Exam #1 Review
General Study Suggestions: Begin by reviewing your lecture notes. If there is
anything that you don’t understand, make an appointment with me or read
through that section again in your book. Review the questions that we
discussed during lecture. Finally, go through this review and be certain that
you understand the referenced homework questions. **The exam questions
will be very similar to the homework questions! Review any suggested
excercises at the end of homework assignments.
Format and composition: There will be 25 multiple choice questions worth 2
points a piece. These are followed by 8 short answer, matching or fill-in-theblank questions worth 10 points a piece. All students must answer #26
regarding Gram-positive and Gram-negative cell wall structure. Then, choose
to answer any four of the next seven questions. Circle the questions that you
would like to answer. Topics covered by these free response questions:
- Macromolecules
- The cell membrane
- Environmental influences, carbon and energy sources (lab 5 and 6)
- Compare/contrast procaryotic and eucaryotic cells
- Growth curve
Microbiology is the study of organisms that are too small to be seen with the
unaided eye. Although humans utilized microorganisms to make bread and beer as
early as 2100 B.C., it was not until 1673 that Antoni van Leeuwenhoek, using a
hand-crafted microscope, first viewed these tiny organisms which he called
“animalcules”.
I. The origin of microorganisms (lecture #1)
A. Scientists struggled for over a hundred years to reject the idea of
spontaneous generation and support the idea that all forms of life arise from
other living things of the same kind (biogenesis). Be familiar with all the
scientists involved in this debate and understand their contributions.
Practice: The idea of spontaneous generation postulated that
a. organisms could evolve into the next generation of organisms.
b. organisms could spontaneously combust.
c. organisms could spontaneously arise from other living
organisms.
d. living organisms could arise from nonliving material.
Which scientist(s) was/were most involved in investigating the
idea of spontaneous generation.
a. Redi
b. van Leeuwenhoek
c. Pasteur
d. Escherich
e. both a and c
**review homework #1, question 1, 2 and 3**
B. Review and understand Koch’s Postulates!
II. Microbiology: Implications and Applications (lecture #1)
A. Fixing nitrogen, replenishing oxygen and degradation (decomposition) are
essential (vital) activities of microorganisms.
B. Microorganisms also have a very big economic impact.
Practice: Microorganisms are involved in
a. Food production
b. Food preservation
c. Bioremediation
d. Production of antibiotics
e. All of the above
*List several impacts and economic applications of microorganisms.
C. Genetic Engineering = Introduction of genes from one organism into
another to give it new features or abilities.
Practice: List two ways in which microorganisms can be genetically
engineered to help in treatment of disease.
**review homework #1, question 4 and 5**
D. Medical Microbiology = The study of disease-causing microorganisms
(called pathogens).
1. In 1906, the three leading causes of death were infectious diseases
(cdc.gov) Now, many infectious diseases have been eradicated.
2. Despite the eradication of many infectious diseases we must fight
newly emerging diseases, the resurgence of old diseases and
microorganisms that are becoming resistant to current treatment
techniques. We are also just beginning to understand that many
conditions, such as peptic ulcers, are caused by bacteria and cancers,
such as cervical cancer, are caused by viruses.
Practice: Which one of the following is a reason for the
resurgence of old diseases?
a. A decline in the vaccination of children
b. An increase in international travel
c. both a and b
d. none of the above
E. **Note: Despite their notoriety, most microorganisms are not
pathogenic. In fact, those covering our body play a protective role by
competing with pathogenic microbes.**
F. Practice: Bacteria are good model organisms for study because
a. they are large in size.
b. they share many biochemical/physiological properties with
more complicated organisms.
c. they can assemble into multicellular organisms.
d. have complicated growth requirements.
III. Macromolecules (proteins, carbohydrates, nucleic acids and lipids)
*Be sure to review and understand the game questions for this section.
A. Proteins
Practice: Which one of the following is NOT a protein function?
a. Transporting molecules from one location to another.
b. Coordinating motion.
c. Providing the genetic code for all of a cell’s properties.
d. Providing mechanical support in eucaryotic cells.
Proteins are composed of amino acids. Be familiar with the general
structure of an amino acid (central carbon, amino group, carboxyl
group, hydrogen atom and an R-group.)
Practice: How many different amino acids are there to choose
from when assembling a protein?
a. 5
b. 10
c. 20
d. 25
*Be able to recognize the names and abbreviations (both 3- and
1-letter) of these amino acids. I will provide the table with amino
acid structures but I will not provide 1-letter abbreviations or
information regarding the nature of the R group. Thus, be
familiar with how amino acids are categorized according to the
nature of their R group.
**review homework #2, questions 2 through 6**
The amino acids are linked together by peptide bonds to form
polypeptide chains. Each amino acid in a polypeptide chain is called
a residue.
Practice: What molecule is lost in the formation of a peptide
bond?
Proteins have three or four levels of structure. The genetically
determined sequence of their amino acids (e.g. Ile-Gly-Met-Phe...) is
their primary structure. The regularly repeating structures (e.g.
alpha-helix, beta-sheet and beta-turn) into which the polypeptide
chain folds is called the secondary structure. The regularly repeating
structures fold upon themselves to give a protein an overall 3-d
structure called the tertiary structure. If a protein has more than one
polypeptide chain, the way in which these chains arrange themselves
with respect to one another is called the quaternary structure.
Practice: The helices and sheets of amino acids form a protein’s
a. primary structure
b. secondary structure
c. tertiary structure
d. quaternary structure
What does it mean if a molecule/structure is amphipathic?
B. Carbohydrates
Carbohydrates function as a source of carbon and energy (both
immediate and reserve). They are components of cell walls
(glycoproteins and glycolipids) and some external cell structures
(capsule/slime layer).
1. Monosaccharides = simple sugars (glucose, fructose and galactose 6 carbon monosaccharides, ribose - 5 carbon monosaccharide)
*Be familiar with the structure of glucose and the reaction by which it
forms a ring structure (a hemiacetal). Note the introduction of a special
carbon called the anomeric carbon. Also be familiar with how the
carbon atoms are numbered in glucose.
Practice: Are monosaccharides likely water soluble?
2. Disaccharide (two sugars) - maltose, lactose, sucrose.
Monosaccharide subunits are joined by a glycosidic linkage.
Practice: What molecule is lost in the formation of a glycosidic
linkage?
3. Oligosaccharides (short chains (2 to 10) of sugars)
4. Polysaccharides (long chains of sugars that often have branches
(e.g. glycogen)) *Glycosidic linkages in straight chain polysaccharides
are 1,4 (between the 1st and the 4th carbon). Branched
polysaccharides also have 1,6 glycosidic linkages.
Practice: Which is/are TRUE of carbohydrates?
a. They may serve as a source of food.
b. The contain carbon, hydrogen and oxygen in a 1:2:1
ratio.
c. They may be bonded to proteins to form glycoproteins.
d. They are a component of some bacterial capsules.
e. all of the above.
Practice: What is the difference between cellulose and glycogen?
C. Nucleic Acids
1. DNA and RNA - composed of nucleotides which are composed of
a 5 carbon sugar, a nitrogenous base and a phosphate group. Practice
numbering the carbon atoms on the 5-carbon sugar. Why are these
numbers so important to understanding the structure of not only
nucleotides but the nucleic acids which they form?
Practice: DNA contains
a. sugars
b. 3’-5’ phosphodiester bonds
c. triacylglycerols
d. peptide bonds
e. c and d
2. Bases
Purines - adenine and guanine (double-ring structure)
Pyrimidines - cytosine, thymine and uracil (single ring)
Practice: Which of the following is found in RNA but not
in DNA?
a. adenine
b. cytosine
c. thymine
d. uracil
3. In nucleic acids, the nucleotide subunits are bound covalently (the 5’
phosphate binds to the 3’ hydroxyl). This linkage is termed a 3’,5’phosphodiester linkage. What molecule is lost in the formation
of this phosphodiester linkage?
4. Covalent bonding of many nucleotides forms a single strand of
nucleotides which, in DNA, then binds to a complementary strand via
hydrogen bonds. The complementary strand runs in the opposite
direction (antiparallel) to the first strand. Together they form a doublestranded helix.
a. A single strand of nucleotides joined by 3’,5’-phosphodiester
bonds always has polarity/directionality. It always has a 3’ end
and a 5’ end.
b. When the H-bonds that hold the two strands of DNA together
are broken, this is called denaturation or melting.
c. **If given a DNA sequence, be sure that you understand how
to determine its correct complimentary sequence!!
**review homework #2, questions 7 and 8**
D. Lipids
Practice: Which is/are TRUE about lipids?
a. They are a major structural component of all cell membranes.
b. They can serve as energy stores.
c. They function in cell signaling and recognition.
d. All of the above.
1. Triacylglycerols, steroids, sterols, waxes and phospholipids
*Know the basic structure of a triacylglycerol
**Be able to recognize the structure of a phospholipid.
**review homework #2, question 9 and 10**
2. ALL CELL MEMBRANES ARE SEMIPERMEABLE
PHOSPHOLIPID BILAYERS. Know how phospholipids come
together to form a PL bilayer. Be able to draw and label the
hydrophilic and hydrophobic portions of a phospholipid bilayer.
Practice: Why are fats packed with power?
**review homework #2, question 1**
IV. Classification and Nomenclature
A. Domains
Practice: Which of the following is/are not domains into which all
living organisms can by classified?
a. Helminths
b. Bacteria
c. Archaea
d. Eucarya
e. Humanoidaea
f. a and e
g. d and e
1. Members of the domain Bacteria and Archaea are procaryotes, they
are generally 0.3 to 2 micrometers in size; they are single-celled and
have no membrane-bound nucleus or organelles. Their genetic
material is simply stored in a region called the nucleoid. Procaryotes
are surrounded by a cell membrane and generally a rigid cell wall.
They multiply by binary fission and some move using flagella. Bacteria
differ from archaea in that their cell wall is composed of peptidoglycan.
Archaea have a different overall cell wall composition that LACKS
PEPTIDOGLYCAN. While bacteria live in all environments, archaea
are frequently found in extreme environments.
2. Members of the domain Eucarya can be either single-celled or
multicellular. They always have a membrane-bound nucleus and
organelles. Some eucaryotic cells have a cell wall but it is NEVER
MADE OF PEPTIDOGLYCAN. On average, eucaryotic cells are
larger than procaryotic cells (5 to 50 micrometers). Are there
exceptions?
B. Nomenclature.
Practice: The scientific name of an organism includes its
a. family and genus.
b. first name and last name.
c. genus and species.
d. domain.
e. c and d
**The genus is written first and capitalized followed by the species name
which is lowercase. Both are either italicized or underlined!! If there is a
strain designation, it follows the species name.
**review homework #3, question 10**
V. Procaryotic cell structure and function
A. Cell shapes and arrangements
Be able to recognize and or draw all of the cell shapes.
Practice: Which one of the following is not a bacterial cell shape?
a. spirillum
b. coccobacillus
c. coccus
d. oblongccus
e. square
*Bacteria that vary their shape are called pleomorphic. Starlike bacterial
shapes can result from bacterial surface extensions called prosthecae.
Know and be able to recognize all of the cell arrangements.
**review homework #2, question 11 and 12**
B. Procaryotic cell components
**Knowledge of the structure of a bacterial cell is important to
understanding natural host defense systems, synthesis of antimicrobial
substances and identification and characterization of bacteria.
1. The nucleoid- gel-like mass containing some RNA and protein but
mostly a single, circular, supercoiled piece of dsDNA.
The bacterial chromosome is a single, circular piece of doublestranded (ds) DNA. If this piece of DNA were cut to form a piece
of linear DNA, the linear piece of DNA would be 1,000 times as
long as the cell itself. However, when packaged into the bacterial
cell, this DNA takes up only 10% of the total cell volume. How
can this be accomplished?
a. The DNA is tightly packaged within a membrane bound
nucleus.
b. The DNA is twisted into a supercoiled form.
c. The DNA is converted into small circular pieces of dsDNA
called plasmids.
d. none of the above
2. Plasmids - Small, generally circular pieces of DNA that can
replicate on their own (often give a bacterium a new trait such as
resistance to an antibiotic). They are not generally a part of the
chromosome = extrachromosomal. Many plasmids can be transferred
from 1 cell to another (conjugative).
**review homework #2, question 19**
3. Ribosomes - Protein factories (70 S)
Practice: What are the two subunits of the procaryotic
ribosome? Of what two macromolecules is a ribosome composed?
**review homework #2, question 17**
4. Inclusion bodies
a. Generally used for storage (backup food supply) and include
granules that store phosphate, glycogen, and amino acids. Some
storage granules are bound by a single-layered membrane.
Some bacteria have sulfur storage granules
What are volutin and cyanophycin granules? What do
magnetosomes allow a bacterium to do?
b. Gas vacuoles = aggregates of large numbers of gas vesicles.
Practice: Which one of the following microorganisms is
most likely to have gas vacuoles?
a. Bacillus subtilis (a soil bacterium)
b. Escherichia coli (a gut bacterium)
c. Anabaena flos-quae (an aquatic, photosynthetic
cyanobacterium)
**review homework #2, questions 15 and 16**
5. Cytoplasmic membrane
Practice: Which is not true of the cytoplasmic membrane?
a. it defines the boundaries of the cell.
b. It is a semipermeable barrier.
c. It consists mainly of a fixed, static phospholipid
bilayer.
d. It uses proteins as selective gates and sensors.
e. all of the above are true.
**review homework #2, questions 13**
*IMPORTANT: There will be a question regarding the
cytoplasmic membrane and the Fluid Mosaic Model.
a. Transport - small hydrophobic molecules and small gas
molecules can diffuse across the membrane (simple diffusion) but
large, hydrophilic molecules and charged molecules require
transporters.
b. Energy transfer across the plasma membrane.
Procaryotic cells that are capable of some type of
respiration or photosynthesis have the components of the
electron transport chain across their membrane. These
components are electron carriers. They transfer electrons
from one to the other and this leads to the ejection of
protons. As protons are ejected out of the cell, a proton
gradient forms across the membrane. This proton gradient
is called the proton motive force (PMF). This PMF is like
reserve energy (like a battery). When the protons are
allowed to flow back through a protein into the cell, the
reserve energy can be harnessed to make ATP!! In
procaryotes, this battery-like energy can also be used to
power other cellular processes (e.g. flagella rotation and
certain transport systems).
**review homework #2, question 14**
5. The cell wall
a. Contains peptidoglycan in bacteria. Peptidoglycan contains
glycan chains of alternating NAM and NAG. A tetrapeptide
chain is attached to each NAM (composed largely of unusual
amino acids). These tatrapeptide chains are then joined (directly
in Gram-negative bacteria and via a glycine peptide interbridge
in Gram-positive bacteria).
b. The peptidoglycan layer in bacteria can be thought of like a
wire mesh. It is very rigid, yet it is porous.
c. Because eucaryotic cells do not contain peptidoglycan, it
makes a good target for antimicrobial substances (penicillin and
lysozyme).
**review homework #3, questions 1 through 3**
Practice: Which is/are true about the cell wall of bacteria?
a. It determines the shape of the bacteria.
b. It prevents the bacteria from bursting in
hypotonic solutions.
c. It contains peptidoglycan.
d. It may be targeted by antimicrobials.
e. all are true.
Practice: Draw the cell wall of both a Gram-positive and a Gramnegative bacteria. Be certain to note which molecules are
responsible for the cells’ overall negative charges as well as being
recognized by our body’s immune system. **There will be an
important question about this!**
Practice: What is the difference between teichoic and
lipoteichoic acid?
Practice: The cell wall of a Gram-negative bacterium
a. has a thick peptidoglycan layer.
b. has a thin peptidoglycan layer.
c. is characterized by an outer membrane
containing LPS.
d. has gel-like fluid between the inner and outer
membranes called the periplasm.
e. b, c and d
f. none of the above.
*Note- An LPS molecule has three regions. The upper
region, the O-specific polysaccharide, is recognized by
host defense systems. It also changes in some bacteria (e.g.
Salmonella) allowing them to evade the immune system.
The central region contributes to the negative charge of
the cell wall. The lowest lipid A region is the toxic region
that allows LPS to act as an endotoxin (elicits fever and
shock).
**review homework #3, question 5**
Also in Gram-negative cell walls, lipoproteins join the
outer membrane to the peptidoglycan layer. Porin
proteins span the outer membrane to form pores through
which small molecules can pass.
d. The cell wall protects bacteria from destruction by osmotic
pressure.
Practice: The simple diffusion of water is called
a. permeosis
b. osmosis
c. aquaosis
d. turgorperosis
If the concentration of solutes inside a cell is less than that
outside the cell = a hypertonic enviroment. Water flows out
of the cell, the cytoplasmic membrane shrinks and pulls away
from the cell wall (plasmolysis).
Practice: Describe what happens when a cell is placed in a
hypotonic environment.
**review homework #3, question 6**
Note the difference between a spheroplast and a protoplast
**review homework #3, question 4**
6. Glycocalyx - an outer layer, generally made of polysaccharide that
surrounds some bacteria. If this layer is highly organized then it is
called a capsule. If the layer is irregular, it is called a slime layer.
7. S-layer - an outer protective layer, made of distinctly structured
protein or glycoprotein.
Practice: Both capsules and S-layers
a. are glycocalyx.
b. are structures external to a bacterial cell wall.
c. protect against phagocytosis.
d. b and c
**review homework #3, question 7**
8. Flagella - function in motility - use PMF to spin like propellers, a
basal body anchors the flagella within the cell wall / cytoplasmic
membrane, a curved hook connects the basal body to the filament. The
filament extends into the environment. The filament is made of the
protein flagellin. Procaryotic flagella spin like propellers.
a. Distribution - monotrichous (polar), amphitrichous,
lophotrichous and Peritrichous flagella.
**review homework #3, question 8 and 9**
b. Counterclockwise movement of flagella = a run.
c. Clockwise movement = a tumble.
Practice: A motile bacterium is placed into a medium
with a chemical attractant at the opposite end.
Describe the process by which the bacterium moves
towards the attractant. Include a picture.
**review homework #3, question 9**
7. Pili (fimbriae) - shorter and thinner than flagella, with a
hollow core. Allow for adherence to specific surfaces,
movement of populations of cells on solid media and
conjugation. The Prescott book distinguishes between fimbriae
and pili. It terms anything not involved in conjugation as
fimbriae.
VI. Eucaryotic cells (Lecture 4)
A. There is a great deal of variance among eucaryotic cells - from protozoan
cells to yeast cells to human cells. Algae, fungi and protozoa (protists) are
eucaryotic representatives of the microbial world.
B. Structure of the eucaryotic cell.
1. Cytoskeleton - provides structure and shape of cell, three
components:
a. Microtubules - largest element of cytoskeleton, composed of
hollow cylinders of tubulin, form mitotic spindles, cilia and
flagella and cell “highways”.
b. Microfilaments - smallest element of cytoskeleton, composed
of actin, involved in motion (pseudopod formation).
c. Intermediate filaments - most stable structural element, play
a tension bearing role.
Practice: Microfilaments
a. are a component of the cytoskeleton.
b. are long, twisted polymers of a protein called actin.
c. form eucaryotic flagella.
d. are the most stable structural elements
e. a and b
f. c and d
**review homework #3, question 11**
2. Nucleus
a. Bound by both an inner and outer membrane. The space
between the two membranes is called the perinuclear space. The
membrane has large nuclear pores through which proteins can
pass (Why is this important?)
b. Linear pieces of DNA are packaged by wrapping one and
three quarters times around a histone octamer to form a core
particle. Neighboring core particles are linked by DNA. This
linker DNA associates with another histone called H1. Together,
the core particle, H1 and some of the linker DNA form a
nucleosome. How does the charge of DNA / histones affect
this packaging process? Chromatin is the complex of DNA
and proteins that together form the chromosomes. How does
euchromatic differ from heterochromatin?
c. A region within the nucleus, called the nucleolus, is the site of
ribosome assembly.
Practice: The nucleus
a. is a double membrane sac containing DNA as is
found in eucaryotes.
b. Is a single phospholipid membrane sac containing
procaryotic DNA.
c. is a smaller structure contained within the
eucaryotic nucleolus.
d. cannot transport molecules to the cytoplasm due
to the double membrane barrier.
**review homework #3, question 12 and 13**
3. The Endoplasmic Reticulum
a. Rough ER - Site of synthesis of proteins targeted for the
membrane, for secretion or for specific organelles. (Studded
with 80S ribosomes (*60S and 40S subunits))
What is the medical importance of the fact that
procaryotes have 70S ribosomes and eucaryotes 80S?
b. Smooth ER - Site of lipid and steroid hormone synthesis,
location of calcium ion storage. (No ribosomes cover the surface,
thus smooth).
*vesicles bud off of both of these organelles carrying the
recently synthesized compounds. These vesicles are targeted for
the Golgi.
Practice: Which one of the following would be the site of
synthesis and folding, but not final modification of a
protein needed outside the cell?
a. The Golgi apparatus
b. The mitochondria
c. The smooth ER
d. The rough ER
**review homework #3, question 16**
4. The Golgi apparatus - molecules from ER are further modified
(e.g. addition of carbohydrate or phosphate groups). Vesicles bud off
of Golgi and carry modified molecules to their destination. The Golgi
has a cis and a trans face that differ substantially from one another.
Practice: The Golgi Apparatus
a. is the site of modification of molecules from the ER.
b. has an acidic pH and is filled with hydrolytic, digestive
enzymes.
c. is found exclusively in plants and algae.
d. is considered the “powerhouse” of the eucaryotic cell.
e. both b and c
**review homework #3, question 14**
5. Lysosomes - acidic interior, filled with digestive enzymes to
hydrolyze macromolecules.
6. Mitochondria - powerhouses of the cell!
Practice - draw this organelle and label all parts. Where are the
components of the electron transport chain?
Practice - Which one of the following organelles contains its own
DNA genome and 70S ribosomes?
a. lysosomes
b. the endoplasmic reticulum
c. mitochondria
Which statement/s regarding mitochondria is/are FALSE?
a. Mitochondria are capable of converting CO2 into
organic compounds.
b. Mitochondria reproduce by binary fission.
c. Nearly all eucaryotic cells contain mitochondria.
d. Mitochondria contain their own DNA genome
**review homework #3, question 15**
7. Chloroplasts
Practice - draw this organelle and label all parts. Where are the
components of the electron transport chain?
Practice - Both chloroplasts and mitochondria synthesize ATP
using the electron transport chain, in what ways are these two
organelles different (in terms of the origin of the electrons that
fuel the electron transport chain)?
Practice: Which of the following explains the origin of
mitochondria and chloroplasts?
a. The Chemiosmotic Hypothesis
b. The Endosymbiont Theory
c. The Fluid Mosaic Model
d. Spontaneous generation
8. Plasma membrane
In many ways the plasma membrane of a eucaryotic cell is similar to
that of a prokaryotic cell (e.g Both are composed of a semipermeable
phospholipid bilayer (fluid-mosaic). Both contain transport proteins.
Practice - List the ways in which the plasma membrane of a
eucaryotic cell is different than that of a procaryotic cell.
a. Endocytosis
1. phagocytosis - Used to engulf large particles - cell
sends out long extensions called pseudopods. These
surround debris and form a phagosome which fuses with
a lysosome to form a phagolysosome (often termed cell
eating).
2. pinocytosis
a.) Fluid-phase
b.) Receptor mediated
c.) caveolae-forming
**review homework #3, question 18 and 19**
Practice: Which statement/s is/are TRUE?
a. Phagocytosis and pinocytosis are both types of
endocytosis.
b. Receptor mediated endocytosis is a type of
pinocytosis.
c. During phagocytosis, a phagolysosome is formed.
d. During caveolae-forming endocytosis, no
lysosome fusion occurs, thus many pathogens enter
cells this way.
e. all of the above
b. Exocytosis
9. Flagella and cilia
Practice: How are flagella different in procaryotes and
eucaryotes?
All of the following are true of eucaryotic flagella EXCEPT
a. Eucaryotic flagella are composed of 9 pairs of microtubule
doublets.
b. Eucaryotic flagella sometimes have lateral hairs called flimmer
filaments.
c. Eucaryotic flagella are composed of a basal body, a hook and
a filament.
d. Eucaryotic flagella function in motility by wave-like motion
(base to the tip or tip to the base).
Cilia
a. are also called pili.
b. are also called fimbriae.
c. are shorter than flagella.
d. move in two phases.
e. a and b
f. c and d
*IMPORTANT: It is a good test of understanding to compare
features of procaryotic and eucaryotic cells.
**review homework #3, question 20**
Practice: Which statement does NOT correctly summarize a
difference between procaryotic and eucaryotic cells?
a. The electron transport chain of aerobically respiriing
procaryotic and eucaryotic cells is found across the cytoplasmic
membrane.
b. Whereas procaryotes generally have a single chromosome,
eucaryotes usually have more than 1 chromosome for the
storage of genetic material.
c. Eucaryotic cells have a membrane-bound nucleus whereas
procaryotic cells have only a gel-like mass called the nucleoid.
d. Whereas procaryotic cells secrete enzymes to digest
macromolecules, eucaryotes generally bring in large molecules
via endocytosis.
Which of the following is useful in distinguishing between
procaryotic and eucaryotic cells?
a. the use of DNA for the storage of genetic information
b. the presence of ribosomes for the synthesis of proteins
c. the presence of membrane-delimited organelles within the
cytoplasm
d. all of the above
For the following 5 cell components, please determine whether
they are generally present:
a. only in procaryotes
b. only in eucaryotes
c. only in bacteria
d. in both procaryotes and eucaryotes
____16) Endoplasmic reticulum
____17) A single circular chromosome
____18) N-acetylmuramic acid (NAM)
____19) diaminopimelic acid
____20) flagella
V. Microbial nutrition and growth (Lectures 5 and 6)
A. Uptake of nutrients (transport)
Practice: Transporters using this type of transport require no energy
but become saturated at high substrate concentrations.
a. active transport
b. simple diffusion
c. facilitated diffusion
d. none of the above
B. Protein secretion - be familiar with the Sec-dependent pathway!
C. Bacterial cells reproduce via binary fission: a parent cell replicates its DNA,
elongates, a septum forms and eventually cleaves off two distinct daughter
cells. With this type of growth, the increase in cell numbers is exponential.
Practice: If a single cell lands on an agar plate and begins to divide,
how many cells will there be after the tenth cycle of division?
D. A researcher may also be interested in calculating the number of cells in a
population of cells that originated from more than a single cell.
The following equation can be used for this purpose:
Nt = No X 2n
where Nt = the # of cells in a population after a given time
No = The original number of cells in a population
n = the number of cycles of division (depends on doubling time)
Practice: 100 cells of Vibrio fischeri are used to inoculate a large bottle
of sterile media. If this bacteria has a doubling time of 2.5 h, how
many cells are present in the culture after an overnight incubation (16
h)?
C. In the lab, organisms are generally grown in closed (batch) systems (Why
are these systems called closed systems??). The Growth Curve describes
growth in closed systems. Please spend some time reviewing this growth
curve in your notes. There will be an exam question regarding this!
Practice: During which growth phase do cells begin to synthesize
secondary metabolites in response to increasing cell population
and buildup of waste products?
a. Lag phase
b. Initial log phase
c. Late log phase
d. Stationary phase
e. Death phase
Practice: (T or F) All of the cells in a culture die during the
death phase.
Practice: Which statement/s regarding the stationary phase of
growth is / are FALSE?
a. It is during the stationary phase that culture growth stops.
b. During the stationary phase, cells no longer synthesize any
metabolites.
c. The total number of viable cells stays constant during the stationary
phase.
d. Secondary metabolites are produced during the stationary phase.
e. it is during the stationary phase that cells are most sensitive to
antibiotics.
f. b and e
D. Why is growth in nature different from growth in a closed (batch)
system? A question of this nature would also make a good free response
question.
Nutritional Factors that Influence Microbial Growth (What do microbes need in
order to grow?)
*Revisit your crossword puzzle!
A. To remember the major elements, don’t forget the acronym: CHNOPS.
(Practice: What does each one of the letters in this acronym stand for?)
Some metal ions (calcium, potassium, magnesium and iron) are also
considered major elements.
B. Other metal ions (manganese, molybdenum, zinc, nickel, cobalt and
copper) are required only in very small amounts, they are called trace
elements.
C. Some organisms cannot synthesize all of their growth factors (amino
acids, nucleotides and vitamins) so they must take these in.
D. It is very important to be able to classify organisms based on their
ENERGY and CARBON sources. *Be very familiar with the similarities and
differences between photoautotrophs, photoheterotrophs ,
chemoautotrophs (chemolithoautotrophs) and chemoheterotrophs
(chemoorganoheterotrophs).
Practice: Which of the following use/s organic carbon as a carbon
source?
a. chemoheterotrophs
b. photoautotrophs
c. chemoautotrophs
d. both a and b
e. both b and c
Practice: Which of the following is/are considered primary
producers (self-feeders)?
a. chemoheterotrophs
b. photoautotrophs
c. chemoautotrophs
d. both a and b
e. both b and c
Environmental Factors that Influence Microbial Growth.
A. Temperature - microorganisms have a range of temperatures over
which they can grow. [Be familiar with this range for psychrophiles,
psychrotrophs, mesophiles, thermophiles and hyperthermophiles].
Within this range of temperatures there is an optimal temperature at
which the enzymes function best and thus the organism divides most
rapidly. It is not important to memorize this optimal temperature for
every classification of bacteria, however it is important to be able to
recognize where it lies if shown a growth rate curve. *Note that the
optimal growth temperature is always closer to the maximum growth
temperature than the minimum. Realize that the damage done to cells
at temperatures below the minimum is reversible damage. In contrast,
the damage caused by temperatures above the maximum is
irreversible.
Practice: What cellular events are reflected by the initial
rise in growth rate with increasing temperature until the
optimum is reached, followed by the steep decrease in
growth rate beyond the optimum?
Practice: For a summer internship, a student decides to
work for a researcher who studies bacteria found in
hydrothermal ocean vents. These microorganisms are most
likely
a. mesophiles
b. hyperthermophiles
c. psychrophiles
d. oceanophiles
Practice: Yersinia pestis is a pathogenic member of the
family Enterobacteriaceae. This organisms causes the
bubonic plaque and is most likely a
a. psychrophile
b. psychrotroph
c. mesophile
d. hyperthermophile
*NOTE: Refrigeration can be used to retard the growth of mesophiles
and freezing stops the reproduction of most microorganisms.
However, freezing DOES NOT KILL bacteria. In fact, we store our
microorganisms for lab in liquid nitrogen.
Practice: The following graph shows the growth rate of an organism vs.
the temperature. Notice the three cardinal temperatures: the minimum,
optimum and the maximum.
Temperature
Which statement/s about these cardinal temperatures is / are TRUE?
a. At their optimum temperature, organisms divide most rapidly because
their enzymes function best.
b. Damage done to cells below the minimum is reversible whereas damage
done above the maximum is irreversible.
c. The optimum growth temperature for psychrotrophs is lower than the
optimum growth temperature for mesophiles.
d. all of the above.
e. only a and c
B. Oxygen - Know the difference in oxygen requirements for obligate
aerobes, obligate anaerobes, facultative anaerobes,
microaerophiles and aerotolerant anaerobes.
Practice: A student is working in the lab with Clostridium
sordellii. She inoculates a BHI agar deep and notes that,
after incubation, there is only growth in the bottom regions
of the tube. The student concludes that this bacterial
isolate is a facultative anaerobe. Is the student right? Why
or why not?
Oxygen, itself, is not particularly toxic. However, it can be converted
naturally into two toxic forms: superoxide (O2 -) and hydrogen peroxide
(H2 O2 ). Both of these species cause damage to cell membranes, DNA
and proteins. Some organisms can detoxify superoxide and hydrogen
peroxide using the enzymes superoxide dismutase and catalase
respectively (be familiar with these detoxification reactions). **Most
strict anaerobes do not have these two enzymes!
Practice: Which of the following is/are most likely to lack
the enzyme catalase?
a. Rhodococcus equi (an obligate aerobe)
b. Clostridium botulinum (an obligate anaerobe)
c. Nocardia brasiliensis (an obligate aerobe)
d. both a and b
e. both b and c
A General Microbiology student is attempting to identify an
unknown bacterium. To these ends, the student places a little bit
of the bacterial growth into a drop of hydrogen peroxide.
Profusive bubbles form. What conclusions can the student
make?
a. The unknown bacterium is likely an obligate anaerobe.
b. The unknown bacterium is equipped with the enzyme
catalase.
c. The unkown bacterium can detoxify hydrogen peroxide by
converting it to water and oxygen gas.
d. b and c
e. a and b
C. pH
1. Acidophiles live in environments where the pH ranges from
1 to 5.5.
2. Neutrophiles live in environments where the pH ranges from
5.5 to 8.
3. Alkaliphiles live in environments where the pH ranges from
8 to 13.
4. Despite the pH of the environment that an organism lives in,
the pH inside the cell is maintained at approximately 7.
Practice: Sulfolobus is a thermoacidophile that lives in the
Norris Geyser Basin at Yellowstone Hot Springs. If one
were to measure the pH inside of a cell of this
microorganisms the value would be closest to which one of
the following?
a. 1
b. 7
c. 10
d. 14
For thought: Helicobacter pylori lives in an acidic
environment but is not an acidophile. How is this
accomplished?
D. Water availability
Practice: Use your own words to describe what is meant by water
availability.
1. When cells are in a hypertonic environment they may shrink
and die = plasmolysis. This is why salt is an effective
preservative.
2. Some organisms require high salt concentrations in their
environment (Halobacterium salinarium) = Halophiles.
Practice: During a trip to the 2002 Olympic Games in Salt
Lake City, a nutty professor attempted to isolate an
organism from the Great Salt Lake. The organism that the
professor isolated is most likely a / an
a. thermophile
b. obligate anaerobe
c. halophile
d. alkaliphile
e. both a and c
f. both b and d
Some organisms can tolerate high solute concentrations in their
environment but do not require them = osmotolerant. If the
solute is salt, these organisms are called halotolerant
(Staphylococcus).