Cellular Level of Organization

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Cellular Level of Organization
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Cells

• There are approximately 200 different types of
  cells that make up the basic structures of the
  human body.
• Cell division creates new cells. A parent cell
  divides into two new daughter cells.
• Different types of cells carry out different
  functions in the body.

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Parts of a Cell

• Plasma membrane
• Cytoplasm
• Cytosol
• Organelles
• Nucleus
• Chromosomes
• Genes

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3 main parts of a cell

• Plasma membrane the cells flexible outer
  surface.
• Cytoplasm all the cellular contents between the
  plasma membrane and the nucleus.
• Nucleus a large organelle that houses most of
  the cells DNA. Chromosomes and genes are
  contained here.

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Typical Structures
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Plasma Membrane

• A flexible, yet sturdy barrier that surrounds and
  contains the cytoplasm of a cell.
• Fluid mosaic model.
• Lipid Bilayer
• Membrane proteins
• Membrane Permeability Selective

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Plasma Membrane continued

• Gradients
• Concentration
• Electrochemical
• Osmosis
• Diffusion
• Active Transport

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Lipid Bilayer

• Phospholipids 2 layers
• Amphipathic polar and nonpolar
• Hydrophilic
• Hydrophobic

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Membrane Proteins

• Integral Proteins extend into or through the
  lipid bilayer.
• Transmembrane proteins
• Peripheral Proteins attached to either the
  inside or outside of the membrane.

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Functions of Membrane Proteins

• Ion channel
• Transporter
• Receptor
• Enzyme
• Cell Identity Marker
• Linker

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Membrane Permeability

• Selectively Permeable
• Permeable to nonpolar, uncharged molecules, such
  as oxygen, carbon dioxide, steroids.
• Impermeable to ions and charged or polar
  molecules, such as glucose.
• Slightly permeable to water and urea.

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Gradients

• Concentration Gradient A difference in the
  concentration of a chemical from one place to
  another.
• Electrochemical Gradient The combination of the
  effects of the concentration gradient and the
  membrane potential.

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Transport Across the Membrane

• Passive Transport does not require cellular
  energy.
• Substances move down their concentration or
  electrochemical gradients using only their own
  kinetic energy.
• Active Transport requires cellular energy in
  the form of ATP.

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3 Types of Passive Transport

• Diffusion through the lipid bilayer.
• Diffusion through membrane channels.
• Facilitated diffusion.

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Endocytosis

• Material enters the cell in vesicles.

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Exocytosis

• Material leaves the cell in vesicles.

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Diffusion

• Materials diffuse from areas of high
  concentration to areas of low concentration.
  They move down their concentration gradient.
• Equilibrium molecules are mixed uniformly
  throughout the solution.

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Factors Influencing Diffusion

• Steepness of the concentration gradient.
• Temperature.
• Mass of the diffusing substance.
• Surface Area.
• Diffusion distance.

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Osmosis

• The net movement of a solvent (water) across a
  selectively permeable membrane.
• Water moves from an area of higher water
  concentration to an area of lower water
  concentration.

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Osmotic Pressure

• A solution containing solute particles that
  cannot cross the membrane exerts a force called
  osmotic pressure.
• The greater the number of solute particles the
  greater the pressure.

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Tonicity

• A solutions tonicity measures the solutions
  ability to change the volume of cells by altering
  their water content.
• Isotonic cell maintains shape
• Hypotonic cell swells and bursts
• Hypertonic cell shrinks - crenation

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Cytoplasm

• 2 components
• Cytosol fluid portion that surrounds
  organelles.
• 55 of total cell volume
• Water with dissolved and suspended components
• Ions, glucose, amino acids, fatty acids,
  proteins, lipids, ATP, and waste products.
• Organelles specialized structures
• Specific shapes
• Specific functions

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Cytoskeleton

• Network of protein filaments.
• Structural framework for the cell.
• 3 Types of filaments
• Microvilli small increase surface area
• Intermediate filaments
• Microtubules largest in cilia and flagella
  participate in cell division.

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Centrosome

• Located near the nucleus
• Plays a critical role in cell division

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Cilia and Flagella

• Comprised of microtubules.
• Cilia short, hairlike projections that extend
  from the surface of the cell.
• Line respiratory tract
• Movement is paralyzed by nicotine
• Flagella longer than cilia
• Usually move an entire cell
• Sperms tail

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Ribosomes

• Sites of protein synthesis
• Free Ribosomes located in cytosol
• Attached to nuclear membrane and ER
• In mitochondria

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Endoplasmic Reticulum ER

• Plasmic cytoplasm reticulum network
• Network of folded membranes
• Transports substances throughout cell
• Rough ER ribosomes attached synthesizes
  proteins
• Smooth ER synthesizes fatty acids and steroids

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Rough ER
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Smooth ER
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Golgi Complex

• Consists of 3 20 golgi cisternae (membranous
  sacs)
• Modifies, sorts, and packages proteins for
  distribution
• Proteins leave through secretory vesicles,
  membrane vesicles, or transport vesicles.

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Lysosomes

• Lyso dissolving somes bodies
• Contain powerful digestive enzymes and hydrolytic
  enzymes
• Lysosomal enzymes can destroy their own cell
  autolysis (due to pathology)

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Lysosome
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Mitochondria

• Generate ATP powerhouses of the cell

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Mitochondrian with Matrix
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Mitochondria
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Nucleus

• Spherical or oval shaped
• Most prominent feature in the cell
• Most structures have a single nucleus, although
  mature RBCs have none
• Contain genes arranged in chromosomes
• Genome total genetic information for an organism

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Nucleus
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Nucleus
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Cell Division

• Somatic Cell Division replaces dead or injured
  cells and adds new ones for growth.
• Mitosis
• Produces 2 identical daughter cells
• Reproductive Cell Division produces gametes
  sperm and oocytes.
• meiosis

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Cell Cycle

• 2 major phases
• Interphase the cell is not dividing
• Mitotic phase the cell is dividing

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Interphase

• The cell replicates its DNA during this phase.
• Produces additional organelles and cytosolic
  components.

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Mitotic Phase

• Nuclear Division Mitosis
• Cytoplasmic Division - Cytokinesis

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Mitosis

• Prophase
• Chromatin fibers condense and shorten.
• Metaphase
• The microtubules align the centromeres of the
  chromatid pairs.
• Anaphase
• The centromeres split separating the two members
  of each chromatid pair.
• Telophase
• Identical chromosomes uncoil and a nuclear
  envelope forms around each mass.

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Cytokinesis

• Division of the parent cells cytoplasm and
  organelles into two daughter cells.

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Cellular Diversity

• The body of an average human adult is composed of
  nearly 100 trillion cells.
• Approximately 200 different types.
• The largest cell is the oocyte

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