BIOL 251A Exam 1 Material

What type of bacterial cell wall is depicted in this image? A. Gram positive B. Gram negative C. Acid-fast D. Encapsulated

B This is a Gram negative cell wall. There is a thin layer of peptidoglycan between the plasma membrane and the outer membrane. A Gram positive cell wall has a much thicker layer of peptidoglycan and lacks the outer membrane. Acid-fast cell waslls contain mycolic acid. Bacterial cells may be encapsulated, but no capsule is depicted in this image.

This is Mycoplasma pneumoniae. It is 0.1-0.25 µm. How would you classify it? A. Eukaryote B. Prokaryote C. Virus

B and C Based on its size, this organism was originally thought to be a virus, but it is in fact a very small bacterium. Mycoplasmas may be the smallest, free-living organisms. Their cell volume is only about 5% of the size of a typical bacillus and one species has only 517 genes. Theoretically, 265-350 genes are required for a free-living existance.

Why can viruses not be cultivated in plain culture media like bacteria? A. Normal culture media does not contain enough protein for viruses to replicate. B. Normal culture media does not contain enough ATP for viruses to replicate. C. Viruses require host cells to be able to replicate. D. Viruses are too small to be isolated in the laboratory.

C

Select the major features of a prokaryotic cell. A. Lack membrane bound organelles B. DNA found in the nucleus C. DNA associated with histones D. Chemically simple cell walls E. Divide by binary fission F. Divide by mitosis G. DNA is typically a single, circular chromosome

A, E, and G Prokaryotic cells generally lack membrane-bound organelles. Their DNA usually exists as a singular, circular chromosome that is not enclosed by a membrane. Additionally, prokaryotic DNA is not associated with histones. The cell walls of prokaryotes usually contain peptidoglycan and the cells divide by binary fission. Eukaryotic cells do contain membrane-bound organelles. Their DNA may exist as one or more circular or linear chromosmes that are surrounded by the nuclear membrane. Additionally, eukaryotic DNA is associated with histones. Eukaryotic cells have chemically simple cell walls (such as cellulose in plant cell walls) and the cells divide by mitosis or meiosis.

Which of the following is NOT part of a bacteriophage replication cycle? A. Virion binds to a host cell surface protein that provides an important host function B. The virion injects its genome into the host cell C. The capsid of the virion enters the host cytoplasm D. The viral genome directs the host ribosomes to synthesize viral components

C. Bacteriophages inject their genomes into the host bacterial cells. The bacteriophage capsid does not enter the cell during this process.

A bacterial cell is measured to be 4000 nm in length. Express this measurement in micrometers (um).

4um

This is a Gram stain from a sputum (mucus) sample of a patient with a respiratory infection. Are the bacterial cells in this image Gram positive or Gram negative? A. Gram positive B. Gram negative C. Neither D. Both

A The bacterial cells in this image are small, round, and purple. The purple color indicates that they are Gram positive. The red streaks in the image are strands of mucus in the sputum sample.

Are viruses alive? A. Yes B. No

A and B

Selected the characteristics of a microbe A. Too small to be seen with the unaided eye B. Composed of cells C. Primary role is to cause illness D. Found almost everywhere

A. Too small to be seen with the unaided eye D. Found almost everywhere

What is unusual about the ribosomes found in the chloroplasts and mitochondria? A. They are larger than eukaryotic ribosomes B. They are smaller than eukaryotic ribosomes C. They are similar to prokaryotic ribosomes D. Nothing. They are the same as other ribosomes in the eukarytotic cell.

B and C They are the same size and prokaryotic ribosomes! The ribosomes found in the mitochrondria and chloroplasts are smaller than normal eukarytotic ribosomes. They are the same size (70S) as prokaryotic ribosomes. This is one piece of evidence that supports the endosymbiotic theory, which states that organelles arose when smaller cells were engulfed by larger cells. The smaller cells were able to survive inside the larger cell, providing some advantage to that larger cell. Over time, the smaller cell became a permanent resident and lost its ability to survive on its own. This theory is also supported by the size of these organelles (similar to bacteria), the presence of unique DNA in the mitrochondria and chloroplasts and the fact that these organelles can replicate independently.

Select the major features of a eukaryotic cell. A. Lack membrane bound organelles B. DNA found in the nucleus C. DNA associated with histones D. Cell walls usually contain peptidoglycan E. Chemically simple cell walls F. Divide by binary fission G. Divide by mitosis H. DNA is typically a single, circular chromosome

B, C, E, and G Eukaryotic cells contain membrane-bound organelles. Their DNA may exist as one or more circular or linear chromosmes that are surrounded by the nuclear membrane. Additionally, eukaryotic DNA is associated with histones. Eukaryotic cells have chemically simple cell walls (such as cellulose in plant cell walls) and the cells divide by mitosis or meiosis. Prokaryotic cells generally lack membrane-bound organelles. Their DNA usually exists as a singular, circular chromosome that is not enclosed by a membrane. Additionally, prokaryotic DNA is not associated with histones. The cell walls of prokaryotes usually contain peptidoglycan and the cells divide by binary fission.

Which of the following may be found in eukaryotic cells, but not in prokaryotic cells? (Select all that apply.) A. Cytoplasm B. Mitochondria C. Nucleus D. Cytoplasmic membrane E. Flagella F. DNA G. Ribosomes H. Endoplasmic reticulum I. Golgi body

B, C, H, and I Eukaryotic cells contain membrane-bound organelles, including the nucleus, mitochondria, endoplasmic reticulum, and Golgi body, among others. Each organelle is responsible for a particular function and contains the necessary enzymes for this function. Prokaryotes lack these organelles and similar cellular functions occur in the cytoplasm.

This is Epulopiscium fishelsoni, an organsism found in the gut of the Red Sea surgeon fish. It is 80 µm x 600 µm. Based only on this information, how would you classify this organism? A. Prokaryote B. Eukaryote C. Virus

B. Eukaryote

Which of the following statements is true? (Select one.) A. There is no difference between fungal spores and bacterial endospores. B. Bacterial endospores are used for reproduction C. Fungal spores are used for reproduction

C A single bacterial cell gives rise to a single endospore and the vegetative cell is destroyed in the process. This endospore germinates into a single vegetative cell. The formation of bacterial endospores is not a method of reproduction as there is no increase in the number of cells. Conversely, in fungi, one organism can produce many spores. Each of these spore then goes on to germinate into a new fungus. The parent organism still survives and many new organisms result. Thus, fungal spore formation is a method of reproduction.

Which of the following statements about bacterial endospores is TRUE? A. Endospores are used for reproduction B. A cell can produce many endospores C. Endospores allow a cell to survive environmental changes by producing a dormant period D. A cell produces one endospore and keeps growing E. Endospores are easily stained using a Gram stain

C Bacterial endospores are specialized "resting" cells. They are dormant and do not actively grow or multiply. Endospores can survive exposure to a variety of conditions, including heat, cold, desiccation, radiation, and toxic chemicals. Bacterial endospores are not reproductive structures. During sporulation, a single vegetative cell produces a single endospore. When the endospore is released, the vegetative cell is destroyed. The thick protective layers of a bacterial endospore prevent endospores from being stained using normal staining methods, like the Gram stain. Special procedures must be used to stain and visualize bacterial endospores.

Why should bacterial cells not be placed in a solution of pure water? A. The cells will lose water, causing plasmolysis B. The cells will lose water, causing them to burst C. The cells will take on water, causing them to burst D. The cells will take on water, causing plasmolysis

C Pure water contains no solutes and is therefore a hypotonic solution. When cells are placed in a hypotonic solution, water will move into the cell in an attempt to equalize the solute concentrations on each side of the plasma membrane. This will eventually cause the cell wall to rupture, killing the cell by osmotic lysis

This is a Gram stain from a sputum (mucus) sample of a patient with a respiratory infection. What is the cell shape and arrangement of the bacterial cells in this image? A. Diplobacilli B. Streptobacilli C. Staphylococci D. Cocci in tetrads E. Streptococci F. Individual spirochetes

C The bacterial cells in this image are spherical or cocci in shape. The also appear in clusters, indicating a staphylococcal arrangement. This image shows the bacterium Staphylococcus aureus. This organism is commonly found in the upper respiratory tract and occasionally causes illness in the lower respiratory tract.

Simple diffusion differs from facilitated diffusion in that facilitated diffusion... A. requires ATP. B. does not require ATP. C. moves molecules from an area of high concentration to an area of low concentration. D. moves molecules from an area of low concentration to an area of high concentration. E. requires transporter proteins. F. does not require transporter proteins.

E Both simple diffusion and facillitated diffusion are passive transport processes. They move molecules down their concentration gradient, from an area of high concentration to an area of low concentration. As a passive processes, no energy input (ATP) is required for either simple or facillitated diffusion. Facillitated diffusion, however, requires the use of transporter proteins to move molecules across the cellular membrane. In simple diffusion, molecules can pass directly though the plasma membrane. Active transport mechanisms require energy input in the form of ATP and can move molecules against their concentration gradient, from an area of low concentration to an area of high concentration.

What is the total magnification with a 10X ocular lens when using the high-dry objective (40X)? A.10X B. 40X C. 50X D. 100X E. 400X F. 4000X

E Total magnification is calculated by multiplying the magnification of the ocular lens by the magnification of the objective lens. Therefore: 40X x 10X = 400X total magnification