Learning Objectives
Chapter 3-4
At the conclusion of the lectures and the assigned reading the student should be able to:
1. list the characteristics that originally were used to describe prokaryotes
2. discuss the prokaryote controversy
3. draw a phylogenetic tree of life, labeling the 3 domains and where the last universal
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common ancestor would be found
explain the criteria that was used to generate the phylogenetic tree of life
draw and label 6 major morphologies of bacterial cells
distinguish between a spirillum and a spirochete
explain why being a small cell is advantageous to being a large cell (4 reasons)
list the diameter and length of Escherichia coli
draw (in 2-dimensions) and label the building blocks for a bacterial membrane and label
hydrophobic and hydrophilic regions
label the components of the cell membrane shown in Fig. 3.7
explain the function of hopanoids in bacterial membranes and sterols in eukaryotic
membranes
list four types of modifications to the bacterial membrane that are used by some Archaea
to give their membranes the ability to withstand high temperatures
define lipid MONOlayer and distinguish this from a lipid bilayer
distinguish between active and passive transport
explain why cells cannot rely on passive transport as a means of acquiring nutrients
describe the structure of a typical transporter protein
discuss the location of a transporter protein in the cell and how it selectively allows
certain molecules to enter into a cell (describe what happens to the transporter protein
during transport)
describe the structure of the Gram-positive cell wall and indicate the number of layers of
peptidoglycan
label the components of the Gram-positive cell wall in Fig 3.22
list one component of the cell wall present in Gram-positive cell walls that is absent in
Gram-negative cell walls
define peptidoglycan and draw a diagram (no chemical structures are necessary) of
peptidoglycan including the crosslinks
distinguish the peptidoglycan layer of Gram-negative cell walls from that of most
Grampositive cell walls
list 4 components of the cell wall present in Gram-negative cell walls that is absent in
Gram-positive cell walls
label the components of the Gram-negative cell wall shown in Fig. 3.24
write out the name of the component in the Gram-negative outer membrane that causes
high fevers
discuss the purpose of porins
compare and contrast the crosslinking in Gram + and Gram – cell walls
explain how penicillin inhibits bacterial growth
29. explain why alcohol readily decolorizes Gram-negative, but not Gram-positive bacteria
30. write out the name of three bacterial genera that lack peptidoglycan and list the types of
molecules that help stabilize their membranes
31. define pleomorphic
1. Prokaryotic cells: Do not have a nucleus, do not have organelles, have 70s ribosomes
(smaller than eukaryotes, which have about 80s)
2. Prokaryote controversy= Bacteria and Archaea are grouped together as prokaryotes
because they lack a nucleus and generally do not have membrane-bound
organelles. Even though they are grouped together, they are still very distinct.
3. Based on rRNA, the phylopgenetic tree of life. LUCA Last Universal Common Ancestor =
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same as ‘origin’:
The criteria that was used to generate the phylogenetic tree of life was rRNA (ribosomal
RNA) The study of ribosomal RNA found three different domains.
Six major morphologies of bacteria:
Coccus (coxi)
Rod/Bacillus
Spirillum
Spirochete- cause lyme and siphilis
Budding and Appendage (Hypha and stalk)
Filamentous
Spirillum have external flagellum and are gram (-) while spirochetes have internal flagellum
Smaller is better; more Surface to Volume allows more nutrients to be taken up. There is
more membrane to generate a proton motive force. More cells can be supported by limited
amounts of nutrients. Evolutionary advantage b/c there is a larger pool of potential
mutations.
Escherichia Coli – 1.3um X 4 um or 1300 X 4000 nm
Phospholipids are the building blocks for a bacterial membrane. They have a hydrophilic
head (phosphate and glyceol) and hydrophobic tails(FAs)
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Plasma membrane= lipid membrane. Contains membrane
proteins. Integral=Spans entire membrane, creates a channel. Pewripheral=inner surface OR
outer surface. Can be enxymes or receptors. Amino acids w/ in membrane are hydrophobic
Rigid membrane planar molecules ass strength, prevent freezing. Bacterial membrane:
Hapnoids Eukaryotic Membrain: Sterols
Archea membranes are stronger than bacteria and can withstand higher temps b/c:
1. Do not have a bilayer, they have a mono layer (much stronger)
2. Instead of FAs, they have isoprene
3. Have ether linkage (bacteria have ester)
4. Isoprene can be branched (fluidity) and can have rings(rigid), adding even more strength
and structure.
Lipid monolayer= utilized by most archea, has one layer of phospholipid – hydrophilic headhydrophobictail-hydrophilichead Lipid bilayer, most common for eukaryotes and bacteria
has two layers of hydrophilic head-hydrophobic tail, then hydrophobic tail and hydrophilic
head.
Active transport across a cell membrane requires energy to move a substance in/out against
a gradient. Energy either comes from breaking high E ATP bonds or from proton motive
force. Passive transport does not require E and substances move in/out based on diffusion
and gradient.
Cells cannot rely on passive transport as means to obtain nutrients because ???
Typical transporter protein= made up of 12 alpha helices, form a channe;, and require ATP
to open/close their gate by changing shape.
Transporter proteins are located within the cellular membrane and open to the inner and
outer surface of the cell. Transporter proteins are selectively permeable based on their
shape and affinity for their particular substrate. During transport, the protein changes shape
and moves a substance across a concentration gradient.
GRAM (+) call wall=thick, strong, 25 layers of NAM/NAG. Tetra peptides cross link NAMand
NAM and together are called PEPTIDOGLYCANS. Techoic Acid anchors the cell wall to the
cell membrane; acts as rebar.
Screen shot – practice label.
Gram (+) bacteria have techoic acid, Gram (-) do not.
Peptidoglycan= is the combination of NAM and NAM crosslinked by tetrapeptides. It is very
strong and helps protect the cell from environmental stress. DRAW! (slide 25?)
Peptidoglycan in gram (+) cell walls have an extra glycine bridge and are about 25 layers
thick. Gram (-) peptidoglycan cell walls are only about 1-2 layers thick.
Cell wall of gram (-) bacteria has 1. An outer membrane 2. Lipopolysachride (LPS) 3. Porins 4.
Lipoproteins
Screen shot – practice label.
25. LPS Lipopolysacahride is a potent pyrogen, referred to as an ENDOTOXIN. Causes very high,
deadly fevers. (botulism) LPS= takes over most of the phospholipids on the outer membrane
of the bilayer on g(-) bacteria and makes outer shag on gram (-) bacteria.
26. Porins= only in gram (-) bacteria; open protein channels made up of three -barrels.
27. Gram (+) bacteria have an extra glycine bridge (peptide innerbridge) to crosslink NAM and
NAG, whereas gram (-) do not. They have sm. Tetrapeptide bridge of diaminopimelic acid.
28. How does penicillin inhibit bacterial growth? : When a bacterium is dividing in the presence
of penicillin, the cross linking activities og peptidoglycan are inhibited and cell wall
formation is unable to occur. Water rushes in and then…pop!
29. Alcohol readily decolorizes gram(-) stain but not gram (+) stain because it dissolves the lipids
of the outer cell membrane, allowing the vioilet.iodine to leak out of the cell wall/tghinner
peptidoglycan layer.
30. Planktomyces, Chlamydiae, and Mycoplasm lack peptidoglycan. These polymorphic bacteria
have sterols to create cell wall/membranes to halp stabilize them. Penicillin would not
inhibit the growth of these bacteria b/c there are no peptidoglycan structures to inhibit.
31. Pleomorphic bacteria are bacteria that have the ability to assume different shapes based on
their environment. (Could be rod, spirillum, curved rods, etc.)
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