Download Cytology

Cytology
The Study of Cells
Themes
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Emergent properties: interactions among cell
components produces ‘life’
Structure and function: cell processes based upon
ordered structures
Interactions: exchange and respond to external
environment
Evolution: adaptations of structure
Relative sizes
How Cells Are Studied
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Microscope: # 1 tool
 1665 Robert Hooke; “Cells”
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Magnification = how much larger object is made
to appear
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Resolution = minimum distance between 2 points
that can still be seen as 2 points; ‘focused’
How Cells Are Studied
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Two types of microscopes:
 Light: 1500x; light passes through lens
 Electron Microscope: electrons instead of
light waves (smaller) electromagnets aim
electron beam
How Cells Are Studied
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3 types of electron microscopes:
 Transmission Electron Microscope; TEM;
electrons pass through subject, 100,000x
 Scanning Electron Microscope;
SEM;
electrons bounce off a thin gold plate on the surface
of the object; 60,000x; 3d
 Scanning-tunneling STM; 1,000,000 x
TEM
SEM
How Cells Are Studied
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Cell Fractionation:
Disrupt cell; centrifuge organelles to
the bottom
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‘Pellet’
Separate and isolate pellets
Study function independently
Panoramic View of the Cell
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Prokaryote
Bacteria
No nucleus (nucleoid)
No membrane-bound
organelles
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Ribosomes
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Eukaryote
Animal, plants, fungi,
protists
Nucleus (DNA)
Membrane-bound
organelles
Eukaryotic Cells
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Cell membrane
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Cytoplasm = region (matrix) between cell membrane
and nucleus
 Cytosol = semi-fluid medium in the cytoplasm
Eukaryotic Cells
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Eukaryotes more complex than prokaryotes
More DNA
 More organelles
 Enables larger size due to more efficient metabolism
(specialized organelles)
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Size of Cells
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Limited by surface area /volume ratio
-Volume increases 8 x faster than S.A.
- Problems with diffusion
Limited by the amount of DNA
 DNA must be able to keep up with demands of the
cytosol
Eukaryotic Cells
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Compartmentalization:
 Eukaryotic cells have 1000x the volume of
prokaryotic cells
 Need way to process cell activities
 How can you create more area?
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Internal membranes!!!!
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Increase surface area;
 Specialized molecules are embedded within so they
can carry on some metabolism; (chemiosmosis)
Partitions create compartments to isolate chemical
reactions
Structure and function
Nucleus
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Nucleus: 2 parts:
 DNA
 Nuclear envelope
Nucleus
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Nuclear envelope:
 Phospholipid bilayer
 Pores
Most of the genes
 Mitochondria, chloroplasts
Nucleus
DNA:
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Chromatin = DNA wrapped around protein
(histone)
Chromosomes = coiled, condensed
chromatin
Genes = sections of DNA that code for
proteins
Nucleus
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Nucleolus: large, obvious structure in non-dividing
cells
Composed of ribosomes in production
May have 2 or more per cell
Nucleus
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Protein synthesis:
 mRNA transcribed in Nucleus
 Through nuclear pores into cytoplasm
 Attaches to ribosomes to be translated into amino acid
sequences (primary structure)
Ribosomes
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Protein synthesis
Non-membrane bound (prokaryotes)
Prokaryotes have slightly different ribosome molecular
structure (antibiotics tetracycline, streptomycin)
Ribosomes
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Free ribosomes; float in cytosol; proteins within the cell; muscle
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Bound ribosomes (ER); proteins for secretion; pancreas, liver,
etc
Endomembrane System
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Vesicles
Nuclear envelope
Endoplasmic reticulum
Golgi
Lysosomes
Vacuoles
Plasma membrane
Endomembrane System
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Membranes vary in structure and function
Dynamic; constantly changing in composition,
behavior, and thickness
Endomembrane System
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Vesicles = membrane-enclosed sacs that are
pinched off portions of membranes moving from
one membrane to another
Endomembrane System
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Endoplasmic reticulum (ER)
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Endo = within; reticulum = network
Network of tubules and sacs (cisternae)
Creates passages, chemical ‘laboratories’
Continuous with outer nuclear membrane
Endoplasmic Reticulum
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2 types: Smooth and Rough
Smooth - Makes lipids, steroids phospholipids;
adrenal glands; gonads, skin oil glands
Carbohydrate metabolism; liver, enzyme converts
glycogen into glucose
Detoxifies poisons/drugs: adds OH
Store Ca for muscle contraction
Endomembrane System
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Rough ER: make proteins
Endomembrane System
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Golgi = stacked, flattened discs; sacs (cisternae)
Stores, modifies and routes products from ER
Enzymes modify products of ER
Manufactures some macromolecules (pectins)
Sorts products for secretion
Endomembrane System
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Lysosomes = membrane-bound organelle with
hydrolytic enzymes
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Intracellular digestion - phagocytosis;
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Lipases, carbohydrases, proteases, nucleases
Amoeba, macrophages
Recycle - worn out organelles
Remodeling - metamorphosis
Lysosome formation
Endomembrane System
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Vacuoles: membrane-bound sac, larger than
a vesicle
2 types and functions:
 Food vacuole: phagocytosis; intracellular
digestion
 Water vacuoles – store water and excrete
water
Endomembrane System
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Contractile vacuole; fresh-water
protozoa (paramecium)
Excretes excess water out;
osmosis
Central Vacuole
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Large vacuole found in plant
cells
Tonoplast; membrane around
vacuole
Storage - minerals, water
(turgor pressure), poisons
Helps provide shape, rigidity
in plant cells
Other Membranous Organelles
Mitochondria and chloroplasts
 Peroxisomes
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Energy Transducers
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Mitochondria and Chloroplasts
Double layer membrane
Not part of endomembrane
Contain DNA and ribosomes
 Semiautonomous; grow and reproduce in cells
on their own
Mitochondria
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Sites of cellular aerobic respiration
Found in nearly all eukaryotic cells
Number of depends upon metabolic activity
and cell type
Mitochondria
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Matrix: enclosed by inner membrane;
Kreb’s
Cristae; embedded cytochromes for
ETC
Intermembrane space: proton
gradient
Chloroplasts
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Plastids: plant cells
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Amyloplast: store starch
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Chromoplast: store pigments; chromo = ‘color’;
flowers
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Chloroplast - chloro = ‘green’
Chloroplast
Thylakoid: folded
membrane
 Grana: stacks of thylakoid
 Intermembrane space
 Stroma: matrix of
chloroplast
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Peroxisomes
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Organelles with ‘teams’ of enzymes for
specific metabolic pathways; produce
peroxide
Catalase = enzyme that catalzyes hydrogen
peroxide into water and oxygen
Fats and alcohol; seed germination
Cytoskeleton
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Network of protein fibers within cytosol
Function:
 Framework
 Support
 Movement
 Cilia/flagella
 Mitotic spindle
Framework
Motility: motor molecules
Cytoskeleton
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3 parts:
Microtubules
Microfilaments
Intermediate filaments
Microtubules
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Straight, hollow fibers (tubulin)
Support, cell shape
Organelle movement; motor molecules
Spindle; during mitosis
 Move chromosomes
Microtubules
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Centrioles: animal cells
only
Plants have centrosomes
(MTOC)
Centrioles = cylindrical
structures outside the
nucleus; replicate during
prophase; grow spindle
between
Microtubules
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Cilia; short, hairlike, oarlike movement
(perpendicular to action)
Flagella: long; few or one; undulate;
movement parallel to direction
Cilia/Flagella
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Structure:
Microtubule core (9+2 arrangement); ATP
needed
Basal body = anchors cilia/flagella into cell
Microfilament
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Actin filaments
Smallest of cytoskeleton structure
Globular actin (protein) wound in a helix
Muscle contraction (along with myosin)
Cleavage furrows during mitosis
Cyclosis; cytoplasmic streaming (plants)
Elongation of pseudopodia in amoeba;
macrophages
Macrophage
Intermediate Fibers
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Between microtubules and microfilaments in
size
Tension (structure) framework (?) for
cytoskeleton
NOT disassembled, reassembled frequently
Cell Surface: Plants
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Plant cells: cell walls composed of cellulose
within a matrix of polysaccharides and protein
 Fungi – chitin
 Bacteria - peptidoglycans
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Primary Cell wall = between two plant cells
Cell Surface: Plants
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Middle lamella = sticky pectins
(polysaccharides); ‘glues’ cells together
Secondary cell wall = between the membrane
and primary cell wall
Cell Surface: Animals
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Glycocalyx = (‘sweet husk’) sticky
oligosaccharides (‘few’); ‘glues’ cells together,
stick to lipids, proteins of adjacent cells.
Strength, identification with other cells
Intercellular Junctions
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Joints between cells (tissue formation)
Plants = Plasmodesmata
Animals = tight junctions, desmosomes, gap
junctions;
Cell Surface: Plants
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Plasmodesmata = linking channels between
two plant cells
Cell-to-cell communication; one solid organism
Animal Cell Junctions
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Tight junctions = cells closely ‘knit’ together;
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block intercellular junctions; prevents
intercellular fluid loss (brain block, tubular
leakage)
Cells are ‘fused’ together
Animal Cell Junctions
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Desmosomes =(‘binding body’) intercellular
junctions that are tight but allow some
substances to ‘leak’
Strengthen linkages between cells
Also called anchoring junctions
Anchoring junctions
Animal Cell Junctions
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Gap junctions = channels between cells;
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allows some substances to pass through,
especially in tissues that need to communicate
Heart muscle cells, stem cells
Gap junctions