1. Chapter 3 Cells and Tissues

2. OBJECTIVES
◊ Identify and discuss the basic structure and functiono 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
◊ Compare and discuss DNA and RNA and their function in protein synthesis
◊ Discuss the stages of mitosis and eplaine the importance of cellular
reproduction
◊ 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
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3. CELLS Size and shape Composition
Human cells vary considerably in size; all are microscopic
Cells differ notably in shape
Composition
Cytoplasm containing specialized organelles surrounded by a plasma membrane
Organization of cytoplasmic substances important for life
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4. CELLS
Structural parts
Plasma membrane
Cytoplasm
Nucleus
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5. CELLS Structural parts
Plasma membrane forms outer boundary of cell (Figure 3-1)
Thin, two-layered membrane of phospholipids containing proteins
Is selectively permeable
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7. CELLS Cytoplasm (Figure 3-2) Organelles
Ribosomes
May attach to rough ER or lie free in cytoplasm
Manufacture proteins; often called protein factories
Endoplasmic reticulum (ER)
Network of connecting sacs and canals
Carry substances through cytoplasm
Rough ER collects and transports proteins made by ribosomes
Smooth ER synthesizes chemicals; makes new membrane
Golgi apparatus
Group of flattened sacs near nucleus
Collect chemicals that move from the smooth ER in vesicles and process them: called the chemical processing and packaging center
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9. CELLS Cytoplasm Organelles (cont.)
Mitochondria
Composed of inner and outer membranes; contains one DNA molecule
Involved with energy-releasing chemical reactions; called power plants of the cell
Lysosomes
Membrane-enclosed packets containing digestive enzymes
Have protective function (eat microbes)
Formerly thought to be responsible for apoptosis (programmed cell death)
Centrioles
Paired organelles that lie at right angles to each other near nucleus
Function in cell reproduction
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10. CELLS Cytoplasm Organelles (cont.)
Cilia
Fine, hairlike extensions found on free or exposed surfaces of some cells
Capable of moving in unison in a wavelike fashion
Flagella
Single projections extending from cell surfaces; much larger than cilia
“Tails” of sperm cells only example of flagella in humans
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11. CELLS
Nucleus
Controls cell because it contains 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
46 chromosomes contain DNA, which contains the genetic code
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12. CELLS Relationship of cell structure and function
Regulation of life processes
Relationship of structure to function apparent in number and type of organelles seen in different cells
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13. MOVEMENTS OF SUBSTANCES THROUGH CELL MEMBRANES
Passive transport processes do not require added energy and result in movement “down a concentration gradient”
Diffusion (Figure 3-3)
Substances scatter themselves evenly throughout an available space, the particles moving from high to low concentration
Passive process—not necessary to add energy to the system
Osmosis is diffusion of water (some solutes cannot cross the membrane during osmosis)
Dialysis is diffusion of small solute particles
Filtration—movement of water and solutes caused by hydrostatic pressure on one side of membrane
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15. MOVEMENTS OF SUBSTANCES THROUGH CELL MEMBRANES
Active transport processes occur only in living cells; movement of substances is “up the concentration gradient”; this requires energy from ATP
Ion pumps (Figure 3-4)
An ion pump is 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
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
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17. CELL REPRODUCTION
DNA structure—large molecule shaped like a spiral staircase; sugar (deoxyribose) and phosphate units compose sides of the molecule; base pairs (adenine-thymine or guanine-cytosine) compose “steps”; base pairs always the same but sequence of base pairs differs in different DNA molecules; a gene is a specific sequence of base pairs within a DNA molecule; genes dictate formation of enzymes and other proteins by ribosomes, thereby indirectly determining a cell’s structure and functions; in short, genes are heredity determinants (Figure 3-5)
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18. CELL REPRODUCTION Genetic code
Genetic information—stored in base-pair sequences on genes; expressed through protein synthesis
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 (Figure 3-5)
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20. CELL REPRODUCTION Genetic code (cont.) Transcription Translation
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
Translation
Involves synthesis of proteins in cytoplasm by ribosomes
Requires use of information contained in mRNA
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21. CELL REPRODUCTION
Cell division—reproduction of cell involving division of the nucleus (mitosis) and the cytoplasm; 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
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
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22. CELL REPRODUCTION Stages of mitosis (Figure 3-6) 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
Metaphase—second stage
Chromosomes align across center of cell
Spindle fibers attach themselves to each chromatid
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24. CELL REPRODUCTION Stages of mitosis (cont.) Anaphase—third stage
Centromeres break apart
Separated chromatids then called chromosomes
Chromosomes are pulled to opposite ends of cell
Cleavage furrow develops at end of anaphase
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25. CELL REPRODUCTION Stages of mitosis (cont.) 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
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26. TISSUES (Tables 3-6 through 3-8)
Epithelial tissue
Covers body and lines body cavities
Cells packed closely together with little matrix
Classified by shape of cells (Figure 3-7)
Squamous
Cuboidal
Columnar
Transitional
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28. TISSUES Epithelial tissue (cont.)
Also classified by arrangement of cells into one or more layers: simple or stratified
Simple squamous epithelium—single layer of scalelike cells adapted for transport (e.g., absorption) (Figure 3-8)
Stratified squamous epithelium—several layers of closely packed cells specializing in protection (Figure 3-9)
Simple columnar epithelium—tall, column-like cells arranged in a single layer; contain mucus-producing goblet cells; specialized for absorption (Figure 3-10)
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32. TISSUES Epithelial tissue (cont.)
Stratified transitional epithelium—up to 10 layers of roughly cuboidal-shaped cells that distort to squamous shape when stretched; found in body areas that stretch, such as urinary bladder (Figure 3-11)
Pseudostratified epithelium—single layer of distorted columnar cells; each cell touches basement membrane
Simple cuboidal epithelium—single layer of cubelike cells often specialized for secretory activity; may secrete into ducts, directly into blood, and on body surface (Figure 3-12)
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35. TISSUES Connective tissue
Most abundant and widely distributed tissue in body, with many different types, appearances, and functions
Relatively few cells in intercellular matrix
Types
Areolar—glue that holds organs together
Adipose (fat)—lipid storage is primary function (Figure 3-13)
Fibrous—strong fibers; example is tendon (Figure 3-14)
Bone—matrix is calcified; functions as support and protection (Figure 3-15)
Cartilage—chondrocyte is cell type (Figure 3-16)
Blood—matrix is fluid; function is transportation (Figure 3-17)
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36. TISSUES Muscle tissue (Figures 3-18 to 3-20) Types
Skeletal—attaches to bones; also called striated or voluntary; control is voluntary; striations apparent when viewed under a microscope (Figure 3-18)
Cardiac—also called striated involuntary; composes heart wall; ordinarily cannot control contractions (Figure 3-19)
Smooth—also called nonstriated (visceral) or involuntary; no cross striations; found in blood vessels and other tube-shaped organs (Figure 3-20)
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