Ch02 Cell

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12/6/2012 1 1 Human Anatomy, First Edition McKinley & O'Loughlin Chapter 2 : The Cell: Basic Unit of Structure and Function 2-2 The Cell Cells: structural and functional units of all living organisms. building blocks of the human body. adult human body contains ~ 75 trillion cells. Each cell type performs specific functions. ~200 cell types in humans subcategories of most 2-3 Common Characteristics of Cells Perform the general functions necessary to sustain life: Obtain nutrients and other materials from its surrounding fluids. Fuel molecules, O 2, building blocks, minerals,etc Dispose of wastes products Urea (from nitrogen), CO 2 , metabolic waste Maintain shape and integrity Size and shape are related to function Cell division: Mitosis: growth and repair Meiosis: gamete formation 2-4 Study of Cells Cytology: study of cells Microscopic anatomy Individual cells observable by light microscopy Subcellular structures observable by electron microscopy. TEM SEM Unit of measure: micrometer (um) RBC: 7-8um 5 2-6 Cells Parts of a cell Cell Membrane (or plasma membrane) Cytoplasm Cytosol Organelles Membranous Organelles Non-membranous Organelles Inclusions Nucleus

description

Cells

Transcript of Ch02 Cell

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    Human Anatomy, First EditionMcKinley & O'Loughlin

    Chapter 2 :

    The Cell: Basic Unit of Structure and

    Function

    2-2

    The Cell

    Cells:

    structural and functional units of all living organisms.

    building blocks of the human body.

    adult human body contains ~ 75 trillion cells.

    Each cell type performs specific functions.

    ~200 cell types in humans

    subcategories of most

    2-3

    Common Characteristics of Cells

    Perform the general functions necessary to sustain life: Obtain nutrients and other materials from its

    surrounding fluids. Fuel molecules, O2, building blocks, minerals,etc

    Dispose of wastes products Urea (from nitrogen), CO2, metabolic waste

    Maintain shape and integrity Size and shape are related to function

    Cell division: Mitosis: growth and repair

    Meiosis: gamete formation 2-4

    Study of Cells

    Cytology: study of cells

    Microscopic anatomy

    Individual cells observable by light microscopy

    Subcellular structures observable by electron microscopy.

    TEM

    SEM

    Unit of measure: micrometer (um)

    RBC: 7-8um

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    Cells

    Parts of a cell

    Cell Membrane (or plasma membrane)

    Cytoplasm

    Cytosol

    Organelles

    Membranous Organelles

    Non-membranous Organelles

    Inclusions

    Nucleus

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    Plasma (Cell) Membrane

    the outer, limiting barrier

    separates the internal

    contents of the cell from external materials.

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    Cytoplasm

    general term for all cellular contents located between the plasma membrane and the nucleus.

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    Nucleus

    control center of the cell

    controls protein synthesis

    directs the functional and structural

    characteristics of the cell.

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    Plasma membrane: composition

    Lipids Phospholipids

    Head: hydrophilic

    Tail: hydrophobic

    Form lipid bilayer

    Cholesterol

    Glycolipids Carbohydrate component

    Part of glycocalyx

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    Plasma membrane: composition

    Protein

    Integral membrane proteins

    Peripheral membrane proteins

    Some serve as enzymes, ion channels or receptors

    Glycoproteins

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    Plasma membrane: functions

    Selectively permeable barrier

    Nutrient in

    Waste out

    Communication

    Intercellular connections

    Physical barrier

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    Transport Mechanisms

    Passive Transport

    Active Transport

    Bulk Transport

    Solution= solvent (H2O)+ solute

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    Passive Transport

    Movement of substances along a concentration gradient [Hi] to [Low]

    ATP is not required

    Types: Simple Diffusion: solutes

    Facilitated Diffusion: solutes

    Bulk Filtration: solution

    Osmosis: solvent

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    Facilitated Diffusion

    Requires the participation of specific transport proteins that help specific substances or molecules move across the plasma membrane.

    Carrier-mediated

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    Bulk Filtration

    Involves the diffusion of both solvents and solutes together across the selectively permeable membrane.

    Pressure gradients

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    Osmosis

    Involves the diffusion of a solvent (H2O), across a selectively permeable membrane.

    Can cause a volume change

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    Active Transport

    Movement of a substance across a plasma membrane against a concentration gradient.

    Materials must be moved from an area of low concentration to an area of high concentration.

    requires cellular energy in the form of ATP (adenosine triphosphate)

    uses transport proteins (carrier-mediated)

    ATP is continually synthesized by mitochondria

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    Ion Pumps

    Active transport processes that move ions across the membrane are called ion pumps.

    ion pumps allow a cell to maintain its internal concentrations of small molecules or ions

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    Bulk Transport - Exocytosis

    Used by cells that secrete

    Usually movement of large molecules

    Movement out of the cell.

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    Bulk Transport - Endocytosis

    process by which the cell acquires materials from the extracellular fluid: (3 Forms) Phagocytosis:

    Cell forms pseudopodia engulfs a particle internalize it into a vacuole

    Pinocytosis: incorporation of droplets of extracellular fluid (solution)

    Taken into the cell in small vesicles

    Receptor-mediated endocytosis: receptors in the cell membrane

    Bind with specific molecules

    Invagination forms around them to create a cytoplasmic vesicle

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    Cytoplasm: cytosol

    Matrix; intracellular material

    Different in different cell

    Mostly water

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    Cytoplasm: Organelles

    Complex, organized structures

    Have unique, characteristic shapes.

    Each type performs a different function for the cell.

    Are essential for normal cellular structure and activities.

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    Membranous Organelles

    Include:

    Endoplasmic Reticulum

    Rough Endoplasmic Reticulum (RER)

    Ribosomes

    Make protein for export

    Peroxisomes made here

    Smooth Endoplamic Reticulum (SER)

    Lipids and carbohydrates

    Detoxification

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    Membranous Organelles

    Peroxisomes

    Vesicles formed from RER

    Use oxygen to detoxify

    Mediated by specific enzymes

    Most abundant in liver

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    Membranous Organelles

    Golgi Apparatus Modifies, stores and sorts material from

    RER

    Receiving region (cis-face)

    Shipping region (trans-face)

    Produces Lysosomes Autophagy: removal of old organelles

    Autolysis: destruction of the cell

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    Mitochondria

    Mitochondria are organelles with a double membrane.

    Produce large amounts of ATP.

    Are called the powerhouses of the cell.

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    Non-Membranous Organelles

    Not made of a membrane.

    Usually made of protein

    Include: Ribosomes: free and fixed

    Cytoskeleton Microfilaments

    Intermediate fibers

    microtubules

    Centrosome centrioles

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    Ribosomes

    Small, dense granules Protein

    RNA

    Site of protein synthesis.

    Each ribosome has a small and a large subunit. small subunit is about one-half the size of

    the large subunit.

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    The Cytoskeleton

    Made of filamentous proteins

    Helps give the cell its shape

    Coordinates cellular movements.

    Three categories:

    microfilaments

    intermediate filaments

    microtubules

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    Non-membranous Organelles

    Centrioles and the centrosome Centrosome

    Area close to the nucleus

    Organization site for microtubules

    Centrioles (exist as a pair) In the centrosome

    Perpendicular to each other

    9 sets of microtubule triplets

    Important in cell division (spindle)

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    Microvilli, Cilia and Flagella

    Appendages extending from the surface of some cells. Microvilli:

    short, cytoplasmic extensions

    For absorption

    Cilia: usually occur in large numbers

    work together to move materials or fluids along the surface of a cell.

    Flagella:

    longer than cilia, and usually occur as single appendages.

    Move the cell

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    The Nucleus

    Control center of cellular activities.

    Usually, it is the largest structure within the cell

    Appears as a single spherical or oval structure.

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    The Nucleus

    Enclosed by a double membrane called the nuclear envelope.

    The nuclear envelope:

    controls the entry and exit of materials

    between the nucleus and the cytoplasm.

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    Nucleolus

    The cell nucleus may contain one or more nucleoli.

    Nucleoli:

    are responsible for making the small and

    the large subunits of ribosomes.

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    Chromatin and DNA

    DNA is the genetic material housed within the nucleus. DNA is a polymer of nucleotides (sugar,

    phosphate, nitrogen base)

    Is a double helix.

    Chromatin: Strands of DNA and histone proteins

    Euchromatin: uncoiled; active

    Heterochromatin: coiled. inactive

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    Insert Figure 2.18

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    Chromosome

    The chromosome is the most organized level of genetic material.

    Each chromosome contains a single, long molecule of DNA and associated proteins.

    Chromosomes become visible only when the cell is dividing.

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    The Cell Cycle

    The life cycle of the cell is called the cell cycle.

    New cells must be made continuously in order for an organism to grow and replace its damaged cells.

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    Mitosis and Meiosis

    There are two types of cell division.

    Mitosis: is the cell division process that takes place in somatic cells.

    Meiosis: is the cell division process that takes place in gonads to produce gametes.

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    Mitosis

    Interphase

    Prophase

    Metaphase

    Anaphase

    Telophase

    Cytokinesis

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    The Stages of Mitosis

    Prophase the first and longest stage of mitosis Early prophase chromatin threads condense

    into chromosomes Chromosomes are made up of two threads called chromatids

    Chromatids are held together by the centromere

    Centriole pairs separate from one another

    The mitotic spindle forms

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    The Stages of Mitosis

    Prophase (continued)

    Late prophase centrioles continue moving away from each other

    Nuclear membrane fragments

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    Early Prophase and Late Prophase

    Figure 2.21

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    The Stages of Mitosis

    Metaphase the second stage of mitosis

    Chromosomes cluster at the middle of the cell

    Centromeres are aligned along the equator

    Anaphase the third and shortest stage of mitosis

    Centromeres of chromosomes split

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    Metaphase and Anaphase

    Figure 2.21

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    The Stages of Mitosis

    Telophase begins as chromosomal movement stops

    Chromosomes at opposite poles of the cell uncoil

    Resume their thread-like extended-chromatin

    form

    A new nuclear membrane forms

    Cytokinesis completes the division of the cell into two daughter cells

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    Telephase and Cytokinesis

    Figure 2.21

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    Tumor

    Normal tissue development exhibits a balance between cell division and cell death.

    If this balance is upset and cells multiply faster than they die, abnormal growth results in a new cell mass that is called a neoplasm, or tumor.

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    Cancer

    Benign neoplasms usually grow slowly and are confined within a connective tissue capsule.

    Cells within these tumors dedifferentiatethat is, they revert to a less specialized state, and cause an increase in their own vascular supply to support their growth.

    These tumors are usually not lethal, but they have

    the potential to become life-threatening if they compress brain tissue, nerves, blood vessels, or airways.

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    Cancer

    Cancer is the general term used to describe a group of diseases characterized by various types of malignant neoplasms.

    unencapsulated

    contain cells that dedifferentiate

    increase their vascular supply

    grow rapidly

    spread easily to other organs by way of the blood

    or lymph (metastasis)

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    Cancer

    Cancer cells lose control of their cell cycle.

    they divide too frequently and grow out of control

    cancer cells lose contact inhibition

    they overgrow one another and lack the ability to stop growing and dividing when they crowd other cells

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    Cancer Cells

    Exhibit dedifferentiation and revert to an earlier, less specialized developmental state.

    Produce chemicals that cause local blood vessel formation resulting in increased blood vessels in the developing tumor (angiogenesis).

    Have the ability to squeeze into any space (invasiveness) permitting them to leave their place of origin and travel elsewhere in the body.

    Acquire the ability to metastasizethat is, spread to other organs in the body.