Chapter 3: Cells - Hole's Essentials of Human Anatomy & Physiology (PDF)

Because learning changes everything.® Chapter 03 Cells HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fifteenth Edition Charles J. Welsh and Cynthia Prentice-Craver © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw H...

Because learning changes everything.® Chapter 03 Cells HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fifteenth Edition Charles J. Welsh and Cynthia Prentice-Craver © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  3.1: Introduction A cell is the smallest unit of life A cell continually carries out metabolic activities essential for life, as well as specialized functions, and adapts to changing conditions Cells interact to form tissues, organs, and organ systems The human body consists of 30 trillion cells that vary considerably in shape and size, yet have much in common Differences in cell shape and arrangement make different functions possible Examples: Nerve cells have long extensions that conduct electrical impulses, while epithelial cells in the mouth are flat, thin, and densely packed, to provide a protective barrier Genes control a cell’s actions and responses © McGraw Hill, LLC 2  Figure 3.1 Cells Vary in Shape and Function Access the text alternative for these images © McGraw Hill, LLC 3  3.2: Composite Cell A composite cell includes many different cell structures; most cells contain most of these structures, but no cell contains all of them. A cell consists of three main parts: Nucleus: Contains DNA (genetic material) and directs cell’s activities Cytoplasm: Organelles and fluids that make up the majority of the cell; between nucleus and cell membrane Cell membrane: Boundary that encloses the cell Within the cytoplasm are specialized organelles (little organs) that perform specific functions for the cell Organelles are suspended in a fluid called the cytosol © McGraw Hill, LLC 4  Figure 3.2: Illustration of a Composite Cell Access the text alternative for these images © McGraw Hill, LLC 5  Cell Membrane Cell membrane is also called plasma membrane Boundary that contains the cell contents Regulates the movement of substances in and out of the cell Participates in signal transduction, a method of communication with other cells Helps cells adhere to other cells General Characteristics: Extremely thin, flexible, and elastic Selectively permeable – regulates entry/exit of substances Has complex surface features, with adaptations to increase surface area © McGraw Hill, LLC 6  Cell Membrane Structure: Lipids Composed mainly of lipids and proteins, and some carbohydrates The basic framework of the cell membrane consists of a double layer (bilayer) of phospholipids, with fatty acid tails turned inward and the water-soluble heads facing the surfaces The phospholipids can move, forming a stable fluid film Lipid-soluble molecules (respiratory gases, steroid hormones) can pass through the phospholipid portion of the membrane Cell membrane is impermeable to water-soluble molecules Embedded cholesterol molecules stabilize the membrane, and help make it less permeable to water-soluble substances © McGraw Hill, LLC 7  Cell Membrane Structure: Proteins 1 Many types of proteins are found in the cell membrane Proteins are classified by their relationship to the phospholipid bilayer: Integral: span width of bilayer; may protrude on 1 or both sides Transmembrane: integral proteins that protrude on both sides Peripheral: associate with one side of bilayer Membrane proteins vary in shape: rod-like, globular, fibrous Membrane proteins vary in function: Some proteins function as receptors or growth factors on the cell surface, starting signal transduction Other proteins transport ions or molecules across cell membrane, such as ion channels © McGraw Hill, LLC 8  Cell Membrane Structure: Proteins 2 Membrane protein functions, continued: Other proteins have carbohydrates attached (glycoproteins) and are used for cell identification; this helps identify cells as “self,” protecting them from attack by the immune system Proteins that protrude into the cell will anchor supportive rods and tubules, forming a cytoskeleton Membrane proteins called cellular adhesion molecules (CAMs) help determine a cell’s interactions with other cells © McGraw Hill, LLC 9  Figure 3.3: Structure of the Plasma Membrane Access the text alternative for these images © McGraw Hill, LLC 10  The Cytoplasm The cytoplasm makes up most of cell volume, and consists of a clear liquid (cytosol), a supportive cytoskeleton, and networks of membranes and organelles Organelles perform specific functions for the cell Ribosomes: Tiny, spherical structures composed of RNA and protein Provide structural support and enzyme activity for protein synthesis Not membranous Found in cytoplasm or bound to rough endoplasmic reticulum © McGraw Hill, LLC 11  Organelles 1 Endoplasmic reticulum (ER): Made up of membrane-bound flattened sacs and vesicles Functions as a transport network throughout the cell 2 types of endoplasmic reticulum: Rough ER: contains ribosomes, and functions in protein synthesis Smooth ER: does not contain ribosomes, and functions in lipid synthesis, absorption of fats, and metabolism of drugs © McGraw Hill, LLC 12  Figure 3.4: The Endoplasmic Reticulum (a): Don W. Fawcett/Science Source Access the text alternative for these images © McGraw Hill, LLC 13  Organelles 2 Vesicles: Membranous sacs Store or transport substances within or between cells Golgi apparatus: Composed of flattened, membranous sacs Refines, packages, and transports proteins formed in the rough ER Vesicles formed in the ER travel to the Golgi apparatus, which may modify their contents by adding sugar molecules to the proteins, to stabilize their structure or to enable folding. A new vesicle pinches off the Golgi apparatus and may then move to the cell membrane to secrete its contents to the outside (exocytosis) © McGraw Hill, LLC 14  Figure 3.5: The Golgi Apparatus (a): Biophoto Associates/Science Source Access the text alternative for these images © McGraw Hill, LLC 15  Organelles 3 Mitochondria: Elongated fluid-filled sacs The inner membrane of a mitochondrion is folded into cristae, which increase surface area House many chemical reactions that extract energy from nutrients (cellular respiration) and produce ATP Store the energy in the chemical bonds of ATP Very active cells contain thousands of mitochondria Mitochondria have their own DNA and reproduce by dividing © McGraw Hill, LLC 16  Figure 3.6: Mitochondria (a): Bill Longcore/Science Source Access the text alternative for these images © McGraw Hill, LLC 17  Organelles 4 Lysosomes: Membranous sacs Formed by budding off Golgi apparatus Contain enzymes that break down nutrients, ingested materials, debris, worn out cell parts, cholesterol (in some cells), toxins, and drugs Peroxisomes: Membranous sacs similar in appearance to lysosomes Contain a different set of enzymes than lysosomes Their enzymes function in the breakdown of fatty acids and hydrogen peroxide, and detoxification of alcohol © McGraw Hill, LLC 18  Other Cellular Structures 1 In the cytoplasm, there are several structures, which are not organelles, but rather part of the cytoskeleton. Microfilaments and microtubules are thin, threadlike structures that serve as the cytoskeleton of the cell: Microfilaments: made of the protein actin; cause various cellular movements; group together to form myofibrils in muscle Microtubules: made of the globular protein tubulin, are attached in a spiral to form a long tube; important in cell division Intermediate fibers: made of different proteins in different cells, are abundant in skin cells and neurons © McGraw Hill, LLC 19  Figure 3.7: The Cytoskeleton (a): Dr. Gopal Murti/Science Source Access the text alternative for these images © McGraw Hill, LLC 20  Other Cellular Structures 2 Centrosome: A nonmembranous structure, made up of two hollow cylinders called centrioles, that function in the distribution of chromosomes during cell division; made of nine groups of three microtubules Cilia: Motile extensions from the cell; short cilia are abundant on the free surfaces of certain epithelial cells and move in a wave (respiratory linings, for example) to move fluids or whole cells Flagella: Another type of motile extension from cell; usually a cell only has 1 flagellum; the only human cell with a flagellum is a sperm cell; the flagellum allow the sperm to swim toward the egg cell © McGraw Hill, LLC 21  Figure 3.8: The Centrosome (Centrioles) (a): Don W. Fawcett/Science Source Access the text alternative for these images © McGraw Hill, LLC 22  Figure 3.9: Cilia and Flagella (a): Oliver Meckes/Science Source; (b): Colin Anderson/Brand X Pictures/Getty Images Access the text alternative for these images © McGraw Hill, LLC 23  The Cell Nucleus The nucleus contains genetic material, DNA, which controls cell activities The fairly large nucleus is surrounded by a double-layered nuclear envelope, containing relatively large nuclear pores that allow the passage of certain substances Contains a fluid called nucleoplasm The nucleolus is a small, dense body in the nucleus, composed of RNA and protein; it is the site of ribosome production Chromatin consists of loosely coiled fibers of protein and DNA found in the nucleus Condensed DNA is referred to as chromosomes; this form of DNA is present during cell division © McGraw Hill, LLC 24  Figure 3.10: The Cell Nucleus (b): Dr. Gopal Murti/Science Source Access the text alternative for these images © McGraw Hill, LLC 25  Structures and Functions of Cell Parts 1 TABLE 3.1 Structures and Functions of Cell Parts Cell Part(s) Structure Function Cell membrane Membrane composed of protein and Maintains integrity of cell and controls passage of lipid molecules materials into and out of cell Ribosomes Particles composed of protein and Synthesize proteins RNA molecules Endoplasmic Complex of interconnected Transports materials within the cell, provides reticulum membrane-bounded sacs and canals attachment for ribosomes, and synthesizes lipids Vesicles Membranous sacs Contain and transport various substances Golgi apparatus Stack of flattened, membranous sacs Packages protein molecules for transport and secretion Mitochondria Membranous sacs with inner Release energy from nutrient molecules and change partitions energy into a usable form Lysosomes Membranous sacs House enzymes that digest worn cellular parts or substances that enter cells © McGraw Hill, LLC 26  Structures and Functions of Cell Parts 2 TABLE 3.1 Structures and Functions of Cell Parts Cell Part(s) Structure Function Peroxisomes Membranous sacs House enzymes that catalyze diverse reactions, including breakdown of hydrogen peroxide and fatty acids, and alcohol detoxification Microfilaments Thin rods and tubules Support the cytoplasm and help move substances and microtubules and organelles within the cytoplasm Centrosome Nonmembranous structure composed Helps distribute chromosomes to new cells during of two rodlike centrioles cell division Cilia and flagella Motile projections attached beneath Cilia propel fluid over cellular surfaces, and a the cell membrane flagellum enables a sperm cell to move Nuclear envelope Double membrane that separates the Maintains integrity of nucleus and controls passage nuclear contents from the cytoplasm of materials between nucleus and cytoplasm Nucleolus Dense, nonmembranous body Site of ribosome synthesis composed of protein and RNA Chromatin Fibers composed of protein and DNA Contains information for synthesizing proteins © McGraw Hill, LLC 27  3.3: Movements Into and Out of the Cell The cell membrane is a selective barrier that controls which substances pass through it Mechanisms of movement across the membrane may be passive, requiring no energy from the cell, or active, requiring cellular energy Examples of passive transport mechanisms: diffusion, facilitated diffusion, osmosis, and filtration Examples of active transport mechanisms: active transport, endocytosis, and exocytosis © McGraw Hill, LLC 28  Passive Mechanisms: Diffusion Diffusion (Simple diffusion): Movement of molecules or ions in a liquid or gas from a region of higher concentration to one of lower concentration This is referred to as moving down the concentration gradient Caused by the random motion and collisions of particles At diffusional equilibrium, particles have become uniformly distributed; they continue to move, but there is no net change in concentration Diffusion enables oxygen and carbon dioxide molecules to be exchanged between the air and the blood in the lungs, and between blood and cells Diffusion across cell membranes occurs only if cell membrane is permeable to the substance and there is a concentration gradient A sugar cube placed into a glass of water will disperse over time, by the process of diffusion © McGraw Hill, LLC 29  Figure 3.11: Example of Diffusion: Dissolving a Sugar Cube in a Glass of Water Access the text alternative for these images © McGraw Hill, LLC 30  Figure 3.12: Example of Diffusion Across a Permeable Membrane Access the text alternative for these images © McGraw Hill, LLC 31  Figure 3.13: Example of Diffusion: Exchange of O2 and CO2 Between the Capillaries & Body Cells Access the text alternative for these images © McGraw Hill, LLC 32  Passive Mechanisms: Facilitated Diffusion Facilitated diffusion is a method of transport of substances across the cell membrane, using membrane proteins to carry the substances across the phospholipid bilayer One type of facilitated diffusion involves the use of ion channels to transport ions across the cell membrane Substances transported by facilitated diffusion, such as glucose and amino acids, cannot pass through the phospholipid bilayer, since they are water-soluble or too large; they require the help of a specific carrier molecule The number of carrier molecules in the cell membrane limits the rate of this process © McGraw Hill, LLC 33  Figure 3.14: Facilitated Diffusion Access the text alternative for these images © McGraw Hill, LLC 34  Passive Mechanisms: Osmosis Osmosis: Movement of water across a selectively permeable membrane, into an area that contains an impermeant solute Osmosis is a special case of diffusion, in which water moves across a selectively permeable membrane, from an area of greater water concentration (where there is lower osmotic pressure and a lower concentration of solutes) to an area of lower water concentration (where there is greater osmotic pressure and a higher concentration of solutes) During osmosis, water moves from a region of lower solute concentration to a region of higher solute concentration The cell membrane is permeable to water but impermeable to water-soluble solutes Osmotic pressure is the pressure needed to lift a volume of water; the greater the concentration of impermeable solutes in a solution, the greater its osmotic pressure © McGraw Hill, LLC 35  Figure 3.15: Osmosis Access the text alternative for these images © McGraw Hill, LLC 36  Tonicity Tonicity refers to composition of dissolved solutes in a solution surrounding a cell Tonicity affects the size and shape of a cell The greater the impermeable solute concentration in a solution, the greater its osmotic pressure Water moves toward solutions with greater osmotic pressure Cell membranes are usually permeable to water, but impermeable to many solutes, so water equilibrates by osmosis, and equilibrates the osmotic pressure in the intracellular and extracellular fluids A solution with the same osmotic pressure as body fluids is called isotonic; 0.9% NaCl solution is isotonic to human cells A solution with higher osmotic pressure than body fluids is hypertonic; cells placed in a hypertonic solution will lose water and shrink A solution with lower osmotic pressure than body fluids is hypotonic; cells placed in a hypotonic solution will gain water and swell © McGraw Hill, LLC 37  Figure 3.16 Effects of Isotonic, Hypertonic, and Hypotonic Solutions on Red Blood Cells (a–c): David M. Phillips/Science Source Access the text alternative for these images © McGraw Hill, LLC 38  Passive Mechanisms: Filtration Filtration: The process of forcing molecules through membranes due to the exertion of pressure Blood pressure, due to the action of the heart, is a type of hydrostatic pressure, which is used as the force for filtration Filtration is used by the body to produce tissue fluid from blood plasma; water and small solutes are sent through the walls of capillaries, to deliver O2 and nutrients to the cells, while large particles, like plasma proteins, remain in the capillaries Particles are generally limited in movement by their size in relation to the size of the openings in the wall of the capillary © McGraw Hill, LLC 39  Figure 3.17 Filtration of Small Molecules Through Capillary Walls Access the text alternative for these images © McGraw Hill, LLC 40  Active Mechanisms: Active Transport Active mechanisms move substances from a region of lower concentration to a region of higher concentration and require ATP (adenosine triphosphate) as an energy source and a carrier molecule. Active Transport: Process of moving substances from an area of low concentration to an area of high concentration, through carrier molecules in cell membranes, using ATP for energy The carrier proteins may also be called pumps, since they move substances against the concentration gradient (example: the Na+ – K+ ATPase pump) As much as 40% of a cell's energy may be used to fuel this process Substances moved by active transport: Na+ , K+ , Ca+ 2 , H+ , some sugars, and some amino acids © McGraw Hill, LLC 41  Figure 3.18 Active Transport: The Na+-K+ ATPase Pump Access the text alternative for these images © McGraw Hill, LLC 42  Active Mechanisms: Endocytosis & Exocytosis In endocytosis and exocytosis, large substances are moved into or out of a cell without crossing the cell membrane In endocytosis, molecules that are too large to be transported by other means are conveyed into the cell inside a vesicle that forms from a section of the cell membrane Exocytosis is the movement of materials out of the cell in a vesicle that fuses with the cell membrane and opens up to the outside to secrete the material © McGraw Hill, LLC 43  Three Types of Endocytosis Pinocytosis: Process by which cells engulf liquids and the molecules dissolved in it “Cell drinking” Small indentation in cell membrane surrounds fluid, creating a vesicle Phagocytosis: Process by which the cell takes in solid particles, such as when a white blood cell engulfs a bacterium “Cell eating” Once the vesicle enters the cell, it combines with a lysosome and the contents are digested by lysosomal enzymes Receptor-mediated endocytosis: Process by which the cell takes in very specific molecules (ligands) that bind to specific receptors on the cell membrane to initiate vesicle formation © McGraw Hill, LLC 44  Figure 3.19 Pinocytosis and Phagocytosis Access the text alternative for these images © McGraw Hill, LLC 45  Figure 3.20 Lysosomal Digestion of a Phagocytized Particle Access the text alternative for these images © McGraw Hill, LLC 46  Figure 3.21 Receptor-Mediated Endocytosis Access the text alternative for these images © McGraw Hill, LLC 47  Movements Through Cell Membranes: Passive Mechanisms TABLE 3.2 Movements Through Cell Membranes Process Characteristics Source of Energy Example Passive mechanisms Diffusion Molecules move through the phospholipid Molecular motion Exchange of bilayer from regions of higher concentration to oxygen and regions of lower concentration. carbon dioxide in the lungs Facilitated diffusion Ions move through channels, or molecules Molecular motion Movement of move by carrier proteins, across the membrane glucose through from a region of higher concentration toward a cell membrane one of lower concentration. Osmosis Water molecules move through a selectively Molecular motion Distilled water permeable membrane toward the solution with entering a cell more impermeant solute (greater osmotic pressure). Filtration Smaller molecules are forced through porous Hydrostatic Molecules membranes from regions of higher pressure to pressure leaving blood regions of lower pressure. capillaries © McGraw Hill, LLC 48  Movements Through Cell Membranes: Active Mechanisms TABLE 3.2 Movements Through Cell Membranes Process Characteristics Source of Energy Example Active mechanisms Active transport Carrier molecules transport molecules or Cellular energy Movement of various ions through membranes from regions of (ATP) ions, sugars, and lower concentration toward regions of amino acids through higher concentration. membranes Endocytosis Pinocytosis Membrane engulfs droplets containing Cellular energy Uptake of water and dissolved molecules from surroundings. solutes by all body cells Phagocytosis Membrane engulfs particles from Cellular energy White blood cell surroundings. engulfing bacterial cell Receptor-mediated Membrane engulfs selected molecules Cellular energy Cell removing endocytosis combined with receptor proteins. cholesterol molecules from its surroundings Exocytosis Vesicle fuses with membrane and releases Cellular energy Neurotransmitter contents outside of the cell. release © McGraw Hill, LLC 49  3.4: The Cell Cycle Cell Cycle: The series of changes a cell undergoes from the time it is formed until it divides Main phases are interphase, mitosis, and cytokinesis (division of the cytoplasm) Daughter cells might then undergo changes to become specialized Whether the cell cycle progresses at certain times, called checkpoints, is controlled by interaction of special proteins A restriction checkpoint determines fate of cell: to continue cell cycle and divide, to enter a non-dividing stage as a specialized cell, or to die Most cells do not divide continually. Cells have a maximum number of times they can divide, because of built-in “clocks” (telomeres) on the tips of chromosomes, which shorten with each cell division © McGraw Hill, LLC 50  Figure 3.22 Phases of the Cell Cycle Access the text alternative for these images © McGraw Hill, LLC 51  Interphase Interphase: Phase of the cell cycle, before cell division begins, in which the cell grows and synthesizes new molecules, membranes, DNA, and organelles This is a time of great synthetic activity, rather than a time of rest During the G1 and G2 (“gap” or “growth”) phases of interphase, the cell grows, and structures other than DNA are duplicated During the S (“synthesis”) phase of interphase, the DNA of the cell is replicated in preparation for cell division © McGraw Hill, LLC 52  Cell Division 2 types of cell division: Meiosis: Only used for sperm & egg cell production Ensures that mature gametes have ½ the normal number of chromosomes as normal body cells Cell Division (Mitosis + Cytokinesis): More common type of cell division, used to increase number of cells for growth, development and wound healing Mitosis is division of the nucleus Cytokinesis is the division of the cytoplasm Regulated carefully, so that each of two daughter cells receives an exact copy of the original cell's genetic material (DNA) © McGraw Hill, LLC 53  Stages of Mitosis 1 Mitosis occurs in a series of four stages, but the process is actually continuous: 1. Prophase: The first stage of mitosis DNA condenses into visible chromosomes (each consisting of two chromatids connected by a centromere) Centrioles migrate to opposite poles Microtubules of the cytoskeleton organize into spindle fibers The nuclear membrane and nucleolus disassemble © McGraw Hill, LLC 54  Stages of Mitosis 2 2. Metaphase: Spindle fibers attach to centromeres on the chromosomes Chromosomes randomly align midway between centrioles 3. Anaphase: Chromatids are pulled apart Chromatids are now considered individual chromosomes Chromatids are pulled along the shortening spindle fibers toward opposite centrioles © McGraw Hill, LLC 55  Stages of Mitosis 3 4. Telophase: The final stage of mitosis Begins when the chromosomes have completed their migrations to opposite sides of the dividing cell A nuclear envelope and nucleolus assemble for each forming cell The spindle fibers disassemble The chromosomes unwind, and take back their chromatin form © McGraw Hill, LLC 56  Figure 3.23 Stages of Mitosis (a–e): Ed Reschke Access the text alternative for these images © McGraw Hill, LLC 57  Cytoplasmic Division (Cytokinesis) Cytokinesis: Begins during anaphase of mitosis, when cell membrane constricts around middle of cell Constriction, called the cleavage furrow, continues throughout telophase; it eventually pinches the newly formed cells apart Contractile ring of microfilaments attaches to inside of cell membrane; it divides the cytoplasm The two new cells may have slightly different amounts of cytoplasm and organelles, but they share identical genetic information (DNA) © McGraw Hill, LLC 58  Cell Differentiation Differentiation: The process by which a cell develops/specializes into a specific type of cell with specialized functions Humans have >290 types of differentiated cells Cell differentiation allows cells to specialize by using different parts of the complete genome that is present in each cell; in each type of cell, some genes are “turned on” while others are “turned off” Stem cells retain the ability to divide without specialization; their presence in the cell allows for continuous growth and renewal Ability of a stem cell to divide, giving rise to at least one other stem cell, is called self-renewal. Progenitor cells are daughters of stem cells that are partially specialized. Stem and progenitor cells allow cells to retain the ability to produce cells that will become the differentiated cells in each area of the body. © McGraw Hill, LLC 59  Figure 3.24 Stem and Progenitor Cells and Differentiation Access the text alternative for these images © McGraw Hill, LLC 60  Cell Death Not all cells divide or differentiate; some die Apoptosis is a form of programmed cell death that is a normal part of development, rather than being derived from injury or disease Removes overgrown tissues, damaged cells, extra cells in fetus Steps of apoptosis: Cell becomes rounded and bulges Nuclear membrane breaks down Chromatin condenses and enzymes cut up the chromosomes Cell shatters into many membrane-bound pieces Scavenger cells engulf and destroy the fragments © McGraw Hill, LLC 61  End of Main Content Because learning changes everything. ® www.mheducation.com © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.