Portage Learning BIOD 171 Microbiology Lecture Exam Key 1 6 (Answered)

1. True or False: A virus is considered a microorganism.

False. Viruses are not living and as such are not considered microorganisms. Viruses can, however, be classified as microbes, a more general term that includes microorganisms and viruses.

2. What is the smallest biological unit of life?

A cell.

3. At a generalized level, all cells are comprised of what?

Macromolecules*
*A student may also answer: Proteins, Lipids, Nucleic acids and Polysaccharides but they must answer with all four to be fully correct.

1. How many different types of amino acids are available from which to make proteins?

20

2. Define an essential amino acid.

An essential amino acid cannot be produced by the human body and as such must be take in from the environment through alternative sources (i.e) food.

1. What are the two major types of nucleic acids and their roles?

DNA- deoxyribonucleic acid
RNA- Ribonucleic acid
DNA- Cellular life has DNA and a role that DNA has is long-term storage of information, it holds the characteristics of living organisms.
RNA- Is the carrier of information in form of amino acid sequence. It converts the information in the DNA and synthesizes proteins

1. Complete the following DNA strand and indicate how many bonds are formed for each complementary pair:

3’ GGTCATCG 5’ 5’ CC AGC 3’

3’ GGTCATCG 5’
5’ CCAGTAGC 3’
There are 2 bonds formed between A and T, and 3 bonds between G and C.

1. The plasma membrane (select all that are true):
A. Restricts movement of materials in and out of the cell B. Is often a triple layer comprised of lipids
C. Prevents essential nutrients from escaping
D. Contains hydrophobic tails pointing outward

A and C

2. How many carbon atoms are present in the monosaccharide glucose? A. 1
B. 3
C. 6

D. 12

C. The molecular formula of Glucose is C6H12O6

True of False: The genetic material within a prokaryotic cell is contained within a membrane-enclosed region.

False. Only eukaryotic cells contain its genetic material within a nucleus

True or False: Prokaryotic cells can be subdivided into Bacteria and Archaea.

True

Describe the 4 basic bacterial morphologies.

Coccus (round/spherical), bacillus (rod), vibrio (curved rod) or spirillum (spiral/corkscrew).

True or False: Archaea is noted for its ability to survive under harsh conditions.

True. Archaea can often be found in harsh conditions such as high salt levels, high acid conditions, high temperatures and even oxygen-poor conditions.

1. Which of the following microorganisms are considered to be Eukarya? Select all that apply. A. Animalia
B. Plantae
C. Fungi

D. Protista

A,B,C,D

2. True of False: All multicellular microorganisms classified as Animalia are heterotrophic.

True

3. Microorganisms classified as Plantae obtain most of their energy by converting _____ energy into _______ energy.

Light (sunlight); chemical (sugars)

1. A defining characteristic of fungi is the presence of chitin in the cell walls. Which of following also contain chitin? Select all that apply.
A. Mushrooms
B. Bacteria

C. Yeast D. Molds

A, C and D all contain chitin.

2. True or False: A defining characteristic of Protista is the inability of colonies to form tissue layers.

True.

1. Cell walls are found in which of the following (select all that apply): A. Plants
B. Fungi
C. Bacteria

D. Mammalian cells E. Algae

A, B, C, E

2. The function of the ribosome is (select all that apply): A. Lipid synthesis
B. Protein synthesis
C. To produce energy (ATP)

D. Protein modification and distribution E. Waste disposal via hydrolytic enzymes

B. Ribosomes are located in the cytoplasm of prokaryotic cells and in the ER of eukaryotic cells.

1. Identify the following cellular components by matching the number with the description.

A. Cell wall
B. Lysosome
C. Centriole
D. Rough endoplasmic reticulum E. Plasma membrane
F. Nucleus
G. Golgi apparatus

1F 2B 3E 4G 5D

1. True or False: Metabolism is a controlled set of biochemical reactions that occur in living organisms in order to maintain life.

True.

2. True or False: Enzymes are polysaccharides that catalyze chemical reactions.

False. Enzymes are proteins that catalyze chemical reactions.

3. What are usually metal ions known to assists enzyme during the catalysis reaction?

Cofactors are usually metal ions and assist enzyme during the catalysis reaction.

1. Define catabolism.

Catabolism is the process of breaking down larger molecules into useful energy sources.

2. Upon cellular injury, which metabolic process is involved during the growth and repair phases of the cell?

The anabolic process would be active as it (by definition) is involved in the building up of small complexes into larger complexes.

1. Describe the energy transfer process relative to both ATP and ADP.

ATP has the energy (phosphate group) to donate while ADP can accept energy in the form of a phosphate group. Thus, ATP can be reduced (ATP →ADP + Pi) while ADP can be built into ATP (ADP + Pi →ATP).

2. An organism that derives its energy (generates ATP) from photons of light is called a _________?

Phototrophic microorganism.

An organism that derives its energy by removing electrons from elemental sulfur would be classified as a __________?

Lithotroph

4. A reactive intermediate would be present in which phosphorylation process? A. Photophosphorylation
B. Substrate-level phosphorylation
C. Oxidative phosphorylation

B. The chemical compound losing the phosphate group is referred to as the phosphorylated reactive intermediate.

1. The catabolism of a single molecule of glucose goes through what 3 distinct transitions?

The breakdown of glucose goes through (1) Glycolysis then (2) Fermentation or Respiration and finally through (3) the electron transport chain (ETC).

2. What is the most energetic transition in the catabolism of glucose?

The electron transport chain yields 34 ATP while both glycolysis and fermentation (or respiration) each yield only 2 ATP.

3. Identify the reactants of the following chemical equation: Glucose + 2NAD+ → 2 NADH + 2 Pyruvate + 2 ATP

The reactants are to the left of the arrow: Glucose and 2NAD+

4. The presence of what molecule ‘signals’ to the cell that glycolysis is about to start?

Glucose-6-phosphate (G6P)

5. True or False: In the absence of oxygen fermentation produces 2 ATP.

False. Fermentation only reduces NADH back to NAD+

1. What is the primary byproduct of the TCA cycle? Select all that apply. A. NAD+
B. FAD

C. NADH D. FADH2

C and D. The TCA cycle produces an abundance of reduced electron carriers (NADH and FADH2).

2. True or False. The reactants of the TCA cycle directly enter and fuel the electron transport system.

False. The products of the TCA cycle (reduced electron carriers) enter and drive the production of ATP via the electron transport system.

1. In the absence of glucose, which of the following can be used as alternative energy sources? Select all that apply. A. Lactose
B. Nucleic acids
C. Carbohydrates

D. Lipids

A, C, D can all be used as alternative energy sources.

2. For the catabolism of proteins and lipids, which of the following enzymes are used? Select all that apply. A. Ligases
B. Proteases
C. Transferases

D. Lipases

B and D. Proteases breakdown proteins while lipases breakdown lipids.

3. True or False. The β-oxidation pathway catabolizes the fatty acid chains of lipids.

True

1. Describe the relationship between chloroplasts and chlorophyll.

Both chloroplasts and chlorophyll are associated with photosynthesis. Chloroplasts are the double membrane- enclosed organelles that contain the photosynthetic pigment chlorophyll.

2. True or False: Chloroplasts are specific to algae and plants.

True

3. The process of photophosphorylation produces which of the following: select all that apply. A.ATP
B. Glyceraldehyde-3-phosphate
C. CO2

D. NADPH E. H2O

A and D.

1. In phosphorylation, the light reactions always occur where?

The process of converting light energy into chemical energy (photophosphorylation) always occurs in the membrane.

2. True or False: The Calvin cycle must occur in the absence of light.

False. The term ‘dark reactions’ (also known as the Calvin Cycle) simply denotes the second stage in photosynthesis—dark reactions do not actually require darkness in order to occur.

1. How many turns (or repititions) of the Calvin Cycle are required to generate one molecule of glucose?

Six.

2. Complete the following equation by placing the appropriate numbers where indicated. __CO2 + __ATP + __NADPH + __H20 → __C6H12O6 + __ADP + __NADP+
6CO2 +18ATP+12NADPH+12H20→C6H12O6 +18ADP+12NADP+
1. Match the following reactions to its corresponding enzyme:

1. A-B + H2O → A-OH + B-H 2. A-B→ B-A
3. A + B → A-B
4. A-B → A + B

A- Lyases
B- Transferases

C- Oxioreductaces D- Hydrolases
E- Ligases
F- Isomerases

1D 1. A-B + H2O → A-OH + B-H 2F 2. A-B→ B-A
3E 3.A+B→A-B
4A 4.A-B→A+B

1. A micrometer is defined as A. 10-3
B. 10-6
C.10-9

D. 10-12

Hydrolases Isomerases Ligases Lyases

B. A micrometer is one-millionth of a meter.

2. True or False: A nanometer is longer than a micrometer.

False. A nanometer is 1,000 times smaller than a micrometer.

1. Resolution and contrast are two critical factors that influence your ability to see an object. Explain each.

Resolution refers to the distance between two objects at which the objects still can be seen as separate. Poor or low resolution means two (or more) objects may appear as one.

Contrast is the difference in light absorbance between two objects. Poor contrast gives a high background and makes the visualization of multiple objects difficult. For instance, trying to identify 2 dark colored objects at night (low light = low contrast) versus the same 2 objects in the middle of a sunny afternoon (bright light against 2 dark objects = high contrast).

1. Assuming a fixed ocular, identify the part of the microscope you would adjust to enhance the magnification of a sample. A. Objective
B. Condenser
C. Iris diaphragm

D. Eye piece

A. Only the oculars (eyepiece) and the objectives contribute to the magnification of the sample. Since the eyepiece is fixed, only the objectives could be altered.

2. What is the total magnification (relative to your eye) of a sample imaged with a 20x objective and a 15x eyepiece? Show your math.

20 x 15 = 300x magnification

1. True or False: Staining is often required to image a cell that is adherent and flat (thin).

True. Adherent, flat and unstained cells are almost invisible due to the limits on both resolution and contrast. Therefore, cell staining is often required to adequately image the sample.

2. Which of the following could NOT be seen clearly by the unaided eye? Select all that apply. A. Bacteria with diameter of 24 μm
B. Protozoa with diameter of 150 μm
C. Virus with a diameter of 0.2 μm

D. Skin cell with diameter of 1500 μm

A and C. The unaided eye can, on average, clearly resolve objects > 100 μm

1. Label the following unmarked microscope components (numbered arrows) by matching it with the components provided (letters).

A. Stage
B. Fine Adjustment Knob C. Iris Diaphragm
D. Neck
E. Condenser Lens
F. Eyepiece
G. Objective
H. Base
I. Coaxial Controls

1F 2D 3B 4G 5A 6H

1. For each of the following questions select from the list below the single best answer: Phase-Contrast
Dark Field
Fluorescence

Confocal
This type of microscope is best suited for visualizing GFP, RFP and YFP proteins. Fluorescence
2. This type of microscope can provide detailed images of live cells without staining. Phase-Contrast

3. This type of microscope is used to greatly increase the contrast between samples and background by reflecting light off of the specimen.

Dark Field

4. This type of microscope is capable of capturing images in multiple focal planes, rendering a specimen in 3D

Confocal

1. Identify what type of electron microscope was used to capture the following image and explain your choice.

The image was captured using a Scanning Electron Microscope (SEM). The above image shows the trademark ‘shell’ image (no subcellular organelles are visible) reminiscent of SEM. Only TEM is capable of visualizing subcellular substrucutres.

1. Gram-Positive cells appear _______ in color due to a ______ peptidoglycan layer in the cell wall.

Purple; Thick

2. Gram-Negative cells appear _______ in color due to a ______ peptidoglycan layer in the cell wall.

Pink; Thin

1. True or False: The distinguishing characteristic of Gram-Negative bacteria is the presence of LPS in the outer membrane.

True.

2. True or False: If you wish to study the motility of an organism you cannot heat fix, but you can chemically fix the specimen.

False. Both heat and chemical fixation strategies will kill the cell, making motility observations impossible.

1. You want to observe the size and shape of a cell. What is the easiest staining technique that you could perform? Name at least one dye you would use during this process.

Simple stain. You could use any of the following: methylene blue, crystal violet, safranin or fuschin.

2. You suspect a patient may have TB. Once a sample has been obtained it is sent off to the lab for an acid-fast stain. If the patient were infected with TB, describe what you would expect to see on the stained slide.

You would expect to see red cells (TB+) on a blue background (TB negative).

3. True or False: If a patient is suspected of having malaria, a Giemsa stain would be an appropriate differential test to perform.

True. Giemsa stains are often used in the clinical setting to aid in the diagnosis of blood parasites.

1. True or False: Growth media is best suited for distinguishing between two similar species of bacteria.

False. Growth media is designed to simply support (and not restrict) microbial growth.

2. A researcher is asked to determine which of two vials contains E coli and which contains Salmonella. Knowing both are Gram-Negative while only one of them is capable of fermenting lactose, which type of media would be best suited:
A. Growth media
B. Differential media

C. Selective media
D. Selective and Differential media

B. Differential media distinguishes between two, often related, microbes.

3. What are the requirements of a fastidious microbe?

A fastidious microbe is an organism with complex growth requirements such that if absent it will not grow. Enriched medias thus contain these specific and essential nutrients required for the growth of a particular subset of microorganisms.

1. True or False: LB agar is classified as a selective, non-differential media.

False. LB agar is the most basic type of agar and like LB media supports the growth of virtually all microbes without restriction.

2. What is agar used for in microbiology?

Agar is used to create a solid, smooth surface on which microbes can grow.

1. Match the following hemolytic class with its description of activity.

1. Alpha hemolysis

B

2. Beta hemolysis

C

3. Gamma hemolysis

A

A. No hemolytic activity

B. Incomplete hemolytic activity

C. Complete hemolytic activity

1. Columbia CNA agar is most closely related to which media: A. Trypticase Soy Agar
B. MacConkey Agar
C. Blood agar

D. EMB agar

C. CNA agar is similar to BAP as it is also enriched with blood and allows for differentiation based on hemolytic patterns.

2. True or False: Chocolate agar gets its brown color from cocoa to produce an enriched media.

False. Chocolate (cocoa) is never added to the media. The name is derived simply based on the color that actually comes from the presence of ‘cooked’ (lysed) red blood cells in the media.

3. A researcher is studying a strain of E. coli currently growing on a MacConkey plate. However, the researcher can’t remember if E. coli is Gram-Positive or Gram-Negative. Would a Gram stain be necessary to confirm? Why or why not?

No. A Gram stain would not be necessary, as only Gram-Negative microbes will grow on MacConkey agar. Thus, E. coli is a Gram-Negative microbe.

1. In an attempt to detect the presence of the pathogenic strain of E. coli O157:H7, a researcher spread a culture onto a MacConkey agar with failed results. What type of agar should they (correctly) try next? Why?

The microbe should be plated on SMAC (Sorbitol-MacConkey agar) as it is specifically formulated to detect O157:H7. Pathogenic E. coli (O157:H7) cannot ferment sorbitol while non-pathogenic E. coli can ferment both soribitol and lactose. Therefore, colonies that ferment (acidic conditions; non-pathogenic) can be differentiated from non-fermenters (neutral to basic conditions; pathogenic).

1. In Eosin Methylene Blue (EMB) agar, what color indicates the presence of E. coli?

Metallic Green.

2. Which type of agar media is best suited to support the growth of Staphylococcus? A. MacConkey agar
B. Blood agar
C. Columbia CNA agar

D. Mannitol salt agar E. Chocolate agar.

D. Mannitol salt agar

1. What is the process of spreading a bacterial culture onto a petri dish?

Plating.

2. Describe the primary advantage of using a petri dish over growing a liquid culture?

The primary advantage is that cells are held into place. When grown in a nutrient broth, bacterial cells can multiply but are free to move around in solution. When grown on agar within a petri dish the fixed in such as way as to form colonies.

3. True or False: The visualization of colonies on a petri dish represents bacterial cells that have multiplied ~2-3 times.

False. When an individual colony is visible on agar the bacterial cell has multiplied often a million times over.

1. True or False. The purpose of a quadrant streak is to produce individual colonies of a bacterial population.

True. The purpose of the quadrant streak is to generate individual colonies such that a single (pure) bacterial sample can be isolated.

2. A dilution gradient is formed when carrying out what generalize plating strategy?

A quadrant (aka phase-dilution) streak. The resulting gradient should always contain within it the growth of individual colonies.

3. In what phase of a dilution streak would you expect to find the highest concentration of bacteria, P2 or P4?

P2 (Phase 2) would contain a higher concentration of bacteria than Phase 4 (P4). The phases rank (from highest to lowest), P1 > P2 > P3 > P4.

1. True or False. When performing a dilution streak a new (or sterilized) loop must be used for each phase.

True. Failure to do so would prevent the establishment of a dilution gradient, as the same bacterial concentration would be spread across both phase regions.

2. In order to encourage growth of a slow growing microbe what might a researcher do during a phase dilution streak?

A researcher may either (1) opt to perform only a 3-phase dilution streak or (2) pass the loop through the previous phase multiple times (as opposed to only once).

3. True or False. To restrict the growth of a pathogenic microbe a researcher might decrease an incubator from 37°C to 25°C.

True. Pathogenic strains of bacteria tend to grow faster than non-pathogenic strains at 37°C, so researchers may set incubators at 25°C to restrict its growth.

When given an unknown bacterial sample the first step is to expand the current bacterial population. Which form of media best suites this need? Why?
A. MSA agar
B. LB media containing ampicillin and neomycin

C. MacConkey agar D. Blood agar

D. Blood agar. All other options (A, B and C) are all forms of selective media, meaning they may potentially inhibit the growth of the unknown sample. Although blood agar is considered a differential media, it is, most importantly, a non-selective media. Given the alternatives, this is the best option.

1. The concept of treating all samples, whether known or unknown, as potentially hazardous (or pathogenic) materials is known as __________.

Universal precautions.

2. List at least 3 observations a researcher would be sure to note while assessing an unknown microbial sample.

A lab researcher would be certain to note: 1. Size and shape
2. Any observable motility
3. Gram status (positive or negative)

4. The presence of any chemical reactions
5. Changes in color localized to the organism or the surrounding media 6. Capture (or draw) images of any of the characteristics described above

1. While observing an unknown sample of limited amounts, a researcher must determine the following observations: (1) the presence of any motility and (2) its Gram status using the same sample—the liquid sample cannot be divided. Which would you determine first and why?

You must determine motility before determining the Gram status. Motility requires a wet mount, while Gram staining requires heat fixing the sample. If one were to begin with the Gram stain the heat fixation process would kill the organism, making any observations regarding motility impossible. The correct approach would be to place the liquid culture on a glass slide and determine its motility status. Next, the same liquid culture can be heat fixed and Gram stained.

2. A facultative anaerobe is a microorganism capable of growth under what conditions?

A facultative anaerobe is capable of growth under aerobic (with oxygen) and anaerobic (without oxygen) conditions.

1. As Streptococcus is catalase negative would it thrive or die in the presence of peroxides? Why?

Streptococcus would not survive in the presence of peroxides—it is unable to breakdown peroxides (catalase negative). Left unchecked, peroxides would damage the cellular integrity of Strep causing lysis/cell death.

2. Streptococcus is most often streaked onto

A. Chocolate agar B. EMB agar
C. Blood agar
D. Spirit Blue agar

C. Strep is often cultured on Blood agar plates to determine its hemolytic properties, which aids in the classification (and differentiation) process.

3.True or False. The Lancefield groups are used to subdivide antigenic groups of gamma-hemolytic Streptococcus.

False. The Lancefield groupings are used to subdivide beta-hemolytic Strep.

4. Greater than 90% of all human streptococcal infections belong to:

A. Group B B. Group D C. Group A D. Group C

C. Group A is the causative agent behind > 90% of all Strep infections.

5. Left untreated, strep throat can progress to ______ , which displays _____ hemolytic activity.

A. Strep. Pharyngitis; beta
B. Strep. Septicemia; gamma C. Rheumatic fever; beta
D. Strep. Pharyngitis; alpha

C. Strep throat (also known as strep. Pharyngitis) can lead to Rheumatic fever if left untreated. Strep. Pharyngitis displays beta-hemolytic activity.

1. True or False. Under most circumstances, staphylococcus can be found in ~30% of human population where it remains pathogenic.
False. While staphylococcus can be found in ~30% of the human population, it remains non-symptomatic.

False. While staphylococcus can be found in ~30% of the human population, it remains non-symptomatic.

2. When a bacterium neither harms nor benefits from the host from which it obtains nutrients, it is referred to as being ___________.

Commensal.

3. In order to differential screen staphylococcus species, agar plates should contain what additive?

Bile salts. Staphylococcus species are capable of growth in the presence of bile salts.

1. Match the following symptoms with their respective diseases:

1. Childhood skin disease near mouth/nose

   A. Folliculitis

2. Infection of thin, transparent scleral tissue

C

D

3. Infection occurs at time of birth

E

4. Pus-filled lesions on skin or hair

A

B. Scalded-skin syndrome

C. Impetigo

D. Conjunctivitis

E. Ophthalmia Neonatorum

5. Ruptured pustules; treated with Penicillin

B

2. True or False. Staphylococcus is the only causative agent of conjunctivitis.

False. There are bacterial (staph) and viral forms of conjunctivitis, both resulting in the inflammation of the conjunctiva and ‘pink eye.’

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