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Chapter 3: Cells and Their Functions Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Overview Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease The Cell Cytology • The study of cells The Cell • The basic unit of life • Shows life characteristics – Organization – Homeostasis – Metabolism – Growth – Responsiveness – Reproduction Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Microscopes Cytology • The study of cells Microscope • An instrument that magnifies structures not visible with the naked eye • Types of microscopes: – Compound light microscope – Transmission electron microscope – Scanning electron microscope Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Figure 3-1 Cilia photographed under three different microscopes. Which microscope shows the most internal structure of the cilia? Which shows the cilia in three dimensions? Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Structure General Cell Organization • Plasma membrane – Selectively permeable – Also called the cell membrane • Nucleus • Cytoplasm – Cytosol – Organelles Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Figure 3-2 A generalized animal cell, sectional view. What is attached to the ER to make it look rough? What is the liquid part of the cytoplasm called? Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Structure Plasma Membrane • Encloses cell contents • Regulates what enters and leaves cell • Participates in many cell activities (e.g., growth, reproduction, cell-to-cell interactions) • Plasma membrane components – Phospholipid bilayer – Cholesterol • – Main lipid in plasma membrane* Proteins Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Structure Table 3-1 Proteins in the plasma membrane and their functions. Type of Protein Function Channels Pores in membrane that allow passage of specific substances *Transporters Shuttle substances across membrane Receptors Allow for attachment of substances to membrane; used for cell-to-cell signaling Enzymes Participate in chemical reactions at membrane surface *Linkers Give structure to membrane and attach cells to other cells Cell identity markers Proteins unique to a person’s cells; important for immunity Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Structure Nucleus • Largest organelle of cell • Surrounded by nuclear membrane • Contains – Chromosomes • Units of heredity; govern all cellular activity – Nucleolus • Assembles ribosomes Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Structure Cytoplasm • Material between nuclear membrane and plasma membrane – Cytosol • Fluid portion of cytoplasm – Organelles • Specialized cell structures that perform different cell functions Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Organelles* • Mitochondria – Power plants • Golgi apparatus – Sort and modify proteins • Lysosomes – Remove wast and foreign material • Peroxisomes – Contain enzymes that destroy harmful substances produced in metabolism • Vesicles – Storage sacs/microbodies Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Structure Table 3-2 Cell parts (cytoplasmic organelles). Name Description Function Endoplasmic reticulum (ER) Membranous network; only rough ER has ribosomes; smooth ER does not Rough ER sorts and modifies proteins; smooth ER synthesizes lipids *Ribosomes Small bodies in cytoplasm or attached to rough ER Manufacture proteins Mitochondri a Large bodies with internal folded membranes Manufacture ATP Golgi apparatus Layers of membranous sacs Prepares proteins for export *Lysosomes, Small sacs of enzymes Peroxisomes Digest intracellular substances Vesicles Small storage sacs Store materials; move materials into or out of cell Centrioles Rod-shaped near nucleus Separate chromosomes during cell division Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Structure Surface Projections • Structures that extend from the cell – Cilia • Short, hairlike projections • Move fluids around cells – Flagellum • Long, whiplike extension from the cell • Moves cell Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Structure Cellular Diversity •Cell shape is related to cell function. – A neuron’s long fibers transmit electric energy from place to place in the nervous system. – Small round red blood cells slide through tiny blood vessels. •Cell organelle number is related to cell function. – Lipid-producing cells have lots of smooth ER. – Metabolically active cells have lots of mitochondria to manufacture ATP. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Figure 3-5 Cellular diversity. Which of the cells shown would best cover a large surface area? Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Movement of Substances Across the Plasma Membrane Selective Permeability • Plasma membrane regulates what enters and leaves • Travel across membrane is based on several factors – Molecular size – Solubility – Electrical charge • Types of travel – Movement that does not require cellular energy – Movement that requires cellular energy Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Movement of Substances Across the Plasma Membrane Movement That Does Not Require Cellular Energy Process Definition Example Diffusion Solute travels across plasma membrane down its concentration gradient Movement of lipidsoluble materials across plasma membrane Facilitated diffusion Solute diffuses with help of a transporter Movement of glucose into cell Osmosis Solvent travels across plasma membrane down its concentration gradient Movement of water across plasma membrane Filtration Mechanical force pushes solute and solvent across plasma membrane Movement of solutes and water out of blood under force of blood pressure Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Figure 3-6 Diffusion of a solid in a liquid. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Movement of Substances Across the Plasma Membrane How Osmosis Affects Cells • Another way to think about osmosis is in terms of solute concentration. High Solute Low Solute Osmosis High Water Low Water Water Follows the Salt Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Movement of Substances Across the Plasma Membrane Solutions and Their Effects on Cells Solution Description Examples Effect on Cells Isotonic Has same solute concentration as cell 0.9% salt; 5% glucose None Hypotonic Has lower solute concentration than cell <0.9% salt; <5% glucose Cell takes in water and may burst (lysis) Hypertonic Has higher solute concentration than cell >0.9% salt; >5% glucose Cell loses water and shrinks (crenation) Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Figure 3-10 The effect of osmosis on cells. What would happen to red blood cells in the body if blood lost through injury were replaced with pure water? Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Figure 3-11 Filtration. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Movement of Substances Across the Plasma Membrane Movement That Requires Cellular Energy Process Definition Example Active transport Solute moves through plasma membrane against its concentration gradient with help of transporters Ion movement in nervous system and muscular system Endocytosis Large amounts of solute and solvent are transported into cell using vesicles Phagocytosis of waste materials by white blood cells Exocytosis Large amounts of solute and solvent are transported out of the using vesicles Release of neurotransmitters from neurons Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Protein Synthesis Overview • Proteins give a cell its structure and function. • DNA directs protein synthesis. – Nucleotides make up DNA – DNA organized into genes – Genes organized into chromosomes • RNA participates in protein synthesis but is not part of chromosomes. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Figure 3-15 Structure of DNA. Two of the DNA nucleotides (A and G) are larger in size than the other two (T and C). How do the nucleotides pair up with regard to size? Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Protein Synthesis Role of RNA Types Function mRNA - Is built on a strand of DNA in the nucleus and transcribes the nucleotide code - Moves to cytoplasm and attaches to a ribosome rRNA - With protein makes up the ribosomes, the sites of protein synthesis in the cytoplasm - Involved in the process of translating the genetic message into a protein tRNA - Works with mRNA and rRNA to translate the genetic code into protein - Each molecule of tRNA carries an amino acid that can be used to build a protein at the ribosome. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Protein Synthesis Two-Step Process of Protein Synthesis • Transcription – First step; occurs in nucleus – DNA code is transcribed into mRNA by nucleotide base pairing • Translation – Second step; occurs in cytoplasm – mRNA leaves nucleus and travels to ribosomes – Ribosomes and tRNA translate mRNA into protein’s amino acid sequence Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Division Types of Cell Division • Meiosis – Produces gametes (n) – Cuts chromosome number in half to prepare for union of egg and sperm during fertilization • Mitosis – Produces somatic cells (2n) – Parent stem cell gives rise to two identical daughter cells Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Division Preparation for Mitosis • DNA replicates during interphase • Identical strands held together at centromere until they separate during mitosis DNA replication during interphase Mitosis Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Division Stages of Mitosis Description Prophase - DNA strands coil into chromosomes - Nucleolus and nuclear membrane disappear - Centrioles move to opposite poles and form spindle Metaphase - Chromosomes line up across center of cell - Chromosomes attach to spindle Anaphase - Centromeres split - Identical chromosomes move toward opposite centrioles Telophase - Chromosomes continue to move toward centrioles - Nuclear membrane forms around each group of chromosomes - Plasma membrane pinches off in middle of cell to form two new identical daughter cells Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Figure 3-18 The stages of mitosis. If the original cell shown has 46 chromosomes, how many chromosomes will each new daughter cell have? Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Cell Aging • As cells multiply, changes occur that may lead to their damage or death. – Free radical injury – Enzyme injury – Gene mutation – Slowing cell activity – Apoptosis Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Cohen: Memmler’s The Human Body in Health and Disease Word Anatomy Word Part Meaning Example cyt/o cell Cytology is the study of cells. endo- in, within The endoplasmic reticulum within the cytoplasm. hypo- deficient, below, beneath A hypotonic solution’s concentration is lower than cytoplasm’s. hyper- above, over, excessive A hypertonic solution’s concentration is higher than cytoplasm’s. exo- outside, out of, away In exocytosis, the cell moves material out from vesicles. pro- before, in front Prophase is the first stage of mitosis. meta- change During metaphase chromosomes change position and line up across the equator. ana- upward, back, again During anaphase, chromosomes move to opposite sides of the cell. tel/o end Telophase is the last stage of mitosis. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins