Cellular Form and Function PDF

Cellular Form and Function  Modern Cell Theory cytology – scientific study of cells All organisms composed of cells and cell products. Cell is the simplest structural and functional unit of life. – cells are alive An organism’s structure and functions are due to the activ...

Cellular Form and Function  Modern Cell Theory cytology – scientific study of cells All organisms composed of cells and cell products. Cell is the simplest structural and functional unit of life. – cells are alive An organism’s structure and functions are due to the activities of its cells. Cells come only from preexisting cells, not from nonliving matter. – therefore, all life traces its ancestry to the same original cells Cells of all species have many fundamental similarities in their chemical composition and metabolic mechanisms. Cells: Prokaryote vs Eukaryote  Prokaryote cells are smaller and simpler Commonly known as bacteria 10-100 microns in size Single-celled(unicellular) or Filamentous (strings of single cells) Prokaryotic (bacterial) Cell Prokaryotic Cells Two groups: Archaebacteria:recently discovered live in extreme environments (salt lakes, hot springs, deep in ocean) Eubacteria most common well-studied (Escherichia coli/E. coli) inhabit soil, surface water, organisms  Prokaryote lifestyle unicellular: all alone colony: forms a film filamentous: forms a chain of cells  Prokaryote Feeding Photosynthetic: energy from sunlight Disease-causing: feed on living things Decomposers: feed on dead things Eukaryotes are bigger and more complicated Have membrane bound organelles Have chromosomes can be multicellular include animal and plant cells  Organelles are membrane-bound cell parts Mini “organs” that have unique structures and functions Located in cytoplasm  Eukaryotic Cell Animal cell Plant cell  Viruses = Parasites of Cell Viruses Replicate themselves in host cells Contain DNA or RNA surrounded by a capsid (protective coat) Outside host cell, virus is nonliving particle (virion) Inside host cell, virus is parasite Uses host cells’ machinery to make more virus particles Turnip yellow mosaic virus (spheres) Tobacco mosaic virus (cylinders) Bacteriophage T4 HIV Poliovirus  Cell Shapes Copyright © The McGraw-Hill Companies, Inc. 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Squamous Cuboidal Columnar Polygonal Stellate Spheroid Discoid Fusiform (spindle-shaped) Fibrous Figure 3.1 3-14  Cell Size Human cell size – most from 10 - 15 micrometers (µm) in diameter egg cells (very large)100 µm diameter – barely visible to the naked eye nerve cell at 1 meter long – longest human cell – too slender to be seen with naked eye Limitations on cell size – surface area to volume ratio of a cell has to be big enough in order for efficient nutrient absorption and waste removal  Cell Structure All cells have three (3) basic parts: – Plasma/Cell Membrane – Nucleus- DNA containing region – Cytoplasm- semi-fluid substance between plasma membrane and nucleus  Cytoplasm – material between plasma membrane and the nucleus Cytosol – largely water with dissolved protein, salts, sugars, and other solutes Cytoplasmic organelles – metabolic machinery of the cell Form and function of organelles THE CELL INTERIOR  Nucleus Contains nuclear envelope, nucleoli, DNA (form of chromatin), and distinct compartments rich in specific protein sets Gene-containing control center of the cell Contains the genetic library with blueprints for nearly all cellular proteins Dictates the kinds and amounts of proteins to be synthesized Nucleus Figure 3.28a  Nuclear Envelope Selectively permeable double membrane barrier containing pores Encloses jellylike nucleoplasm, which contains essential solutes Outer membrane is continuous with the rough ER and is studded with ribosomes Inner membrane is lined with the nuclear lamina, which maintains the shape of the nucleus Pore complex regulates transport of large molecules into and out of the nucleus Nucleus Figure 3.28a  Nucleoli Dark-staining spherical bodies within the nucleus Site of ribosome production  Ribosomes Ribosomes - small granules of protein and RNA – found in nucleoli, in cytosol, and on outer surfaces of rough ER, and nuclear envelope they ‘read’ coded genetic messages (messenger RNA) and assemble amino acids into proteins specified by the code  Endoplasmic Reticulum parts of it are covered by ribosomes and are called rough endoplasmic reticulum (RER) – Functions in protein and phospholipid synthesis Other parts lack ribosomes and so are called smooth endoplasmic reticulum (SER) – Functions mostly in cell detoxification, synthesis of steroid hormones and other lipids  Smooth and Rough ER Copyright © The McGraw-Hill Companies, Inc. 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Rough endoplasmic reticulum Ribosomes Cisternae (c) Smooth endoplasmic reticulum Figure 3.26c 3-28  Golgi Apparatus Stacked and flattened membranous sacs called cristernae Functions in modification, concentration, and packaging of proteins Transport vessels from the ER fuse with the Golgi apparatus Proteins then pass through the Golgi apparatus Secretory vesicles leave the Golgi stack and move to designated parts of the cell Golgi Apparatus Figure 3.20a Role of the Golgi Apparatus Figure 3.21  Lysosomes Spherical membranous bags containing digestive enzymes Digest ingested bacteria, viruses, and toxins Degrade nonfunctional organelles Breakdown glycogen and release thyroid hormone Breakdown nonuseful tissue Breakdown bone to release Ca2+  Peroxisomes Membranous sacs containing oxidases and catalases Detoxify harmful or toxic substances Neutralize dangerous free radicals – Free radicals – highly reactive chemicals with unpaired electrons (i.e., O2–)  Mitochondria Organelle specialized for the synthesis of ATP – ATP is adenosine triphosphate – It is the energy currency of the body Have a variety of shapes: spheroid, rod-shaped, bean-shaped, etc Surrounded by a double membrane – Inner membrane has folds called cristae – Space between the cristae is called the matrix  Mitochondrion Copyright © The McGraw-Hill Companies, Inc. 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Matrix Outer membrane Inner membrane Figure 3.29a,b Mitochondrial ribosome Intermembrane space Crista 1 µm (Left): Dr. Donald Fawcett & Dr. Porter/Visuals Unlimited 3-35  Cytoskeleton The “skeleton” of the cell Dynamic, elaborate series of rods running through the cytosol Consists of microtubules, microfilaments, and intermediate filaments Cytoskeleton Figure 3.24  Other Cellular Structures Microvilli – Finger-like projections on the cell surface that increase the absorptive surface and play a sensory role Cilia – Long, hair-like projections on the cell surface that aid in movement along the cell surface – Also have a sensory role Flagella – Longer than cilia, usually solitary although some single-celled organisms may have more than 1 – Functions in the movement of whole cells, e.g. sperm FLAGELLA MICROVILLI CILIA Transport across the plasma membrane THE PLASMA MEMBRANE  The Plasma Membrane very thin, oily film with diverse proteins embedded defines the boundaries of the cell, governs it’s interactions with other cells, and controls the passage of materials into and out of the cell phospholipid bilayer amphiphilic made from lipids and proteins  Plasma Membrane Copyright © The McGraw-Hill Companies, Inc. 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Extracellular fluid Peripheral protein Glycolipid Glycoprotein Carbohydrate chains Extracellular face of membrane Phospholipid bilayer Channel Peripheral protein Intracellular Cholesterol face of Transmembrane membrane protein Proteins of Intracellular fluid cytoskeleton (b) Figure 3.6b 3-46  Transport Mechanisms plasma membrane – a barrier and a gateway between the cytoplasm and ECF – selectively permeable – allows some things through, and prevents other things from entering and leaving the cell passive transport mechanisms requires no ATP – random molecular motion of particles provides the necessary energy – filtration, diffusion, osmosis active transport mechanisms consumes ATP – active transport and vesicular transport carrier-mediated mechanisms use a membrane protein to transport substances from one side of the membrane to the other Filtration, diffusion and osmosis PASSIVE TRANSPORT  Diffusion The passive movement of molecules or particles along a concentration gradient. Particles move from area of high concentration to an area of low concentration In the cell it’s a type of passive transport (does not use ATP) Movement of molecules in and out of the cell across the cell membrane along a concentration gradient  Diffusion Factors affecting diffusion rate through a membrane Down gradient a. temperature - ↑ temp., ↑ Up motion of particles gradient b. molecular weight - larger molecules move slower c. steepness of concentrated gradient - ↑difference, ↑ rate d. membrane surface area - ↑ area, ↑ rate e. membrane permeability - ↑ permeability, ↑ rate  Facilitated Diffusion ⚫ facilitated diffusion - transport of solute through a membrane down its concentration gradient using a channel or carrier protein ⚫ does not consume ATP ⚫ solute attaches to binding site on carrier, carrier changes confirmation, then releases solute on other side of membrane ECF ICF Figure 3.18 1 A solute particle enters 2 The solute binds to a receptor 3 The carrier releases the the channel of a membrane site on the carrier and the solute on the other side of protein (carrier). carrier changes conformation. the membrane. 3-51 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.  Osmosis Side A Side B o movement of water molecules from an area of high concentration to an area of low concentration Figure 3.15a solute-solid particle water particles Passive Membrane Transport – Review Process Energy Source Example Simple diffusion Kinetic energy Movement of O2 through membrane Facilitated diffusion Kinetic energy Movement of glucose into cells Osmosis Kinetic energy Movement of H2O in & out of cells  Tonicity ability of a solution to affect fluid volume and pressure in a cell – depends on concentration and permeability of solute Hypotonic solution – has a lower concentration of solutes than intracellular fluid (ICF) high water concentration – cells absorb water, swell and may burst (lyse) in the absence of a cell wall Hypertonic solution – has a higher concentration of solutes than the intracellular fluid low water concentration – cells lose water + shrivel (crenate) Isotonic solution – concentrations in cell and ICF are the same – cause no changes in cell volume or cell shape – normal saline  Effects of Tonicity on RBCs (Animal Cell) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Hypotonic (b) Isotonic (c) Hypertonic © Dr. David M. Phillips/Visuals Unlimited Figure 3.16a Figure 3.16b Figure 3.16c 3-55 ACTIVE TRANSPORT  Active Transport Uses ATP to move solutes across a membrane Requires carrier proteins vesicular transport is an active process in which materials move into or out of the cell enclosed as vesicles VESICULAR TRANSPORT Phagocytosis Pinocytosis Receptor-mediated endocytosis ENDOCYTOSIS  Phagocytosis or “Cell-Eating” Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Particle 1 A phagocytic cell encounters a particle of foreign matter. 7 The indigestible residue is voided by Pseudopod exocytosis. Residue 2 The cell surrounds the particle with its pseudopods. Nucleus Phagosome 6 The phagolysosome fuses with the 3 The particle is phagocytized plasma membrane. Lysosome and contained in a Vesicle fusing phagosome. with membrane Phagolysosome 5 Enzymes from the lysosome digest the 4 The phagosome fuses foreign matter. with a lysosome and becomes a phagolysosome. Figure 3.21 3-61 Keeps tissues free of debris and infectious microorganisms.  Pinocytosis http://en.wikipedia.org/wiki/File:Pinocytosis.svg  Receptor Mediated Endocytosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Extracellular molecules Receptor Coated pit Clathrin- coated Clathrin vesicle 1 Extracellular molecules bind to 2 Plasma membrane sinks inward, 3 Pit separates from plasma receptors on plasma membrane; forms clathrin-coated pit. membrane, forms clathrin-coated receptors cluster together. vesicle containing concentrated molecules from ECF. (all): Company of Biologists, Ltd. Figure 3.22 (1,2 and 3) 3-63  Exocytosis ⚫ Secreting material ⚫ replacement of plasma membrane removed by endocytosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dimple Fusion pore Secretion Plasma membrane Linking protein Secretory vesicle (a) 1 A secretory vesicle approaches 2 The plasma membrane and (b) the plasma membrane and docks vesicle unite to form a fusion on it by means of linking proteins. pore through which the vesicle The plasma membrane caves in contents are released. at that point to meet the vesicle. Courtesy of Dr. Birgit Satir, Albert Einstein College of Medicine Figure 3.24a,b 3-64