Cytology

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Cytology Study of the Cell

• Structures and Their Functions

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Cell Background Information

• Cells fundamental unit of all plant and animal
  tissues
• Cytology the study of the structure and function
  of cells
• 2 Types of Cells
• Gametes (a.k.a. germ, reproductive)
• Spermatozoa (males) Oocyte (females)
• Somatic cells (soma body)
• All other cells of the body

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Cell Theory (3 Major Concepts)

• Cells are the building blocks of life
• Cells are produced by the division of preexisting
  cells
• Cells are the smallest units that perform vital
  physiological functions

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Cell Structures and Basic Functions

• Extra-cellular fluid liquid found outside of
  cells
• Interstitial fluid- liquid found between cells
• Plasma liquid found in blood
• Cytoplasm
• Cytosol the liquid part of the cell
• Organelles intracellular structures of the cell

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Cell Structures and Basic Functions

• Cell Membrane - protection support
• Nucleus
• Control metabolism, storage processing of
  genetic information
• Nucleolus site of rRNA synthesis
• Nuclear envelope - barrier between the nucleus
  and the cytosol

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Cell Structures and Basic Functions

• Ribosome protein synthesis
• Golgi apparatus - UPS
• Storage packaging of lysosomal enzymes
• Lysosomes Garbage Personnel
• Removal of damaged organelles pathogens
• Mitochondria Power Plant
• Produce 95 of the energy required by the cell

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Cell Structures and Basic Functions

• Rough Endoplasmic Reticulum (ER)
• Modification packaging of newly synthesized
  proteins
• Smooth Endoplasmic Reticulum (ER)
• Lipid Carbohydrate synthesis
• Centrioles essential for movement of the
  chromosomes during cell division

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Cell Membrane
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Phospholipid Bilayer
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The Cell (Plasma) Membrane

• Structure
• Membrane Lipids Form most of the surface
• Phospholipid Bilayer (Draw)
• Membrane Proteins 2 Types
• Integral Proteins part of the membrane
• Transmembrane Protein spans width of the
  membrane
• Peripheral Proteins bound to the inner/outer
  surface of the membrane
• Easily removed

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The Cell (Plasma) Membrane

• 4 General Functions
• Physical Isolation
• Barrier between the inside of the cell and the
  extra-cellular fluid
• Regulation of Exchange with the Environment
• Controls entry of nutrients and elimination of
  wastes
• Sensitivity
• Contains variety of receptors ? cell recognition
• Structural Support
• Connections between the membrane extra-cellular
  materials ? stable structure

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The Cell (Plasma) Membrane

• 6 Functions of Membrane Proteins
• Anchoring Proteins attach to other structures
• Recognition Proteins (identifiers) immune
  system
• Enzymes catalyze reactions in outside the
  cell
• Receptor Proteins sensitive to certain
  extra-cellular molecules
• Carrier Proteins binds to solutes transport
  (change shape)
• Channels central pore allows movement of water
  and small solutes across the membrane
• Leak channels permit at all times
• Gated channels - open/close for regulation

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The Cell (Plasma) Membrane

• Structure Continued
• Membrane Carbohydrates
• Components of complex molecules
• 4 Important Functions
• Lubrication and Protection
• Anchoring and Locomotion
• Sticky ? anchors the cell in place
• Participates in movement of specialized cells
• Specificity in binding
• Recognition
• Immune response normal/abnormal
• Blood type (A, B, AB, O)

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The Cytoplasm

• General term for the material located inside the
  cell membrane and outside the nuclear envelope
• Contains many more proteins than the
  extra-cellular fluid (15-30 of cells weight)
• 2 Major subdivisions
• Cytosol (intracellular fluid)
• Organelles

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The Cytosol

• 3 Important Differences from Extra-Cellular Fluid
• Cytosol high concentration K, low Na
• Extra-cellular Fluid low concentration K, high
  Na
• Cytosol high conc. suspended proteins
• Extra-cellular Fluid - low conc. suspended
  proteins
• Cytosol small quantities of carbohydrates
  large reserves of amino acids and lipis
• Inclusions masses of insoluble materials
• ex. Stored nutrients

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Organelles
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Organelles

• Each performs specific functions that are
  essential to normal cell structure, maintenance
  and metabolism
• 2 categories
• Non-membranous organelles
• Not completely enclosed by a membrane ? all
  contents are in direct contact with the cytosol
• ex. Centrioles, cilia, flagella, ribosomes,
  cytoskeleton
• Membranous organelles
• Isolated from the cytosol by their membranes
• Ex. Endoplasmic reticulum, Golgi apparatus,
  lysosomes, mitochondria, nucleus

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Cilia and Flagella

• Cilia
• Anchored to a compact basal body situated just
  beneath the cell surface
• Exposed portion is completely covered by the cell
  membrane
• Beat rhythmically ? moves fluids past the cell
• Flagella
• Resemble cilia, but are much longer
• Move a cell through the surrounding fluid

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Microvilli

• Small, finger-shaped projections of the cell
  membrane that greatly increase the surface area
  of the cell exposed to the extra-cellular
  environment

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The Cytoskeleton

• Internal protein framework that gives the
  cytoplasm strength and flexibility
• Organizational details are as yet poorly
  understood, because the network is extremely
  delicate ? hard to study in an intact state

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The Cytoskeleton - Microfilaments

• Actin, myosin
• 3 Major Functions
• Anchor the cytoskeleton to integral proteins of
  the cell membrane
• Interacting with other proteins ? determine the
  consistency of the cytoplasm
• Produce active movement of a portion of a cell or
  even change the shape of the entire cell

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The Cytoskeleton Intermediate Filaments Thick
Filaments

• 3 Major Functions of Intermediate Filament
• Provide strength and stability to shell shape
• Stabilize the positions of organelles
• Stabilize the position of the cell with respect
  to surrounding cells through specialized
  attachment to the cell membrane
• Thick filaments appear only in Muscle Cells

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The Cytoskeleton
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The Cytoskeleton - Microtubules

• Hollow tubes built from globular proteins
• Largest components of the cytoskeleton
• 5 Major Functions
• Form the primary components of the cytoskeleton
• Change the shape of the cell (may assist cell
  mvt)
• Can attach to organelles other intracellular
  materials that the move along the axis of the
  microtubule
• Requires energy essential to normal cell
  function
• During cell division form the spindle apparatus
• Form structural components of organelles (ex.
  centrioles, cilia, flagella)

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Centrioles

• A cylindrical structure composed of short
  microtubules
• All animal cells capable of reproducing
  themselves contain a pair of centrioles
• Centrosome cytoplasm surrounding the
  centrioles heart of the cytoskeletal system

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Ribosomes

• Manufacture proteins, using information provided
  by the DNA of the nucleus
• The number in a particular cell varies with cell
  types
• Not visible with a light microscope
• Contain proteins and ribosomal RNA (rRNA)
• 2 Major Types
• Free ribosomes scattered throughout the
  cytoplasm
• Fixed ribosomes attached to ER
• A functional ribosome has 2 subunits that are
  normally separate and distinct and differ in size
• Small ribosomal subunit Large ribosomal subunit

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The Endoplasmic Reticulum (ER)

• Network of intracellular membranes that is
  connected to the nuclear envelope
• 4 Major Functions
• Synthesis proteins, carbohydrates lipids
• Storage - synthesized molecules materials
• Transport
• Detoxification drugs toxins neutralized by
  enzymes
• Cisternae chambers

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Smooth ER

• No ribosomes
• Variety of functions 4 Responsibilities
• Synthesizing phospholipids cholesterol
  maintenance growth
• Synthesizing steroid hormones in the reproductive
  organs and those of the adrenal gland
• Synthesizing storing glycerides triglycerides
  in liver fat cells
• Synthesizing storing glycogen in skeletal
  muscle liver cells

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Rough ER

• Functions as a combination workshop shipping
  depot
• Contains fixed ribosomes
• Protein synthesis
• Transport vesicles deliver the products to the
  Golgi apparatus
• The amount varies with the type of cell

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Golgi Apparatus

• Consists of flattened membrane discs (cisternae)
• Resemble a stack of dinner plates
• Most often lye near the nucleus of the cell
• Communicate with the ER and the cell surface by
  the formation, movement and fusion of vesicles

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Golgi Apparatus3 Major Functions

• Modifies and packages secretions (hormones,
  enzymes) for release through exocytosis
• Renews or modifies the cell membrane
• Packages special enzymes within vesicles for use
  in the cytosol

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Golgi Apparatus3 Types of Vesicles

• Secretory Vesicles containing secretions that
  will be discharged from the cell by exocytosis
• Membrane renewal vesicles when vesicles fuse
  with the surface of the cell, they add new lipids
  proteins to the cell membrane ? change the
  membrane properties over time
• Lysosomes remain in the cytoplasm contain
  digestive enzymes

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Lysosomes

• Vesicles filled with digestive enzymes
• Small, often spherical, and their contents look
  dense and dark in electron micrographs
• Produced by the Golgi apparatus
• Function in the defense against diseases
• Perform essential clean-up and recycling
  functions inside the cell

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Lysosomes

• Primary lysosomes (contain inactive enzymes)
  enzyme activation occurs when the lysosome fuses
  with the membranes of damaged organelles ?
  Secondary lysosomes (contains active enzymes)
  enzymes break down the lysosomal contents
  nutrients reenter the cytosol the remaining
  material is eliminated by exocytosis

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Lysosomes

• Do not know how to control lysosomal activities
  or why the enclosed enzymes do not digest the
  lysosomal walls unless the cell is damaged
• Problems with lysosomal enzyme production cause
  30 serious diseases in children
• Lack of a specific lysosomal enzyme results in
  the build up of waste products and debris
  normally removed and recycled by lysosomes
• May die when vital cells can no longer function

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Peroxisomes

• Smaller than lysosomes carry a different group
  of enzymes
• Produced by the growth subdivision of existing
  preoxisomes
• Enzymes produced at free ribosomes
• Absorb and break down fatty acids other organic
  compounds
• Present in all cells
• Their numbers are highest in metabolically active
  cells

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Mitochondria

• Small organelles that can have a variety of
  shapes long slender to short fat
• Number varies with cells energy demands
• RBCs lack
• Unusual double membrane
• Outer membrane surrounds the organelle
• Inner membrane contains numerous folds (cristae)
  ? increase the surface are exposed to the fluid
  contents (matrix) of the mitochondrion
• Metabolic enzymes in the matrix catalyze the
  reactions that provide energy for cellular
  functions

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Mitochondria

• Most of the chemical reactions that release
  energy occur in the mitochondria, but most of the
  cellular activities that require energy occur in
  the surrounding cytoplasm ? cells must store
  energy in a form that can be moved from place to
  place (high energy bonds ATP)

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MitochondriaMitochondrial Energy Production

• Most cells generate ATP other high-energy
  compounds through breakdown of carbohydrates,
  especially glucose
• Glycolosis (1 Glucose Molecule ? 2 Pyruvic Acid)
• Aerobic metabolism ATP production requiring
  oxygen (a.k.a. cellular respiration)
• Produces 95 ATP needed for cellular life
• Several inheritable disorders result from
  abnormal mitochondrial activity ? reduced ability
  to produce ATP

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Membrane Flow

• When a cells environment changes, it alters the
  structure and properties of its cell membrane
• With the exception of mitochondria, all
  membranous organelles in the cell are either
  interconnected or in communication through the
  movement of vesicles
• The continuous movement and exchanges membrane
  flow

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The Nucleus
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The Nucleus

• The control center of cellular operations
• Determines the structural functional
  characteristics of the cell by controlling which
  proteins are synthesized and in what amounts
• Most cells contain a single nucleus, but
  exceptions exist
• Nuclear envelope surrounds the nucleus and
  separates it from the cytosol double membrane
• Nuclear pores chemical communication between the
  nucleus and the cytosol occurs

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The NucleusChromosome Structure

• DNA in the nucleus that stores instructions for
  protein synthesis
• DNA is contained in chromosomes
• Humans 23 pairs of chromosomes
• 1 from mother, 1 from father
• In cells that are not dividing, the chromosomal
  material is loosely coiled, forming a tangle of
  fine filaments (chromatin) ? gives the nucleus a
  clumped, grainy appearance
• Chromosomes dont become visible until just
  before cell division begins
• 2 copies of each chromosome exists
• Chromatid - each copy
• Centromere - single point at which they join