the kinetic energy of the particles. Passive Transport: Simple Diffusion Nonpolar, hydrophobic molecules such as respiratory gases, some lipids, small alcohols, and ammonia can diffuse across the lipid bilayer without the help of transport proteins It is important for gas exchange, absorption of some nutrients, and excretion of some wastes. Passive Transport: Facilitated Diffusion Transmembrane proteins help solutes that are too polar or too highly charged move through the lipid bilayer An integral membrane protein assists a specific substance across the membrane.  The integral membrane protein can be either a membrane channel or a carrier. Facilitated Diffusion Channel-mediated facilitated diffusion: a solute moves down its concentration gradient across the lipid bilayer through a membrane channel.  Most membrane channels are ion channels  Some membrane channels are gated Passive Transport: Channel- Mediated Facilitated Diffusion Facilitated Diffusion Carrier-mediated facilitated diffusion: a solute binds to a specific transporter on one side of the membrane and is released on the other side after the transporter undergoes a conformational change.  Substances that move across the plasma membrane by carrier-mediated facilitated diffusion include glucose, fructose, galactose, and some vitamins Passive Transport: Carrier-Mediated Facilitated Diffusion Diffusion: A Comparison Passive Transport: Osmosis The net movement of a solvent through a selectively permeable membrane from an area of high concentration to an area of low concentration Passive Transport: Osmosis Water molecules penetrate the membrane by diffusion through the lipid bilayer or through aquaporins, transmembrane proteins that function as water channels. Water moves from an area of lower solute concentration to an area of higher solute concentration. Movement of water can generate hydrostatic pressure. Osmosis occurs only when the membrane is permeable to water but not to certain solutes. The primary difference between simple and facilitated diffusion is that facilitated diffusion requires a membrane protein to act as a channel or carrier for a substance while simple diffusion means substances can slip through the lipid bilayer without a channel or carrier. a) True b) False In the passive processes of simple diffusion and osmosis, substances and water move down their concentration gradients, moving from areas of higher concentrations to areas of lower concentrations. a) True b) False Gases such as oxygen and carbon dioxide can pass through a plasma membrane by simple diffusion, because they are uncharged, nonpolar molecules. a) True b) False Tonicity Tonicity of a solution relates to how the solution influences the shape of body cells There are important medical uses of isotonic, hypotonic, and hypertonic solutions. Tonicity Isotonic: Same concentration of particles as the intracellular fluid or extracellular fluid e.g. 0.9% NaCl Hypertonic: Concentration is greater than body fluids e.g. 3% NaCl Hypotonic: Lower concentration; more dilute than body fluids e.g. 0.45% NaCl END OF PART 1