Advanced Biology Key
Chapter 18 &27 Review
Study the viral pathogens list you were given in class. Be able to identify the diseases or conditions
associated with each virus.
1. Compare and contrast the viral structure to that of any living cell. In living cells, genetic information
is stored as a nucleic acid. The cell has the ability to control metabolism (homeostasis), direct
reproduction, create necessary molecules such as some amino acids, nucleic acids, proteins, and
carbohydrates. A cell has a plasma membrane and other organelles, such as the ribosomes, Golgi
bodies, and vacuoles for storage.
A virus has none of these things. It has genetic material in the form of a nuclei acid, but without a
host cell to accidentically copy the nucleic acid, the virus is helpless to reproduce. It requires no
nutrition, expends no energy, and simply lies around, waiting for a host to pick it up, so its particles
can be copied and spread to other organisms. They are interesting only in that this is their sole
purpose, and it cannot even be called its sole purpose in life
2.
What is “transformation” as related to microbiology?
Transformation is when the characteristics of an organism (usually a bacteria) changes as a result of
taking in naked DNA from its surroundings. For example, a bacterial colonizing a host may have a
natural resistance to antibiotics, but succumbs to the host’s immune system. The resistant bacteria
will be taken apart and broken down, and if, while its DNA is exposed, and another bacteria
incorporates it into its own genome, the “DNA thief” may now be resistant to the antibiotic. This can
also be done deliberately in the laboratory.
3.
How is a retrovirus different from other viruses?
Retroviruses have RNA for their genetic material, and retro- enzymes such as reverse transcriptase.
A typical, "minimal" retrovirus consists of:
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an outer envelope which was derived from the plasma membrane of its host
many copies of an envelope protein embedded in the lipid bilayer of its envelope
a capsid; a protein shell containing
two molecules of RNA and
molecules of the enzyme reverse transcriptase
4.
What is a prion?
Prion' is a term used to describe the mysterious infectious agent responsible for several
neurodegenerative diseases found in mammals, including Creutzfeldt-Jakob disease (CJD) in humans;
it refers to the hypothesis that the infectious agent causing those diseases consists only of protein,
with no nucleic acid genome. (All previously known pathogens, such as bacteria and viruses, contain
nucleic acids, which enable them to reproduce.) The prion hypothesis explained why the mysterious
infectious agent is resistant to ultraviolet radiation, which breaks down nucleic acids, but is
susceptible to substances that disrupt proteins
5.
Differentiate between prokaryotic and eukaryotic cells.
Eukaryotic cells have specialized, membrane-bound organelles, including the plasma membrane. They
have a nucleus which isolates the genetic material from the rest of the cell, and highly organized
processes by which to produce whatever substances are required of it. There may or may not be a cell
wall in addition to the membrane, which is used as a major feature of classification, as is the number
of chromosomes that make up the genome.
The prokaryotic is smaller and not as organized. There is no membrane-bound nucleus to isolate the
genetic material, although a plasma membrane keeps the cell intact; wherever in the cytoplasm the
genetic material happens to be located is referred to as the plasmid. The genetic material tends to be
a single, circular chromosome referred to as a “plasmid.” Most have a cell wall, and the composition
of this is the basis for their classification. The kingdom Eubacteria has a cell wall that contains
peptidoglycan, while the kingdom Archaebacteria does have peptidoglycan in their cell walls. The
ribosomes are different from those found in eukaryotes, which can be useful in prescribing antibiotics
that block protein synthesis, and yet won’t interfere with host synthesis.
6.
What is a chemotroph?
They oxidize inorganic compounds to obtain energy to drive the synthesis of their organic compounds.
Instead of getting the chemical bond energy from organic molecules (instead of from carbs, proteins,
fats, etc).
7.
Bacteria can be good and bad for human existence. Give an example of each of these situations,
if bacteria were to be wiped off the face of the planet (as some crazy doctors have suggested we do!)
Bacteria can be bad for humans, in that they can spoil food and cause illness. Some people think we
would be better off without any of them on the planet. Without them, however, while we would
eliminate many illness, and would not lost crops to them, neither would dead organic matter be
returned to the nitrogen, carbon and oxygen cycle. Nutrients would become depleted, and plant life
would not thrive. As photosynthetic organisms became extinct, organisms that depend on them for
survival would begin to starve, and so on throughout the pyramid of energy…right through us!
8.
What were the first bacteria on Earth believed to be like?
The first living organisms were believe to be anaerobic archaebacterial (aka cyanobacteria). They
were likely chemoautotrophs, as oxygen would have been a by-product if they had been
photosynthetic, and the fossil record indicates that they had been around for quite some time before
oxygen appeared in the strata.
9.
How does penicillin work?
Penicillin works by inhibiting cell wall synthesis, by interfering with peptidoglycan. Without
peptidoglycan, the cell wall cannot properly be completed, leaving the bacteria unprotected.
10.
What is the difference between gram + and gram – bacteria?
Gram positive or negative bacteria are so named based on their response to the gram staining
technique of slide preparation. Gram staining was developed by Hans Christian Gram, and uses a
counterstaining technique. First, the slide is stained with crystal violet; those organisms with
peptidoglycan in their cell walls will retain the stain and turn purple (Gram +). Gram – bacteria will
not retain the crystal violet, but will turn red or pink if a counterstain is added that does not adhere to
the gram + bacteria (this is called differential staining)
11.
Differentiate between an endotoxin and exotoxin.
Endotoxins are an integral part of the cell wall of gram – bacteria; an exotoxin is released from inside
a gram - OR gram + bacteria
12.
Why does the kingdom Monera no longer exist?
As technology advanced, scientists began to discover too many differences between various species of
“bacteria” . The Domain Archaea contains the “extremophiles”…the methanogens, halophiles and
thermoacidiphiles
The Domain Bacteria contains the pathogenic bacteria, cyanobacteria, and all groups (spirochetes,
chlamydias, etc)
13.
What is primarily responsible for the existence of antibiotic-resistant bacterial strains?
Overprescribing antibiotics, taking anti’s for viral infections, and not finishing medication once it has
been started (or starting to take unfinished medication from a previous illness without checking with
your doctor!)
The main groups of bacteria are as follows, and their major characteristics recognized.
Actinomycetes
Chlamydias
Actinomycetes are a specific group as bacteria.
Morphologically they resemble fungi because of
their elongated cells that branch into filaments
or hyphae. During the process of composting
mainlythermophilic (adapted to high
temperatures) and thermotolerant
actinomycetes are responsible for decomposition
of the organic matter at elevated
temperatures. In the initial phase of composting
the intensive increase of microbial activity leads
to a self-heating of the organic material. High
temperatures in composting help to kill viruses,
pathogenic bacteria,e.g. coliforms, and weed
seeds present. Actinomycetes live predominantly
aerobically, i.e. they need oxygen for their
metabolism. The compost material should
therefore be well aerated. Generally,
actinomycetes grow on fresh substrates more
slowly than other bacteria and fungi. During the
composting process the actinomycetes
degrade natural substances such as chitin or
cellulose. Natural habitats of thermophilic
actinomycetes are silos, corn mills, air
conditioning systems and closed stables.
Chlamydia is a genus of bacteria that are obligate
intracellular parasites. Chlamydia infections are
the most common bacterial sexually transmitted
diseases in humans and are the leading cause of
infectious blindness worldwide.
Enteric bacteria
Pseudomonads
From the viewpoint of a bacteria looking for a
place to colonize a human or animal, the
digestive tract represents a very attractive
environment. It provides shelter from the outside
world, yet is easily accessible, provides nutrients
in great number and variety, and is less likely to
trigger an immune response. It is therefore not
surprising that many bacteria live in the human
guts, most of them harmlessly, with some even
playing useful functions for their host. However,
some species of bacteria can be highly
pathogenic when they enter and colonize the
human digestive tract. Such enteric bacterial
pathogens typically cause gastroenteritis, but can
also have life threatening consequences. Below is
a non-exclusive list of enteric bacterial pathogens
on which we are currently working.
Spirochetes
Any bacterium of the family Pseudomonadaceae,
a large and varied group comprising four major
genera and several hundred species. The
individual cells are rod-shaped, often curved,
averaging about 1 μm (micrometre; 1 μm = 10-6
metre) in diameter and several micrometres in
length. The cells of most species are separate and
not joined in filaments; many are motile,
propelled by one or more flagella (whiplike
appendages), usually located terminally. The cells
of some aquatic species are attached to surfaces
by long strands or stalks (holdfasts).
Spirochetes are long and slender bacteria,
usually only a fraction of a micron in
diameter but 5 to 250 microns long. They are
tightly coiled, and so look like miniature
springs or telephone cords. Members of this
group are also unusual among bacteria for the
arrangement of axial filaments, which are
otherwise similar to bacterial flagella. These
filaments run along the outside of the
protoplasm, but inside an outer sheath; they
enable the bacterium to move by rotating in
place. You can see these filaments in the
picture of Treponema above, which is the
only genus to lack the outer sheath.
The ecological roles of spirochetes are varied;
the group includes both aerobic and anaerobic
species, and both free-living and parasitic
forms. One species, in the genus
Cristispira, has only been found growing
on the crystalline style in the digestive tract of
certain bivalve mollusks. Some species of
Treponema live in the rumen of a cow's
stomach, where they break down cellulose
and other difficult to digest plant
polysaccharides for their host.
Perhaps the best-known spirochetes are those
which cause disease. These include syphilis
and Lyme disease, as well as other less wellknown ones.
Discuss the “lifestyles” of each of the following:
Photoautotrophs
Uses light energy to convert energy from inorganic
sources to make their own food
photoheterotrophs
Not much different than an photoautotroph, except these cannot use
Carbon dioxide as their sole source of
Carbon—in other words, they need
carbon from some other source than
air
Chemoautotrophs
Organisms that use inorganic substances
To fuel metabolic processes, such as sulfur
Or phosphorous, instead of sunlight
saprobic chemoheterotrophs
organisms such as fungi that break
down organic matter to access the
chemicals needed to fuel metabolic
processes
Parasitic chemoheterotrophs
Organisms that require a host from which to obtain the chemicals necessary to fuel metabolic
processes