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Microbiology Exam 1#

prokaryotes, bacteria, etc.
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How is osmosis different from simple diffusion?
Water movement is driven by the concentration of solutes rather than its own concentration.
Nonspecific permeases
allow a variety of molecules to cross the cytoplasm membrane
What will happen to a cell that is placed in a solution containing a high concentration of sugar, a molecule that cannot pass across the cell membrane?
the cell will lose its interior water, causing it to shrivel up and possibly die
How is simple diffusion different from other types of passive transport?
Simple diffusion does not require a permease
Why is no energy required in passive transport?
The concentration gradient drives the movement
Once equilibrium is reached,
molecules move, but there is no net movement in a particular direction
Which of the following would not move freely across the cytoplasmic membrane?
positively charged hydrogen ions
What makes phospholipid membranes good at keeping some molecules out and allowing others to freely pass?
They have both hydrophilic ad hydrophobic regions
Integral proteins are mostly involved in
transport function
How does water enter and exit a cell?
By simple diffusion or by use of an integral transport protein
A glycoprotein
is a type of peripheral protein above that can be used as a receptor or in enzymatic functions
Molecules would be blocked by a cell membrane
ions
Hydrophobic molecules would enter a cell
through integral transport proteins
What is a hallmark of passive transport across a cell membrane?
It occurs along an electrochemical gradient, and may involve the use of transport proteins
A positively charged sodium ion
would require the use of integral protein channels to pass through a cell membrane
Active Transport
-requires ATP
-requires the use of transport proteins
Active transport type that employs diffusion
symport
What type of transport uses two transport proteins?
Symport
Sodium and potassium ions need to be pumped simultaneously against their concentration gradients. Which one of the transport proteins would be most effective at this?
Antiport
Why are ATPases associated w/active transport proteins?
They provide transport proteins w/the energy needed to pump molecules against their concentration gradients
Efflux pumps can be used to pump antibiotics out of a cell once they enter to protect the cell. This will be done against the concentration gradient of the antibiotic. Which of the active transports would most likely be used?
Uniport b/c a uniport would pump the antibiotic out w/out needing to bring additional molecules into the cell, and would not allow the antibiotic to diffuse back in
Why is a ATP necessary for active transport?
ATP provides energy to transfer material against its concentration gradient
Which type of active transport protein moves two molecules into the cell at the same time?
Symport
Which transport protein employs transporters that move molecules only in one direction?
uniport and symport
Which type of active transport protein uses one protein to pump two different molecules?
Antiport and Symport
Where is the genetic information of the cell stored?
nucleus
The structural framework in a cell is the
cytoskeleton
Where in a cell is ATP made?
Mitochondria
What carries instructions for making proteins from the nucleus into the cytoplasm?
mRNA
One of the ways smooth ER differs from rough ER is that rough ER is covered by
ribosomes
What is part of the endomembrane system
Golgi apparatus, ER, lysosomes and vesicles; it manufactures, processes and transports lipids and proteins. The Golgi apparats processes and packages proteins
What organelles break down worn-out organelles?
Lysosomes
Where are lipids made in the cell?
smooth ER
What structure acts as a selective barrier, regulating the traffic of materials into and out of the cell?
plasma membrane
What is the mechanism of action of penicillin in a prokaryotic cell?
Penicillin weakens the cell wall
Plasmids
Prokaryotic plasmids may carry genes that provide antibiotic resistance to the cell
Difference between Gram-Positive and Gram-Negative cells
only gram-negative cells have a lipopolysaccharide layer
Which type os solution would cause a bacterium w/a week or damaged cell wall to burst as water moves into the cell?
Hypotonic solution
Structure or function of ribosomes
In eukaryotes, the ribosomes found in the chloroplasts and mitochondria are 70S ribosomes, which are similar to he size of the prokaryotic ribosome
Evidence of the endosymbiotic theory
-ribosomes contain w/in mitochondria and chloroplasts are very similar to prokaryotic ribosomes
-mitochondria and chloroplasts contain circular DNA, similar to the DNA in prokaryotes
-The same antibiotics that inhibit protein synthesis in prokaryotes also inhibit protein synthesis w/in mitochondria and chloroplasts
Distinguishing characteristics of Prokaryotic cells
-Their DNA is not associated w/histones
-Their DNA is not enclosed w/in a membrane
-They have cell walls containing peptidoglycan
-They lack membrane-enclosed organelles
What happens when a bacterial cell is placed in a solution containing 5% NaCl?
Water will move out of the cell
Which organelle most closely resembles a prokaryotic cell?
mitochondrion
What structures are found in prokaryotic cells?
Flagellum, axial filament, pilus, peritrichous flagella
Glycocalyx
-is used to adhere to surfaces
-may be composed of polypeptide
-may be composed of polysaccharide
-may be responsible for virulence
Chemical components of a bacterial cell wall
N-acetylmuramic acid
peptidoglycan
teichoic acids
peptide chains
The difference between simple diffusion and facilitated diffusion is that facilitated diffusion
requires transporter proteins
Where are phospholipids most like found in a prokaryotic cell?
Plasma membrane?
Energy reserves
sulfur granules
lipid inclusions
polysaccharide granules
metachromatic granules
Considered to be microorganisms
-bacteria and viruses
-microscopic algae
-fungi (including yeasts and molds)
Which microorganisms are acellular and contain a nucleic acid core surrounded by a protein coat?
viruses
In the scientific name, Escherichia coli, Escherichia is the
genus
How did Pasteur's 1861 experiment disprove the theory of spontaneous generation?
Pasteur used open-ended, long-necked flasks w/necks bent into curves; other did not
Which of the following is the concept, proposed by the German scientists Virchow in 1858, that challenged the hypothetical process called "spontaneous generation"?
Biogenesis
Which scientist, in 1876, established a sequence of experimental steps for directly linking a scientific microbe to a specific disease?
Koch
Example of bioremediation
use of bacterial enzymes in drain cleaners to remove clogs
Human diseases can be caused by a complex aggregation of microbes known as a "biofilm"?
Endocarditis
Emerging Infectious disease that is a spongiform encephalopathy caused by a prion
Creutzfeldt-Jakob disease
The presence of several types of bacteria on the surface of the tongue indicates the presence of
normal microbiota
Statement regarding the experiments that "proved" spontaneous generation
microorganisms were already present
Regarding Pasteur's experiment w/the S-neck flask
-there was air involved
-all microorganisms were killed before beginning
-there was a food source involved
-any possibility of contamination was removed
Insect control by microorganisms
The microorganisms are specific for the insect pest
Who proved that microorganisms cause disease?
Koch
Findings that were essential of Jenner's vaccination process?
a weakened microorganism may produce immunity
An agent that reproduces in cells but is Not composed of cells and contain RNA as its genetic material is a
virus
Fungi differ from bacteria in that fungi
have a nucleus
Bacteria differ from viruses in that bacteria
-are composed of cells
-can live without a host
-have DNA and RNA
Biofilms
-on rocks provide food for animals
-in pipes black the flow of water
-on medical implants cause infections
-in your body protect mucous membranes from harmful microbes
Regular use of antibacterial cleaning products
promotes survival of bacteria that are resistant
A multicellular organism that has a mouth and lives in an animal host is a
helminth
What is the type of bond holding hydrogen and oxygen atoms in the H2O molecule?
covalent bond
glucose+fructose => sucrose + water
dehydration synthesis reaction
What type of bond between molecules of water in a beaker of water?
hydrogen bond
What type of bond is holding K+ and I- ions in Kl?
Ionic bond
Lactose + H2O=> Glucose + Galactose
hydrolysis reaction
Which type of molecule contains the alcohol glycerol?
lipid
Which type of molecule is composed of (CH2O) units?
carbohydrate
Which type of molecule contains -NH2 groups?
protein
What is the type of bond between carbon, hydrogen, and oxygen atoms in organic molecules?
covalent bond
Structurally, ATP is most like which type of molecule?
nucleic acid
What do genes consist of?
nucleic acids
Which molecule is composed of a chain of amino acids?
protein
Primary making up plasma membranes in cells
lipids
starch, dextran, glycogen, and cellulose are polymers of
glucose
Oil-degrading bacteria are naturally present in the environment but cannot degrade an oil spill fast enough to avoid ecological damage. How can the actions of these bacteria be sped up?
Provide nitrogen and phosphorus
Why do electron microscopes have higher resolving power than light microscopes?
electrons have a smaller wavelength than visible light, leading to higher resolution
Which of the lenses are found on electron microscopes but not on light microscopes?
projector lens
Which type of microscope would allow the viewer to see ribosomes inside a cell?
a transmission electron microscope
Characteristic shared by both electron and light microscopes?
both employ the use of objective lenses
What is the fate of the electrons that interact w/a specimen in an electron microscope?
they may be absorbed, reflected, or refracted by the specimen
Why is a specimen smaller than 200 nm not visible w/a light microscope?
Anything smaller than 200 nm cannot interact w/visible light
What happens to the light rays wen they hit the specimen?
they are reflected, refracted, or absorbed by the specimen
What is the role of the ocular lens?
to recreate the image in the viewer's eye
What is meant by light rays being divergent?
it is spreading out
In a typical bright field microscope, which point does magnification begun?
the objective lens
What is the role of lenses in microscopy?
lenses focus either light or electrons to create a magnified image of a specimen
What is the resolution limit of the human eye, unaided by the instruments of microscopy?
200 x 10-6
Physical Requirements for Growth
-temperature
-pH
-Osmotic Pressure
Bacterial Growth is defined as
increase in bacterial cell population
In which phase is the rate of cell death equal to the rate of cell growth?
lag and stationary phase
Why is cell growth typically graphed logarithmically?
Cell growth is rapid, and plotting the log of the number of cells versus the generation on a logarithmic graph produces a linear graph
Why might cells begin to die at a faster rate than new cells are made?
Lack of nutrients and an increase in cellular waste products
Bacterial Growth
When the log of the number of cells is plotted versus the generation, the graph is linear
What results when a single bacterium reproduces?
Two genetically identical daughter cells
If you begin with six cells, how many cells would you have after three rounds of division?
forty-eight cells
A step in bacterial cell division
disappearance of nuclear envelope
Which step of binary fission is the reason for genetically identical daughter cells?
replication of the bacterial chromosome
What enables the copied chromosomes to separate during binary fission?
The chromosomes are attached to different parts of cell membrane, which elongates and thus separates the chromosomes
How long does it take for the daughter cells from one round of replication to replicate themselves?
no time is required-they are fully mature and ready to divide immediately after separation if conditions are right
Steps of bacterial replication in the correct order, starting from a parent cell
1.chromosome replication
2.cell elongation
3.septum formation
4.separation of daughter cells
What would happen if the septum did not form during binary fission?
The parent cell would now have two copies of the chromosome
Starting with 3 cells, how many cells would result from three rounds of replication?
24
Aerobic bacteria that have developed (or retain) the ability to continue growing in the absence of molecular oxygen are called
facultative anaerobes
Which type of culture media is best for the growth of most chemoheterotrophic organisms?
complex media
Which process is best for the short-term storage of bacterial cultures/
refrigeration
Lag phase
intense activity preparing for population growth, but no increase in population
Log phase
logarithmic, or exponential, increase in population
Stationary phase
period of equilibrium; microbial deaths balance production of new cells
Death phase
population is decreasing at a logarithmic rate
During which phases of the bacterial growth curve are there no changes in the number of living cells
lag phase and stationary phase
Intense activity preparing of population growth occurs in which phase of the bacterial growth curve?
Lag phase
What does a spectrophotometer directly measure?
absorbance of light
Represents an ideal number of colony-forming units for effective enumeration using the direct method?
100
Salts and sugars work to preserve foods by creating a
hypertonic environment
An advantage of the standard plate count?
determines the number of viable cells
An advantage of the direct microscopic count
requires no incubation time
A culture medium on which only gram-positive organisms grow and a yellow halo surrounds Staphylococcus aureus colonies is call a
selective medium and differential medium
A culture medium consisting of agar, human blood, and beef hear is a
complex medium
During which growth phase will gram-positive bacteria be most susceptible to penicillin?
log phase
Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?
Facultative halophiles
Patients with indwelling catheters are susceptible to infections because
biofilms develop on catheters
Microorganisms
bacteria
viruses
microscopic algae
fungi (including yeast and molds)
Microorganisms that are acellular and contain a nucleic acid core surrounded by a protein coat
virus
In metabolism, energy that is not used
is given off as heat
The reactions involved in producing larger compounds from smaller compounds is called
anabolism
Where does the energy required for anabolic reactions come from?
catabolic reactions
The use of amino acids to make proteins
is an example of anabolism
How does noncompetitive inhibitor reduce an enzyme's activity?
The inhibitor binds to the enzyme in a location other than the active site, changing the shape of the active site
What would be the likely outcome if you increased the concentration of substrate for an enzyme in the presence of a noncompetitive inhibitor?
no change in enzyme activity would be observed
How is nevirapine used to treat HIV infections?
It alters the active site of reverse transcriptase, decreasing that enzyme's activity
How does a competitive inhibitor slow enzyme catalysis?
They compete w/the substrate for the enzyme's active site
What enables competitive inhibitors to bind to a specific enzyme?
competitive inhibitors have structures that resemble the enzyme's substrate
If high amounts of sulfanilamide are in the presence of an enzyme whose substrate is PABA, what outcome is expected?
The enzyme will stop functioning
competitive inhibitors
decrease the rate of enzyme activity
Why do all enzymatic reactions need activation energy?
Energy is required to disrupt a substrate's stable electron configuration
What is meant by the statement "Enzymes are biological catalysts"?
Enzymes speed up the chemical reactions in living cells
Why are enzymes important biological systems?
Enzymes decrease the amount of activation energy required for chemical reactions to occur
What is the fate of an enzyme after it dissociates from the products of the reaction?
The enzyme returns to its original configuration, ready to bind more substrate
features of a substrate that can be accommodated by an enzyme's active site?
shape
size
and electron configuration of the substrate
The first step of any enzymatic reaction is
binding of the substrate by the enzymes
The amino acids in an enzyme can facilitate the reaction by
accepting or donating electrons
A reaction that involves the transfer of electrons from one molecule to another is referred to as
a redox reaction
During an oxidation reaction
the donor molecule loses an electron and becomes oxidized
Why is a reduction the term used to describe the gain of an electron?
The electron acceptor's net charge decreases
Redox reactions
redox reactions involve an oxidation reaction coupled with a reduction reaction
Where would you expect to find electron transport chains in a prokaryote?
along the plasma membrane
Which compounds provide electrons to the electron transport system?
NADH & FADH2
What does oxygen get reduced to at the end of the electron transport chain?
water
What does the electron transport chain do to the concentration of hydrogen ions (protons)?
The concentration of protons is higher outside the membrane than inside
The process of generating ATP using a proton gradient is referred to as
chemiosmosis
Why does lack of oxygen result in the halt of ATP synthesis?
The chain shuts down and can no longer pump hydrogen ions across the membrane, and the proton gradient cannot be maintained.
Why might some cells uncouple the electron transport chain?
Cells can use the energy from the proton gradient for functions other than producing ATP, such as heat generation
How does cyanide poisoning result in the decrease of ATP production?
Cyanide permanently reduces cytochrome a3, preventing other components to change into the oxidized state. This causes the proton gradient to break down, stopping ATP synthesis.
Result in the breakdown of the proton gradient
oxygen deprivation
cyanide poisoning
Fermentation
it is an alternative way to return electron carriers to their oxidized state
What is he role of pyruvic acid in fermentation?
It takes the electrons from NADH, oxidizing it back into NAD+
What is the fate of the NAD+ newly regenerated by fermentation?
It returns to glycolysis to pick up more electrons.
An acid produced by fermentation
Lactic acid and propionic acid
What is the intermediate product formed by pyruvic acid during alcoholic fermentation?
Acetaldehyde
Why is ATP required for glycolysis?
ATP makes it easier to break apart glucose into two three-carbon molecules.
Glycolysis literally means
sugar splitting
How many net ATPs can be made from one molecule of glucose in glycolysis?
2
What carbon molecule remain at the end of glycolysis?
pyruvic acid
Glycolysis
is also called the Embden-Meyerhof pathway
What occurs at the bridge step?
Decarboxylation of pyruvic acid
How many electrons carriers are reduced in the Krebs cycle only?
Four
What is he function of GTP?
An energy carrier
What is the fate of metabolites during respiration?
They are oxidized completely to carbon dioxide and water
Lipases break down
lipids
The Pentose Phosphate Pathway
is an example of anabolism
Oxidative phosphorylation
is a catabolic process
The reactions that occur between glucose and pyruvic acid
can either be anabolic or catabolic
How food fuels cellular respiration
1.eating food provides fuel and building blocks for your body
2.after food is broken down the digestive system, it is transported to cells via the circulatory system
3.fuel molecules are broken down further in glycolysis and the citric acid cycle
4.ATP is produced with the help of the ETC