Microbiology Ch.4

How are Gram-positive and Gram-negative flagella different?

A Gram-positive flagellum has only two rings in its basal body; Gram-negatives each have four.

Which of the following scenarios is an example of bacterial motility?

A bacterium moving towards a food source

How is the genetic information of bacterial cells organized differently from that of eukaryotic cells?

Bacterial DNA floats free within the cytoplasm and is not enclosed within a nuclear envelope, whereas eukaryotic DNA is enclosed in a membrane-bound structure known as the nucleus.

The chromosomes line up in the center of the cell during which phase of mitosis?

Metaphase

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

Monotrichous

Which of the following would not move freely across the cytoplasmic membrane?

Positively charged hydrogen ions

How is simple diffusion different from other types of passive transport?

Simple diffusion does not require a permease.

What must happen before a cell can begin mitosis?

The chromosomes must be duplicated.

Why is no energy required in passive transport?

The concentration gradient drives the movement.

Which transport protein employs transporters that move molecules only in one direction?

Uniport and Symport

The correct order of events during meiosis is

prophase I, metaphase I, anaphase I, telophase I, cytokinesis, meiosis II.

Why is ATP necessary for active transport?

ATP provides energy to transfer material against its concentration gradient.

The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?

Anaphase

Which type of active transport protein uses one protein to pump two different molecules?

Antiport and Symport

During meiosis, segments of nonsister chromatids can trade places. This recombination of maternal and paternal genetic material is a key feature of meiosis. During what phase of meiosis does recombination occur?

prophase I.

Which of the following is NOT a classic sign and/or symptom of a urinary tract infection?

Blood in the urine

Which molecule shown in the animation, the square or the circle, is moving against its concentration gradient?

Both the circle and the square

How does water enter and exit a cell?

By simple diffusion or by use of an integral transport protein

The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?

Telophase

Membrane transport refers to the mechanisms by which solutes cross the plasma membrane, but there are additional prokaryotic cell structures through which a solute would pass when entering or exiting a cell. Sequence the path of a solute from the external environment to the cytoplasm of a prokaryotic cell.

External Environment: capsule; cell wall; plasma membrane

A cell wall is a requirement for all living bacteria. Choose True or False.

False

At this point in writing your tutorial, you have to find a way to get across to the students the importance of a cell wall to a bacterium. How do you convey that the bacterial cell will be at the mercy of its environment? The cell wall will need to act as a support mechanism to neutralize the inflow or outflow of water that would alter the shape of the cell. The cell cannot search out for a better place in the environment that has more available water; or if there is water that it has a high enough solute concentration that the cell will not gain water. Because that's the problem for a bacterial cell, it cannot control the tonicity due to solute concentrations in the surrounding water. Water will flow in or out depending on solute concentrations and the only thing a bacterial cell can do to keep from collapsing due to water loss or rupturing due to too much water coming in is to have a strong cell wall that will hold its shape regardless of the osmotic pressures. The rigidity of the cell wall will maintain a set shape regardless of water flow. The proteins and lipids that anchor the cytoplasmic membrane to the cell wall will tether the membrane to the peptidoglycan layer so that when environmental conditions result in the loss of water from the cell, the membrane will not collapse in on itself. Similarly, changes in environmental conditions that would result in the inflow of water would expand the volume of the cell to the limits of the cell wall and no more. The composition of the cell wall allows for the expansion and contraction of the cell wall in response to the gain or loss of water from the cell. Choose True or False.

False

With the description of the different cell walls, membranes, and associated proteins set in the students' minds, you now need to introduce them to the idea that the cell wall can also act as a foundation to build things upon. Bacterial appendages require a strong foundation that will offer the support needed to move and function in a dynamic world. For example, flagella are long, whiplike protein structures that are used by many Gram-positive and Gram-negative bacteria for locomotion. In order to function effectively, a flagellum must be firmly anchored to the cell wall. How will you be able to get across the idea that the peptidoglycan cell wall is strong enough to support such a mechanism? With a protein rod that passes through the cell wall and protein rings used to anchor it in the membranes, these basal bodies are the rudimentary biological motors that use ATP power to spin the hook and the flagella attached to it. Bacterial flagella have a biological motor that spins within the cell wall and is powered by ATP. This allows the flagella to spin in a whiplike motion to propel the bacterium. Is this statement True or False? Choose the answer that you think is correct.

False

What structural part of a bacterial flagellum is composed of flagellin?

Filament

Which of the following structural features of E. coli is most responsible for the signs and symptoms of a urinary tract infection?

Fimbriae

Which of the following statements about bacterial flagella is true?

Flagella can rotate 360 degrees.

Which of the following is part of the endomembrane system?

Golgi apparatus

The thickness of this sugar-protein scaffold of peptidoglycan can be used to separate most bacteria into two groups. In your tutorial, you want to illustrate to the students that the thickness of the peptidoglycan layer can be used by microbiologists to differentiate many bacteria by only using an easy staining method that all microbiologists will have to master. This staining procedure, known as the Gram stain, is based on the retention of dyes within the cell wall for a positive result or the rinsing away of the dyes and leakage of the membrane for a negative result. A thicker cell wall will allow for retention of dye crystals that will give the bacterial cell a blue-purple color (positive result), but the thinner cell walls will not allow for the retention of these crystals during rinsing, which will mean that these cells will then be colorless unless another dye that does not require interaction with the cell wall to maintain its retention is used (negative result). In addition to differences in cell wall thickness, Gram-positive and Gram-negative bacteria also differ in the proteins and lipids associated with their cell walls, as well as the composition of their cell membranes. Gram-positive walls are composed of an underlying cytoplasmic membrane, with the thick peptidoglycan layer on the outside offering support. Proteins anchor the membrane and the cell wall together to provide support and structure between the two. Gram-negative staining walls have a different layout. You try to explain in your tutorial that even though these bacteria stain "negative" they do have a thin layer of peptidoglycan sandwiched in between two lipid bilayer membranes. Place each attribute into the bin of the bacterial group it belongs to, based on whether the bacterium is a Gram-positive or a Gram-negative cell.

Gram-positive bacterial cell wall: teichoic acids, thick layer of peptidoglycan, single lipid bilayer membrane Gram-negative bacterial cell wall: dual lipid bilayer membranes, thin layer of peptidoglycan, lipopolysaccharides, and periplasmic space

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 bacterial cell walls?

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

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

Ions

What is the advantage to spirochetes of the corkscrew movement provided by axial filaments?

It allows the cells to move more easily through viscous human tissues and fluids, such as mucus.

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.

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

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

Lophotrichous and monotrichous

Which organelle would play the most direct role in eliminating bacteria engulfed by a phagocytic white blood cell?

Lysosome

How is osmosis different from simple diffusion?

Water movement is driven by the concentration of solutes rather than its own concentration.

Why are most Gram-negative bacteria resistant to the actions of penicillin?

Penicillin is unable to pass through the outer membrane of the cell wall.

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 terms refers to a bacterium moving towards a light source?

Positive phototaxis

The symptoms that Shelly is experiencing result from the interactions between Streptococus pyogenes (a prokaryote) and the cells (eukaryotes) within Shelly's body. Although there are similarities between these two types of cells, there are also important differences. Drag each of the structures to the appropriate bin to indicate whether it is found in prokaryotes only, in eukaryotes only, or in both.

Prokaryote only: Capsule Eukaryote only: Nucleus, Golgi complex, Rough endoplasmic reticulum, and Mitochondria Both Prokaryote and Eukaryote: Flagella, Plasma membrane, Ribosomes, and Cytoplasm

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

Prokaryotes contain peptidoglycan in their cell walls.

This activity requires that you sort cell structures according to whether they are found in prokaryotic cells or eukaryotic cells. Drag each of the following terms into the appropriate box, indicating whether it applies to prokaryotic cells or eukaryotic cells.

Prokaryotic cells: Circular chromosome, not enclosed within a nuclear envelope; Peptidoglycan-containing cell wall; 70s ribosomes; Flagella that rotate, composed of flagellin Eukaryotic cells: Lysosomes; 80s ribosomes; Endoplasmic reticulum; Flagella that wave, composed of microtubules; Mitochondria; Cellulose or chitin-containing cell wall; Linear chromosomes enclosed within a nuclear envelope; Golgi apparatus

The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?

Prophase

The basal body is comprised of which structural component(s) of flagella?

Rod and Rings

Which statement best describes how streptomycin attacks bacterial cells?

Streptomycin targets the 70S ribosome and inhibits protein synthesis

Which type of active transport protein moves two molecules into the cell at the same time?

Symport

How do axial filaments differ from regular bacterial flagella?

The axial filament is located between the cell membrane and the outer 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.

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

The penicillin will not have any impact on Shelly's cells because it targets peptidoglycan, which is found only in bacteria.

Why are receptors on the cell surface necessary for bacterial movement?

The receptors sense the stimulus and send signals to the flagella.

What makes phospholipid membranes good at keeping some molecules out, and allowing others to freely pass?

They have both hydrophilic and hydrophobic regions.

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 membrane transport mechanism requires ATP?

active transport

Nonspecific permeases

allow a variety of molecules to cross the cytoplasmic membrane.

The rings

anchor the flagellum to the cell membrane.

Hydrophobic molecules would enter a cell

by passive transport directly across the membrane.

Pathogenic bacteria

can be identified and classified by differences in their flagellar proteins.

The immune response of a host against an invading bacterium is often triggered by surface components on the bacterium that are recognized as "non-self" or "foreign" by the host. These non-self components, often protein or polysaccharide in nature, are referred to as antigens. The host responds to these antigens by making antibodies that will react with invading bacteria and mark them or tag them for destruction by phagocytes. Indicate the bacterial structures that are likely to be antigens, to which host antibodies bind, marking the invader for phagocytosis.

capsule cell wall flagella fimbriae

Which of the following is NOT characteristic of the glycocalyx found in bacteria?

creates a slimy, slippery coating that prevents bacteria from attaching to surfaces

At the end of the mitotic (M) phase, the cytoplasm divides in a process called _________________.

cytokinesis

The structural framework in a cell is the

cytoskeleton.

Axial filaments are composed of

endoflagella

Meiosis starts with a single diploid cell and produces

four haploid cells.

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

During prophase I of meiosis,

homologous chromosomes stick together in pairs.

An important characteristic of antibacterial drugs is their selective toxicity. If antibacterial drugs were not selectively toxic, then they would kill or interfere with the hosts' cells as well as bacterial cells. Examining cellular differences between bacterial (prokaryotic) cells and host (eukaryotic) cells suggests strategies to achieve selective toxicity. We can capitalize on these differences and take advantage of them in the design of antibacterial drugs Identify antibacterial strategies that would likely be selectively toxic for bacteria.

inhibition of fimbriae synthesis inhibition of peptidoglycan synthesis interfering with translation at 70s ribosomes

A cell preparing to undergo meiosis duplicates its chromosomes during

interphase.

A glycoprotein

is a type of peripheral protein above that can be used as a receptor or in enzymatic functions.

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

Once equilibrium is reached,

molecules move, but there is no net movement in a particular direction

Taxis is

movement towards or away from a stimulus.

There are some structures that are common to all prokaryotic cells, and others that are only found in some bacterial species or strains. Select the structures below that are found in all bacterial cells.

nucleoid cytoplasm plasma membrane ribosomes

Where is the genetic information of the cell stored?

nucleus

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.

As a bacterium approaches a food source, one would expect

runs to become more frequent.

Peptidoglycan is a polymer of millions of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) sugars based on glucose molecules linked together in long chains cross-braced with four amino acids that link individual polymer chains together in a chain-link fence pattern. Layers of cross-braced NAG and NAM sheets are stacked vertically and held together by proteins with lipid anchors attached to the cell's cytoplasmic membrane to form a scaffold of sugars and proteins that is able to hold the bacterial cell's shape, even in response to extreme osmotic pressures. How would you expect a microbiology student to be able to describe the composition of peptidoglycan? What is the composition of the peptidoglycan layers found in the cell wall of bacteria? Pick the answer that lists the composition of the bacterial cell wall.

short amino acid chains, NAG, NAM, and some lipid proteins

Where are lipids made in the cell?

smooth endoplasmic reticulum (ER)

Axial filaments are found on

spirochetes.

Tumbles occur when

the flagella rotate clockwise.

Peritrichous bacteria make a run when

the flagella turn counterclockwise and become bundled.

Integral proteins are mostly involved in

transport function.

Which of the following eukaryotic organelles is correctly matched with its function?

vacuole--storage of materials

A positively charged sodium ion

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