Cell Membrane - Concepts of Biology PDF

CONCEPTS OF BIOLOGY Chapter 3 CELL STRUCTURE AND FUNCTION PowerPoint Image Slideshow This work is licensed under cc by 4.0 license. Credit: OpenStax: modified by M. F. Sega &...

CONCEPTS OF BIOLOGY Chapter 3 CELL STRUCTURE AND FUNCTION PowerPoint Image Slideshow This work is licensed under cc by 4.0 license. Credit: OpenStax: modified by M. F. Sega & J. Wedincamp for ALG 18 grant through addition of ppt slides with texts made using Openstax textbook information. PLASMA MEMBRANE Components: Lipids Double layer of phospholipids and cholesterol & other lipids Proteins Carbohydrates Attached to either lipids or proteins Function Allows selective passage in & out the cell FIGURE 3.8 – PLASMA MEMBRANE The plasma membrane is a phospholipid bilayer with embedded proteins. There are other components, such as cholesterol and carbohydrates, which can be found in the membrane in addition to phospholipids and protein. This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. CYTOSKELETON It is composed of proteins and assembled into 3 different types: Microtubules – made of tubulin proteins helps with: transporting vesicles/organelles within the cell, mitotic spindle (in cell division), movement of cells (see flagellum, cilia) Intermediate filaments – helps with the shape of the cells Example: Keratin Microfilaments – made of actin proteins helps with: movement of cells (see pseudopods), contraction in the muscle cells, Cleavage furrow during Cell division FIGURE 3.17 There are four kinds of connections between cells. (a) A plasmodesma is a channel between the cell walls of two adjacent plant cells. (b) Tight junctions join adjacent animal cells. (c) Desmosomes join two animal cells together. (d) Gap junctions act as channels between animal cells. (credit b, c, d: modification of work by Mariana Ruiz Villareal) This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. PLASMA MEMBRANE Components: Lipids Proteins Glycoproteins Fluid Mosaic model – explains the organization of the membrane components as: a “mosaic” of many types of molecules (see above) that are in constant movement (making the membrane look like a fluid) FIGURE 3.18 The fluid mosaic model of the plasma membrane structure describes the plasma membrane as a fluid combination of phospholipids, cholesterol, proteins, and carbohydrates. This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. PLASMA MEMBRANE FUNCTIONS It is a boundary of the cell with many functions: Selective permeability – allow some substances in and out the cell Immunity – distinguish between “self” and “non-self” Blood transfusion Organ transplant Viral/ bacterial infection Change in shape – immune cells squeeze between the blood vessels’ cells and go to the pathogen location (skin etc.) FIGURE 3.19 HIV docks at and binds to the CD4 receptor, a glycoprotein on the surface of T cells, before entering, or infecting, the cell. (credit: modification of work by US National Institutes of Health/National Institute of Allergy and Infectious Diseases) This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. MEMBRANE TRANSPORT Membrane transport types: Passive Doesn’t use energy Molecules are moving from high concentration to low Active Requires energy Molecules are moving from low concentration to high Done with the help of proteins called pumps PASSIVE TRANSPORT Types of passive transport: Diffusion – transport of substances (or solute when in solution) Osmosis or Diffusion of water – transport of solvent molecules (water) Facilitated diffusion – transport of solute with help from membrane proteins: Channels Transporters Solution = solvent + solutes FIGURE 3.20 – DIFFUSION Diffusion through a permeable membrane follows the concentration gradient of a substance, moving the substance from an area of high concentration to one of low concentration. (credit: modification of work by Mariana Ruiz Villarreal) This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. OSMOSIS Osmosis is the diffusion of water molecules (solvent) until the concentration of the solute is equal on both sides of the membrane. Direction of water flow is: - From higher concentration of free water molecules to low - Or from low concentration of solute molecules to high FIGURE 3.21 – OSMOSIS In osmosis, water always moves from an area of higher concentration (of water) to one of lower concentration (of water). In this system, the solute cannot pass through the selectively permeable membrane. This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. OSMOSIS Solutions with higher concentrations of solute are called hypertonic Solutions with lower concentrations of solute are called hypotonic Solutions with the equal concentrations of solute are called isotonic What is the direction of H2O flow (in terms of tonicity of solutions)? In the previous slide (fig 3.21) identify which solutions are hyper- hypo- or isotonic: Left Beaker left side Right side Right beaker Left side Right side FIGURE 3.22 – OSMOSIS & ANIMAL CELLS Osmotic pressure changes the shape of red blood cells in hypertonic, isotonic, and hypotonic solutions. (credit: modification of work by Mariana Ruiz Villarreal) This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. FIGURE 3.23 – OSMOSIS & PLANT CELLS The turgor pressure within a plant cell depends on the tonicity of the solution that it is bathed in. (credit: modification of work by Mariana Ruiz Villarreal) This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. ACTIVE TRANSPORT Moving molecules Against their concentration gradient; can be done only using energy (ATP). Proteins in the membrane called pumps can use ATP to push chemicals from low concentration to high concentration. Example: NA/K-pump FIGURE 3.24 Electrochemical gradients arise from the combined effects of concentration gradients and electrical gradients. (credit: modification of work by “Synaptitude”/Wikimedia Commons) This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. FIGURE 3.25 – ACTIVE TRANSPORT The sodium-potassium pump move potassium and sodium ions across the plasma membrane. (credit: modification of work by Mariana Ruiz Villarreal) This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources. BULK TRANSPORT Moving big particles, fragments of cells, is called bulk transport. Endocytosis – bringing them into the cells Phagocytosis – when big molecules/particles are brought inside Pinocytosis – when large amount of liquid in brought in Receptor-mediated endocytosis – when only specific molecules enter the cell (the ones that matches with the receptors in the membrane, see fig. 3.26). Exocytosis – taking them out the cell FIGURE 3.26 – ENDOCYTOSIS Three variations of endocytosis are shown. (a) In one form of endocytosis, phagocytosis, the cell membrane surrounds the particle and pinches off to form an intracellular vacuole. (b) In another type of endocytosis, pinocytosis, the cell membrane surrounds a small volume of fluid and pinches off, forming a vesicle. (c) In receptor-mediated endocytosis, uptake of substances by the cell is targeted to a single type of substance that binds at the receptor on the external cell membrane. (credit: modification of work by Mariana Ruiz Villarreal) This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources.  EXOCYTOSIS - FIGURE 3.27 In exocytosis, a vesicle migrates to the plasma membrane, binds, and releases its contents to the outside of the cell. (credit: modification of work by Mariana Ruiz Villarreal) This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted. Any images credited to other sources are similarly available for reproduction, but must be attributed to their sources.