Anatomy & Physiology Chapter 3 - Cellular Form and Function PDF

Chapter 3 Cellular Form and Function ANATOMY & PHYSIOLOGY The Unity of Form and Function Ninth Edition Kenneth S. Saladin © 2022 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitt...

Chapter 3 Cellular Form and Function ANATOMY & PHYSIOLOGY The Unity of Form and Function Ninth Edition Kenneth S. Saladin © 2022 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill.  Introduction All organisms are composed of cells Cells are responsible for all structural and functional properties of a living organism Important for understanding Workings of human body Mechanisms of disease Rationale of therapy © McGraw Hill 2  3.1 Concepts of Cellular Structure Expected Learning Outcomes Discuss the development and modern tenets of the cell theory. Describe cell shapes from their descriptive terms. State the size range of human cells and discuss factors that limit their size. Discuss the way that developments in microscopy have changed our view of cell structure. Outline the major components of a cell. © McGraw Hill 3  Development of the Cell Theory 1 Cytology—scientific study of cells Began when Robert Hooke coined the word cellulae to describe empty cell walls of cork in 17th century Theodor Schwann concluded, about two centuries later, that all animals are made of cells Louis Pasteur demonstrated in 1859 that “cells arise only from other cells” Refuted idea of spontaneous generation—living things arising from nonliving matter © McGraw Hill 4  Development of the Cell Theory 2 Cell theory All organisms composed of cells and cell products Cell is the simplest structural and functional unit of life An organism’s structure and functions are due to activities of cells Cells come only from preexisting cells Cells of all species exhibit biochemical similarities © McGraw Hill 5  Cell Shapes and Sizes 1 About 200 types of cells in human body with varied shapes: Squamous—thin, flat, scaly Cuboidal—squarish-looking Columnar—taller than wide Polygonal—irregularly angular shapes, multiple sides Stellate—star-like Spheroid to ovoid—round to oval Discoidal—disc-shaped Fusiform—thick in middle, tapered toward the ends Fibrous—thread-like Note: A cell’s shape can appear different if viewed in a different type of section (longitudinal versus cross section) © McGraw Hill 6  Common Cell Shapes Access the text alternative for slide images. © McGraw Hill Figure 3.1 7  Cell Shapes and Sizes 2 Human cell size Most cells between 10 to 15 μm in diameter Egg cells (very large) 100 μm diameter Some nerve cells over 1 m long Limit on cell size: an overly large cell cannot support itself, may rupture For a given increase in diameter, volume increases more than surface area Volume proportional to cube of diameter Surface area proportional to square of diameter © McGraw Hill 8  The Relationship Between Cell Surface Area and Volume Access the text alternative for slide images. © McGraw Hill Figure 3.2 9  Basic Components of a Cell 1 Light microscope (LM) revealed plasma membrane, nucleus, and cytoplasm (fluid between nucleus and surface) Transmission electron microscope (TEM) improved resolution (ability to reveal detail) Scanning electron microscope (SEM) improved resolution further, but only for surface features © McGraw Hill 10  Comparison of Microscopy Techniques Figure 3.3a and b Access the text alternative for slide images. © McGraw Hill a: © Alvin Telser/McGraw-Hill Education; b: © Biophoto Associates/Science Source 11 © McGraw Hill 12  Basic Components of a Cell 2 Plasma (cell) membrane Surrounds cell, defines boundaries Made of proteins and lipids Cytoplasm Organelles Cytoskeleton Inclusions (stored or foreign particles) Cytosol (intracellular fluid, ICF) Extracellular fluid (ECF) Fluid outside of cells includes Figure 3.4 tissue (interstitial) fluid © McGraw Hill 13  3.2 The Cell Surface Expected Learning Outcomes Describe the structure of the plasma membrane. Explain the functions of the lipid, protein, and carbohydrate components of the plasma membrane. Describe a second-messenger system and discuss its importance in human physiology. Describe the composition and functions of the glycocalyx that coats cell surfaces. Describe the structure and functions of microvilli, cilia, and flagella. © McGraw Hill 15  The Plasma Membrane 1 Plasma membrane—border of the cell Appears as pair of dark parallel lines when viewed with electron microscope Has intracellular and extracellular faces Functions Defines cell boundaries Governs interactions with other cells Controls passage of materials in and out of cell Figure 3.4 © McGraw Hill 16  The Plasma Membrane 3 Access the text alternative for slide images. Figure 3.5b © McGraw Hill 18  Membrane Lipids 1 98% of membrane molecules are lipids Phospholipids 75% of membrane lipids are phospholipids Amphipathic molecules arranged in a bilayer Hydrophilic phosphate heads face water on each side of membrane Hydrophobic tails—are directed toward the center, avoiding water Drift laterally, keeping membrane fluid © McGraw Hill 19  Membrane Lipids 2 Cholesterol 20% of the membrane lipids Holds phospholipids still and can stiffen membrane Glycolipids 5% of the membrane lipids Phospholipids with short carbohydrate chains on extracellular face Contributes to glycocalyx—carbohydrate coating on cell surface © McGraw Hill 20  Membrane Proteins 1 Membrane proteins 2% of the molecules but 50% of the weight of membrane Integral proteins—penetrate membrane Transmembrane proteins pass completely through Hydrophilic regions contact cytoplasm, extracellular fluid Hydrophobic regions pass through lipid of the membrane Some drift in membrane; others are anchored to cytoskeleton Access the text alternative for slide images. Figure 3.6 © McGraw Hill 21  Membrane Proteins 2 Peripheral proteins Adhere to one face of the membrane Usually tethered to the cytoskeleton Functions of membrane proteins include: Receptors, second-messenger systems, enzymes, channels, carriers, cell-identity markers, cell-adhesion molecules Access the text alternative for slide images. Figure 3.7 © McGraw Hill 23  Membrane Proteins 3 Receptors—bind chemical signals Second messenger systems—communicate within cell receiving chemical message Enzymes—catalyze reactions including digestion of molecules, production of second messengers Channel proteins—allow hydrophilic solutes and water to pass through membrane Some are always open, some are gated Ligand-gated channels—respond to chemical messengers Voltage-gated channels—respond to charge changes Mechanically-gated channels—respond to physical stress on cell Crucial to nerve and muscle function © McGraw Hill 25  Membrane Proteins 4 Carriers—bind solutes and transfer them across membrane Pumps—carriers that consume ATP Cell-identity markers—glycoproteins acting as identification tags Cell-adhesion molecules—mechanically link cell to extracellular material © McGraw Hill 26  Second Messengers Chemical first messenger (epinephrine) binds to a surface receptor Receptor activates G protein An intracellular peripheral protein that gets energy from guanosine triphosphate (GTP) G protein relays signal to adenylate cyclase which converts ATP to cAMP (second messenger) cAMP activates cytoplasmic kinases Kinases add phosphate groups to other enzymes turning some on and others off Up to 60% of drugs work through G proteins and second messengers © McGraw Hill 27  A Second-Messenger System Access the text alternative for slide images. © McGraw Hill Figure 3.8 28  The Glycocalyx Fuzzy coat external to plasma membrane Carbohydrate moieties of glycoproteins and glycolipids Unique in everyone but identical twins Functions Protection Cell adhesion (e.g. CAMs) Immunity to infection Fertilization Defense against cancer Embryonic development Transplant compatibility © McGraw Hill 29  Extensions of the Cell Surface - Microvilli 1 Extensions of membrane (1 to 2 μm) Gives 15 to 40 times more surface area Best developed in cells specialized in absorption On some absorptive cells they are very dense and appear as a fringe—“brush border” Some microvilli contain actin filaments that are tugged toward center of cell to milk absorbed contents into cell © McGraw Hill 31  Extensions of the Cell Surface - Microvilli 2 Figure 3.9a Figure 3.9b Access the text alternative for slide images. © McGraw Hill a: © Don W. Fawcett/Science Source; b: © Biophoto Associates/Science Source 32  Extensions of the Cell Surface - Cilia 1 Cilia—hair-like processes 7 to 10 μm long Single, nonmotile primary cilium found on nearly every cell “Antenna” for monitoring nearby conditions Helps with balance in inner ear; light detection in retina Multiple nonmotile cilia Found on sensory cells of nose Ciliopathies—defects in structure and function of cilia Motile cilia—respiratory tract, uterine tubes, ventricles of brain, ducts of testes 50 to 200 on each cell Beat in waves sweeping material across a surface in one direction Power strokes followed by recovery strokes © McGraw Hill 33  Extensions of the Cell Surface - Cilia 3 Figure 3.10 Access the text alternative for slide images. © McGraw Hill a: © Steve Gschmeissner/Science Photo Library/Getty Images; ; c: © Don Fawcett/Science Source 35  Ciliary Action Access the text alternative for slide images. © McGraw Hill Figure 3.11 37  Extensions of the Cell Surface - Flagella Tail of a sperm—only functional flagellum in humans Whip-like structure with structure like cilium Much longer than cilium Stiffened by coarse fibers that support the tail Movement is undulating, snake-like, corkscrew No power stroke and recovery strokes © McGraw Hill 39  3.3 Membrane Transport Expected Learning Outcomes Explain what is meant by a selectively permeable membrane. Describe various mechanisms for transporting material through cellular membranes. Define osmolarity and tonicity and explain their importance. © McGraw Hill 42  Membrane Transport Plasma membrane and organelle membranes are selectively permeable—allowing some things through, but preventing others from passing Passive mechanisms require no ATP Random molecular motion of particles provides necessary energy Filtration, diffusion, osmosis Active mechanisms consume ATP Active transport and vesicular transport Carrier-mediated mechanisms use a membrane protein to transport substances across membrane © McGraw Hill 43  Simple Diffusion 1 Simple diffusion—net movement of particles from place of high concentration to place of lower concentration Due to constant, spontaneous molecular motion Molecules collide and bounce off each other Substances diffuse down their concentration gradient Does not require a membrane Substance can diffuse through a membrane if the membrane is permeable to the substance Nonpolar, hydrophobic, lipid-soluble small molecules © McGraw Hill 46  Simple Diffusion 2 Factors affecting diffusion rate through a membrane Temperature: ↑ temp., ↑ motion of particles Molecular weight: larger molecules move slower Steepness of concentrated gradient: ↑ difference, ↑ rate Membrane surface area: ↑ area, ↑ rate Membrane permeability: ↑ permeability, ↑ rate © McGraw Hill 47  Osmosis 1 Osmosis—net flow of water through a selectively permeable membrane Water moves from the side where it (water) is more concentrated to the side where it is less concentrated Solute particles that cannot pass through the membrane “draw” water from the other side Figure 3.14 Access the text alternative for slide images. © McGraw Hill 48  Osmosis 3 Osmotic pressure—hydrostatic pressure required to stop osmosis Increases as amount of nonpermeating solute rises Reverse osmosis—process of applying mechanical pressure to override osmotic pressure Allows purification of water Allows heart to drive water out of capillaries (capillary filtration) © McGraw Hill 51  Osmolarity and Tonicity 1 One osmole (osm) = 1 mole of dissolved particles Takes into account whether solute ionizes in water 1 M glucose is 1 osm/L 1 M NaCl is 2 osm/L Osmolarity—number of osmoles per liter of solution Body fluids contain a mix of many chemicals, and osmolarity is the total osmotic concentration of all solutes Blood plasma, tissue fluid, and intracellular fluid are 300 milliosmoles per liter (mOsm/L) © McGraw Hill 52  Osmolarity and Tonicity 2 Tonicity—ability of a surrounding solution (bath) to affect fluid volume and pressure in a cell Depends on concentration of nonpermeating solutes Hypotonic solution—causes cell to absorb water and swell Has a lower concentration of nonpermeating solutes than intracellular fluid (ICF) Distilled water is an extreme example Hypertonic solution—causes cell to lose water and shrivel (crenate) Has a higher concentration of nonpermeating solutes than ICF Isotonic solution—causes no change in cell volume Concentrations of nonpermeating solutes in bath and ICF are the same Normal saline (0.9% NaCl) is an example © McGraw Hill 53  Effects of Tonicity on RBCs Figure 3.15a Figure 3.15b Figure 3.15c Hypotonic, isotonic, and hypertonic solutions affect the fluid volume of a red blood cell. Notice the crenated and swollen cells. Access the text alternative for slide images. © McGraw Hill (a-c): © David M. Philips/Science Source 54  Carrier-Mediated Transport 1 Transport proteins in membrane carry solutes into or out of cell (or organelle) Specificity Transport proteins are specific for particular solutes Solute (ligand) binds to receptor site on carrier protein Solute is released unchanged on other side of membrane Saturation As solute concentration rises, the rate of transport rises, but only to a point—transport maximum (Tm) Transport maximum—transport rate at which all carriers are occupied Two types of carrier-mediated transport Facilitated diffusion and active transport © McGraw Hill 55  Carrier-Mediated Transport 2 Three kinds of carriers Uniport—carries one type of solute Example: calcium pump Symport—carries two or more solutes simultaneously in same direction (cotransport) Example: sodium–glucose transporters Antiport—Carries two or more solutes in opposite directions (countertransport) Example: sodium–potassium pump removes Na+ , brings in K+ Three mechanisms of carrier-mediated transport Facilitated diffusion, primary active transport, secondary active transport © McGraw Hill 57  Carrier-Mediated Transport 3 Facilitated diffusion—carrier moves solute down its concentration gradient Does not consume ATP Solute attaches to binding site on carrier, carrier changes conformation, then releases solute on other side of membrane Figure 3.17 Access the text alternative for slide images. © McGraw Hill 58  Carrier-Mediated Transport 4 Active transport—carrier mediated transport of solute through a membrane up (against) its concentration gradient The carrier protein uses ATP for energy Examples: Calcium pump uses ATP while expelling calcium from cell to where it is already more concentrated Sodium–potassium pump uses ATP while expelling sodium and importing potassium into cell © McGraw Hill 60  Carrier-Mediated Transport 5 The sodium–potassium pump (Na+ − K+ pump) Each pump cycle consumes one ATP and exchanges three Na+ for two K+ Keeps K+ concentration higher and Na+ concentration lower within the cell than in ECF Necessary because Na+ and K+ constantly leak through membrane Figure 3.19 Access the text alternative for slide images. Half of daily calories utilized for Na+ − K+ pump © McGraw Hill 61  Vesicular Transport 1 Vesicular transport—moves large particles, fluid droplets, or numerous molecules at once through the membrane in vesicles— bubble-like enclosures of membrane; utilizes motor proteins energized by ATP Endocytosis—vesicular processes that bring material into cell Phagocytosis—“cell eating,” engulfing large particles Pseudopods; phagosomes; macrophages Pinocytosis—“cell drinking,” taking in droplets of ECF containing molecules useful in the cell Membrane caves in, then pinches off pinocytic vesicle Receptor-mediated endocytosis—particles bind to specific receptors on plasma membrane Clathrin-coated vesicle Exocytosis—discharging material from the cell © McGraw Hill 67  Phagocytosis, Intracellular Digestion, and Exocytosis Access the text alternative for slide images. © McGraw Hill Figure 3.20 68  Vesicular Transport 2 Receptor-mediated endocytosis More selective endocytosis Enables cells to take in specific molecules that bind to extracellular receptors Clathrin-coated vesicle in cytoplasm Uptake of LDL from bloodstream Figure 3.21 Access the text alternative for slide images. © McGraw Hill (1-3): Courtesy of the Company of Biologists, Ltd. 69  3.4 The Cell Interior Expected Learning Outcomes Describe the cytoskeleton and its functions. List the main organelles of a cell, describe their structure, and explain their functions. Give some examples of cell inclusions and explain how inclusions differ from organelles. © McGraw Hill 74  The Cytoskeleton 1 Cytoskeleton—network of protein filaments and cylinders Determines cell shape, supports structure, organizes cell contents, directs movement of materials within cell, contributes to movements of the cell as a whole Composed of: microfilaments, intermediate fibers, microtubules © McGraw Hill 75  Organelles Internal structures of a cell, carry out specialized metabolic tasks Membranous organelles Nucleus, mitochondria, lysosomes, peroxisomes, endoplasmic reticulum, and Golgi complex Non-membranous organelles Ribosomes, centrosomes, centrioles, basal bodies © McGraw Hill 79  The Nucleus 1 Nucleus—usually largest organelle (5 μm in diameter) Most cells have one nucleus A few cell types are anuclear or multinucleate Nuclear envelope—double membrane around nucleus Perforated by nuclear pores formed by rings of proteins Regulate molecular traffic through envelope Hold the two membrane layers together © McGraw Hill 80  The Nucleus 2 Nuclear envelope is supported by nuclear lamina Web of protein filaments Provides points of attachment for chromatin Helps regulate cell life cycle Nucleoplasm—material in nucleus Chromatin (thread-like) composed of DNA and protein Nucleoli—masses where ribosomes are produced Figure 3.27 Access the text alternative for slide images. © McGraw Hill 81  The Nucleus as Seen by Electron Microscope Figure 3.26a Figure 3.26b Access the text alternative for slide images. © McGraw Hill a: © Richard Chao; b: © E.G. Pollock 82  Endoplasmic Reticulum 1 Endoplasmic reticulum—system of channels (cisterns) enclosed by membrane Rough endoplasmic reticulum—parallel, flattened sacs covered with ribosomes Continuous with outer membrane of nuclear envelope, often largest organelle Produces phospholipids and proteins of nearly all cell membranes Synthesizes proteins that are packaged in other organelles or secreted from cell © McGraw Hill 84  Endoplasmic Reticulum 2 Smooth endoplasmic reticulum Lack ribosomes Cisterns more tubular and branching Cisterns thought to be continuous with rough ER Synthesizes steroids and other lipids Detoxifies alcohol and other drugs Calcium storage Rough and smooth ER are functionally different parts of the same network © McGraw Hill 85  Endoplasmic Reticulum 3 Access the text alternative for slide images. © McGraw Hill Figure 3.28c 86  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 © McGraw Hill 87  Golgi Complex 1 Golgi complex—a system of cisterns that synthesizes carbohydrates and puts finishing touches on protein synthesis Receives newly synthesized proteins from rough ER Sorts proteins, splices some, adds carbohydrate moieties to some, and packages them into membrane-bound Golgi vesicles Some vesicles become lysosomes Some vesicles migrate to plasma membrane and fuse to it Some become secretory vesicles that store a protein product for later release © McGraw Hill 88  Golgi Complex 2 Figure 3.29 Access the text alternative for slide images. © McGraw Hill © David M. Phillips/Science Source 89  Lysosomes Lysosomes—package of enzymes bound by a membrane Generally round, but variable in shape Functions Intracellular hydrolytic digestion of proteins, nucleic acids, complex carbohydrates, phospholipids, and other substances Autophagy—digestion of cell’s surplus organelles Autolysis—“cell suicide”: digestion of a surplus cell by itself © McGraw Hill 90  Mitochondria Mitochondria—organelles specialized for synthesizing ATP Continually change shape from spheroidal to thread-like Surrounded by a double membrane Inner membrane has folds called cristae Spaces between cristae called matrix Matrix contains ribosomes, enzymes used for ATP synthesis, small circular DNA molecule Multiple molecules of mitochondrial DNA (mtDNA) “Powerhouses” of the cell Energy is extracted from organic molecules and transferred to ATP © McGraw Hill 95  A Mitochondrion Figure 3.32 Access the text alternative for slide images. © McGraw Hill © Keith R. Porter/Science Source 96  Evolution of the Mitochondrion Mitochondria evolved from bacteria that invaded another primitive cell, survived in its cytoplasm, and became permanent residents. The bacterium provided inner membrane; host cell’s phagosome provided outer membrane Mitochondrial ribosomes resemble bacterial ribosomes mtDNA resembles circular DNA of bacteria mtDNA is inherited through the mother mtDNA mutates more rapidly than nuclear DNA Responsible for hereditary diseases affecting tissues with high energy demands © McGraw Hill 97