Chapter 3 Cells and Tissues
Objectives Identify and discuss the basic structure and function of the three major components of a cell List and briefly discuss the functions of the primary cellular organelles Compare the major passive and active transport processes that act to move substances through cell membranes 2
Objectives Compare and discuss DNA and RNA and their function in protein synthesis Discuss the stages of mitosis and explain the importance of cellular reproduction 3
Objectives Explain how epithelial tissue is grouped according to shape and arrangement of cells List and briefly discuss the major types of connective and muscle tissue List the three structural components of a neuron 4
Cells Size and shape Human cells vary considerably in size All are microscopic Cells differ notably in shape 5
Cells Composition Cells contain cytoplasm substance found only in cells Organelles are specialized structures within the cytoplasm Cell interior is surrounded by a plasma membrane 6
What cells can be seen with the naked eye Human Ovum Giant Bacteria Epulopiscium fischelsoni was believed to be the largest. It sometimes reaches 500 micrometers or half a millimeter in size, which is the size of a period after a sentence. It lives in the guts of some species of fish off the Australian coastline and in the Red Sea. The largest known bacterium, however, is Thiomargarita namibiensis, a bacterium found off the coast of Namibia in Africa that can reach 750 micrometers in diameter--a veritable giant among bacteria. 7
Cells seen with the naked eye Giant Amoebas- can grow to 1.2 inches in diameter Squid Nerve Cells Bird Eggs-look in your refridgerator 8
Cells Composition Parts of the cell Plasma membrane Forms outer boundary of cell Composed of a thin, two-layered membrane of phospholipids containing proteins Is selectively permeable 9
Plasma membrane 10
Cells Composition Structural parts Cytoplasm internal cell fluid and numerous organelles Ribosomes» May attach to rough ER or lie free in cytoplasm» Made of two tiny subunits of mostly ribosomal RNA» Manufacture enzymes and other protein compounds» Often called protein factories 11
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Cells Composition Structural parts Cytoplasm Organelles» Endoplasmic reticulum (ER) - Network of connecting sacs and canals - Carry substances through fluid cytoplasm - Two types rough and smooth - Rough ER collects, folds, and transports proteins made by ribosomes - Smooth ER synthesizes chemicals; makes new membrane 13
Cells Composition Structural parts Cytoplasm Organelles» Golgi apparatus - Group of flattened sacs near nucleus - Collect chemicals into vesicles that move from the smooth ER outward to plasma membrane - Called the chemical processing and packaging center 14
Cells Composition Structural parts Cytoplasm Organelles» Mitochondria - Composed of inner and outer membranous sacks - Involved with energy-releasing chemical reactions - Often called power plants of the cell - Contains one DNA molecule 15
Cells Composition Structural parts Cytoplasm Organelles» Lysosomes - Membranous-walled organelles - Contain digestive enzymes - Have protective function (eat microbes) - Formerly thought to be responsible for apoptosis (programmed cell death) 16
Cells Composition Structural parts Cytoplasm Organelles» Centrioles - Paired organelles that lie at right angles to each other near the nucleus - Function in cell reproduction 17
Cells Composition Structural parts Cytoplasm Organelles» Microvilli - Small, fingerlike extensions of the plasma membrane - Increase absorptive surface area of the cell 18
Cells Composition Structural parts Cytoplasm Organelles» Cilia - Fine, hairlike extensions found on free or exposed surfaces of some cells - Capable of moving in unison in a wavelike fashion 19
Cells Composition Structural parts Cytoplasm Organelles» Flagella - Single projections extending from cell surfaces - Much larger than cilia - Tails of sperm cells only example of flagella in humans 20
Cells Composition Nucleus Controls cell because it contains DNA, the genetic code instructions for making proteins, which in turn determine cell structure and function Component structures include nuclear envelope, nucleoplasm, nucleolus, and chromatin granules DNA molecules become tightly coiled chromosomes during cell division Each cell has 46 chromosomes in the nucleus 21
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Relationship of Cell Structure and Function Every human cell has a designated function some help maintain the cell; others regulate life processes of the body itself Specialized functions of a cell differ depending on number and type of organelles 23
Relationship of Cell Structure and Function Relationship of structure to function apparent in number and type of organelles seen in different cells Heart muscle cells contain many mitochondria required to produce adequate energy needed for continued contractions Flagellum of sperm cell gives motility, allowing movement of sperm through female reproductive tract, thus increasing chances for fertilization 24
Movements of Substances Through Cell Membranes Passive transport processes do not require added energy and result in movement down a concentration gradient 25
Movements of Substances Through Cell Membranes Diffusion Substances scatter themselves evenly throughout an available space It is unnecessary to add energy to the system Movement is from high to low concentration 26
Movements of Substances Through Cell Membranes Diffusion Osmosis and dialysis are specialized examples of diffusion across a selectively permeable membrane Osmosis is diffusion of water (when some solutes cannot cross the membrane) Dialysis is diffusion of solutes 27
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Movements of Substances Through Cell Membranes Filtration Movement of water and solutes caused by hydrostatic pressure on one side of membrane Responsible for urine formation 29
Movements of Substances Through Cell Membranes Active transport processes occur only in living cells Movement of substances is up the concentration gradient Requires energy from ATP 30
Movements of Substances Through Cell Membranes Ion pumps Ion pump: a protein complex in the cell membrane Ion pumps use energy from ATP to move substances across cell membranes against their concentration gradients Examples: sodium-potassium pump; calcium pump Some ion pumps work with other carriers so that glucose or amino acids are transported along with ions 31
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Movements of Substances Through Cell Membranes Phagocytosis and pinocytosis Both are active transport mechanisms because they require cell energy Phagocytosis is a protective mechanism often used to destroy bacteria Pinocytosis is used to incorporate fluids or dissolved substances into cells 33
Movements of Substances Through Cell Membranes Several severe diseases result from damage to cell transport processes 34
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Movements of Substances Through Cell Membranes Cell transport and disease Cystic fibrosis, characterized by abnormally thick secretions in the airways and digestive ducts, results from failed Cl transport Cholera is a bacterial infection that causes Cl and water to leak from cells lining the intestines, resulting in severe diarrhea and water loss 36
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Cell Reproduction and Heredity DNA molecule and genetic information DNA molecule resembles a long, narrow ladder twisted round and round its axis; shaped in a double helix Each molecule made of a sugar (deoxyribose), bases, and phosphate units Bases are nitrogen-containing chemicals: adenine, thymine, guanine, and cytosine 38
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Cell Reproduction DNA Complementary base pairing each step of DNA ladder contains a base pair; adenine-thymine or cytosine-guanine A gene is a specific segment of base pairs in a chromosome Genetic code sequence of base pairs determines heredity Coded information in genes controls protein and enzyme production Enzymes facilitate chemical reactions Cellular chemical reactions determine cell structure and function 40
Cell Reproduction and Heredity DNA RNA molecules and protein synthesis DNA contained in cell nucleus Protein synthesis occurs in cytoplasm, thus genetic information must pass from the nucleus to the cytoplasm Process of transferring genetic information from nucleus to cytoplasm where proteins are produced requires completion of transcription and translation 41
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Cell Reproduction and Heredity DNA Transcription Double-stranded DNA separates to form messenger RNA (mrna) Each strand of mrna duplicates a particular gene (base-pair sequence) from a segment of DNA mrna molecules pass from the nucleus to the cytoplasm, where they direct protein synthesis in ribosomes and ER 43
Cell Reproduction and Heredity DNA Translation Involves synthesis of proteins in cytoplasm by ribosomes Requires use of information contained in mrna Codon a series of three nucleotide bases that act as a code for a specific amino acid 44
Cell Reproduction and Heredity Cells, genetics, and disease Abnormal DNA that is inherited, or that results from damage, is often the basis of disease Factors that cause damage to DNA molecules include chemical or mechanical irritants, radiation, bacteria, and viruses 45
Cell Reproduction and Heredity Cell division reproduction of cell involving division of the nucleus (mitosis) and the cytoplasm Two daughter cells result from the division Period when the cell is not actively dividing is called interphase DNA replication process by which each half of a DNA molecule becomes a whole molecule identical to the original DNA molecule; precedes mitosis 46
Cell Reproduction and Heredity Cell division Mitosis process in cell division that distributes identical chromosomes (DNA molecules) to each new cell formed when the original cell divides Enables cells to reproduce their own kind Makes heredity possible 47
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Cell Reproduction and Heredity Cell division Mitosis Prophase first stage Chromatin granules become organized Chromosomes (pairs of linked chromatids) appear Centrioles move away from nucleus Nuclear envelope disappears, freeing genetic material Spindle fibers appear 49
Cell Reproduction and Heredity Cell division Mitosis Metaphase second stage Chromosomes align across center of cell Spindle fibers attach themselves to each chromatid 50
Cell Reproduction and Heredity Cell division Mitosis Anaphase third stage Centromeres break apart Separated chromatids now called chromosomes Chromosomes are pulled to opposite ends of cell Cleavage furrow develops at end of anaphase 51
Cell Reproduction and Heredity Cell division Mitosis Telophase fourth stage Cell division is completed Nuclei appear in daughter cells Nuclear envelope and nucleoli appear Cytoplasm is divided (cytokinesis) Daughter cells become fully functional 52
Cell Reproduction and Heredity Changes in cell growth and reproduction Hypertrophy increase in size of individual cells; increasing size of tissue Atrophy decrease in size of individual cells; decreasing size of tissue 53
Cell Reproduction and Heredity Changes in cell growth and reproduction Hyperplasia increase in cell reproduction, increasing size of tissue Anaplasia production of abnormal, undifferentiated cells Uncontrolled cell reproduction results in formation of a benign or malignant neoplasm (tumor) 54
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Tissues Epithelial tissue Covers body and lines body cavities Cells packed closely together with little matrix Classified by shape of cells Squamous Cuboidal Columnar Transitional 56
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Tissues Epithelial tissue Classified by arrangement of cells Simple Stratified Simple squamous epithelium Single layer of scalelike cells Transport (e.g., absorption) is function Stratified squamous epithelium Several layers of closely packed cells Protection is primary function 58
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Tissues Epithelial tissue Simple columnar epithelium Columnar cells arranged in a single layer Line stomach and intestines Contain mucus-producing goblet cells Specialized for absorption Stratified transitional epithelium Found in body areas, such as urinary bladder, that stretch Up to 10 layers of roughly cuboidal-shaped cells that distort to squamous shape when stretched 61
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Tissues Epithelial tissue Pseudostratified epithelium Each cell touches basement membrane Lines the trachea 64
Tissues Epithelial tissue Simple cuboidal epithelium Often specialized for secretory activity Cuboidal cells may be grouped into glands May secrete into ducts, directly into blood, and on body surface Examples of secretions include saliva, digestive juice, and hormones Cuboidal epithelium also forms the urineproducing tubules of the kidney 65
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Tissues Connective tissue Most abundant tissue in body Most widely distributed tissue in body Multiple types, appearances, and functions Relatively few cells in intercellular matrix 67
Tissues Connective tissue Types Areolar glue that holds organs together Adipose (fat) lipid storage is primary function Fibrous bundles of strong collagen fibers; e.g., tendon Bone matrix is calcified; function is support and protection Cartilage matrix is consistency of gristle-like gel; chondrocyte is cell type Blood matrix is fluid; functions are transportation and protection 68
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Tissues Muscle tissue Types Skeletal muscle tissue attaches to bones; also called striated or voluntary; control is voluntary; striations apparent when viewed under a microscope Cardiac muscle tissue also called striated or involuntary; composes heart wall; ordinarily cannot control contractions Smooth muscle tissue also called nonstriated (visceral) or involuntary; no cross striations; found in blood vessels and other tube-shaped organs 72
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Tissues Nervous tissue Function rapid communication between body structures and control of body functions Neurons conduction cells 75
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Tissues Nervous tissue Neurons All neurons have a cell body and two types of processes: axon and dendrite Axon (one) carries nerve impulse away from cell body Dendrites (one or more) carry nerve impulse toward the cell body Glia (neuroglia) supportive and connecting cells 77
Tissues Tissue repair usually accomplished by means of regeneration of tissue Epithelial and connective tissues regenerate easily Muscle and nervous tissues have very limited abilities to repair themselves 78