Exam 2 Overview
Cells – The overview
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Prokaryote vs. Eukaryote (Slide 4 image)
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The Cellular Membrane
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Controls traffic in and out of cell
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Separates living cell from nonliving surroundings
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Selectively permeable
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Hydrophobic vs. Hydrophilic
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Made of phospholipids, proteins & other macromolecules
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Phospholipids
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fatty acid tail (hydrophobic) + Phosphate group head (hydrophilic)
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arranged as bilayer
Membrane Proteins - Proteins determine membrane’s specific functions (cell & organelle membrane have unique collection of
proteins)
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Protein polarity
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Nonpolar/hydrophobic – part inside of membrane, anchors protein into membrane
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Polar/hydrophilic – part outside of membrane, extends into extracellular fluid
Types:
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Peripheral proteins
1.
Loosely bound to membrane
2.
Cell service identity marker (antigens)
Integral proteins - penetrate lipid bilayer
1.
Transmembrane protein (carrier)
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Carrier proteins
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uniport carriers – allow 1 thing to pass
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symport carriers – allow 2 things to pass from same side, must be present at same time
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2.
antiport carriers – allow 1 thing to pass from either side, must be present at same time
Transport proteins (channels & pumps)
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Channel proteins
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Gated channels
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usually closed, highly selective
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Types: voltage gated (Ions K+, Na+, Ca2+, Cl-), Mechanical/tension/pressure,
temperature
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Open/Leak channels – open all the time to allow water/ion movement (diffusion)
Transport across membrane
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Passive Transport – Uses channel & carrier proteins
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High concentration >> Low concentration
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Diffusion - IN = food (carbs, sugars, proteins, amino acids, lipids, salts, O & H2O) & OUT = waste (ammonia, salts,
CO2, H2O, products)
1.
Diffusion = Lipids/nonpolar/hydrophobic molecules) - directly across membrane
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2.
Isotonic vs. Hypotonic vs. Hypertonic
Facilitated diffusion = Polar/Hydrophilic molecules - uses protein. Utilized by molecules that can’t pass directly
through membrane
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Active Transport – Uses carrier proteins only
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Requires ATP
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Low concentration >> High concentration (opposite of the gradient)
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Carrier protein changes shape to transport solute across membrane
Vesicles & Vacuoles - Used for moving large molecules in/out of cell
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Cytoplasm (AKA The Matrix)
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water-like substance
Endocytosis
1.
Phagocytosis = “cellular eating”
2.
Pinocytosis = “cellular drinking”
Exocytosis
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fills the space between plasma mem. and nuclear mem. (aka fills the inside of the cell).
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Cytosol (water/salts/enzymes/molecules) + organelles
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Found in Pro and Eukaryotes
The Cytoskeleton
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Duties
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Keeps cell shape
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Protects cell
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Sometimes enables cell movement (flagella/cilia)
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Plays important roles in intra cellular transport & cell division
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Found in Pro and Eukaryotes
What’s it made of?
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Three fibers:
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Microtubules – Thickest filament, hollow tube, originate from centrosome/centrioles
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Functions:
1.
Shaping the cell
2.
cell motility (internal & extrenal- flagella/cilia) – Protein Dynein is responsible for bending movement and is
powered by ATP
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chromosome separation during cell division
4.
guiding movement of organelles
Microfilaments/Actin - Thinnest filament, maintenance
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3.
Functions:
1.
support cell shape
2.
muscle contraction
3.
make up microvilli in intestinal cells
Intermediate filaments – cell shape, anchorage of nucleus & some organelles
Internal Motility
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Cytoskeleton/microtubules interact with motor proteins
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Vesicles can travel along tracks provided by cytoskeleton
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Eukaryotic cells
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Genomes
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Mitosis = 1 cell >> 2 cells
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Nucleus has 20-30 thousand genes
Organelles – Membrane Bound
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Functions:
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Waste disposal (Lysosome)
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Membranous sac of hydrolytic enzymes
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Enzymes made by rough ER and transferred to Golgi
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Types of destruction = phagocytosis (engulfing another cell) – this forms a food vacuole
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Information Storage (nucleus)
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Protein synthesis (ribosomes & rough ER)
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ribosomal RNA & protein
2.
Operate in cytosol & outside of ER
3.
Facilitate Translation – RNA >> Protein
Lipid synthesis (smooth ER)
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Shipping (Golgi)
Golgi ships proteins in lipid vesicals to various parts of cell and blood
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Radical oxygen disposal (peroxisomes)
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Energy (mitochondria)
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Organization (cytoskeleton)
Prokaryotic cells
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1.
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o
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Ribosomes = protein factories
What’s in it?
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Plasma membrane
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Cytoskeleton
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Ribosomes
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Cell wall
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Nucleiod (instead of a nucleus)
Genetics
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Nucleoid – region of cytoplasm where DNA is located
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Plasmid – small extra piece of chromosome/genetic material
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5-100 genes
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Can provide genetic information to produce:
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Antibiotic resistance
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Virulence factors (molecules that are produced by pathogen that influence host’s function to allow pathogen to
thrive)
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o
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Promote conjugation (transfer of genetic material between bacteria through cell-to-cell contact)
Cytoplasm
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Known as proto-plasm
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Location of most cell functions like growth, metabolism, & replication
Cytoskeleton
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Cellular “scaffolding” or “skeleton” within the cytoplasm
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Allows for bacterial movement & structure within the cell
Organelles
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MINIMAL ORGANELLES
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Instead of the traditional organelles, a prokaryote instead has
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Metachromatic granules (volutin)—phosphate reserves
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Polysaccharide granules—energy reserves
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Lipid inclusions—energy reserves
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Sulfur granules—energy reserves
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Carboxysomes—RuBisCO enzyme for CO2 fixation during photosynthesis
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Gas vacuoles—protein-covered cylinders that maintain buoyancy
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Magnetosomes—iron oxide inclusions; destroy H2O2
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Bacteria
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Types:
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Bacillus (rod shaped)
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Coccus (spherical)
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Spiral (Spirillum)
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Star Shaped
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Rectangular
Terms:
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Pairs = diplococci, diplobacilli (Diplo- prefix)
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Clusters = Staphylococci
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Chains = streptococci, streptobacilli
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Groups of four = tetrads
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Cube-like groups of eight = Sarcinae
Bacterial Cell Wall & Differential Staining
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Bacterial Cell Wall
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Purpose:
1.
Shape
2.
Protection
3.
Distinguishes groups of bacteria – gram(-) & gram(+)
Layers of the Bacteria cell wall
1.
Inner/cytoplasmic/plasma membrane
2.
Peptidoglycan
3.
Outer membrane (absent in some bacteria)
4.
Glycocalyx - *Some bacteria* have this additional layer. Can be 1 of 2 forms
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Slime Layer
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Causes bacteria to adhere to solid surfaces and helps prevent the cell from drying out.
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Caused from glycoproteins loosely associated w/ cell wall
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Capsule
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Causes bacteria to adhere to solid surfaces and to nutrients in the environment
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Caused by polysaccharides firlmy attached to cell wall
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o
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Peptidoglycan – a polymer of interlocking chains of alternating monomers
1.
Provides rigid support
2.
Still permeable to solutes
3.
Backbone = 2 amino sugar derivatives (NAM & NAG) of glucose = “Glycan”
4.
Innards = interlocking peptide bridges = “Peptid”
Some P
Differential Stains
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Gram staining
1.
Gram positive = dye enters the cell and can’t leave due to the think peptidoglycan wall, thus producing a dark purple color
2.
Gram Negative = dye enters the cell, but cell cannot retain dye due to a thin layer of peptidoglycan. Appears red/pink due to the
safranin stain
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Staining steps
1.
Crystal violet enters the cell
2.
Iodine binds to the crystal violet
3.
Alcohol shrinks peptidoglycan layer and removes outer layer if present
4.
Safranin binds to the membrane of a cell with thin peptidoglycan
What gram staining tells us
1.
Gram (-)
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Outer membrane is protective, allowing gram(-) bacteria to survive harsh environment
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Outer membrane contains Porins for channels through the wall, allowing big molecules (such as monosaccharides) through.
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Important because – Lipopolysaccharide (LPS or Lipid-A) is a lipid sugar. Dead gram(-) bacteria release Lipid-A when outer
membrane disintegrates. With a gram(-) bacterial infection, freed lipid-A may trigger fever, vasodilation, inflammation, shock
and blood clotting. Killing large numbers of gram(-) bacteria w/ antimicrobial drugs releases lotf of lipid-A, which can threaten
the patient more than the presence of the bacteria.
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Gram Stain Resistance (Genus)
1.
2.
Metabolism
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SEE CHARTS
Mycobacterium
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Produces mycolic acid as part of its cell way- a wax that protects the bacteria.

Causes leprosy & tuberculosis
Norcardia