NURS 230 TRW Lec3b Cell Membranes PDF

Topic 3 (pt 2): Cytoplasm, Organelles, Nucleus, Cell Processes http://linoit.com/users/YCarrillo/canvases/Cell%20Project CHAPTER 3 IN TEXT Important Topics and Pages Topic 3: Cells (Chapter 3) (Part 2 is Cellular Organelles and Cellular Processes) 1. Give a brief structural description...

Topic 3 (pt 2): Cytoplasm, Organelles, Nucleus, Cell Processes http://linoit.com/users/YCarrillo/canvases/Cell%20Project CHAPTER 3 IN TEXT Important Topics and Pages Topic 3: Cells (Chapter 3) (Part 2 is Cellular Organelles and Cellular Processes) 1. Give a brief structural description and describe the function of each of the following cellular structures: (summary figure on p 94-96) ◦ Cytoplasm P83 ◦ Mitochondria P83-84 ◦ Ribosome P84 ◦ Endoplasmic reticulum (Smooth and rough) P84-85 ◦ Golgi apparatus P85-86 ◦ Peroxisome P86 ◦ Lysosome P86-87 ◦ Nucleus P91-93 2. What is the cytoskeleton, and what are the major components (microtubules, microfilaments and intermediate filaments)? P88-91 3. Briefly define and describe the processes of apoptosis, autophagy, differentiation, cell aging P109-110  Introduction: Inside the Cell Cytoplasm: Material between plasma membrane and nucleus ◦ Cytosol: solution where cellular material is suspended ◦ Organelles: structures inside the cell, specialized functions ◦ Inclusions: various chemical substances http://faculty.ccbcmd.edu/~gkaiser/ SoftChalk%20BIOL%20230/Prokaryotic %20Cell%20Anatomy/proeu/proeu/ proeu_print.html Cytoplasmic Organelles Membranous ◦ Mitochondria ◦ Endoplasmic reticulum ◦ Golgi apparatus ◦ Peroxisomes Membranes allow ◦ Lysosomes compartmentalizing, independent environment Nonmembranous ◦ Ribosomes ◦ Cytoskeleton ◦ Centrioles Mitochondria Provides energy to cell (ATP) ◦ Aerobic cellular respiration ◦ Complex process using glucose + Oxygen ◦ Which process have we looked at requires ATP? Double membranes with cristae ◦ Increase surface area ◦ Inner membrane: proteins, outer: Smooth Matrix: inner section Figure 3.14  Mitochondria Contain own DNA, RNA Resemble bacterial cell http://www.newcastle-mitochondria.com/ patient-and-public-home-page/what-is- Possible evolutionary mitochondrial-dna/ symbiosis A bacterial cell Fission: Able to multiply with increased energy requirements © 2016 PEARSON EDUCATION, INC. Ribosomes Nonmembranous organelles Site of protein synthesis Protein and ribosomal RNA (rRNA) © 2016 PEARSON EDUCATION, INC.  Ribosomes Two switchable forms found in cell: ◦ Free ribosomes: site of synthesis of soluble proteins ◦ Membrane-bound ribosomes: attached to endoplasmic reticulum (ER) -> http://oregonstate.edu/instruction/bi314/summer09/ Rough ER trafficking.html  Endoplasmic Reticulum (ER) Membranous tubes that enclose fluid- filled interiors ER continuous with outer nuclear membrane Two varieties: ◦ Rough ER ◦ Smooth ER Figure 3.15 Rough ER Covered in ribosomes Site of synthesis of proteins (secreted, membrane, etc) Proteins enter cisterns and are modified as they wind through tubes Final protein enclosed in vesicle and sent to Golgi apparatus for further processing Figure 3.15  Smooth ER Network of looped tubules continuous with rough ER Enzymes found in plasma membrane function in: ◦ Lipid metabolism ◦ Absorption, synthesis, and transport of fats ◦ Detoxification of certain chemicals (drugs, pesticides, etc.) ◦ Converting of glycogen to free glucose ◦ Storage and release of calcium (Sarcoplasmic reticulum in skeletal and cardiac muscle) Figure 3.15 Golgi Apparatus Stacked and flattened membranous cistern sacs Modifies, concentrates, and packages proteins and lipids received from rough ER © 2016 PEARSON EDUCATION, INC. Peroxisomes Membranous sacs containing detoxifying substances that neutralize toxins, such as free radicals ◦ Free radicals: toxic, highly reactive molecules, by- products of metabolism Peroxisomes also play a role in breakdown and synthesis of fatty acids (think peroxide-peroxisome) http://cellstructure.pbworks.com/w/page/14755353/Peroxisomes_3rd  Lysosomes Membranous structures containing digestive enzymes (acid hydrolases) ◦ Work best in acidic conditions (Think breakdown “lyse”- lysosome) Digest ingested bacteria, viruses, and toxins Degrade organelles https://micro.magnet.fsu.edu/cells/ Metabolic functions: break down lysosomes/lysosomes.html and release glycogen; break down and release Ca2+ from bone Autolysis: cell digests itself Endomembrane System Consists of membranous organelles discussed so far (ER, Golgi apparatus, secretory vesicles, and lysosomes), as well as the nuclear and plasma membranes These membranes and organelles work together to: 1. Produce, degrade, store, and export biological molecules 2. Degrade potentially harmful substances Cytoskeleton Complex network of rods that make up the ‘scaffolding’ within cells Hundreds of different kinds of proteins link rods to other cell structures Plays a role in movement of cell components Three types: ◦ Microfilaments ◦ Intermediate filaments ◦ Microtubules Cytoskeleton: Microfilaments ◦ Thinnest of all cytoskeletal elements ◦ Semi-flexible strands of protein actin ◦ Actin filaments are constantly breaking down and reforming – dynamic actin ◦ Dense, cross-linked network of microfilaments attached to cytoplasmic side of plasma membrane ◦ Strengthens cell surface and helps to resist compression ◦ Some are involved in cell motility, changes in cell shape, or endocytosis and exocytosis Figure 3.20 Cytoskeleton: Intermediate filaments ◦ Size is in between microfilaments and microtubules ◦ Tough, insoluble, ropelike protein fibers ◦ Composed of tetramer (4) fibrils twisted together, resulting in one strong fiber ◦ Help cell resist pulling forces ◦ Filaments attach to desmosome plaques and act as internal guy-wires ◦ Some have special names ◦ Called neurofilaments in nerve cells and keratin filaments in epithelial cells Figure 3.20 Cytoskeleton: Microtubules ◦ Largest of cytoskeletal elements ◦ Hollow tubes composed of protein subunits called tubulins, constantly assembled and disassembled ◦ Most radiate from centrosome area ◦ Determine overall shape of cell and distribution of organelles ◦ Many organelles are tethered to microtubules ◦ Microtubules act as “tracks” for motor proteins, such as kinesins, dyneins Figure 3.20 Cytoskeleton: Motor proteins ◦Function in motility ◦ Can help in movement of organelles and other https://youtu.be/y-uuk4Pr2i8 substances around cell ◦ Use microtubules as tracks to move their cargo on ◦ Powered by ATP ◦ Eg. Myosin (muscle, will cover later) Centrosome and Centrioles Centrosome, which is located near the nucleus, means “cell center” Microtubule organizing center, consisting of a granular matrix and centrioles Newly assembled microtubules radiate from centrosome to rest of cell ◦ Some microtubules aid in cell division, and some form cytoskeletal track system Centrioles form the basis of cilia and flagella Figure 3.21 Cilia and Flagella Cilia are whiplike, motile extensions on surfaces of certain cells (such as respiratory cells) ◦ Can move substances across surface (eg. Mucus) Flagella are longer extensions that propel the whole cell (example: tail of sperm) Both structures are made up of microtubules synthesized by centrioles: basal bodies Figure 3.22  Power, or Recovery stroke, when propulsive, stroke cilium is returning to its initial position Ciliary function Cilia movements alternate between power stroke and 1 2 3 4 5 6 7 recovery stroke Phases of ciliary motion. Layer of mucus https://youtu.be/HMB6flEaZ wI Cell surface Figure 3.23 Traveling wave created by the activity of many cilia acting together propels mucus across cell surfaces. Microvilli Minute, fingerlike extensions of plasma membrane that project from surface of select cells Eg. intestinal and kidney tubule cells) Used to increase surface area for absorption Have a core of actin microfilaments for Figure 3.24 stiffening of projections Nucleus Largest organelle; contains the genetic library of blueprints for synthesis of nearly all cellular proteins ◦ Responds to signals that dictate the kinds and amounts of proteins that need to be synthesized Most cells are uninucleate (one nucleus), but skeletal muscle, certain bone cells, and some liver cells are multinucleate (many nuclei) ◦ Red blood cells are anucleate (no nucleus) 3.9 Structure of the Nucleus The nucleus has three main structures: ◦ Nuclear envelope ◦ Nucleoli ◦ Chromatin Figure 3.25 The Nuclear Envelope Double-membrane barrier that encloses nucleoplasm ◦ Outer layer: continuous with rough ER, has ribosomes ◦ Inner layer: nuclear lamina, is network of proteins that maintains nuclear shape and acts as scaffolding for DNA Nuclear pores allow substances to pass into and out of nucleus ◦ Nuclear pore complexes regulate substances movement  Surface of nuclear envelope. Fracture line of outer membrane Nuclear pores Nucleus Figure 3.25 Nuclear pore complexes. Each pore Nuclear lamina. The netlike lamina composed Is ringed by protein particles. of intermediate filaments formed by lamins lines the inner surface of the nuclear envelope. Nucleoli Green-stained nucleoli within blue Involved in ribosomal nucleus of an epidermal cell RNA (rRNA) synthesis and ribosome subunit assembly Associated with nucleolar organizer regions that contain the DNA that codes for rRNA Usually one or two per http://www.proteinatlas.org/ cell (may be more) learn/dictionary/cell/nucleoli Chromatin Consists of 30% threadlike strands of DNA, 60% histone proteins, and 10% RNA Arranged in fundamental units called nucleosomes Chemical alterations of histones have an effect on DNA Chromosomes are condensed chromatin ◦ Helps protect DNA during division Chromatin and chromosom e structure Figure 3.26 DNA to Proteins DNA in nucleus transcribed to RNA RNA translated to proteins *We will not cover details of this process Figure 3.34 Apoptosis, Autophagy, and Proteasomes Cells that have become obsolete or damaged need to be taken out of system Autophagy (self-eating) Auto = self Disposing of nonfunctional organelles and cytoplasmic bits by forming autophagosomes Lysosomes can break down http://www.nexcelom.com/Nexcelom-Blog/autophagy/ Apoptosis, Autophagy, and Proteasomes Unneeded proteins marked for destruction by ubiquitins ◦ Proteasomes disassemble ubiquitin-tagged proteins, recycling https://www.researchgate.net/figure/7684824_fig1_Figure-1-Ubiquitin-conjugation-and-the-ubiquitin-proteasome- systemUbiquitin-is the amino acids and ubiquitin Apoptosis, Autophagy, and Proteasomes Apoptosis, known as programmed cell death Does not use lysosomes Mitochondrial membranes leak chemicals that activate enzymes called caspases ◦ Caspases cause degradation of DNA and cytoskeleton, leads to cell death ◦ Phagocytized by https://openi.nlm.nih.gov/detailedresult.php?img=PMC2376094_ppat.1000018.g001&req=4 macrophages Developmental Aspects of Cells All cells of body contain same DNA, but not all cells are identical Genes turned on and off in development Development of features in cells called: cell differentiatio n https://www.quora.com/What-are-the-white-blood-cells-functions Cell Destruction and Modified Rates of Cell Division We need cell division for growth Cell division in adults needed to replace cells, repair wounds Hyperplasia is accelerated growth that increases cell numbers when needed Atrophy is a decrease in size that results from loss of stimulation or use Cell Aging The mechanism of aging is a mystery, several theories: ◦ Wear and tear theory: cumulative effects of chemical insults and free radicals ◦ Mitochondrial theory of aging: free radicals in mitochondria diminish energy production http://www.kebe.us/tag/methuselah/ ◦ Immune system disorders: autoimmune responses, weakening of immune response Cell Aging (cont.) ◦ Genetic theory: cessation of mitosis and cell aging are programmed into genes ◦ Telomeres: strings of nucleotides that protect ends of chromosomes (like caps on shoe laces) ◦ Telomere shortens when cell divides https://www.tasciences.com/what-is-a-telomere/ ◦ Telomerase, enzyme that lengthens telomeres ◦ Found in germ cells of embryos but absent in adult cells, except for cancer cells