Download PROKARYOTIC AND EUKARYOTIC CELLS

09/29/09
What is a
?
Are ALL living organisms made of
What do ALL
Are all
need to
the
to carry out life processes?
?
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I. Types of Cells: General Characteristics
A. Bacterial Cells
B. Archaeal Cells
C. Eukaryal Cells
II. Cell Structures
A. Plasma Membrane
1. Bacterial and Eukaryal Plasma Membrane Structure
2. Archaeal Plasma Membrane Structure
3. Functions of the Plasma Membrane
B. Cell Wall
1. Bacterial Cell Walls
2. Archaeal Cell Walls
3. Eukaryal Cell Walls
C. Structures External to the Cell Wall
1. Glycocalyx
2. Movement Appendages
3. Attachment Appendages
4. Cell Surface Molecules
5. Bacteria only! DNA Exchange Appendages
D. Structures Internal to the Plasma Membrane
1. Structures Common to both Prokaryotic and Eukaryotic Cells
a. Cytoplasm
b. Genetic Material- DNA
1) Chromosomes
2) Plasmids
3) ‘Nucleus’
c. Ribosomes
d. Inclusions
2. Bacteria only! Endospores
3. Eukaryotes only!
Complexity, Compartmentalization, INTERNAL MEMBRANES
a. Cytoskeleton
b. Chloroplasts
c. Mitochondria
d. ER and Golgi Complex
e. Lysosomes and Peroxisomes
f. Vesicles and Vacuoles
III. Progression from Prokaryotic Cells to Eukaryotic Cells
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Draw as you go: Cells
Prokaryotic: Bacteria and Archaea
Eukaryotic: protozoans, unicellular algae, molds, yeast
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I. Three Primary Types of Cells
Bacteria1
Archaea2
Gram Positive, Spirochaetes,
Purple bacteria (Proteobacteria),
Cyanobacteria,
Flavobacteria/Bacteroides,
Green Sulfur Bacteria, Green
Nonsulfur Bacteria,
Thermatogales
2-5 groups tentatively
identified, but include
the following:
Methane-producers,
Extreme Halophiles,
Thermoacidophiles
Eukarya3
Plants, Animals, Fungi
(molds and yeast), and
Protists (algae, protozoans,
slime molds, etc.)
1
http://en.wikipedia.org/wiki/Bacteria
http://en.wikipedia.org/wiki/Archaea
3
http://en.wikipedia.org/wiki/Eukaryote
2
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A. Bacterial Cells
1. Size: Most bacteria range from 0.2 micrometer to 2.0 micrometers in diameter
and 2-8 micrometers in length
2. Shapes and Arrangements TEXT Fig. 4.1
a. Cocci
http://student.ccbcmd.edu/courses/bio141/lecguide/unit1/shape/u1coccus.html
Streptococcus pneumoniae
(diplococcus)
-Cocci:
More resistant to drying than rods.
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Bacterial cells
b. Bacilli TEXT Fig. 4.2 & 4.6
Some structures discussed in the lecture
guide are not listed on this diagram:
glycocalyx slime layer, axial filaments,
endospore
http://student.ccbcmd.edu/courses/bio141/lecguide/unit1/shape/rod.html
Single rods
-Rods: Increased surface area, so can more easily take in dilute
nutrients from the environment.
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c. Curved TEXT Fig. 4.4
1) Spirochetes: Both syphilis and Lyme disease are caused by these
bacteria, and other species are important symbionts in the stomachs of
cows and other ruminants. They are very thin, flexible, spiral-shaped
bacteria that move by means of structures called axial filaments.
Most spirochetes are free living (in muds and sediments), or live in associations with animals (e.g. in the oral cavity or
GI tract). A few are pathogens of animals (e.g. leptospirosis in dogs, Syphilis in humans and Lyme Disease in dogs and
humans).
2) Spirilla have a helical or spiral shape. Unlike spirochetes, they
have a rigid cell wall and are motile by means of ordinary polar
flagella.
Self-reading: Two pathogens of humans are found among the spirilla. Campylobacter jejuni is an important cause of
bacterial diarrhea, especially in children. The bacterium is transmitted via contaminated food, usually undercooked poultry
or shellfish, or untreated drinking water. Helicobacter pylori is able to colonize the gastric mucosal cells of humans, i.e., the
lining of the stomach, and it has been fairly well established as the cause of peptic ulcers.
-Spiral: Corkscrew motion & therefore less resistant to movement.
3) Vibrio: The name Vibrio derives from the Latin because these curved
rods possess a single polar flagellum and appear "to vibrate". They are
often implicated in foodborne diseases.
V. cholerae. Gastrointestinal symptoms and the presense of a rice water stool are presumptive for cholera. Direct
examination of the feces may indicate vibrios.
V. vulnificus. Persons who are immunocompromised, especially those with chronic liver disease, are at risk for V. vulnificus
when they eat raw seafood, particularly oysters. A recent study showed that people with these pre-existing medical
conditions were 80 times more likely to develop V. vulnificus bloodstream infections than were healthy people. The
bacterium is frequently isolated from oysters and other shellfish in warm coastal waters during the summer months. Since it
is naturally found in warm marine waters, people with open wounds can be exposed to V. vulnificus through direct contact
with seawater. There is no evidence for person-to-person transmission of V. vulnificus.
There are exceptions to the usual bacterial shapes: some examples are Trichome
(also referred to as palliside or picket-fences), sheathed, stalked, filamentous,
square, star-shaped, spindle-shaped, lobed, and pleomorphic (def).
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B. Archaeal Cells TEXT Fig. 4.5b
Archaea include some truly weird microbes that thrive in extremely salty water, as well as microbes that live in
temperatures of hundreds of degrees. Even more recently, scientists have begun finding archael cells in an
increasing array of habitats, such as the ocean surface, deep ocean muds, salt marshes, the guts of animals, and
even in oil reserves deep below the surface of the Earth. Archaea have gone from obscurity to being nearly
ubiquitous in only 25 years!
http://www.ucmp.berkeley.edu/archaea/archaeasy.html
1. Very small, usually less than 1 micron.
2. Variety of shapes: coccus (regular spheres, lobed, lumpy), bacillus, spiral, or
other (triangular, square)
Basic Archaeal Shapes : At far left, Methanococcus janaschii, a coccus form with numerous
flagella attached to one side. At left center, Methanosarcina barkeri, a lobed coccus form lacking
flagella. At right center, Methanothermus fervidus, a short bacillus form without flagella. At far
right, Methanobacterium thermoautotrophicum, an elongate bacillus form.
http://www.ucmp.berkeley.edu/archaea/archaeamm.html
-Square shapes help cope with high salinity environments.
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C. Eukaryal Cells
1. Eukaryotic cells are generally larger and much more complex than prokaryotic cells.
2. Many different shapes and sizes.
centriole
s
nucleus
vacuole
Endoplasmic
reticulum
Ribosomes
(on ER)
mitochondrion
plasma
membrane
cytoplasm
cytoskeleton
peroxisomes
Golgi complex
lysosomes
vesicle
Yeast (Candida albicans)
http://www.cat.cc.md.us/courses/bio141/lecguide/u
nit1/proeu/u1fig2.html
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Eukaryotic Animal/Plant Cell
TEXT Fig. 4.22 a p. 99
Comparing sizes: Animation comparing viruses, bacteria, eukaryotic cells
http://www.cellsalive.com/howbig.htm
Eukaryotic cells are highly compartmentalized. A large surface-to-volume ratio, as seen in
smaller prokaryotic cells, means that nutrients can easily and rapidly reach any part of the
cells interior. However, in the larger eukaryotic cell, the limited surface area when compared to
its volume means nutrients cannot rapidly diffuse to all interior parts of the cell. That is why
eukaryotic cells require a variety of specialized internal organelles to carry out metabolism,
provide energy, and transport chemicals throughout the cell (most of the things needed for
a particular function are kept together).
TEXT Table 4.2 p. 101 Principle Differences between Prokaryotic and Eukaryotic Cells
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II. Cell Structures
Structure
Lecture
Guide
page(s)
Bacteria
Archaea
Eukaryota
General info
Plasma Membrane
Cell Wall
Glycocalyx
Movement Appendages
Attachment Appendages
Cell Surface Molecules
DNA Exchange Appendages
Genetic Material-DNA
Ribosomes
Inclusions
Endospores
Cytoskeleton
Chloroplasts
Mitochondria
ER & Golgi Body
Lysosomes & Peroxisomes
Vesicles & Vacuoles
Centrioles
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A. Plasma Membrane
1. Bacterial and Eukaryal Plasma Membrane Structure
Inverted phospholipid bilayer containing proteins
Phospholipid
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TEXT Fig. 4.14
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2. Archaeal Plasma Membrane Structure
Archaeal cell membranes are chemically different from all other living things.
Notice
branching
Archaea
Side
chains
Bacterial, Eukaryal
No branching
a. Glycerol component (found with the phosphate in the ‘head’) is a
‘mirror image’ (stereoisomer) of bacterial and eukaryal cell membrane
glycerol.
b. Linkage (type of bond) between the glycerol and side chains (‘tails’) is
different. This results in different properties.
c. Side chains are not fatty acids in Archaea. Isoprenes1 are common.
1 Isoprenes are a large and diverse group of lipids (they are not fatty acids)
http://www.cem.msu.edu/~reusch/VirtualText/lipids.htm
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Here is the situation. You are hungry. You haven’t eaten for days. You find a large piece
of bread. It is too large to fit in your mouth. What do you do? How did you accomplish
this?
3. Functions of the plasma membrane:
a. Regulation of the movement of materials into and out of the cell; the plasma
membrane is SEMIPERMEABLE (selectively permeable)
1) How do molecules move across the plasma membrane?
a) Diffusion

Simple (passive)
o Special example: osmosis

Facilitated
b) Active transport
c) Group translocation
d) Cytosis
TEXT Fig. 4. 17-4.18: Facilitated diffusion and osmosis
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a) Diffusion: (def.)
Concentration:
# of particles of a specific substance/total # of all particles of all substances
Gradient:
Difference in the concentration of a substance in one area compared to an adjacent area
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
Simple (Passive) Diffusion
-No energy is used.
-Transmembrane protein channels may be required.
Osmosis: TEXT Fig. 4.18 p. 93
Movement of water across a membrane by simple diffusion in response to the concentration of
molecules that cannot cross the membrane (impermeable).
-Water is a solvent (dissolver) for many molecules (solutes; for example salts and sugars).
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Note: The solution refers to the surrounding environmental solution outside of the cell.
1) Isotonic solution: If solute concentration outside of the cell is the same as that inside, the
solution is isotonic.
2) Hypotonic solution: a solution with a lower solute concentration than that inside the cell is
hypotonic.
3) Hypertonic solution: a solution with a higher solute concentration than that inside the cell is
hypertonic.
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Facilitated Diffusion
-Movement WITH (along) the concentration gradient.
-No energy is used.
-Transmembrane ‘trasnporter/porin’ proteins are required.
b) Active Transport
-Movement AGAINST the concentration gradient.
-Energy is required.
-Transporter protein(s) are required.
c) Group Translocation
-Only occurs in prokaryotes, not eukaryotes.

Transported substance is chemically altered during passage through the membrane.

Examples: Carbohydrates, fatty acids, some nucleic acid building blocks.

In E. coli, glucose outside the cell is phosphorylated during transport into the cell.
-Energy is utilized.
-Enzymes are required.
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d) Cytosis
Eukaryotic cells do not undergo group translocation.
-On the other hand, eukaryotic cells undergo transport systems that prokaryotes do
not: Cytosis
A transport process in which 1) a substance is engulfed by the cytoplasmic
membrane to form a vesicle inside the cell containing the substance or 2) when a
vesicle already in the cell fuses with the plasma membrane releasing the contents
of the vesicle out of the cell.
o
Endocytosis- movement into the cell
o
Exocytosic- movement out of the cell
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Functions of the Plasma Membrane
b. Proteins (enzymes) catalyze reactions involved in...
1) Nutrient breakdown
2) Molecule secretion
3) Environmental monitoring/Cell communication (signaling)
4) Cell wall synthesis
Bacteria and Archaea only:
5) Respiration and fermentation (reactions to acquire usable energy)
6) Photosynthesis
7) Chemosynthesis (utilizing inorganic chemicals as an E source)
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B. Cell Wall TEXT: Fig. 4.13 p. 86
1. Bacterial Cell Walls: All the members of domain Bacteria, with the exception of four
genera (Mycoplasma, Ureaplasma, Spiroplasma, and Anaeroplasma) contain cell walls.
For almost all bacterial species, if it has a cell wall, it contains peptidoglycan.
a. Examples of functions:
1) Prevents the cell from bursting (lysis).
2) Maintains shape.
3) Protection from the environment.
However, the cell wall is not a regulatory structure like the cell membrane.
Although it is porous, it is not selectively permeable and will let anything
pass that can fit through its gaps.
b. Bacterial Cell Wall Components:

All bacterial cell walls contain a compound called peptidoglycan2.

Peptidoglycan is composed of a glycan (sugar) component and a peptide
(bonded amino acids) component:
1. Glycan (sugar, carbohydrate) component: 2 monosaccharides
1) NAG (N-acetylglucosamine)
2) NAMA (or NAM; N-acetylmuramic acid)
There is an alternating sequence of NAG and NAMA.
2. Peptide component:
Each NAG-NAM layer is connected, or crosslinked, to the other by a
‘bridge’ made of amino acids. The particular amino acids vary among
different species. The crosslinked peptidoglycan molecules form a network
which covers the cell like a grid.
2 Bacteria without cell walls do not contain peptidoglycan.
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Peptidoglycan can be thought of as a strong, woven mesh that holds the cell shape and prevents it
from bursting. It is not a barrier to small molecules, the openings in the mesh are large and all
types of molecules can pass through them.
TEXT Fig. 4.13 p. 86
Gram positive vs. Gram negative
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Bacterial Cell Walls
c. Gram positive cell walls
A distinguishing factor among Gram-positive bacteria is that roughly 90% of their cell wall is
comprised of peptidoglycan, and a Gram-positve bacteria can have more than 20 layers of
peptidoglycan stacked together to form the cell wall (comprising ~50% of the weight of the entire
cell). Examples of common Gram-positive cells are Staphylococcus aureus and Streptococcus
cremoris, a bacterium used in dairy production.
Another chemical in the G+ cell wall is teichoic acid. Teichoic acid is covalently bonded to
NAMA and links various layers of the peptidoglycan mesh together.
Self-reading: The cell wall is the site of action of many important
antibiotics and antibacterial agents. Penicillin inhibits cells wall
synthesis. Lysozyme an enzyme found in tears and saliva-attacks
peptidoglycan. It hydrolyzes the NAG - NAMA linkage.
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Bacterial Cell Walls
d. Gram negative cell walls
Gram negative cell walls have a more complicated structure; but it is comprised of only 20%
peptidoglycan. Outside of the plasma (cytoplasmic) membrane is an open area called the
periplasmic space. Beyond this is a thin layer of peptidoglycan. External to the peptidoglycan is an
additional membrane, the outer membrane (OM).
(OM)
-Electron micrograph of a Gram negative cell wall.
The Outer Membrane (OM)

OM is beneficial to the bacterium. The outer membrane is beneficial to the bacterial cell
because it may be able to restrict substances which may damage or prevent the synthesis of
peptidoglycan (for example, certain antibiotics).

OM is bad for us. The OM is similar to the inner, cell membrane, but it also contains
lipopolysaccharides (LPS-endotoxins). Many species of Gram- bacteria are pathogenic
usually due to these lipopolysaccharides. The Black Plague which wiped out a third of the
population of Europe was caused by the tiny G- rod, Yersinia pestis. Many enteric
(intestinal/bowel related) illnesses can also be attributed to this group of bacteria, such as
Salmonella food poisoning. http://medic.med.uth.tmc.edu/path/00001443.htm
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Bacterial Cell Walls
Gram negative cell wall
Outer Member (OM)
of the Gram- cell wall.
Lipo-proteins
strongly bind the
peptioglycan to the
outer membrane.
Periplasmic space.
Cell Membrane
proteins.
o The side of the OM that faces the outside contains the lipopolysaccharide.
o Porins are proteins that form pores in the outer membrane wide enough to allow
passage of most small hydrophilic molecules. This allows migration of these
molecules into the periplasmic space for transport across the cytoplasmic
membrane.
o Summary of functions of the outer membrane in Gram negative cells:

Selective barrier.

Keeps enzymes in periplasm (see next page).

Stabilizes cells exchanging DNA.

Pathogenic properties.

Bacteriophage (bacterial virus) receptors - although this is a function the cell
would rather not have.
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Bacterial Cell Walls
Periplasmic space

The periplasmic space in-between the inner, cell membrane and the peptidoglycan contains
many different proteins. These proteins function to detect the environment, and modify, and
transport needed nutrients into the cell. Some examples of periplasmic proteins include:
A. Hydrolytic enzymesExamples: 1. Proteases - degrade proteins
2. Endonucleases - degrade nucleic acids
B. Binding proteins - recognize specific nutrients (for example, sugars and vitamins)
and transport them across membrane.
C. Chemoreceptors - Helps the cell interpret chemical composition of its environment
Let's sum up the differences between G + and G- cells:
Property
Thickness of wall
Gram Positive Gram Negative
20-80 nm
10 nm
Number of layers in wall 1
2
Peptidoglycan content
>50%
10-20%
Teichoic acid in wall
+
-
Lipopolysaccharide
0
13%
Sensitive to penicillin
+
- (not as much)
Digested by lysozyme
+
- (not as much)
http://www.bact.wisc.edu/MicrotextBook/BacterialStructure/MoreCellWall.html
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Bacterial Cell Walls
e. Bacteria Lacking Cell Walls
Ex: Mycoplasma pneumoniae
Bacteria without cell walls are not affected by penicillin or lysozyme.
For most bacterial cells, the cell wall is critical to cell survival, yet there are some
bacterial cells without cell walls. Mycoplasma species are one example, and they are
very wide-spread. They are the smallest known cells (0.2-0.3 micrometers) – almost
as small as the largest viruses (poxviruses). They also have the smallest genome of
any cell-about 650 genes (about 1/5 the number in E. coli). Mycoplasma are know to
cause many plant diseases. Due to the lack of a cell wall, Mycoplasma have
unusually tough membranes (3 layers) that are more resistant to rupture than other
bacteria. The presence of sterols in the membrane also contributes to their durability.
Many Mycoplasma are also pleomorphic.3
Click below for more info on Mycoplasma pneumoniae
http://www.emedicine.com/med/topic1540.htm
3 Having no defined shape. Bacterial cells that have no cell wall will often be pleomorphic. However, there are also
microbes with cell walls that have this property, and the growth state of the microbe sometimes influences this.
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2. Archaeal Cell Walls
a. Archaeal cells have more variations in their cell wall chemistries4.
b. They never contain true peptidoglycan, but a few have a similar molecule (NAG is
present but a different molecule replaces NAM). Penicillin is ineffective in
inhibiting the synthesis and lysozyme cannot break the bonds in this type of cell wall.
c. Some archaea do not have cell walls (eg Thermoplasma).
3. Eukaryotic Cell Walls
a. Plants, fungi, and some protists contain a cell wall, but the chemical
composition is different from Bacteria and Archaea.
b. There is never peptidoglycan.
c. Animals and protozoa do not have cell walls.

4 Methanosarcina

Halococcus sp. contain sulfated polysaccharides similar to Methanosarcina sp.

Halobacterium sp. contain negatively charged acidic amino acids in their cell walls which
counteract the positive charges of the high Na+ environment. Therefore, cells lyse in NaCl
concentrations below 15%.

Methanomicrobium sp. & Methanococcus sp. cell walls are exclusively made up of proteins.
sp. cell walls contain non-sulfated polysaccharides
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C. Structures External to the Cell Wall (anchored to the cell wall or the plasma
membrane)
1. Glycocalyx: Substances that completely surround the outside of the cell wall.
a. Functions
1) Attachment to surfaces.

Most prokaryotic cells adhere to each other.

Some bacteria adhere to rocks (aquatic bacteria) and other solid
surfaces.

Some pathogenic bacteria adhere to animal tissues (ex:
respiratory tract).

Some are involved in plaque formation leading to dental caries.
2) Protection from environment (slows dehydration).
3) Entrapment of nutrients.
b. Bacterial Glycocalyx: (Capsules and Slime layers)
Usually the capsule is chemically polysaccharides. It is thick and firmly attached to the cell wall,
very dense. Found in pneumonia causing pathogens such as Streptococcus pneumoniae,
Haemophilus influenzae, and Klebsiella pneomoniae. Capsulated variants are pathogenic whereas
non-capsulated variants of the same species are non-pathogenic. Capsules protect the bacteria against
human white blood cells that engulf and digest the bacterial cells.
-Ex: Streptococcus pneumoniae
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Notes:
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c. Slime layers: Chemically similar to capsules but less firmly attached,
thinner, and less dense.
Functions: Basically the same as the capsule but they are not associated
with pathogenicity.
d. Eukaryotic and Archaeal cells also have a sticky glycocalyx which
functions for: cell-to-cell attachment, cell recognition, or strengthening of
cell surface.
2. Movement Appendages
a. Flagella: Protein appendages, anchored in the plasma membrane

Some Bacterial, Archaeal, and Eukaryotic species have flagella,
but the molecular structure differs between the three groups.

Arrangements:
TEXT: Fig. 4.7 p. 81, Fig. 4.9 p. 83
b. Axial filaments: Bundles of fibers found beneath an outer sheath but
outside of the cell wall. Only found in bacterial spirochete
TEXT: Fig. 4.11 p. 84
3. Attachment appendages5
5 Also

‘Attachment Pili’: Attachment for pathogenic bacteria to human tissues
(Often, also called fimbriae). Ex. Neisseria gonorrhoeae

Other attachment configurations include protein networks to which the cells
may anchor themselves in large groups.
may act as receptor sites for attachment of some pathogens.
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4. Cell Surface Molecules
5. Bacteria only! DNA Exchange Appendages
(Ex. E. coli)
Conjugation Pili (‘sex’ pili)
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D. Structures Internal to the Plasma Membrane
1. Structures Common to Both Prokaryotic and Eukaryotic Cells
a. Cytoplasm: All components internal to the plasma membrane
Approximately 80% water. Approximately 20% enzymes, organic
compounds, dissolved subst., organelles, DNA...
b. Genetic Material- DNA
Comparing Prokaryotic and Eukaryotic DNA:
1) Prokaryotic:

Nuclear Region (Nucleoid): Area in the cytoplasm which
contains the large, circular bacterial chromosome (s)6

Plasmids: Free-floating, smaller, circular5 pieces of DNA that
are in no way connected to the large bacterial chromosome in
the nucleoid
o Usually, the genes on plasmids are not essential to the
life of the bacteria but benefit the organism in some
way.
o The genetic information supplements the chromosomal
genetic information with…
o Plasmids can be copied and transferred to another
bacterial cell
o Often bacterial plasmids are used in genetic
engineering.
6 Some species (relatively rare) of bacteria have been known to have linear chromosomes and plasmids.
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2) Eukaryotic:

Several linear chromosomes contain the DNA

Nucleus TEXT Fig. 4.24 p. 102
c. Ribosomes
1) Sites of protein synthesis
2) ~10,000 ribosomes in Archaea & Bacteria depending on growth rates
but many more in Eucarya
3) Composed of proteins and rRNA
4) Comparing Bacterial, Archeal and Eukaryal ribosomes:
a) Bacterial and Archael ribosomes are similar in size to each other
(both smaller than eukaryotic ribosomes) but have different rRNA
and protein components.
b) All three cell types have different rRNA molecules and proteins.
However the archaeal and eukaryal rRNA components are more
similar to each other than to bacteria.
c) Because the three cell types have differences in their ribosome
size and molecular structure, different chemicals will interfere in
protein synthesis.
Examples:
o Archaea and Eukarya are not sensitive to antibiotics that inhibit bacterial ribosomes:
tetracycline, erythromycin, chloramphenicol, streptomycin
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o However, the diptheria toxin & anisomycin affects ribosomes of archaea but not bacteria.
d. Inclusions
1) Structures that appear as granules or globules and serve as storage
deposits.
2) Not separated by membranes.
3) Examples of stored materials:

Nutrient and Energy reserves (carbon, etc.).

Metabolic deposits: Ex: sulfur deposits as a result of metabolism
(some photosynthetic bacteria).
http://trishul.sci.gu.edu.au/courses/ss12bmi/microbe_structure.html

Metachromatic granules.
4) Most eukaryotes also have inclusions which function as reserves of
materials.
2. Bacteria only! Endospores (‘spores’)
a. Tough, inner, dormant (‘resting’) structures that allow the bacterium to
survive under poor environmental conditions (ex: low in nutrient supplies).
b. They are Gram-positive and usually rod-shaped, but there are exceptions. Mainly
found in the genera Bacillus and Clostridium.
c. Resistant to: heat, acid, radiation, chemicals, disinfectants, dehydration, and lack of
nutrients due to the thick coat, dehydrated nature, and a chemical called dipicolinic
acid.
Example- heat resistance:
Species
C. botulinum: endospore-forming
2-6 hours at 100oC (boiling water)
C. tetani: endospore-forming
1-3 hours at 100oC
E. coli & S. aureus: non-endospore formers
7
Time required to kill a suspension
in
Killed almost immediately at
100oC, 30 minutes at 70o C7
o
F = (1.8 x oC) + 32
37
d. The spore can be differentiated into 4 distinct parts:
-Core: Only contain a few essentials for life- Nucleic acids, ribosomes, low/no levels of enzyme
activity, dipicolonic acid & low water content.
-Cortex: Surrounds the core, mainly peptidoglycan
-Coat: Surrounds the cortex, mainly protein
-Exosporium: The outer most thin layer
e. Sporulation and Germination
TEXT Fig. 4.21 p. 97
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Importance of endospores: Self-reading
-Some spore-formers are pathogens of animals, usually due to the production of powerful toxins. Bacillus anthracis
causes anthrax, a disease of domestic animals (cattle, sheep, etc.) which may be transmitted to humans. Clostridium
botulinum causes botulism, a form of food poisoning. Clostridium tetani is the agent of tetanus.
-Food industries often heat-treat products to reduce microbial spoilage & kill pathogens; spore-formers are a problem
(look for swelling of tins).
-Many are found in soils --> where spores may germinate to produce toxins --> infect wounds.
-Some strains were being developed for biological warfare e.g., B. anthracis (anthrax).
-Some strains produce important biopesticides (biotechnology) e.g., B. thuringiensis produces toxic proteins against
mosquito & blackfly larvae. Commercial variants are available which produce toxins towards slightly different insect
pests; for example Bt corn (the toxin kills corn borer).
-Spores which have ‘germinated’ have been found in 7200 year old temples, mummies, and from the GI tract of a
bee preserved in amber (over one-million years old).
http://trishul.sci.gu.edu.au/courses/ss12bmi/microbe_structure.html
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3. Eukaryotes only: Complexity, Compartmentalization, MEMBRANES
a. Cytoskeleton: Functions to maintain structure, move cellular components
around the cell, and cell movement.
-Composed of protein rods and tubules in a complex network throughout the cell
b. Chloroplasts: Found in photosynthetic eukaryotes (plants and algae)
c. Mitochondria
1. Function in cellular respiration: Glucose is broken down and the energy
is stored in ATP.
2. ‘Powerhouse’ of the cell
d. Endoplasmic reticulum (ER) and Golgi complex
1. Organelles composed of folded and elongated stacked membranes,
respectively.
2. Involved in...
1) Molecule modification
2) Membrane synthesis
3) Molecule storage
4) Molecule transport
e. Lysosomes & Peroxisomes: Contain digestive and detoxifying enzymes,
respectively
f. Vacuoles and Vesicles: Storage, transport, excretion of waste
g. Centrioles
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III. Progression from Prokaryotic Cells to Eukaryotic Cells
Endosymbiotic Theory:
-Mitochondria and Chloroplasts
A. Prokaryotic-like cell engulfed smaller prokaryotic-like cell in a manner similar to
endocytosis; the engulfed cell was not destroyed and remained in a symbiotic relationship
with the larger cell.
B. Supporting evidence:
1. Mitochondria & chloroplast ribosomes are the same size as bacteria and archae;
rRNA sequence shows similarity to some archaea & bacteria.
2.
3.
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Exam Review
Cellular Organization
1. Know the 3 domains of life, the major groups within each domain, and the types of
information that was used to create this classification scheme.
2. Bacterial Cells: Know the general characteristics of Bacteria (size, shapes, arrangements). Be
able to label bacterial structures on a drawing of a bacterial cell.
3. Archaeal Cells: Know the general characteristics concerning Archaeal cells (size, shapes,
habitats).
4. Eukaryal Cells: Know the general characteristics concerning Eukaryotic cells. Know one
hypothesis for the compartmentalization of eukaryotic functions into various organelles.
5. Know the chemical composition of the plasma membrane and its functions. Be able to
describe the term ‘semipermeable’ or ‘selectively permeable’.
6. Understand the five ways that cells transport substances across the plasma membrane (be able
to compare/contrast them). Be able to describe osmosis and isotonic/hypotonic/hypertonic
solutions.
7. What differences are there between eukaryal and prokaryotic transport across the plasma
membrane (i.e., group translocation and cytosis)?
8. Know the functions of some of the various proteins in the plasma membrane.
9. Know examples of functions of the cell wall. Be able to describe the chemical components of
a bacterial cell wall.
10. Know the differences between Gram positive and Gram negative cell walls. Know the
structure and the importance of the outer membrane to Gram negative bacteria.
11. How do the bacterial cell walls affect disease and disease treatment?
12. Be able to give an example of a bacterium without a cell wall.
13. Briefly describe Archaeal cell walls and their differences from bacterial cell walls.
14. Briefly describe Eukaryotic cell walls and their chemical composition.
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15. Be able to define/describe and list the functions of the glycocalyx.
16. Be able to describe the experiments performed on Streptococcus pneumoniae concerning the
capsule and the importance of the experiments concerning knowledge of bacterial gene transfer
and the identity of the genetic material.
17. Be able to define/describe and list the functions of the following bacterial structures outside
of the cell wall: movement appendages, attachment appendages, cell surface molecules.
18. Compare transformation and conjugation.
19. Be able to define/describe the terms cytoplasm, organelle, membrane-bound.
20. Compare Prokaryotic and Eukaryotic DNA (definitions/descriptions): nucleus, nucleoid,
plasmids.
21. Be able to define/describe and list the functions of ribosomes and inclusions. Compare
Bacterial, Archael, and Eukaryotic ribosome structure.
22. Know the importance of bacterial plasmids to bacterial gene transfer, resistance, toxins, and
genetic engineering.
23. Define and know the characteristics of endospores and examples of spore-forming bacteria.
What are endospores resistant to? What is the structure of an endospore, and what is its chemical
composition? Know the importance of endospores to disease, food spoilage, wounds, biological
warfare, and biotechnology. Define the terms sporulation, germination, vegetative cell.
24. Be able to describe structures only found in eukaryotic cells.
25. Describe the Endosymbiotic theory: Organelles involved, theory description, supporting
evidence.
26. Be able to list bacterial structures targeted by antibiotics and other drugs. Why are these
structures targeted? Be able to list antibiotics and chemicals that do not affect bacteria but that
do affect Archaea and Eukaryal cells.
27. Be able to show similarities and differences between the Archaea and other forms of life.
28. In what way are bacteria more like eukaryotes than archaea?
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29. What structures do all cell types have in common? Although these structures are found in all
types of cells, how are they different -in the details?
30. Be able to answer the following type of question:
Which one of the following cellular molecules or structures is primarily involved in the
following life process: Response to the environment(example)
a. Endoplasmic reticulum
c. Ribosomes
b. Cell surface molecules
d. Inclusions
31. Be able to answer the following type of question:
According to available information, state whether the descriptions in questions 10-16 best depict:
a) Bacterial cells only, b) Archaeal cells only, c) Eukaryotic cells only, d) All three types of cells
or e) archaeal and eukaryotic cells only.
(Example)
1. Phospholipids in the plasma membreane may contain branched isoprene chains and an ether
linkage between the isoprenes and L-glycerol
2. Undergo passive diffusion across the plasma membrane
32. Know the definitions of all terms in the handouts.
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