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Cytology I – Study of Cells
Biology 20
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Which cell type has organelles such as
mitochondria, nuclues, Golgi bodies, etc?
• A) prokaryotic
• B) eukaryotic
• C) bacterial
• D) viral
• E) none of these
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Cellular Basis of Life
1. Basic unit of Life
2. Composed of one or more cells
3. Arises from pre-existing cells
Asexual (Mitosis)/Sexual (Meiosis)
4. Surrounded by a membrane
5. Transform energy
6. Information retention (genes)
Cell Theory
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What level in life’s hierarchy possess all the
attributes of life?
• A) molecular
• B) organ
• C) tissue
• D) cellular
• E) all of these
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Cell Doctrine
• All living things are composed of cells
• Cell is the smallest unit that exhibits all of
the attributes of life
• All cells come only from preexisting cells
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Two Basic Cell Types Classified by
Internal Organization
Prokaryotic Cells
• Plasma membrane
• No nucleus
• Cytoplasm: fluid
within membrane
• No true organelles
• 1 – 10 um
Eukaryotic Cells
• Plasma membrane
• Nucleus: information
center
• Cytoplasm: fluid within
membrane
• Organelles:
compartments with
specialized functions
• 10 – 100 um
What type of cell do you have?
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Figure 3.6
Ribosomes
Cytoplasm
Nucleoid
(DNA)Cell
membraneCell wall Capsule Flagellum
SEM (false color) 2 μm SEM (false color) 2 μm SEM (false color) 2 μm
a.
b. c. d.
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Figure 3.2
Range of electron microscope
Range of light microscope
Range of human eye
AtomsSmall
moleculesProteins Viruses Most bacteria and
archaeaMost plant and
animal cellsFrog eggs Ant
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b) Prokaryotic cells such as this bacterium have arigid cell wall surrounding the plasma membrane.The genetic material is not surrounded by amembrane, and there are no organelles in the cell.The elongated bacterium in the center of the photois about to divide in two, as its genetic material isconcentrated at both ends of the cell.
a) A eukaryotic animal cell has a largenucleus and numerous small organelles.The cytoplasm is enclosed by a flexibleplasma membrane.
Nucleus
Organelles
Cytoplasm
Cell wall
Plasmamembrane
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Cell structure reflects eukaryotic cell’s function
Figure 3.2
a) A portion of several musclecells of the heart (X 1,500).
b) Nerve cells of the centralnervous system (X 830).
c) Cells lining a tubule of a kidney (X 250).
• How are these cells similar?
• What makes these cells different?
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Figure 3.23
40 µm 35 µm 50 µmLM LM LM400 µmLMa. b. c. d.
Cell structure reflects eukaryotic cell’s function
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Why are cells so small?
• Efficiency in:• Acquisition of nutrients
• Disposal of wastes
• What makes this possible?• High surface areas to volume ratio
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The cells of an ant and an elephant are,
on average, the same small size; an
elephant just has more of them. What is
the advantage of small cell size?
a) small cells are less likely to burst than large cell;
b) small cells are less likely to be infected by bacteria;
c) small cells can better take up what they need from their environment;
d) it takes less energy to make an organism out of small cells;
e) small cells can "morph" more easily than larger cells.
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Figure 3.5
Receptor protein
Channelprotein(always open)
Gatedchannelprotein(closedposition)
Carbohydrategroups
Cytoskeletonfilaments
Phospholipid
Cytoplasm
Lipidbilayer
Transportprotein
Glycoprotein
Extracellular environment
Cholesterol
Plasma or cell membrane
• Hydrophobic
interactions
• Fluid Mosaic Model
• 8 hm
• Boundary
• Selectively
permeable
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Water
Water
Phospholipid
bilayer
Hydrophilic
Hydrophobic
Hydrophilic
Phospholipid
bilayer
Ions and large, polar,
or charged molecules
Lipids and small,
nonpolar molecules
Figure 3.11
Plasma or cell membrane
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Fluid Components
• 1) Phospholipid
– Hydrophilic
– Hydrophobic
– Amphipathic
• 2) Cholesterol
– Cold prevents packing
– Hot limits movement
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Mosaic Components
• 3) Proteins
– Intergral: w/in membrane
– Peripheral: inside cell (cytoplasmic)
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Membrane Protein Functions
• 1) Transport• In or out of the cell
• Molecule specific
• 2) Ion channel• Na+, K+, Ca++, Cl-.
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Membrane Protein Function
• 3) Enzymatic
– Chemical rxn
– Energy production
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Membrane Protein Function
• 4) Receptor site• For chemical messengers
• Signal transduction
• Cell recognition
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Membrane Protein Function
• 5) Cytoskeleton attachment• Cell shape
• Coordinate extracellular &
intracellular changes
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Membrane Protein Functions
6) Cell adhesion
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Figure 3.27
GAP JUNCTION
CELLS OF SMALL INTESTINE
TIGHT JUNCTION
ANCHORING (ADHERING)
JUNCTION
Membrane Protein Functions
6) Cell adhesion
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Mosaic Components
• 4) Carbohydrates• Glycoproteins
• glycolipids
• Function:• Cell-cell recognition
• Ex. Blood type
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Which component of the cell membrane is
the cell’s ID tag (or identifies the cell as its
particular type?
A) cholesterol
B) carbohydrates
C) phospholipids
D) proteins
E) All of these
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Which of the following allows for cell to cell
recognition?
A) cholesterol
B) carbohydrates
C) phospholipids
D) proteins
E) I think it’s two of these
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Membrane Permeability
• Size:• Small molecules
• Charge:• Uncharged easy
• Charged: can not
• Lipid solubility• Hydrophobic molecules
• Carrier proteins• Assist small charged
• Assist non-soluble
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Membrane Transport
• Simple Diffusion• [High] [Low]
• Down its [gradient]
• Passive no energy
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Membrane Transport
• Facilitated diffusion• Carrier protein
• Passive no energy
• Ions, water
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Table 4.2
Membrane Transport
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Lower
concentration
Diffusion through the lipid
layer. Lipid-soluble molecules
such as O2 and CO2 diffuse
freely through the plasma
membrane.
Diffusion through channels.
Some polar and charged
molecules diffuse through
protein channels that span
the membrane. Water
is a typical example.
Facilitated transport. Certain
molecules bind to a protein,
triggering a change in protein
shape that transports the
molecule across the membrane.
Glucose typically enters cells by
this method.
Higher
concentration
3 types of passive transport
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Sodium ions (Na+) diffuse across the cell
membrane, but they need assistance.
This would be an example of:
a) simple diffusion
b) facilitated diffusion;
c) active transport;
d)osmosis;
e) huh?
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Membrane Transport
• Osmosis• Diffusion of water
• Across a selectively
permeable membrane
• Passive
• Hypotonic• Lower [solute] & High [H2O]
• Isotonic• Equal/same [solute] &
equal/same [H2O]
• Hypertonic• Higher [solute] & Low [H2O]
Hypotonic hypertonic
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Membrane Transport - Osmosis
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Figure 4.16
Membrane Transport - Osmosis
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Membrane Transport - Osmosis
• Isotonic solution
– Equal/same [solute]
– Ex.
• Inside cell: 3% NaCl, 97% H2O
• Beaker: 3% NaCl, 97% H2O
– Animal cells Normal
– Plant cells normal
3% NaCl
97% H2O
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Membrane Transport - Osmosis
• Hypotonic solution
– Lower [solute], has more water
• Inside cell: 3% NaCl, 97% H2O
• Beaker: 0% NaCl, 100% H2O
– H2O: more IN than out
– Animal cells burst/lyse
– Plant cells turgid (stiff)
– Why?
0% NaCl
100% H2O
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Membrane Transport - Osmosis
• Hypertonic solution
– Higher [solute], less water
• Inside cell: 3% NaCl, 97% H2O
• Beaker: 50% NaCl, 50% H2O
– H2O: more OUT than in
– Animal cells shrinks
– Plant cells plasmolysis 50% NaCl
50% H2O
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Osmosis – hypertonic solutions
• Animal cells
– Shrinks/shrivels
• Plant cells
– Plasmolysis
• Cell membrane separates
from cell wall
5% NaCl
95% H2O
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The amount of water movement is indicated by the sizes of the arrows.
Scanning of electron micrographs of red blood cells
placed in similar solutions.
0.9% salt 10% salt DI water
HypotonicHypertonicIsotonic
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Figure 4.17
HypotonicHypertonicIsotonic
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Figure 4.18
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Tonicity & the potato
Initial (3 cm)
Hypertonic
Isotonic
Hypotonic
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You're rushed to the ER and given an IV
(intravenous) saline (salt) solution to rehydrate
you. The nurse was not sleeping during
biology this time and happened to give you an
isotonic IV solution. What would happen to
your RBC's (red blood cells) in your blood
vessels?
a) shrivel;
b) lyse/burst;
c) nothing;
d) you're thinking lawsuit aren't you?
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Membrane Transport
• Active Transport• [lower] [higher]
• Against [gradient]
• Carrier protein
• REQUIRES energy
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Active Transport – Na+/K+ pump
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Membrane Transport
• Bulk transport Large molecules• Endocytosis = in take
1. Phagocytosis = cell eating
2. Pinocytosis = cell drinking
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Figure 4.20
Membrane Transport
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Membrane Transport
• Large molecules• Endocytosis = in take
1. Phagocytosis = cell eating
2. Pinocytosis = cell drinking
3. Receptor mediated
Substance triggers receptor protein
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Figure 4.21
Membrane Transport
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Membrane Transport
• Bulk Transport Large molecules
• Exocytosis
– Getting rid of substances
– Transport vessicle fuses w/ cell
membrane
Contractile
vacuole
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c) Photomicrograph showingvarious stages of endocytosis.
a) Endocytosis. In endocytosis, material is surrounded bythe cell membrane and brought into the cell.
Extracellular environment
Plasma membrane
Cytoplasm
Vesicle
b) Exocytosis. In exocytosis, a membranous vesicle fuseswith the plasma membrane, expelling its contents outsidethe cell.
Comparison of endocytosis & exocytosis