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Introduction to
Cytology or Cell Biology
How do we observe cells?
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Light microscope
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Visible light passes through object
Lens magnify image
Electron microscope
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Scanning - surface of object
Transmission - sees through objects
100,000 X to Millions magnification power
How do we know what
happens in each part of the
cell?
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Radioisotopes are used to "trace" different
chemical reactions through a cell.
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Separate cellular structures with a blender
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Centrifuge material and analyze each layer.
People who were important in
early cell discovery:
Zacharias Jannsen
(1590)
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Helped invent the First
compound microscope
Robert Hooke (1665)
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Observed dead cork - called them
“cells“
Compound Microscope
Anton Von Leeuwenhoek
(1674)
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- living cells in pond water; one celled
organisms -- animalcules
Robert Brown (1831)
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identifies the nucleus of a cell
Mattias Scleiden (1838)
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stated that plants are made up of cells
Theodor Schwann (1839)
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stated that animals are made up of
cells
Rudolph Virchow
(1858)
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1.
2.
Studied the pathology of cells. (ability to cause
disease)
All cells arise from preexisting cells.
New cells can only arise from other living
cells by the process of cell division or
reproduction
Cell Theory
1.
2.
3.
All living things are composed of
cells
Cells are the fundamental building
block of life
All cells come from pre-existing cells
(life begets life)
PROCESSES OF CELLS
All life processes involve energy changes.
1. Nutrition - food is needed for energy and building
materials.
2. Digestion - breaking down reactions of food into
usable parts.
3. Absorption - water, food, ions and other materials
4. Biosynthesis - cells organize many organic
substances for cell activity.
5. Respiration - cell energy is released when certain
organic molecules are split - energy is used for cell
activity.
6. Excretion - waste materials passed from cell to
environment
7. Secretion - synthesized molecules which are passed
out of a cell and which affect the activities of other
cells (vitamins, hormones)
8. Reproduction - cells divide; unicellular - more
organisms, multicellular - more cells.
9. Movement - motion of all types; cellular contractions,
flowing substances within the cell
10. Egestion - elimination of insoluble compounds and
nondigestible particles
Eukaryotic cells – advanced cells
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Have nucleus
Plasma membrane
Cytoplasm - everything between plasma
membrane and nucleus
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Organelles
Fluid
Cytoskeleton – threads of microtubules
and microfilaments in cytoplasm
Animal vs Plant Cell
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Animal cells have unique structures
 Centrioles
 Lysosome
 Flagellum
1.
2.
3.
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Plant cells have unique structures
 Large central vacuole
 Cell wall
1.
 Chloroplasts
3.
2.
Cytoskeleton Fibres
Mitochondrion
Mitochondrion
Chloroplast
Vesicle
Golgi Body
Central
Vacuole
Smooth
ER
Rough
sdfER
Cell
Wall
Plasma
Membrane
Nucleolus
Pore
DNA
Envelope
Ribosomes
Centriole
Plasma Membrane
OUTSIDE OF CELL
Sugar Chain
Lipid Bilayer
Protein Marker
Cholesterol
INSIDE OF CELL
Proteins
Embedded
Protein
Cell Membrane Side Profile
Different membranes
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All have similar functions & structures
Plasma membrane separates inside of cell from
outside of cell
Other membrane define organelles to form
compartments of eukaryotic cells
Forms a selectively permeable layer
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Lets some things in or out but not all
Like a window screen
Nucleus
Nucleus - Structures
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Envelope
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Chromatin
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Double membrane
Pores to get messages in and out
DNA threads
Protein balls called histones - wrapping
Nucleolus - site of ribosome production
Nucleolus – where rRNA or
Ribosomes are made
Ribosomes
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Consists of 2 parts, which are made in nucleus
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Make protein in the Cytoplasm
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Produce proteins from ‘recipes’ in the nucleus
copied into mRNA
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Some (proteins) will remain in cytoplasm
Some will be exported out of cell
Some will attach to membranes in cell
Ribosomes are found on the endoplasmic
reticulum and in the cytoplasm
Endoplasmic Reticulum
Rough
ER
Smooth
ER
Rough Endoplasmic Reticulum
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Rough ER - attached to nucleus
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Ribosomes stud surface
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Produces
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Membrane proteins - stay in cell
Secretory proteins - exported from cell
RER makin’ Proteins!
Smooth Endoplasmic
Reticulum
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No ribosomes, so not protein factories
More like transport system
Makes steroids, lipids
Liver cells have lots of smooth ER
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Detoxify chemicals
Supply and demand
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Increases tolerance to drug
So higher doses needed for same effect
Golgi apparatus – the Post
Office of the Cell
Golgi apparatus – what it does
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Refines, stores and marks molecules for
shipment
Looks like stack of hollow pancakes
Products of ER arrive & leave via transport
vesicles
Moving from one sac to the next
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Molecules get modified
Labeled and / or stored
Called the cell “Post office” because it marks
and directs products in the cell
Lysosome
Lysosome
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Greek for breakdown body
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Sac of strong digestive enzymes
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Recylcer
Compartmentalized for safety
Can release to breakdown entire cell – “suicide
sack”
Functions
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Digest food vacuoles
Digest invading bacteria
Digest old organelles
Lysosome
Lysosomal diseases
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Genetic disorders
‘Recipe’ is messed up so protein doesn’t work
If recipe for lysosome enzyme
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What should get broken down doesn’t
Ex. Tay Sachs
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Lipids aren’t broken down
Build up occurs
Eventually causes death
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Usually in before age 5
Mitochondria
Mitochondria
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Site of cellular respiration
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Conversion of food into energy (ATP)
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Double membrane
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ATP is what cells use to make things happen (drive
chemical reactions)
Big bag stuffed in smaller bag
Folds of inner bag called cristae
Space inside inner bag called matrix
Also once free living bacteria
Efficiency - gasoline engines converts 25% of energy
mitochondria converts 54% of energy
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contains some of its own DNA (amount
varies within organisms)
believed to evolved from a primitive
cell engulfing it and creating a
symbiotic relationship
DNA in mitochondria obtained only
from mother of organism.
Plant Organelles Chloroplasts - in
plants
Chloroplast
1. chlorophyll is green chemical that releases
electrons, working like a solar panel in sunlight
2. forms glucose
3. photosynthesis
6CO2 + 6H2 O ---> C6H12 O6 + 6O2
Chloroplasts
Structure of Chloroplast
 Double membrane
 Grana
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Stack of thylakoids
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Stroma
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Hollow disk
Where sunlight energy is captured and converted to
chemical energy
Thick fluid filling chloroplast
Contains some DNA
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Once free-living bacteria
Cytoskeleton
Microtubules
Actin filaments
Role of the Cytoskeleton
Network of fibers
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Give shape to cells
Allow movement of cell
Move organelles around
Made of microtubules and
microfilaments
Cilia
Flagella
9+2 Arrangment in
Cilia or Flagella
Basal Body of a Flagella or Cilia
•Note the triplet rings of tubulin protein
•9+0 arrangement
•Nine sets of rings, with no set in middle
•Used to set up 9+2 arrangment in cilia or flagella
Centrioles
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Cell reproduction; goes
to poles of cell during
cell division and helps
cell divide
Centrioles at Work in Cell Division
Cell Specialization
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Different kinds of cells suited for a
different activity.
Division of Labor
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Different cells divide their labor each
has a specific function and supports
each other.
Levels of structure
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1.
2.
3.
4.
5.
Cell
Tissue
Organ
Organ system
Organism
Tissue Level
A group of cells that are alike in structure and
activity in an organism muscles
- Skeletal muscle cells – motion
- Cardiac muscle cells – heartbeat
- Bones - support
- Nerve cells - coordination, perception
and automatic body functions
Organ Level
several tissues working as a unit
Animals
heart
brain
stomach
Plants
roots
stem
leaf
Organ System
many organs involved in carrying out a function
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digestive
nervous
skeletal
excretory
respiratory
endocrine – (hormones)
circulatory
muscular
reproductive
Organism
complete living thing
cell
tissue
organ
organ system
organism