EDUCATION

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EDUCATION

• Education is a progressive discovery of our own
  ignorance.
• -Will Durant

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The Amazing Cell

• Chapter 3
• Anatomy and Physiology

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Cells

• Basic unit of living things.
• Can exist alone as a single, free, living plant
  or animal, or can combine to form elaborate and
  complex organisms.
• Multicellular organisms are when cells have
  differentiated and become grouped into
  specialized tissues that work collaboratively to
  sustain life for the animal as a whole.
• We must understand the cell before we can
  understand the anatomy and physiology of the
  tissues and systems the cell makes up

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Evolution of Cells

• Evolved about 3 billion years ago.
• Primitive cells are thought to have resembled
  present-day bacteria and contained a single
  strand of DNA in a gelatinous protoplasm.
• Prokaryotes- before nucleus, cells without
  nucleus were thought to have developed first.
• Has DNA but not in a separate compartment
• Eukaryotes- true nucleus, developed later and
  are found in all multicellular organisms.
• Has distinct nucleus surrounded by protective
  nuclear envelope.

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Size Limitations

• Size of most cells is restricted to 10-30 µm in
  diameter because of relationship between surface
  area and volume of a cell.
• Why is this important
• Smaller cells can feed themselves efficiently to
  carry on functions.
• Large cells could not take in nutrients fast
  enough to support cell and would therefore die.
• Also a small cell is better governed by a single
  nucleus. Larger cells need multiple nuclei.
• What is an example of this and why?

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Mammalian Cell Anatomy

• Contain essential structures
• Cell membrane (also known as plasma membrane).
• Separates cell from environment.
• Cytoplasm
• Everything inside the cell membrane aside from
  nucleus and genetic material.
• Nucleus
• Contains the genetic material of the cell.

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Other optional parts of a cell

• Cilia
• Mitochondria
• Endoplasmic Reticulum (ER)
• Ribosomes
• Golgi apparatus
• Lysosome
• Peroxisomes

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Cell Membrane

• Flexible, elastic barrier between inner cytoplasm
  and outer environment.
• Contains infoldings and outpouchings that provide
  extra surface area.
• Why is this important?
• Capable of self-repair.
• Governs the movement of atoms and molecules in
  and out of the cell.
• Consists primarily of protein, phospholipids,
  cholesterol, lipids, and carbohydrates.

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Membrane Structure

• Lipid bilayer composed of two layers of
  phospholipid molecules
• Hydrophilic heads are on outside
• Hydrophobic fatty acid tails are on
• the inside
• Most lipid soluble molecules easily
• pass through membrane
• Water-soluble molecules do not
• readily pass through
• Fluid mosaic Proteins suspended in bilayer and
  move easily throughout membrane to create a
  constantly changing pattern

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Cell Membrane Structure Continued

• Composed of Structural and Globular proteins.
• What are these also called?
• What do they do?
• Proteins that occur within the bilayer are called
  integral proteins.
• Globular proteins that span the entire width of
  the membrane and may create channels through
  which other molecules can pass.

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Integral Proteins

• Channels they create may be
• Selective
• permit only certain molecules in or out of the
  cell
• Pores
• allow the passage of molecules freely

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Peripheral Proteins

• Type of globular protein which can be bound to
  the inside or outside surfaces of the cell
  membrane.
• Sometimes act as enzymes
• May be involved in changing the cells shape
  (muscle contraction).

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Cell Membrane External Surface

• Glycocalyx coating on the cell surface of some
  cells made of glycoprotein and glycolipids.
• Unique to each cell provides markers for
  recognition and for interactions.
• Composed of 2 groups of molecules
• Cell Adhesion Molecules (CAMs)
• Sticky glycoproteins that cover cell surface.
  Help cells move past one another and signaling.
• Signal circulating cells like WBCs to areas of
  inflammation or infection
• Membrane Receptors
• Integral proteins and glycoproteins that act as
  binding sites on the cell surface.
• Involved with signaling as well.

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Flagella and Cilia

• Extensions of the plasma membrane that extend
  into the extracellular space.
• Both contain 9 pairs of microtubules that
  encircle a central pair of microtubules.
• Cilia- occur in large numbers on the exposed
  surface of some cells. Shorter than flagella and
  move synchronously to create waves of motion for
  propulsion.
• Functions
• In upper respiratory tract, propel bacteria and
  mucus from the lungs
• In oviduct, pulls egg from ovary into oviduct.

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• Flagella- significantly longer than cilia and
  usually occur singularly.
• Attached to individual cells and aid in
  propulsion.
• Example
• Tail of sperm is flagellum

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Cytoplasm

• The inner substance of the cell, excluding the
  nucleus.
• Components include
• Cytosol
• Cytoskeleton
• Organelles
• Inclusions

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Cytosol

• The fluid of the cell
• Viscous, semi-transparent liquid composed of
  dissolved electrolytes, amino acids, and simple
  sugars.
• Proteins suspended within fluid give fluid its
  thick, jellylike consistency.
• Are enzymes that are important in metabolic
  activities of the cell.

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Cytoskeleton

• Three dimensional frame for the cells, is neither
  rigid or permanent.
• Flexible and fibrous and changes in accordance to
  activities of the cell.
• Gives support and shape to the cell, enables cell
  to move and provides direction for metabolic
  activity.
• Also anchors organelles.
• Types of fibers that comprise cytoskeleton
• Microtubules
• Intermediate fibers
• Microfilaments.

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• Microtubules
• Thickest fibers and are long and hollow
• Form cables that organelles attach too.
• Proteins move these organelles along microtubules
  throughout cell.
• Can be easily disassembled and reasembled to form
  new paths or take on new direction.
• Composed of tubulins.

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• Intermediate fibers
• Woven, ropelike fibers that possess high tensile
  strength and are able to resist pulling forces on
  the cell by acting as internal guy wires.
• Toughest and most permament part of the
  cytoskeleton.
• Composed of proteins
• May take on different names
• Tonofilaments-in epithelial cells
• Neurofilaments- in nerve cells

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• Microfilaments
• Located near cell surface on the cytoplasmic side
  of the plasma membrane and are arranged in
  bundles and meshworks.
• Composed of actin and myosin
• Play key role in cells ability to change shape,
  break apart during cell division and form
  outpouchings and involutions.
• Are assembled where and when needed.
• Depends on what cell is doing as to how many are
  found within cell.

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Organelles

• little organs
• Membrane bound structures within cytoplasm that
  have specialized functions.
• Is separated from cytoplasm by own membrane so
  can maintain own internal environment.
• Compartmentalization is good for metabolic
  processes such as food absorption, energy
  production, and excretion.

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Organelles continued

• Include
• Mitochondria
• Ribosomes
• Golgi Apparatus
• Endoplasmic Reticulum
• Lysosomes
• Peroxisomes

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Mitochondria

• One of largest organelles
• Called powerhouse of the cell because produces
  up to 95 of energy that fuels the cell.
• Nutrient molecules (i.e. glucose) are broken down
  to produce intracellular fuel.
• Location of many biochemical reactions.
• Amino acid and fat catabolism
• Where respiration takes place
• What is this?

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Mitochondria continued.

• Active cells have higher energy demands so have
  more mitochondria.
• Heart cells
• Mitochondria can divide through fission-or the
  pinching itself in half.
• Tend to be located at portion of cell where
  energy requirements are the greatest.
• Contain DNA, RNA and enzymes.
• Provide selves with 13 proteins while nucleus
  provides the remainder.

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Mitochondrial shape

• Tend to be elliptical and round with outer smooth
  membrane and inner involuted membrane.
• Inner membrane forms cristae which increase
  internal working area and matrix (enzyme-rich
  liquid housed in mitochondria).
• Cristae are site of ATP production
• what does this do?

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Ribosomes

• Most common organelle in the cell.
• Made of two globular subunits composed of protein
  and rRNA.
• Important in protein synthesis.
• Can attach and detach from membranes and move
  freely within the cell.
• Move back and forth depending on type of protein
  they are making between endoplasmic reticulum and
  cytoskeleton.

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Endoplasmic Reticulum (ER)

• Series of flattened tubes stacked on one another
  and bent into crescent shape.
• Composed of single lipid bilayer
• May be rough or smooth depending on if it
  contains ribosomes or not.
• Rough ER is involved in production of protein.
• Smooth ER is connected to Rough ER and is active
  in synthesis and storage of lipids.
• In liver may also break down drugs and break down
  glycogen into glucose.

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Golgi Apparatus

• Found near nucleus and is similar in structure to
  ER (composed of cisternae)
• Receives proteins produced by ER.
• Proteins are modified here as they move from fold
  to fold.
• Once completed they are packages in vesicles and
  travel out into cell or to cell membrane.

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Lysosomes

• Specialized vesicle formed by Golgi apparatus.
• Contains hydrolytic enzymes which engulf bacteria
  or cell nutrients and digests them.
• Principal responsibility to breakdown nutrient
  molecules.
• Considered stomach of the cell.
• When cells die, lysosomes are released and digest
  other portions of the cell, this is called
  autolysis.
• May also release enzymes outside of cell to
  assist with breakdown of extracellular material.

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Peroxisomes

• Membranous sacs containing enzymes found
  throughout the cell.
• Reproduce through fission.
• Important in detoxification of various molecules.
• Remove free radicals- normal products of cellular
  metabolism but can be harmful in large numbers
• Carry two major enzymes
• Peroxidases-assist in conversion in free radicals
  to hydrogen peroxide.
• Catalases-reduce hydrogen peroxide to water.

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Inclusions

• Packaged units of metabolic products or
  substances that the cell has engulfed.
• May or may not be membrane-bound.
• Vacuoles are larger than vesicles but are of
  similar structure.

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Centrioles

• Small, hollow-like cylinders composed of
  microtubules.
• Found in pairs perpendicular to one another.
• Visible during cell division near nuclear
  envelope
• Help to organize spindle fibers during cell
  division.
• May also form bases of cilia and flagella (basal
  bodies).

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Nucleus

• Largest organelle in the cell.
• Control center or brain of the cell.
• Primary functions are to maintain hereditary
  information of the species and to control
  cellular activities through protein synthesis.
• Some cells may be multi-nucleated while some are
  anucleated.
• What is this and where is it found?
• What is a disadvantage to no nucleus?

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Nuclear Anatomy

• Divided into four parts
• Nuclear Envelope or membrane
• Nucleoplasm
• Chromatin
• Nucleoli

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Nuclear Envelope and Nucleoplasm

• Separated from cytosol by a nuclear envelope
  composed of two lipid bilayers
• Outer layer is continuous with Rough ER.
• Contains nuclear pores- channel through entire
  thickness.
• Allow transport of protein and RNA.
• Area between bilayers is space called perinuclear
  space.

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Nucleoplasm

• The gel-like substance that fills the nucleus.
• Resembles cytosol.

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DNA, RNA and Chromatin

• DNA and RNA are composed of nucleotides.
• What are they?
• How do they pair?
• What does DNA form?
• Chromatin-fibers made up of DNA and globular
  proteins called histones
• Nucleosome- single strand of DNA wound around 8
  histone molecules.
• During cell divison, chromatin condenses into
  super-coiled, x-shaped structure called
  chromosomes.

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Nucleoli

• Not membrane bound
• Where ribosomal subunits are made
• Contain DNA that governs synthesis of rRNA.

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Cell Physiology

• The Cellular Environment
• Body Fluids
• Composed primarily of water
• Intracellular fluid- fluid found inside cell.
• Extracellular fluid- fluid outside cell.
• Interstitial fluid- fluid contained within the
  tissue, except for blood found within lymph and
  blood vessels.

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Ions, Electrolytes, and pH

• What are ions?
• Cations
• Anions
• Electrolytes
• In sick or injured animals, electrolyte
  concentrations and pH of intracellular and
  extracellular fluid can become abnormally high or
  low

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Membrane Processes Excretion and Absorption

• In order to maintain homeostasis cell must
  select what it needs from extracellular fluid and
  bring it into intracellular environment.
• Must excrete waste products or transport
  resources needed in other parts of the body to
  the extracellular compartment.
• Processes may be passive (do not require ATP) or
  active (do use ATP).

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Passive Transport Processes

• Remember No Energy Required!
• 4 Passive Processes
• Diffusion
• Facilitated Diffusion
• Osmosis
• Filtration

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Diffusion

• Kinetic movement of molecules from higher to
  lower concentration via concentration gradient-
  the difference between the concentration of one
  area and the concentration of another.
• Will continue until the molecule is evenly
  dispersed throughout the solution
• Determining factors for Diffusion thru a
  membrane
• 1. Molecular size small can move through
• 2. Lipid solubility lipids can pass lipid
  bilayer
• 3. Molecular charge ions move through special
  channel proteins
• 4. Temperature faster in hot solution

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Facilitated Diffusion

• Selective carrier proteins assist in movement of
  molecules from higher to lower concentration
  speed of diffusion is limited by saturation of
  carrier molecules.

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Osmosis

• Passive movement of water through a semipermeable
  membrane from dilute solution to more
  concentrated one.
• Opposite of diffusion as water, not solute is
  moving. Also requires semipermeable membrane.

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Filtration

• Hydrostatic pressure (caused by the beating
  heart) forces liquid and small molecules through
  a membrane.
• Liquids pushed through a membrane when the
  pressure on one side is greater than that on the
  other side.
• Example?
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Tonicity Terminology

• Isotonic Extracellular fluid has same
  concentration of dissolved substances as
  intracellular fluid
• Hypotonic Cytoplasm (inside) of cell is more
  concentrated than extracellular (outside) fluid
• Hypertonic Extracellular fluid is more
  concentrated than cytoplasm

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Active Transport Processes

• Remember Requires Energy (ATP)!
• Relies on a carrier protein with a specific
  binding site
• Does not require a concentration gradient
• Symport system substances are moving in the
  same direction
• Antiport system substances are moved in
  opposite directions
• Include
• Active Transport
• Endocytosis
• Phagocytosis
• Pinocytosis
• Receptor mediated
• Exocytosis

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Active Transport

• Active movement of molecules by specific carrier
  protein molecules may move against concentration
  gradient.

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Endocytosis

• Phagocytosis
• Cells engulf solid substances
• Pinocytosis
• Cells engulf liquid substances
• Receptor mediated
• Specialized protein receptors bind to ligands
  specific receptors.
• Ligand-small molecules that bond to larger
  chemical groups or molecules.

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Exocytosis

• Excretion of waste products and secretion of
  manufactured substances.
• Packaged in secretory vesicles which fuse with
  cell membrane and are ejected to extracellular
  space.

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Life Cycle of the Cell

• Two types of division of cells.
• Meiosis- Reduction division
• Found in reproductive cells. End up with half of
  what start with.
• Mitosis- exact replication of cell.
• We will focus mainly on Mitosis for this chapter.

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Mitosis

• Life cycle has been divided into two major
  periods
• Interphase
• When cell is growing, maturing, and
  differentiating.
• Cells spend majority of time in this phase.
• Mitotic Phase
• When cell is actively dividing.
• Composed of
• Prophase
• Metaphase
• Anaphase
• Telophase

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Interphase

• Period between cell divisions.
• Nucleus and nucleoli are visible and chromatin is
  arranged loosely throughout the nucleus.
• Divided into three subphases
• Growth 1 (G1)- metabolic activity and cell
  growth time variable (min-yrs) depending on cell
  type
• Synthetic (S)- DNA replication
• Growth 2 (G2)- very brief synthesis of enzymes
  and proteins needed for mitosis

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DNA Replication

• Many cells are continually replicating to
  maintain body tissues, to heal wounds, or to
  enable growth
• DNA must be replicated before the cell can divide
  a copy of DNA is made to be passed to the
  daughter cell
• Occurs during Interphase

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DNA Replication

• Process
• Enzymes called DNA helicases pull apart the
  parental DNA double helix so the bases no longer
  form base pairs
• Next, enzymes called DNA polymerases move along
  each separated parental DNA strand and match each
  base on the strand with free nucleotides that
  have a complimentary base (an A is matched with a
  T)
• Then, DNA polymerase connects the free
  nucleotides together to form new DNA strands
• When replication is complete, the parental strand
  and the new strand wind together to form a double
  helix
• The lead strand, is made continuously the second
  (lagging) strand is made in segments, and
• DNA ligase joins the segments
• The identical DNA strands become chromatids,
  joined together at the centromere to form a
  chromosome

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Lead and Lagging Strands
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Mitotic Phase- Cell Division

• Cytokinesis- division of the cytoplasm.
• Prophase
• Chromatin coils and are composed of two identical
  chromatids
• Spindle apparatus appears
• Normal synthetic processes cease.
• Nuclear envelope disintegrates

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• Metaphase
• Chromosomes are lined up in center of spindle.
• Centromere of each chromosome is attached to a
  spindle fiber.

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• Anaphase
• Centromeres split apart and each chromatid
  becomes its own chromosome.
• Spindle fiber separates, and chromosomes are
  pulled away from each other.
• Cytoplasm constricts along metaphase plate.

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• Telophase
• Final stage of mitosis
• When chromosomal movement stops
• Chromosomes reach poles and begin to unravel.
• New nuclear envelope appears as well nucleoli.
• Cytokinesis ends telophase.
• New daughter cells enter interphase.

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Control of Cell Division

• Some cells divide rapidly others not so fast.
• Examples of each
• Normal cells stop dividing when they come into
  contact with surrounding cells.
• Called Contact inhibition
• Division can be controlled once numbers reach a
  certain point.
• Proteins can also allow cells to enter mitotic
  phase

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Protein Synthesis

• Protein synthesis is essential for life.
• Begins in nucleus
• tRNA transcribes DNA information
• Transcription-Genetic information in DNA is
  copied onto messenger RNA (mRNA)
• Codon- series of 3 RNA nucleotides.
• mRNA sends information to cytoplasm
• Translation- Ribosomes bind to mRNA strand
  (rRNA).
• New protein building as codes are translated from
  nucleotides to amino acids

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Genetic Mutations

• A genetic error.
• Mutations may be so severe that cell dies, but
  may also cause no issues whatsoever.
• Some can be repaired by repair enzymes.
• May occur spontaneously or due to mutagens.
• Viruses
• Ionizing radiation
• Certain chemicals
• What is cancer?
• What is chemotherapy?

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Cell Differentiation and Development

• Differentiation- The progressive acquisition of
  individual characteristics by cells to enable
  them to perform different functions.
• Differentiation is important as it keeps cells
  focused on a particular function.

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