Mastering Biology HW Questions Ch 1-5

A paramecium is approximately 150 micrometers in length. What is this measurement expressed in millimeters (mm)?

0.15 mm

When an object is viewed through a light microscope with oculars that magnify 20x and a high-power objective lens that magnifies 100x, what is the total magnification of the object?

2000x

Chlamydia trachomatis elementary bodies measure approximately 0.25 micrometers in diameter. What is this measurement expressed in nanometers (nm)?

250 nm

A new antibiotic is produced that inhibits the synthesis of acetyl-CoA and the electron transport chain in bacteria. For each glucose molecule that is metabolized, how many fewer ATP molecules will be produced?

36

You have identified the causative agent of the illnesses as Listeria monocytogenes and have laboratory data to support your conclusion. Now you will need to determine the bacterial load of the pathogen within the samples collected. You'd like to know whether the illness is caused by a low level exposure (low bacterial numbers) or a high level of exposure (high bacterial numbers). You will use serial dilutions and plate counts to quantify the number of bacteria in your sample. By using a "serial 10" dilution method, each new tube of diluted bacteria will be 10 times more diluted than the previous tube. A sample of each of these dilutions can then be plated, and the resulting colony forming units counted to yield an estimate of the number of bacteria in your sample. You count 50 colony-forming units on the fourth plate that corresponds to the 10-4 dilution tube. How many bacteria would you estimate to be in the original sample?

5 x 10^5 bacteria per mL

Consider the following situations, and determine when a simple stain could be used instead of a Gram stain.

A microbiologist is trying to determine whether a specimen contains bacteria or fungi.

Which type of microscope would allow the viewer to see ribosomes inside a cell?

A transmission electron microscope

Why is ATP required for glycolysis?

ATP makes it easier to break apart glucose into two three-carbon molecules

What is the intermediate product formed by pyruvic acid during alcoholic fermentation?

Acetaldehyde

Which of the following is true of aerobic respiration compared to anaerobic respiration?

Aerobic respiration uses oxygen as a final hydrogen acceptor, whereas anaerobic respiration uses an inorganic molecule other than oxygen as the final electron acceptor

A student creates a Gram stain on a bacterial specimen that has a mix of gram-negative and gram-positive organisms but accidentally forgets the decolorizer step. What would the outcome of the Gram stain be?

All organisms would appear purple (gram-positive).

Where would you expect to find electron transport chains in a prokaryote?

Along the plasma membrane

What is the function of GTP?

An energy carrier

Why is a specimen smaller than 200 nm not visible with a light microscope?

Anything smaller than 200 nm cannot interact with visible light.

Which of the following statements comparing electron microscopy and light microscopy is FALSE?

Both the electron microscope and the light microscope use the same wavelengths for illumination.

Which of the following correctly matches enzyme components with their correct definition and/or function?

Coenzymes are the organic cofactors important to enzyme activity

Which of the following is found in the cytoplasm of prokaryotic cells but is ABSENT from the cytoplasm of eukaryotic cells?

DNA

What occurs at the bridge step?

Decarboxylation of pyruvic acid

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 following matches the organisms described with the correct domain?

Eukarya--single-celled and multicellular organisms, with a defined nucleus and a variety of nutritional sources

How many electron carriers are reduced in the Krebs cycle only?

Four

Which of the following is true of microbes?

Gene expression in bacteria is very similar to gene expression in humans, which facilitates the use of bacteria in recombinant biotechnology and gene therapy.

At the doctor's office, the doctor drains the abscess and takes a sample for culturing. She also prescribes some broad-spectrum antibiotics to treat the obvious infection. A couple days later, the doctor tells Sam that his wound contained a number of bacteria including Pasteurella multocida. When the dog bit Sam's arm P. multocida entered the wound and started to establish an infection. In order to do so, the bacteria have to grow, which requires energy. One of the most common energy sources used by bacteria is glucose. Why is glucose such a good source of energy for bacteria?

Glucose is a highly reduced compound, containing many carbon-hydrogen bonds and a lot of potential energy

Which of the following statements about glycolysis is true?

Glycolysis is also called the Embden-Meyerhof pathway

Which of the following is part of the endomembrane system?

Golgi apparatus

Porins are present in ___________bacteria because, in these organisms, molecules entering the cell must pass through an extra layer of _______________

Gram-negative; membrane

Which statement regarding the structure or function of ribosomes is correct?

In eukaryotes, the ribosomes found in chloroplasts and mitochondria are 70S ribosomes, which are similar in size to prokaryotic ribosomes

Which of the following statements accurately describes specific bacterial cell walls?

In gram-negative bacteria, the thin layer of peptidoglycan is surrounded by an external membrane made of phospholipids, lipopolysaccharides, and proteins.

Which of the following is true about antibiotics?

In some cases, antibiotics are able to kill pathogenic microbes without harming human cells.

S. aureus has been isolated from George's infected wound. To satisfy Koch's postulates, what would George's doctor need to do with the isolated S. aureus?

Inject the S. aureus into an animal, observe whether the animal gets an infection similar to George's, and isolate the same strain of S. aureus from the infection.

What is the role of iodine in the Gram stain process?

Iodine is a mordant in the Gram stain technique, which functions to intensify the primary stain.

Which of the following molecules would be blocked by a cell membrane?

Ions

Which of the following statements about fermentation is true?

It is an alternative way to return electron carriers to their oxidized state

What is meant by light rays being divergent?

It is spreading out

What is a hallmark of passive transport across cell membranes?

It occurs along an electrochemical gradient, and may involve the use of transport proteins

Which of the following statements regarding active transport is false?

It powers the diffusion of water across the cell membrane.

What is the fate of the NAD+ newly regenerated by fermentation?

It returns to glycolysis to pick up more electrons.

What is the role of pyruvic acid in fermentation?

It takes the electrons from NADH, oxidizing it back into NAD+

A strain of Streptococcus pneumoniae is no longer able to synthesize its capsular polysaccharide. What is a likely outcome?

It will be readily phagocytized upon entering the host

A strain of Neisseria gonorrhoeae has been genetically altered and can no longer produce fimbriae. What is a likely outcome?

It will be unable to adhere to host tissue and establish infection

A disease breaks out among sheep in California. A scientist takes blood from the sheep and grows a previously unknown organism. That organism is then injected into a healthy sheep. The healthy sheep becomes sick with the same symptoms as the original sheep and dies. That sheep's blood is then cultured, and the original organism is isolated. This applies the principles of __________.

Koch's postulates

Which of the following is an acid produced by fermentation?

Lactic acid and propionic acid

What is the role of lenses in microscopy?

Lenses focus either light or electrons to create a magnified image of a specimen

Which of the following types of bacterial cells would have flagella located at only one end of the cell?

Lophotrichous and monotrichous

Further characterization of the S. aureus isolated from George's wound reveals that the strain is MRSA. Why is George's doctor concerned that MRSA has been identified as the causative agent of George's infection?

MRSA is transmissible

When proteins are oxidized, all of the following are true EXCEPT which one?

Microbes produce extracellular enzymes to reduce proteins to their fatty acid and glycerol components so that each component can enter the Krebs cycle

Which of the following types of bacterial cells would have only a single flagellum?

Monotrichous

Which of the following molecules is shared by both Gram-positive and Gram-negative organisms?

N-acetylmuramic acid

Which compounds provide electrons to the system?

NADH and FADH2

How was disproving spontaneous generation associated with developing principles important to microbiology?

Pasteur's experiments with swan-necked flasks supported the concept that microbes in the air were responsible for contaminating nonliving matter.

How will the prescribed penicillin kill S. pyogenes that is causing Shelly's infection?

Penicillin will interfere with peptidoglycan synthesis, ultimately weakening the cell wall and leading to cellular lysis.

Which of the following is a lens found on electron microscopes but not on light microscopes?

Projector lens

Which of the following facts does NOT provide evidence for the endosymbiotic theory?

Prokaryotes contain peptidoglycan in their cell walls.

What carbon molecules remain at the end of glycolysis?

Pyruvic acid

A student from one of the research labs is having trouble preparing a slide for examination and photographing. The bacterial slide that he has brought to you was prepared using a commercially purchased stain. He has asked for your help in determining what he is doing wrong so that he can change the lab protocols and continue on with his project. After examining the slide under oil immersion, you determine that no bacteria are present even though the student is able to show you the culture he used to make that slide that has visible growth in the liquid medium. Which of the following statements does NOT explain the fact that there are no bacteria present on the student's slide?

Rinsing with alcohol during the washing step stripped the bacteria off the glass slide.

Which of the following represents the correct format for the scientific name?

Staphylococcus aureus (italicized)

Most types of bacteria have specific metabolic oxygen requirements. Whether a bacterium requires oxygen or not has a large effect on its physiology. For example, aerobic bacteria, which require oxygen for their metabolic processes, must be able to counter the highly reactive oxygen species such as singlet oxygen (1O2) or a superoxide radical (O2−) that result from reactions within the cell. Bacteria that lack this capability are generally considered anaerobic. Since anaerobic bacteria utilize molecules other than oxygen as their final electron acceptor, they must possess adaptations to facilitate their survival in environments without oxygen. A majority of bacterial species lie somewhere in between these two polar opposites in that they are facultative anaerobes or able to utilize oxygen but also capable of surviving without it. Some particularly specialized facultative anaerobes are microaerophilic and grow only in low concentrations of oxygen. What are the enzymes and their reactions that allow bacteria to grow in the presence of oxygen? Which of the following statements correctly summarizes the enzymatic reactions to reactive oxygen species?

Superoxide dismutase detoxifies superoxides and converts them into hydrogen peroxide and oxygen. Catalase then converts the hydrogen peroxide into water and oxygen.

Based on the concept map only, which of the following is most likely to be true of microbial metabolism?

The Krebs cycle produces molecules necessary for function of the electron transport chain

A key feature of cellular respiration is the removal of electrons from fuel molecules (oxidation) and the ultimate acceptance of these electrons by a low-energy electron acceptor. The process involves the use of electron carriers, NAD+ and FAD, which play crucial roles in multiple steps of the metabolic pathways. The overall equation for cell respiration is shown below. Why do NAD+ and FAD NOT appear in the overall equation?

The NAD+ and FAD are initially reduced then oxidized to their original state, so they do not appear in the net equation.

In 1861, Pasteur conducted his now-famous experiments using flasks with long necks bent into an S-shape. Imagine that you are a scientist working in Pasteur's lab at this time. You decide to tip the flasks so that broth enters the long S-shaped neck. You then return the flask to its upright position. Predict the most likely outcome of tipping one of Pasteur's S-necked flasks.

The broth would become contaminated with microbes because they were trapped in the neck

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 P. multocida that are growing within Sam's abscess are breaking glucose down via glycolysis in order to obtain energy. This process occurs via a series of enzymatic reactions. During a chemical reaction, an enzyme functions as a biological catalyst and lowers the activation energy. How does an enzyme lower the activation energy of a reaction?

The enzyme increases the effectiveness of reactant collisions thereby increasing the number of reactant molecules that reach activation energy

In a typical brightfield microscope (seen in the animation), at which point does magnification begin?

The objective lens

One of the environmental changes that P. multocida encounters during infection is the limitation of nutrients and oxygen. One of the changes that P. multocida (a facultative anaerobe) makes in this environment is to switch to anaerobic metabolism. Predict which of the following is most likely to occur as a result of the switch from aerobic to anaerobic metabolism

The organisms will grow more slowly because they will produce less ATP compared to aerobic metabolism.

You volunteer to help the student with his fixation technique and in choosing a proper stain for the project he is working on. After watching and helping the student correct any problems with his fixation technique, you now need to determine which stains to use. The single criterion for the project is to be able to determine cell shape and size in a pure broth culture after some treatments. No differentiation between cell types is required (i.e., Gram-positive or Gram-negative), so you want to convince the student that a simple stain would be his best option. The charged dyes used in simple staining will penetrate the bacterial cell and will be retained after rinsing the slide with water to remove surplus dye. Which staining procedure would be best to use to stain the slides required for this student's project? Why?

The positively charged methylene blue will be attracted to the negatively charged components of the cell wall and will be retained

Which of the following are FALSE concerning microbes?

The primary role of microbes on the planet involves causing disease in animals and humans.

One of the first set of experiments to refute spontaneous generation was done in 1688 by Francesco Redi. Which of the following statements regarding Francesco Redi's experiments is true?

The results of his experiment demonstrated that living organisms are derived from other living organisms.

Microbes are often identified using biochemical tests that detect specific enzymes of metabolic pathways. E.coli typically ferments lactose, whereas the dysenterybacterium, Shigella, does not. If a pure culture of each bacterium were placed in a tube containing lactose as the only food source, and a chemical indicator changed color if the tube became acid, what would the tubes look like after the bacteria were incubated?

The tube with E. coli would indicate a pH change, and the Shigella tube would indicate no change.

What effect will the penicillin have on Shelly's cells?

There will be no impact on Shelly's cells because penicillin targets the flagella, which are found only in bacteria.

What is the fate of metabolites during respiration?

They are oxidized completely to carbon dioxide and water

What happens to the light rays when they hit the specimen?

They are reflected, refracted, or absorbed by the specimen.

Which of the following is a characteristic shared by both electron and light microscopes?

They both employ the use of objective lenses.

What is the fate of the electrons that interact with a specimen in an electron microscope?

They may be absorbed, reflected, or refracted by the specimen.

What is the role of the ocular lens?

To recreate the image in the viewer's eye

Agars can be used to select for growth of certain types of bacteria and then allow for you to identify the different bacteria that can grow on the plate. These agars may be considered both selective and differential. Is the above statement true or false?

True

You have been asked to lead a demonstration for the undergraduate microbiology lab course about the uses of negative staining when studying bacteria. A "negative" stain does not stain the bacterial cell itself but stains the space between cells. Under magnification, the acidic (negatively charged) nature of the stain will be repelled by the negatively charged bacterial cell wall and will leave the cell colorless in a stained background. Negative stains are used primarily to reveal the presence of negatively charged bacterial capsules; therefore, they are also called capsule stains. Encapsulated cells appear to have a halo surrounding them. The negative stain procedure does not require heat fixation, which limits any chances of alteration in bacterial cell shape and size. The bacterial suspension is added to a drop of stain, such as nigrosin or eosin, and drawn across the glass slide using a coverslip. Nigrosin staining-not safranin staining-of Klebsiella pneumoniae will allow for the visualization of the cell shape and the determination of the presence of a capsule.

True

How many net ATPs can be made from one molecule of glucose in glycolysis?

Two

What does oxygen get reduced to at the end of the electron transport chain?

Water

Which type of solution would cause a bacterium with a weak or damaged cell wall to burst as water moves into the cell?

a hypotonic solution

Which of the following staining procedures is matched with the principal use for that stain?

acid-fast stain for microbes with waxy cell walls

Which of the following measurements is correctly matched with microorganisms of that size?

bacteria--2 micrometers

Amoxicillin is an antibiotic that inhibits the formation of peptide cross-links. Amoxicillin, therefore, would most likely inhibit the growth of ________

both Gram-positive and Gram-negative organisms

The process of generating ATP using a proton gradient is referred to as

chemiosmosis

The structural framework in a cell is the

cytoskeleton

Which of the following types of microscopy provides advantages for viewing live images?

darkfield microscopy

Consider an organism that is eukaryotic, found in both unicellular and multicellular forms, may resemble a plant but is not photosynthetic, has chitin in its cell walls, and absorbs organic nutrients from decomposing material in the environment. This organism would be classified as which of the following types of organisms?

fungi

You are observing a Gram stain of spherical-shaped microorganisms that are linked in a chain and stain purple. How would you describe these bacteria using the correct terminology for the cell shape and arrangement?

gram-positive streptococci

Which of the following describes the correct path of light in a compound light microscope, from the illumination source to the eye of the observer?

illuminator ( condenser lenses ( specimen ( objective lenses ( body tube ( ocular lens ( eye

Which of the following organelles breaks down worn-out organelles?

lysosomes

What carries instructions for making proteins from the nucleus into the cytoplasm?

mRNA

Where in a cell is ATP made?

mitochondria

Where is the genetic information of the cell stored?

nucleus

In which eukaryotic organelle are amino acids and fatty acids oxidized?

peroxisome

What structure acts as a selective barrier, regulating the traffic of materials into and out of the cell?

plasma membrane

Analysis of the second swab has confirmed that the causative organism is Streptococcus pyogenes, a gram-positive organism. Imagine that you are the technician looking at the Gram stain from Shelly's culture. What would you expect to see as you look through the microscope?

purple, spherical-shaped organisms arranged in chainlike formations

One of the ways smooth endoplasmic reticulum (ER) differs from rough endoplasmic reticulum is that rough ER is covered by

ribosomes

Which of the following conditions would increase enzymatic activity in a bacterial cell that normally thrives in the human body?

slightly increasing the temperature within the optimum range

Where are lipids made in the cell?

smooth endoplasmic reticulum (ER)

Much of the energy released in catabolic reactions is captured in ATP for use in other reactions. When the phosphate is transferred directly from an organic molecule to ADP in order to produce ATP, as represented by C--C--C ~P + ADP → C--C--C + ATP, this represents ______

substrate-level phosphorylation

Glycolysis literally means

sugar splitting

What does resolution mean?

the ability of a microscope to distinguish fine details and differentiate between two very close objects

The observations of Hooke and van Leeuwenhoek documenting the existence of microscopic cells formed the basis of what important theory?

the cell theory stating that all living things are composed of cells

Which of the following processes directly produce the most ATP?

the electron transport chain

Tumbles occur when

the flagella rotate clockwise.

Peritrichous bacteria make a run when

the flagella turn counterclockwise and become bundled.

Hydrophobic molecules would enter a cell

through integral transport proteins

All of the following factors contribute to the threat of emerging infectious diseases (EIDs) EXCEPT ________

vaccinations that control epidemiologic spread

A positively charged sodium ion

would require the use of integral protein channels to pass through a cell membrane