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BIOL 2401 Biol 2401 Fundamentals of Anatomy and Physiology Mrs. Willie Grant [email protected] (210) 486-2370 © 2012 Pearson Education, Inc. Chapter 3 The Cellular Level of Organization Lecture Presentation by Lee Ann Frederick University of Texas at Arlington © 2015 Pearson Education, Inc. © 2012 Pearson Education, Inc. An Introduction to Cells Learning Outcomes 3-1 List the functions of the plasma membrane and the structural features that enable it to perform those functions. 3-2 Describe the organelles of a typical cell, and indicate the specific functions of each. 3-3 Explain the functions of the cell nucleus and discuss the nature and importance of the genetic code. 3-4 Summarize the role of DNA in protein synthesis, cell structure, and cell function. 3-5 Describe the processes of cellular diffusion and osmosis, and explain their role in physiological systems. 3-6 Describe carrier-mediated transport and vesicular transport mechanisms used by cells to facilitate the absorption or removal of specific substances. 3-7 Explain the origin and significance of the transmembrane potential. 3-8 Describe the stages of the cell life cycle, including mitosis, interphase, and cytokinesis, and explain their significance. 3-9 Discuss the regulation of the cell life cycle. 3-10 Discuss the relationship between cell division and cancer. 3-11 Define differentiation, and explain its importance. © 2012 Pearson Education, Inc. An Introduction to Cells Cell Theory Developed from Robert Hooke’s research (17th century) Cells are the building blocks of all plants and animals All cells come from the division of preexisting cells Cells are the smallest units that perform all vital physiological functions Each cell maintains homeostasis at the cellular level Sex Cells (Germ Cells) Reproductive cells: Male (sperm); Female (oocyte) Somatic Cells (Soma—body) © 2012 Pearson Education, Inc. An Introduction To Cells In our model cell, a _____________separates the cell contents, called the____________, from its surroundings. The cytoplasm can be subdivided into the ____________a liquid, and intracellular structures collectively known as______________. Organelles are structures suspended within the cytosol that perform specific functions within the cell and can be further subdivided into membranous and nonmembranous organelles. Cells are surrounded by a watery medium known as the______________. The extracellular fluid in most tissues is called_______________. The _____________ is usually the largest and most conspicuous structure in a cell. © 2012 Pearson Education, Inc. Organelles Cytosol Cytoplasm Nucleus Extracellular Fluid Plasma Membrane 1 List the three principle parts of a cell? © 2012 Pearson Education, Inc. Plasma Membrane © 2012 Pearson Education, Inc. Non-membranous (no membrane) Membranous (membrane) Nucleus 3-1 Plasma Membrane Functions of the Plasma Membrane Physical Isolation Barrier Regulation of Exchange with the Environment Ions and nutrients enter Wastes eliminated and cellular products released Sensitivity to the Environment Extracellular fluid composition Chemical signals Structural Support Anchors cells and tissues © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Membrane Lipids Phospholipid bilayer Hydrophilic heads — toward watery environment, both sides Hydrophobic fatty-acid tails — inside membrane Barrier to ions and water — soluble compounds © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Membrane Proteins Integral Proteins—within the membrane Peripheral Proteins—bound to inner or outer surface of membrane Anchoring Proteins (stabilizers)—attach to inside or outside structures Recognition Proteins (identifiers)—label cells as normal or abnormal Enzymes—catalyze reactions Receptor Proteins—bind and respond to ligands (ions, hormones) Carrier Proteins--transport specific solutes through membrane Channels--forms pathway across plasma membrane and regulate water flow and solutes through membrane) © 2012 Pearson Education, Inc. 3-1 Plasma Membrane Membrane Carbohydrates Proteoglycans, glycoproteins, and glycolipids Extend outside cell membrane Form sticky “sugar coat” layer (glycocalyx) Functions of the glycocalyx Lubrication and Protection Anchoring and Locomotion Specificity in Binding (receptors) Recognition (immune response) © 2012 Pearson Education, Inc. The Plasma Membrane 2 What is the glycocalyx? © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Cytoplasm (All materials inside the cell and outside the nucleus) Cytosol (intracellular fluid) Dissolved materials (Nutrients, ions, proteins, and waste products) High potassium/low sodium; High protein; High carbohydrate/low amino acid and fat Organelles Structures with specific functions Nonmembranous organelles—No membrane Direct contact with cytosol Include the cytoskeleton, microvilli, centrioles, cilia, ribosomes, and proteasomes Membranous organelles—Covered with plasma membrane Isolated from cytosol Include the endoplasmic reticulum (ER), the Golgi apparatus, lysosomes, peroxisomes, and mitochondria © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm The Cytoskeleton Microfilaments — thin filaments composed of the protein actin Provide additional mechanical strength; pair with thick filaments of myosin in muscle movement Intermediate filaments — mid-sized between microfilaments and thick filaments; strengthen cell; maintain shape; stabilize organelles; stabilize cell position; durable collagen Microtubules — large, hollow tubes of tubulin protein Attach to centrosome (cytoplasm surrounding centrioles) Strengthen cell and anchor organelles; change cell shape; move vesicles within cell; form spindle apparatus © 2012 Pearson Education, Inc. CYTOSKELETON Microfilaments Intermediate Filaments Microtubules Description Thin/Thick Mid-sized Large Protein Actin/Myosin Collagen Tubulin Function Mechanical strength; Pair with myosin in muscle movement Strengthen cell; maintain shape; stabilize organelles; stabilize cell position Attach to centrosome (cytoplasm around centrioles); strengthen; anchor organelles; change cell shape; move vesicles; form spindle apparatus © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Microvilli Increase surface area for absorption Attach to cytoskeleton Centrioles in the Centrosome Centrioles form spindle apparatus during cell division Centrosome cytoplasm surrounding centriole Cilia Small hair-like extensions Cilia move fluids across the cell surface 3 Which cytoskeleton component helps form the structure of centrioles, cilia, and flagella? © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Ribosomes Build polypeptides in protein synthesis Two types Free ribosomes (polysomes) in cytoplasm Manufacture proteins for cell Fixed ribosomes attached to ER Manufacture proteins for secretion Proteasomes Contain enzymes (proteases) Disassemble damaged proteins for recycling © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Endoplasmic Reticulum (ER) Endo- = within, plasm = cytoplasm, reticulum = network Cisternae are storage chambers within membranes Functions Synthesis of proteins, carbohydrates, and lipids Storage of synthesized molecules and materials Transport of materials within the ER Detoxification of drugs or toxins © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Endoplasmic Reticulum (ER) Smooth endoplasmic reticulum (SER) No ribosomes attached Synthesizes lipids and carbohydrates Phospholipids and cholesterol (membranes) Steroid hormones (reproductive system) Glycerides (storage in liver and fat cells) Glycogen (storage in muscles) Rough endoplasmic reticulum (RER) Surface covered with ribosomes Active in protein and glycoprotein synthesis Folds polypeptide protein structures Encloses products in transport vesicles © 2012 Pearson Education, Inc. Figure 3-5a The Endoplasmic Reticulum Nucleus Rough endoplasmic reticulum with fixed (attached) ribosomes Ribosomes The three-dimensional relationships between the rough and smooth endoplasmic reticula are shown here. Cisternae 4 What are the structural and functional differences between rough and smooth endoplasmic reticulum? © 2012 Pearson Education, Inc. Smooth endoplasmic reticulum 3-2 Organelles and the Cytoplasm Golgi Apparatus Vesicles enter forming face and exit maturing face. Vesicles contain flattened membranous discs called cisternae. Functions Modifies and packages secretions Hormones or enzymes Released through exocytosis Renews or modifies the plasma membrane Packages special enzymes within vesicles for use in the cytoplasm © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Lysosomes Powerful enzyme-containing vesicles Lyso- = dissolve, soma = body Primary lysosome Formed by Golgi apparatus and inactive enzymes Secondary lysosome Lysosome fused with damaged organelle Digestive enzymes activated Toxic chemicals isolated Functions Clean up inside cells (Break down large molecules, Attack bacteria, Recycle damaged organelles, and Eject wastes by exocytosis). Autolysis (Auto—self; Lysis—breakdown) (Self destruction of damaged cells—lysosome membranes breakdown, digestive enzymes released, cell decomposes, cellular materials recycled) © 2012 Pearson Education, Inc. Figure 3-8 Lysosome Functions Activation of lysosomes occurs when: Golgi apparatus Damaged organelle Autolysis liberates digestive enzymes Secondary lysosome Primary lysosome Reabsorption Reabsorption Endosome Secondary lysosome Extracellular solid or fluid A primary lysosome fuses with the membrane of another organelle, such as a mitochondrion A primary lysosome fuses with an endosome containing fluid or solid materials from outside the cell The lysosomal membrane breaks down during autolysis following injury to, or death of, the cell Endocytosis Exocytosis ejects residue Exocytosis ejects residue 5 What are the three general destinations for proteins that leave the Golgi complex? © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Peroxisomes Are enzyme-containing vesicles. The enzymes differ from those of the lysosomes. Break down fatty acids, organic compounds Produce hydrogen peroxide (H2O2) Replicate by division Membrane Flow A continuous exchange of membrane parts by vesicles All membranous organelles (except mitochondria) Allows adaptation and change © 2012 Pearson Education, Inc. Proetin Synthesis 6 How do the entry and exit faces of protein synthesis differ? © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Mitochondria Have smooth outer membrane and inner membrane with numerous folds cristae. These cristae increase the surface area available for chemical reactions and contain some of the enzymes needed for ATP production) Matrix Fluid around cristae Mitochondrion takes chemical energy from food (glucose) and produces energy molecule ATP © 2012 Pearson Education, Inc. 3-2 Organelles and the Cytoplasm Mitochondrial Energy Production Glycolysis (takes place in the cytoplasm) Glucose to pyruvic acid (in cytosol) Citric acid cycle (also known as the Krebs cycle and the tricarboxylic acid cycle or TCA cycle) Pyruvic acid to CO2 (in matrix) Electron transport chain Inner mitochondrial membrane Mitochondrial Energy Production Called aerobic metabolism (cellular respiration) Produces 95% of ATP needed to keep cell alive Mitochondria use oxygen to break down food and produce ATP Glucose + oxygen + ADP carbon dioxide + water + ATP © 2012 Pearson Education, Inc. Figure 3-9a Mitochondria Inner membrane Organic molecules and O2 Outer membrane Matrix Cristae Cytoplasm of cell Cristae Enzymes Matrix Outer membrane Mitochondrion TEM 46,332 Shown here is the three-dimensional organization and a color-enhanced TEM of a typical mitochondrion in section. © 2012 Pearson Education, Inc. Figure 3-9b Mitochondria CYTOPLASM Glucose Glycolysis Pyruvate Citric Acid Cycle ADP phosphate Enzymes and coenzymes of cristae MATRIX MITOCHONDRION This is an overview of the role of mitochondria in energy production. Mitochondria absorb short carbon chains (such as pyruvate) and oxygen and generate carbon dioxide and ATP. © 2012 Pearson Education, Inc. 3-3 Cell Nucleus Nucleus Largest organelle. It is the cell’s control center. Nuclear envelope (double membrane around the nucleus) Perinuclear space (between the two layaers of the nuclear membrane) Nuclear pores (communication passages) How the Nucleus Controls Cell Structure and Function Direct control through synthesis of: structural proteins and secretions Indirect control over metabolism through enzymes © 2012 Pearson Education, Inc. 3-3 Cell Nucleus Contents of the Nucleus DNA (all information to build and run organism) Nucleoplasm (fluid containing ions, enzymes, nucleotides, anad some RNA) Nuclear matrix (support filaments) Nucleoli (related to protein production; made of RNA, enzymes and histones (proteins); synthesize rRNA and ribosomal subunits) Nucleosomes (DNA coiled around histones) Chromatin (loosely coiled DNA (cells not dividing) Chromosomes (tightly coilded DNA (cells dividing) © 2012 Pearson Education, Inc. 3-3 Cell Nucleus Information Storage in the Nucleus (“genetic code”) DNA Instructions for every protein in the body Gene DNA instructions for one protein Genetic code The chemical language of DNA instructions Sequence of bases (A, T, C, G) Triplet code 3 bases = 1 amino acid Gene—functional unit of heredity © 2012 Pearson Education, Inc. 3-4 Protein Synthesis The Role of Gene Activation in Protein Synthesis The nucleus contains chromosomes → Chromosomes contain DNA →DNA stores genetic instructions for proteins → Proteins determine cell structure and function. Gene activation – uncoiling DNA to use it Promoter (control segment) at “start” of gene → Terminator “stop” Transcription Copies instructions from DNA to mRNA (in nucleus) RNA polymerase produces messenger RNA (mRNA) Translation Ribosome reads code from mRNA (in cytoplasm) and assembles amino acids into polypeptide chain Processing (RER and Golgi apparatus produceg protein) Gene Activation Transcription Translation © 2012 Pearson Education, Inc. Processing 3-4 Protein Synthesis The Transcription of mRNA Step 1: Gene activation (DNA strands separate and RNA polymerase binds to the promoter of the gene). Step 2: DNA to mRNA (RNA polymerase moves from one nucleotide to another along length of the template strand. At each site, complementary RNA nucleotides for hydrogen bonds with the DNA nucleotides of the template stand. RNA polymerase strings the arriving nucleotides together into a strand of mRNA). Step 3: RNA processing (On reaching the stop signal at the end of the gene, the RNA polymerase and the mRNA strand detach, and the two DNA strands reassociate). © 2012 Pearson Education, Inc. Figure 3-12 mRNA Transcription DNA Template strand Coding strand RNA polymerase Codon 1 Codon 2 Promoter 1 Gene Triplet 2 2 Triplet 3 3 Triplet 4 4 Complementary triplets Triplet 1 mRNA strand Codon 3 Codon 1 Codon 4 (stop codon) 2 RNA nucleotide KEY After transcription, the two DNA strands reassociate Adenine Uracil (RNA) Guanine Thymine (DNA) Cytosine 7 Where does transcription occur? Where does translation occur? © 2012 Pearson Education, Inc. 3-4 Protein Synthesis Translation mRNA moves from the nucleus through a nuclear pore → to a ribosome in the cytoplasm surrounded by amino acids → binds to ribosomal subunits → tRNA delivers amino acids to mRNA. tRNA anticodon binds to mRNA codon Enzymes join amino acids with peptide bonds Polypeptide chain has specific sequence of amino acids At stop codon, components separate © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. http://www.youtube.com/watch?v=AGzsgTMgSog © 2012 Pearson Education, Inc. Part B Part B © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Membrane Transport The plasma (cell) membrane is a barrier, but nutrients must get in and products and wastes must get out Permeability determines what moves in and out of a cell A cell that lets nothing in or out is impermeable A cell that lets anything pass is freely permeable The cell restricts movement is selectively permeable Selective permeability membrane restricts materials based on: Size Electrical charge Molecular shape Lipid solubility Transport through a plasma membrane can be: Active (requiring energy and ATP) or Passive (no energy required) Diffusion (passive) Carrier-mediated transport (passive or active) Vesicular transport (active) © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Diffusion All molecules are constantly in motion Molecules in solution move randomly Random motion causes mixing Concentration is the amount of solute in a solvent Concentration gradient is More solute in one part of a solvent than another © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Factors Influencing Diffusion Distance the particle has to move Molecule Size Smaller is faster Temperature More heat, faster motion Concentration Gradient The difference between high and low concentrations Electrical Forces Opposites attract, like charges repel © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Diffusion across Plasma Membranes Can be simple or channel mediated Materials that diffuse through plasma membrane by simple diffusion Lipid-soluble compounds (alcohols, fatty acids, and steroids) Channel-mediated diffusion Water-soluble compounds and ions Factors in channel-mediated diffusion Size Charge Interaction with the channel – leak channels Dissolved gases (oxygen and carbon dioxide) © 2012 Pearson Education, Inc. Figure 3-15 Diffusion across the Plasma Membrane EXTRACELLULAR FLUID Lipid-soluble molecules diffuse through the plasma membrane Plasma membrane CYTOPLASM © 2012 Pearson Education, Inc. Large molecules that cannot diffuse through lipids cannot cross the plasma membrane unless they are transported by a carrier mechanism Channel protein Small water-soluble molecules and ions diffuse through membrane channels 3-5 Diffusion and Osmosis Osmosis: A Special Case of Diffusion Osmosis is the diffusion of water across the cell membrane More solute molecules, lower concentration of water molecules Membrane must be freely permeable to water, selectively permeable to solutes Water molecules diffuse across membrane toward solution with more solutes Volume increases on the side with more solutes © 2012 Pearson Education, Inc. 3-5 Diffusion and Osmosis Osmolarity and Tonicity The osmotic effect of a solute on a cell Two fluids may have equal osmolarity (solute concentration), but different tonicity (how the solution affects a cell). Isotonic (iso- = same, tonos = tension) A solution that does not cause osmotic flow of water in or out of a cell Hypotonic (hypo- = below) Has less solutes and loses water through osmosis A cell in a hypotonic solution gains water (ruptures—hemolysis) Hypertonic (hyper- = above) Has more solutes and gains water by osmosis A cell in a hypertonic solution loses water (shrinks—crenation) © 2012 Pearson Education, Inc. Figure 3-17 Osmotic Flow across a Plasma Membrane. a Isotonic solution b In an isotonic saline solution, no osmotic flow occurs, and the red blood cells appear normal. Hypotonic solution In a hypotonic solution, the water flows into the cell. The swelling may continue until the plasma membrane ruptures, or lyses. c Hypertonic solution In a hypertonic solution, water moves out of the cell. The red blood cells shrivel and become crenated. Water molecules Solute molecules SEM of a normal RBC in an isotonic solution SEM of RBC in a hypotonic solution SEM of crenated RBCs PowerPoint® Lecture Presentations in a hypertonic solution prepared by Jason LaPres Lone Star College—North Harris © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Carrier-Mediated Transport Facilitated Diffusion (Passive) Carrier proteins transport molecules too large to fit through channel proteins (glucose, amino acids) Molecule binds to receptor site on carrier protein Protein changes shape, molecules pass through .Specificity .Saturation Receptor site is specific to certain molecules Limits .Regulation © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Carrier-Mediated Transport Active Transport (Primary or Secondary) Active transport proteins Move substrates against concentration gradient Require energy, such as ATP Ion pumps move ions (Na+, K+, Ca2+, Mg2+) Exchange pump counter transports two ions at the same time Primary Active Transport Sodium–potassium exchange pump Active transport, carrier mediated Sodium ions (Na+) out (3), potassium ions (K+) in (2) 1 ATP moves 3 Na+ and 2 K+ © 2012 Pearson Education, Inc. Figure 3-19 The Sodium-Potassium Exchange Pump EXTRACELLULAR FLUID Sodium potassium exchange pump CYTOPLASM © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Carrier-Mediated Transport Secondary active transport Na+ concentration gradient drives glucose transport ATP energy pumps Na+ back out © 2015 Pearson Education, Inc. © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Vesicular Transport (Bulk Transport) Materials move into or out of cell in vesicles Endocytosis (endo- = inside) is active transport using ATP Receptor mediated Pinocytosis Phagocytosis Receptor-mediated endocytosis Receptors (glycoproteins) bind target molecules (ligands) Coated vesicle (endosome) carries ligands and receptors into the cell © 2012 Pearson Education, Inc. Figure 3-21 Receptor-Mediated Endocytosis Ligands EXTRACELLULAR FLUID Ligands binding to receptors Target molecules (ligands) bind to receptors in plasma membrane. Exocytosis Endocytosis Ligand receptors Areas coated with ligands form deep pockets in plasma membrane surface. Coated vesicle Pockets pinch off, forming endosomes known as coated vesicles. F Primary lysosome Ligands removed CYTOPLASM Receptor-Mediated Endocytosis Secondary lysosome Coated vesicles fuse with primary lysosomes to form secondary lysosomes. Ligands are removed and absorbed into the cytoplasm. The lysosomal and endosomal membranes separate. The endosome fuses with the plasma membrane, and the receptors are again available for ligand binding. © 2012 Pearson Education, Inc. 3-6 Carriers and Vesicles Endocytosis Pinocytosis (“cell drinking”) Endosomes “drink” extracellular fluid Phagocytosis (“cell eating”) Pseudopodia (pseudo- = false, pod- = foot) Engulf large objects in phagosomes Exocytosis (exo- = outside) Granules or droplets are released from the cell © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 3-7 Transmembrane Potential Transmembrane Potential is the potential difference measured across a plasma membrane and expressed in millivolts, that results from the uneven distribution of positive and negative ions across the plasma membrane. Resting potential ranges from –10 mV to -100 mV, depending on cell type © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle Cell Life Cycle Most of a cell’s life is spent in a nondividing state (interphase) Body (somatic) cells divide in three stages DNA replication duplicates genetic material exactly Mitosis divides genetic material equally Cytokinesis divides cytoplasm and organelles into two daughter cells © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle DNA Replication Helicases unwind the DNA strands DNA polymerase Promotes bonding between the nitrogenous bases of the DNA strand and complementary DNA nucleotides dissolved in the nucleoplasm Links the nucleotides by covalent bonds DNA polymerase works in one direction Ligases piece together sections of DNA © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. Figure 3-24 Stages of a Cell’s Life Cycle: Interphase INTERPHASE Most cells spend only a small part of their time actively engaged in cell division. Somatic cells spend the majority of their functional lives in a state known as interphase. During interphase, a cell perfoms all its normal functions and, if necessary, prepares for cell division. When the activities of G1 have been completed, the cell enters the S phase. Over the next 68 hours, the cell duplicates its chromosomes. S This involves DNA replication and the synthesis of histones and other proteins in the nucleus. G1 A cell that is ready to divide first enters the G1 phase. In this phase, the cell makes enough mitochondria, cytoskeletal elements, endoplasmic reticula, ribosomes, Golgi membranes, and cytosol for two functional cells. Centriole replication begins in G1 and commonly continues G1 until G2. In cells Normal dividing at top cell functions speed, G1 may last plus cell growth, just 812 hours. duplication of Such cells pour organelles, all their energy protein synthesis into mitosis, and all other activities cease. If G1 lasts for days, weeks, or months, preparation for mitosis occurs as the cells perform their normal functions. G0 6 to Once DNA replication has ended, there is a brief (25-hour) G2 phase devoted to last-minute protein synthesis and to the completion of centriole replication. S DNA replication, synthesis of histones G2 G2 Protein synthesis THE CELL CYCLE Centrioles in centrosome MITOSIS Nucleus G0 An interphase cell in the G0 phase is not preparing for division, but is performing all of the other functions appropriate for that particular cell type. Some mature cells, such as skeletal muscle cells and most neurons, remain in G0 indefinitely and never divide. In contrast, stem cells, which divide repeatedly with very brief interphase periods, never enter G0. © 2012 Pearson Education, Inc. MITOSIS AND CYTOKINESIS Interphase During interphase, the DNA strands are loosely coiled and chromosomes cannot be seen. Figure 3-11 The Organization of DNA within the Nucleus Telomeres of sister chromatids Nucleus Connects chromatids Centromere Protein area that attaches to spindle fibers Kinetochore Supercoiled region Cell prepared for division Visible chromosome Nondividing cell In cells that are dividing DNA double helix Chromatin in nucleus Nucleosome Histones © 2012 Pearson Education, Inc. DNA strands coiled around histones Proteins in nucleoli 3-8 Cell Life Cycle Mitosis Prophase Nucleoli disappear ▪ Centriole pairs move to cell poles ▪ Microtubules (spindle fibers) extend between centriole pairs ▪ Nuclear envelope disappears ▪ Spindle fibers attach to knetochore Metaphase Chromosomes align in a central plane (metaphase plate) Anaphase Microtubules pull chromosomes apart group near centrioles ▪ Daugheter chromosomes Telophase Nuclear membranes re-form ▪ Chromosomes uncoil Nucleoli reappear ▪ Cell has two complete nuclei © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 10 When does cytokinesis begin? © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc. 3-8 Cell Life Cycle The Mitotic Rate and Energy Use Rate of cell division Slower mitotic rate means longer cell life Cell division requires energy (ATP) Muscle cells, neurons rarely divide Exposed cells (skin and digestive tract) live only days or hours – replenished by stem cells © 2012 Pearson Education, Inc. 3-10 Cell Division and Cancer Cancer Developes in Steps Abnormal cells → Primary tumor → Mestasis → Secondary tumor Tumor (Neoplasm) Enlarged mass of cells Abnormal cell growth and division Benign tumor Contained, not life threatening unless large Malignant tumor Spreads into surrounding tissues (invasion) Starts new tumors (metastasis) © 2012 Pearson Education, Inc. Figure 3-25 The Development of Cancer Abnormal cell Cell divisions Primary tumor cells Secondary tumor cells Growth of blood vessels into tumor Cell Invasion divisions Penetration Escape Circulation 1 Initially the cancer cells are restricted to the primary tumor. 2 Cancer cells gradually lose their resemblance to normal cells. 3 Metastasis begins with invasion as tumor cells “breakout” of the primary tumor and invade the surrounding tissue. 4Cancer cells in the bloodstream escape out of blood vesses to establish secondary tumors at other sites. 5 As malignant tumors grow, organ function begins to deteriorate. © 2012 Pearson Education, Inc. 3-11 Differentiation Differentiation All cells carry complete DNA instructions for all body functions Cells specialize or differentiate To form tissues (liver cells, fat cells, and neurons) By turning off all genes not needed by that cell All body cells, except sex cells, contain the same 46 chromosomes Differentiation depends on which genes are active and which are inactive © 2012 Pearson Education, Inc. Biol 2401 TRANSCRIPTION If the bases of one side of DNA read: A-G-C-T, the complementary (opposite) DNA strand reads: a. A-C-G-T. b. A-G-A-T. c. U-C-G-A. d. T-C-G-A. The bases in a strand of DNA READ: T-C-C-A. The transcribed strand of mRNA reads: a. A-G-G-T. b. G-C-G-A. c. U-C-G-T. d. A-G-G-U. © 2012 Pearson Education, Inc. Biol 2401 © 2012 Pearson Education, Inc. Genetic Code GUCCCGUG AUG CCG AGU UGG AGU AGA UAA CUCAGAAU START methionine © 2012 Pearson Education, Inc. proline serine tryptophane serine arginine STOP Clinical Case—When Your Heart Is in the Wrong Place What other cell, with a “tail” that has the same microtubule structure as motile cilia, might also be affected as a result of Jackson’s primary ciliary dyskinesia? What other consequences could result from Jackson’s disorder once he reaches adulthood: © 2012 Pearson Education, Inc. © 2012 Pearson Education, Inc.
