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Chapter 2 Cells Copyright © McGraw-Hill Education. Permission required for reproduction or display. Learning Outcomes • Explain why it is important to know the cellular basis of a disease • Define differentiated cell • List the four major chemicals in cells • Describe how organelles interact • Describe the structure and function of a biological membrane • List the components of the cytoskeleton Copyright © McGraw-Hill Education. Permission required for reproduction or display. 2 Learning Outcomes • • • • • Distinguish between mitosis and apoptosis Describe the events and control of the cell cycle List the characteristics of a stem cell Define stem and progenitor cell How can the bacteria that live in and on our bodies affect our health? Copyright © McGraw-Hill Education. Permission required for reproduction or display. 3 Introducing Cells • Cellular activities underlie our inherited traits, quirks, and illnesses • Understanding genetic diseases can suggest ways to treat the condition Figure 2.1 Duchenne muscular dystrophy - Lack of dystrophin Copyright © McGraw-Hill Education. Permission required for reproduction or display. 4 Introducing Cells • Our bodies include more than 290 cell types • Somatic (body) cells have two copies of the genome and are said to be diploid • Sperm and egg cells have one copy of the genome and are haploid • Stem cells can divide to give rise to differentiated cells and replicate themselves through selfrenewal Copyright © McGraw-Hill Education. Permission required for reproduction or display. 5 Tissue Types Figure 2.2 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 6 Types of Cells • Prokaryotic cells • Lack a nucleus • Eukaryotic cells • Possess a nucleus and organelles Figure 2.3 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 7 Domains of Life • Biologists recognize three broad categories of organisms • Archaea and Bacteria - Unicellular prokaryotes • Eukarya - Includes both unicellular and multicellular eukaryotes • Cells of domains contain globular assemblies of RNA and protein called ribosomes • Essential for protein synthesis Copyright © McGraw-Hill Education. Permission required for reproduction or display. 8 Chemical Constituents • Cells contain four types of macromolecules Type Carbohydrates Examples Sugars, starches Functions • • Lipids Fats, oils • • • Proteins • • Nucleic Acids DNA, RNA Provide energy Contribute to cell structure Basis of hormones Form membranes Provide insulation, store energy Antibodies Enzymes catalyze biochemical reactions Translate genetic information Copyright © McGraw-Hill Education. Permission required for reproduction or display. 9 Organelles • Divide labor by partitioning certain areas or serving specific functions • Keep related biochemicals and structures close to one another to interact efficiently • Functions • Enable a cell to retain and use its genetic instructions • Acquire energy, secrete substances, and dismantle debris Copyright © McGraw-Hill Education. Permission required for reproduction or display. 10 Figure 2.4 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 11 The Nucleus • Prominent organelle • Surrounded by a layer of nuclear envelope • Contains: • Nuclear pores that allow movement of biochemicals • Nuclear lamina provides mechanical support and holds nuclear pores in place • Nucleolus produces ribosomes • Other contents - Chromosomes, RNA and nucleoplasm Copyright © McGraw-Hill Education. Permission required for reproduction or display. 12 The Nucleus Figure 2.5 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 13 An Animal Cell • Surrounded by the plasma membrane • Contains: • • • • Cytoplasm Stored proteins, carbohydrates, and lipids Pigment molecules Other small chemicals Copyright © McGraw-Hill Education. Permission required for reproduction or display. 14 • Secretion illustrates how organelles function together to coordinate the basic life functions Figure 2.6 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 15 Endoplasmic Reticulum (ER) • Interconnected membranous tubules & sacs • Winds from the nuclear envelope to the plasma membrane • Rough ER contains ribosomes and is involved in protein synthesis • Smooth ER does not contain ribosomes and is important in lipid synthesis • Proteins exit the ER in membrane-bounded, saclike organelles called vesicles Copyright © McGraw-Hill Education. Permission required for reproduction or display. 16 Golgi Apparatus • Stack of interconnected flat, membrane-enclosed sacs • Processing center that adds sugars forming glycoproteins and glycolipids • Products are released into vesicles that bud off to the plasma membrane Copyright © McGraw-Hill Education. Permission required for reproduction or display. 17 Lysosomes • Membrane-bound sacs containing 43 types of digestive enzymes • Dismantle bacterial remnants, worn-out organelles, and excess cholesterol • Engages in autophagy Figure 2.7 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 18 Lysosomes • Cells differ in the number of lysosomes they contain • Absence or malfunction of an enzyme causes a lysosomal storage disease • Tay-Sachs is an inherited disorder Copyright © McGraw-Hill Education. Permission required for reproduction or display. 19 Peroxisomes • Sacs with outer membranes studded with several types of enzymes • Break down lipids, rare biochemicals • Synthesize bile acids • Detoxify compounds from exposure to oxygen free radicals • Abundant in liver and kidney cells Copyright © McGraw-Hill Education. Permission required for reproduction or display. 20 Mitochondria • Surrounded by two membranes • Provide energy by breaking chemical bonds that hold together nutrient molecules in food • Freed energy is stored in adenosine triphosphate (ATP) Copyright © McGraw-Hill Education. Permission required for reproduction or display. Figure 2.8 21 Biological Membrane • A phospholipid bilayer • Phosphate end (hydrophilic) • Fatty acid chains (hydrophobic) Figure 2.9 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 22 Biological Membrane • Proteins aboard lipids: • Contribute to cell’s identity • Transport molecules • Keep out toxins and pathogens • Some membrane proteins form channels for ions Figure 2.10 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 23 Plasma Membrane - Cell-to-Cell Communication • Molecules that extend from the plasma membrane are receptors • Signal transduction • Molecules form pathways that detect signals from outside the cell and transmit them inward • Cellular adhesion • Plasma membrane helps cells attach to certain other cells Copyright © McGraw-Hill Education. Permission required for reproduction or display. 24 Structures and Functions of Organelles Copyright © McGraw-Hill Education. Permission required for reproduction or display. 25 Cytoskeleton Functions • Maintain cell shape • Connect cells to each other • Transport organelles, cellular contents, and motor molecules Copyright © McGraw-Hill Education. Permission required for reproduction or display. 26 Cytoskeleton • Meshwork of protein rods and tubules • Includes three major types of proteins • Microtubules • Microfilaments • Intermediate filaments Figure 2.11 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 27 Figure 2.12 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 28 Cell Division and Death • Growth, development, maintaining health, and healing from disease or injury require an intricate interplay between the rates of: • Mitosis and cytokinesis - Division of DNA and rest of the cell • Apoptosis - Cell death • Precise, genetically programmed sequence of events Copyright © McGraw-Hill Education. Permission required for reproduction or display. 29 Figure 2.13 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 30 The Cell Cycle • The sequence of events associated with cell division Figure 2.14 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 31 Stages of the Cell Cycle - Interphase • • • • Prepares for cell division Replicates DNA and subcellular structures Composed of G1, S, and G2 phases Cells may exit the cell cycle at G1 or enter G0, a quit phase Copyright © McGraw-Hill Education. Permission required for reproduction or display. 32 Stages of the Cell Cycle - Interphase • Chromosomes are replicated during S phase prior to mitosis • Result in each chromosome consisting of two copies joined at the centromere • Proteins forming the mitotic spindle are synthesized • Microtubules form centrioles near the nucleus Copyright © McGraw-Hill Education. Permission required for reproduction or display. 33 Replicated and Unreplicated Chromosomes Figure 2.15 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 34 Mitosis - Prophase • • • • DNA coils tightly Microtubules organize into a spindle Nuclear membrane breaks down Nucleolus is not visible Copyright © McGraw-Hill Education. Permission required for reproduction or display. 35 Mitosis - Metaphase • Chromosomes attach to the spindle at their centromeres • Align along the cell’s equator • Chromosomes are pulled with equal force on both sides Figure 2.16 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 36 Mitosis - Anaphase • Centromeres divide • Chromatids separate and become independent chromosomes • Move to opposite ends of the cell Figure 2.16 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 37 Mitosis - Telophase • Spindle falls apart • Nucleoli and membranes around the nuclei re-form at each end of the elongated cell Figure 2.16 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 38 Mitosis - Cytokinesis • Cytoplasmic division occurs after nuclear division is complete • Organelles and macromolecules are distributed between the two daughter cells • Microfilament band contracts, separating the two cells Copyright © McGraw-Hill Education. Permission required for reproduction or display. 39 Cell Cycle Control • Checkpoints ensure that chromosomes are replicated and apportioned into daughter cells • Internal and external factors can affect a cell’s mitotic clock Copyright © McGraw-Hill Education. Permission required for reproduction or display. 40 Cell Cycle Control Figure 2.17 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 41 Telomeres • Located at the ends of the chromosomes • Contain hundreds to thousands of repeats of a 6base DNA sequence • Lose 50-200 endmost bases after each cell division • After 50 divisions, shortened telomeres signal the cell to stop dividing • Sperm, eggs, bone marrow, and cancer cells produce telomerase that prevent shortening of telomeres Copyright © McGraw-Hill Education. Permission required for reproduction or display. 42 Figure 2.18 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 43 Hormones and Growth Factors • Hormone is made in a gland and transported in the bloodstream to another part of the body • Exerts a specific effect • A growth factor acts locally • Epidermal growth factor (EGF) stimulates cell division in the skin beneath a scab Copyright © McGraw-Hill Education. Permission required for reproduction or display. 44 Apoptosis • Begins when a cell receives a “death receptor” • Killer enzymes called caspases are activated • Destroy cellular components • Phagocytes digest the remains • Dying cell forms bulges called blebs Copyright © McGraw-Hill Education. Permission required for reproduction or display. 45 Figure 2.19 • Mitosis and apotosis work together to form functional body • Cancer can result from too much mitosis or too little apotosis Copyright © McGraw-Hill Education. Permission required for reproduction or display. 46 Stem Cells • A stem cell divides by mitosis • Produces two daughter cells or a stem cell and a progenitor cell, which may be partially specialized • Progenitor cells do not have the capacity of selfrenewal Figure 2.20 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 47 Stem Cells • Cells differentiate down cell lineages of stem, progenitor, and increasingly differentiated cells • Stem cells and progenitor cells are described in terms of their developmental potential • Totipotent - Can give rise to every cell type • Pluripotent - Have fewer possible fates • Multipotent - Have only a few developmental choices Copyright © McGraw-Hill Education. Permission required for reproduction or display. 48 Figure 2.21 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 49 Stem Cells in Health Care • There are 3 general sources of human stem cells • Embryonic stem cells - Created in a lab dish using the inner cell mass (ICM) of an embryo • Induced pluripotent stem (iPS) cells - Somatic cells reprogrammed to differentiate into any of several cell types • Adult stem cells - Tissue-specific or somatic stem cells Copyright © McGraw-Hill Education. Permission required for reproduction or display. 50 Stem Cells in Health Care Figure 2.22 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 51 Stem Cell Applications • Stem cells are being used in four basic ways • Discovery and development of drugs • Observing the earliest sign of disease • Create tissues and organs, for use in implants and transplants, or to study • Stimulating stem cells in the body via the introduction of reprogramming proteins Copyright © McGraw-Hill Education. Permission required for reproduction or display. 52 The Human Microbiome • Ninety percent of the cells in a human body are microorganisms, constitute the human microbiome • Different body parts house different communities of microbes • Genes interact with the microbiome and with environmental factors to mold most traits Copyright © McGraw-Hill Education. Permission required for reproduction or display. 53