IB Topic 2.1-2.3
Prokaryote and
Eukaryote Cells
Cell Theory
A. There are 3 main points
1. All living organisms are composed of
cells.
2. Cells are the smallest unit of life.
3. All cells come from pre-existing cells
Cell theory: history and
evidence
A. The discovery of cells is linked to
technological advancements (microscopes)
B. 1590-Jansen developed the compound
microscope (it had two lenses)
C. 1665-Robert Hooke discovered the cell
1. Looking at cork
D. 1675-Leeuwenhoek discovered unicellular
organisms
E. 1838-Mathius Schleiden
discovered all plants are
made of cells
F. 1839-Theodore Schwann
discovered all animals are
made of cells
G. 1855-Rudolph Virchow
discovers all organisms are
made of cells
**organism=any living thing
Characteristics of Life: (single cell or multi-cell)
1. Order (organization) – from small to large
-Ex: Organelles make up cells.
Cell make up tissues.
Tissues make up organs.
Organs make individuals.
2. Metabolism- organisms take in and release energy
3. Response (to the environment)- response to stimuli
4. Growth and development- heritable programs of DNA direct growth
and development (change in one’s shape during life)
5. Homeostasis- organisms have regulatory mechanisms to maintain
their internal environments
Examples: body temperature, blood sugar, osmoregulation
6. Reproduction- the ability to reproduce ones own kind
7. Evolutionary adaptation- life evolves as a result of interaction
between organisms and their environment
Multicellular organisms
A. Multicellular organisms show emergent
properties
B. Emergent properties arise from
interaction of the components:
- The whole is greater than the parts
(Ex: a heart cannot function without the
whole body)
- A single cell can do nothing on its
own, but when you put all of the cells
together
they can perform many
functions
Multicellular organisms and
differentiation
A. Multicellular organisms differentiate to carry out
specialized functions
B. All cells originated from the same place and all
carry the genetic information to perform any
function (your toe cell could have been a brain cell)
C. In each cell there is only a small amount of
activated genetic material
Ex: All cells have the genes for taste. The only
cells with activated ‘taste’ genes are on your
tongue.
Stem Cells
1.
Have ability to reproduce and
differentiate
1.
Embryo cells all start out as stem cells
2.
Valuable for scientific research
3.
May be able to differentiate stem cells to desired cell type
4.
These may replace damaged cells
Sources:
• Embryonic – cells from human blastocysts
• Fetal – cells from aborted fetuses
• Umbilical cord stem cells – cells from the umbilical cord of
newborns
• Placenta derived stem cells – cells from the placenta and
amniotic fluid of newborns
• Adult – cells from adult tissue (bone marrow, fat...)
Homework-Outline one therapeutic use of
stem cells for humans or some other
animal.
DO NOT USE WIKIPEDIA AS YOUR
RESOURCE!!
You may use any government or university
website. Their websites generally end in
.edu or .gov.
Viewing Cells
1. Light microscopes :
-
See color images
have a larger field of view
prepare samples easily
observe living and non-living material
**We cannot see most cell organelles
2. Electron microscopes:
- must be dead and no real colors
Scanning Electron (SEM):
- electron beams that bounce off the specimen
Transmission Electron (TEM):
- Used electron beams that pass through
specimen
(more detail because they have a higher resolution)
Transmission Microscope (guess what these structures are...)
Scanning Microscope
Microscope Vocabulary
1. Resolution- describes clarity of pictures
-higher resolution = more detailed
pictures
2. Magnification- makes objects larger
3. An increase in magnification may
reduce the resolution
Calculating Linear Magnification
A. The formulaMagnification = size of image
size of specimen
B. Example-the object is magnified by
two
This is the original
object.
Diameter of the image=4cm
Diameter of the specimen=2 cm
Find the magnification.
This is the magnified
image.
Common SI Unit Conversions
1nm (nanometer) = 1 x 10-9 m
1ųm (micrometer) = 1 x 10-6 m
1mm (millimeter) = 1 x 10-3 m
1cm (centimeter) = 1 x 10-2 m
1m (meter) = 1m
1km (kilometer) = 1 x 103 m
Calculating linear magnification
• Take a measurement of the drawing (width or
length)
• Take this same measurement of the specimen
• Remember to convert units if needed to
• Place your values into the equation
• Magnification = length of drawing / length of
actual specimen
• You can also calculate the length of the
specimen if this is unknown: length of the
drawing / magnification.
VIDEO: http://www.youtube.com/watch?v=L1d-02yRsRE
Limitations to Cell Size
A. Cells cannot grow indefinitely
B. They reach a maximum size and divide.
C. Bigger cells are less efficient.
-They have to transport materials further.
-The smaller the surface area to volume ratio
the harder it is for the cell.
How Big Is A Cell?
OBJECT
Eukaryotic
Prokaryotic
Nucleus
Chloroplast
Mitochondrion
Large virus (HIV)
Ribosome
Cell membrane
DNA dbl. helix
H atom
SIZE
10-100 μm
1-5 μm
10-20 μm
2-10 μm
0.5-5 μm
100 nm
25 nm
7.5 nm
2 nm
0.1 nm
Diagram of a typical prokaryote
Prokaryote organelles
1. Cell wall- gives the cell structure and strength (covered by sticky
capsule)
2. Plasma membrane- separates the internal features from the outside
environment
3. Cytoplasm- holds cell’s organelles and
enzymes
4. Pili- help the cell hold on to other
structures and aid in movement
5. Flagella- aid in organism movement
6. Ribosomes- make protein from mRNA
7. Nucleoid- area containing naked DNA
(ring)
8. Slime capsule- a protective barrier
around the cell (may help shield it from
antibiotics)
An electron micrographs of E. coli
** For IB you must be able to identify the structures on a micrograph.
http://www.cellsalive.com/index.htm
Pili: attachment structures on
the surface of some prokaryotes
Nucleoid: region where the
cell’s DNA is located (not
enclosed by a membrane)
Ribosomes: organelles that
synthesize proteins
Bacterial
chromosome
(a) A typical
rod-shaped bacterium
Plasma membrane: membrane
enclosing the cytoplasm
Cell wall: rigid structure outside
the plasma membrane
Capsule: jelly-like outer coating
of many prokaryotes
0.5 µm
Flagella: locomotion
organelles of
some bacteria
(b) A thin section through the
bacterium Bacillus coagulans
(TEM)
Prokaryote reproduction
1. Most prokaryotes divide by binary
fission
Eukaryote Cells
Eukaryote Information
1. All eukaryotes have enclosed nuclei
and other membrane bound organelles
2. Eukaryotes are true cells (‘eu’ = true)
3. Eukaryotic cells are present in protists,
plants, fungi and animal
4. Animal cells have a secretory vesicle
-It secretes glycoproteins that makeup
the extracellular matrix
-The extracellular matrix functions in
support, adhesion and movement
Animal Cell Organelles:
• Nucleus: contains genetic material, controls the cell
• Ribosome: synthesizes proteins from mRNA.
– Free floating, rough ER, chloroplast and mitochondria.
• Rough ER: synthesizes proteins to be excreted by the
cell
• Smooth ER: synthesizes lipids and carbs
• Golgi Apparatus: modifies, packs and ships via vesicles
• Lysosome: digestion (enzymes)
• Peroxisome: produces and breaks down hydrogen
peroxide
• Mitochondrion: aerobic respiration, converts chemical
energy into ATP using oxygen
• A animal cell
ENDOPLASMIC RETICULUM (ER)
Rough ER
Smooth ER
Nuclear envelope
NUCLEUS
Nucleolus
Chromatin
Flagelium
Plasma membrane
Centrosome
CYTOSKELETON
Microfilaments
Intermediate filaments
Ribosomes
Microtubules
Microvilli
Golgi apparatus
Peroxisome
Figure 6.9
Mitochondrion
Lysosome
In animal cells but not plant cells:
Lysosomes
Centrioles
Flagella (in some plant sperm)
Plant Cells
Organelles found in plants only:
- cell wall:
-provides rigid support for the
cells
-made mostly of cellulose
-plays important role in turgor
(hardening of cells by the intake
of water)
-prevents cells from taking in too
much water
- chloroplasts- organelle required
for photosynthesis
- vacuole- membrane bound sac
used for storage of organic
compounds
• A plant cell
Nuclear envelope
Nucleolus
Chromatin
NUCLEUS
Centrosome
Rough
endoplasmic
reticulum Smooth
endoplasmic
reticulum
Ribosomes (small brwon dots)
Central vacuole
Tonoplast
Golgi apparatus
Microfilaments
Intermediate
filaments
CYTOSKELETON
Microtubules
Mitochondrion
Peroxisome
Plasma membrane
Chloroplast
Cell wall
Plasmodesmata
Wall of adjacent cell
Figure 6.9
In plant cells but not animal cells:
Chloroplasts
Central vacuole and tonoplast
Cell wall
Plasmodesmata
Summary of differences between
eukaryotes and prokaryotes!
Prokaryotic Cells
Eukaryotic cells
small cells (< 5 mm)
larger cells (> 10 mm)
always unicellular
often multicellular
no nucleus or any membrane-bound
organelles
always have nucleus and other
membrane-bound organelles
DNA is circular, without proteins
(naked)
DNA is linear and associated with
proteins to form chromatin
(not naked)
ribosomes are small (70S)
ribosomes are large (80S)
no cytoskeleton
always has a cytoskeleton
cell division is by binary fission
cell division is by mitosis or meiosis
reproduction is always asexual
reproduction is asexual or sexual