Transcript Notes on Cells The Origins of Cell Study

Notes on Cells
The Origins of Cell Study
Individual cells are
so small;
they are seen in
detail only with a
microscope.
The Origins of Cell Study
1. 1600’s: Leuwenhoek: Dutch, first
to magnify nature with a
lens
It was really
just a piece of
glass.
2. 1665: Hooke: British,
-first to use a
compound scope
to look at
magnified plant
tissue (cork);
-named cells =
basic unit of all life
forms
1838: Schleiden: German,
(botanist) said all
plants were made
of cells
4. 1839: Schwann: German,
(zoologist) said
all animals were
made of cells
Cell theory: summary of these
discoveries
a. All living things are made up of
cells
b. Cells are the basic unit of
structure and function in living
things
c. New cells are produced from
existing cells
Microscopes
Magnification – the power to
increase an object’s apparent
size
Resolution – the power to show
detail clearly
Magnifying glass – simple microscope
Dissecting Microscope
Light microscope – uses light
Specimen – is the object being
viewed
Must be thin enough to let light
through
Compound light microscope – 2
kinds of lenses
1. Ocular – (eyepiece 10x)
2. Objective lens – (near the
specimen)
Degree of magnification –
determined by the lenses
x – stands for times
Total magnification – multiply the
power of the objective by the
power of the ocular
x
Objective
*Scan
*Low
*High
*Oil
Immersion
Power of Ocular
objective
Total
Magnification
4
10
40
10
10
100
40
10
400
100
10
1000
* objectives used in this class
How do you increase magnification?
Use a 20x ocular
• 2000x is usually as high a
magnification as can be
obtained with a compound
microscope
Why is 2000x the limit for a
compound microscope?
Above 2000x – decreased
resolution
• magnification is no good if
clarity (resolution) is lost
Above 2000x - you must have an
electron microscope
• Transmission Electron Microscope (TEM)
• Scanning Electron Microscope (SEM)
• insect wing
To see more microscopy
images, click here.
Parts of the Light Microscope
ocular
arm
coarse
adjustment
fine
adjustment
light
source
base
stage
diaphragm
stage
clips
low power
objective
high power
objective
Scan
objective
revolving
nosepiece
Cell Types
Prokaryotic – no true nucleus
• no membrane-bound organelles
pro = before
karyo (Greek) = “nut” or
“kernel”
nuclei (Latin) = “a little nut”
• smaller
• no nuclei
• have cell membranes and
cytoplasm
• grow, reproduce, respond to
changes in environment
Ex. Kingdoms Archaebacteria &
Eubacteria
bacteria
blue-green bacteria
(cyanobacteria)
Eukaryotic – true nucleus
eu = true
• do contain nuclei – a structure
that contains genetic material
and controls cell activities
• have cell membrane – thin,
flexible barrier around cells
• have cytoplasm-material inside
cell membrane but not including
nucleus
Ex. 4 other kingdoms
Protista
Fungi
Plantae
Animalia
Where do viruses go?
Viruses: Are particles of nucleic acid, protein,
and in some cases lipids that can reproduce
ONLY by infecting living cells.
Viruses are made of a core of either DNA or RNA
surrounded by a protein coat - capsid.
These are T4 Bacteriophages
A bacteriophage is a
virus which infects
bacteria
Viruses are not considered alive because they
don’t have ALL the characteristics of life.
Example: They can’t reproduce independently
These are the Influenza Viruses
Influenza or "flu" is an
infection of the respiratory
tract that can affect millions
of people every year.
The protein in the capsid “tricks” the
host cell into allowing the virus
inside
• once inside it takes over,
putting the genetic program of
the virus into effect
Common diseases caused by viruses:
Polio, measles, AIDS, mumps,
influenza, yellow fever, rabies,
common cold, cancer
Scaled Comparison
So how do prokaryotes, eukaryotes
viruses compare in size?
Click here for an
interactive demonstration.
What kind of scope would you
need in order to see:
Scaled Comparison
What kind of scope would you use to view:
• Human cells? LM
• Other eukaryotic cells? LM
• Prokaryotic cells? LM, oil immersion
• Details of intracellular structures?
SEM or TEM
• Viruses? SEM or TEM only
Notes on
Cell structures
Cytoplasm
• jelly-like material inside the cell
membrane which contains water,
salts, and organic molecules
• in constant motion – cytoplasmic
streaming
http://www.vcbio.science.ru.nl/eng/image-gallery/show/Fi002/gif
• surrounds organelles
Organelles – specialized structures
that perform important
cellular functions
1. mitochondria
• “powerhouses”
• respiration centers for the release
of energy
• use energy (food molecules) to
make high-energy compounds that
the cell can use to power growth,
development, movement
• ATP (adenosine triphosphate) – most
prevalent macromolecule in cells
that use a lot of energy (muscles)
• ATP is generated by mitochondria
• enclosed by 2 membranes
outer – smooth, form
boundary
Inner – long folds
(cristae) increase
surface area
2. endoplasmic reticulum (ER)
• membrane system of sacs and
tunnels
• covered with ribosomes –
rough ER, place where
proteins are modified
• few or no ribosomes – smooth ER,
contains enzymes that perform
specialized tasks, like production
of lipids
• “intracellular highway”
3. ribosomes
• “protein factories”
• made of RNA and proteins
• where proteins are made (most
numerous organelle) –
produces proteins following
coded instructions that come
from the nucleus
• granulated, attached to ER or
float in cytoplasm
4. Golgi apparatus
• processing,
packaging
and secreting
organelle
• stack of membranes or sacs
which package proteins
produced by rough ER
• “protein packagers”
5. Lysosomes
• contain digestive enzymes
• breakdown carbohydrates,
lipids, and proteins into
particles that can be used by
the cell
• breakdown organelles that are
no longer useful
• remove debris that otherwise
accumulates/clutters the cell
• in animal cells and fungi
• “suicide sacs”
lysis = breakdown
soma = body
6. Centrioles
• rod-shaped bodies close to the
nucleus which guides the cell
during division
• animal cells only
7. Vacuoles
• cavities (containers) which
store enzymes, waste
products, water, salts,
proteins, and carbohydrates
• mainly in plant cells –
plants have a large
central vacuole filled
with liquid
• in mature plants – the vacuole
takes up 90% of the volume of
the cell
• smaller vacuoles are called
vesicles
8. Plastids
• chemical factories to store
food
• only in plants
• can contain pigments
example - chloroplasts
Cytoskeleton: framework of cell
(supports the cell)
• network of protein filaments
• used in cell movement
9. microtubules
• small hollow tubes of protein;
maintains cell shape, forms
tracks along which organelles
are moved
• assembled and broken down
as needed (during cell
division)
• in some cells they form cilia
and flagella that aid in
movement
• act as “bones” in the cell
10. Microfilaments
• protein threads of actin for
cytoplasmic streaming
• smaller than microtubules
• act as “muscles” in the cell
Nucleus – identified in 1831
• control center of the cell
• site of nucleic acid synthesis
1. nuclear envelope (membrane)
• double membrane
(phospholipids and proteins)
• nuclear pores allow
substances to enter and leave
2. nucleoplasm
• protoplasm within the nucleus
• dense, protein rich
3. nucleolus (singular),
nucleoli (plural)
• form ribosomes
• composed of RNA
4. chromatin
• fine strands of DNA and proteins
• genetic material
• chromosomes – coiled up
chromatin when the cell is
dividing
Differences in Plant Cells vs. Animals:
a. Cell wall – provides support and
protection for the plant
cell
• contain pores which allow
H2O, CO2, and O2 to pass
through
• made from fibers of
carbohydrates and proteins
(cellulose)
• cellulose – tough carbohydrate
fibers, makes up wood and
paper
b. vacuoles – one large central
vacuole
• 90% of cell’s volume
c. plastids
Plastids
chloroplast
Pigment
Function
chlorophyll
absorb sun’s
energy
carotene
(orange)
chromoplast
leucoplast
xanthophyll
(pale yellow)
------
store
pigments
store food as
starches, lipids,
or proteins
Cell membrane
• forms outer boundary and
separates the cell from its
surroundings and other cells
• composed of 2 layers of
phospholipids and proteins –
both move like a liquid called
“fluid mosaic model”
• contains protein molecules
that provide attachment point
for carbohydrate molecules to
form chains
• some proteins in cell
membrane form channels and
pumps to help move materials
• regulates what enters and
leaves the cell – selectively
permeable (semipermeable)
(Keeps out some molecules
but allows others to enter)
Endosymbiotic Theory
•
Endosymbiotic Theory proposes that
eukaryotic cells arose from living
communities formed by prokaryotic
organisms.
•
Endo- means inside
• -symbiotic means living together
(relationship)
Endosymbiotic Theory
•
Prokaryotes entered ancestral eukaryotes
•
Prokaryotes did NOT act as a parasite by infecting
the host (eukaryote)
•
Eukaryotes did NOT digest the prokaryotes
•
Instead, the smaller prokaryotes began LIVING
inside the larger cell – giving rise to eukaryotes
Endosymbiotic Theory
• 1st - Mitochondria & Chloroplasts have DNA
similar to bacterial DNA.
• 2nd – Mitochondria & Chloroplasts have
ribosomes whose size & structure resembles
those of bacteria.
• 3rd – Like bacteria, Mitochondria & Chloroplasts
reproduce by binary fission when the cells
containing them divide by mitosis.
Click Here For Animation Tutorial
Endosymbiotic Theory
• Lynn Margulis Explains Endosymbiotic
Theory