chp 2

If an E. coli cell has a surface area-to-volume (S/V) ratio of 4.5, and a Pelagibacter ubique has an S/V ratio of 22, which cell will be able to exchange nutrients and wastes with the environment more efficiently?

Pelagibacter ubique, because its cells are smaller

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.

How does water enter and exit a cell?

By simple diffusion or by use of an integral transport protein

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.

False

Predict why dipicolinic acid is only found in endospores and not vegetative cells.

It binds free water and aids in dehydration, which would be detrimental to vegetative cells.

Based on your understanding of the chapter material and the information in the passage, the speed of bacteria, compared with archaeans, is determined by __________.

a combination of structural, functional, and environmental factors

Teichoic acid molecules in Gram-positive cell walls include phosphate groups. Therefore, they will __________.

bind positive ions like Mg2+ and Ca2+

The enzyme lysozyme kills bacterial cells by cleaving the β

breaches of the cell wall and cell lysis due to osmotic swelling

lipopolysaccharide layer

confers strength and protection and is toxic to many animals because of its lipid A component

Identify which of the following is a major function of the cytoplasmic membrane.

energy conservation

Transport proteins can become saturated with solute, have specificity for certain substances, undergo conformational (shape) changes, and are regulated by the cell. What other type of cellular proteins have these four general characteristics?

enzymes

fimbriae

filamentous proteins that are numerous and that extend from the cell to aid in adhesion and pellicle or biofilm formation

pili

filamentous proteins that extend from the cell to serve various functions such as conjugation, transformation, and twitching motility

periplasm

gel-like space with hydrolytic enzymes for nutrient transport and chemoreceptors to direct movement

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

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?

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

Which is valid cell morphology?

spirochete

capsule

tight, sticky matrix of either polysaccharide or protein that allows prokaryotes to attach to solid surfaces and protect from desiccation; not easily washed off

Integral proteins are mostly involved in

transport function.

Although the archaellum is distinct from the bacterial flagellum, researchers believe that it is an example of divergent evolution and related to the type IV pilus of bacteria. What are some similarities and differences between archaella and the bacterial type IV pilus?

Archaella are important for swimming motility, while type IV pili are important in twitching motility. Archaella have genetic similarities revealed by genomic studies.

Archaea and Bacteria both use whiplike structures in similar ways for locomotion, but the structures have different origins. This is an example of convergent evolution. What are some similarities and differences between archaella and bacterial flagella?

Archaella are powered directly by ATP, but bacterial flagella are powered by a proton motive force. Archaella are made of proteins unrelated to the flagellin in bacterial flagella. Archaella flagella have smaller diameters than bacterial flagella.

A bacterium does not continuously swim at one speed in one direction. Different arrangements and structures of flagella contribute to changes in speed and direction when necessary. How does motility relate to flagellation?

Bacteria with peritrichously arranged flagella change direction by changing the flagellar rotation and "tumbling." Bacteria with amphitrichously arranged flagella change direction by periodically stopping to reorient themselves or by changing the flagellar rotation. In general, organisms with polar flagella move more quickly than peritrichously flagellated organisms.

The resistance of bacterial endospores to heat, harsh chemicals, and radiation has several implications, including all EXCEPT which of the following?

Endospores will not survive passage through the stomach.

A cell wall is a requirement for all living bacteria.

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.

False

Which statement best illustrates the importance of a high surface-to-volume ratio that is found in microorganisms?

If a cell has a high surface-to-volume ratio, there will be enough surface area to get the needed nutrients in to support cellular metabolism and the accumulated waste out.

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.

Explain why the presence of a capsule or slime layer would benefit a bacterial cell.

These outer layers can aid in attachment to solid surfaces.

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

They have both hydrophilic and hydrophobic regions.

Staining increases the visible contrast of cells compared with the background. Because the Gram stain results in some types of bacteria staining purple and other types appearing pink, this is called __________ stain.

a differential

The main functions of the bacterial cell wall include all of the following EXCEPT __________. anchoring wall-associated proteins resisting cell lysis due to osmotic forces conferring a specific shape to the cell actively transporting solutes against the concentration gradient

actively transporting solutes against the concentration gradient

Given that the cytoplasmic membrane has a fluid dynamic nature, with phospholipids and proteins able to move about within the bilayer structure, what force or structure keeps the membrane from falling apart?

hydrophilic/hydrophobic forces

S-layer

interlocking molecules of protein or glycoprotein that prevents osmotic lysis and acts as a semipermeable barrier

A glycoprotein

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

slime layer

loose, easily deformed, sticky matrix of either polysaccharide or protein that allows prokaryotes to form biofilms and avoid dehydration

thick cell wall

made of peptidoglycan, enables prokaryotes to withstand high pressures and hypotonic environments without lysing

The cytoplasmic membrane is termed "semi-permeable" because some substances, like water and alcohols, can pass freely through while others, like sugars, amino acids, and ions, cannot. What molecular characteristics largely determine whether or not a substance can pass through the membrane?

size and hydrophobicity

Transport proteins (transporters) require energy expenditure for each molecule of substrate transported. The reason for this energy requirement is __________.

the solute must be transported against a concentration gradient