Mastering Microbiology CH 3 Homework

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

A bacterium moving towards a food source

Why is ATP necessary for active transport?

ATP provides energy to transfer material against its concentration gradient.

What is required to access Dynamic Study Modules? A)Enrollment in a course that uses Mastering with Dynamic Study Modules B)Previously signing in from a desktop, if using DSM on the mobile app C) A current Mastering username and password D) All of the above

All of the above

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

Antiport and Symport

What is the primary function of Dynamic Study Modules?

Assess what a student already knows, and where he or she may want to focus additional study

Once equilibrium is reached,

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

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

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

Which of the following statements about bacterial flagella is true?

Flagella can rotate 360 degrees

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

A periplasmic space is found in which of the following?

Gram-negative cells only

Nonspecific permeases

allow a variety of molecules to cross the cytoplasmic membrane.

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

Ions

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? A) It requires ATP. B) It powers the diffusion of water across the cell membrane. C) It requires the use of a transport protein.

It powers the diffusion of water across the cell membrane.

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

Lophotrichous and monotrichous

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

Monotrichous

Taxis is

Movement toward or away from a stimulus.

Which of the following terms refers to a bacterium moving towards a light source?

Positive phototaxis

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

Positively charged hydrogen ions

The region between the outer and inner membranes of a Gram-negative bacterial cell is known as the __________, and it is the location of enzymes that assemble peptidoglycan

Periplasmic space

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

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

Simple diffusion does not require a permease

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

Symport

Why is no energy required in passive transport?

The concentration gradient drives the movement.

A patient is infected with Gram-negative bacteria and is experiencing only mild symptoms. When the patient is given an antibiotic causing lysis of the bacterial cells, he suddenly experiences an increase in inflammation and fever, as well as the formation of blood clots. What explanation best describes what happened?

The lysis of the cells releases lipid A from the lipopolysaccharide layer

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

What role do the teichoic acids play within the cell wall of Gram-positive bacteria?

They serve to stabilize the cell wall and hold it in place

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

Uniport and Symport

How is osmosis different from simple diffusion?

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

Which of the following would contain teichoic acids?

a Gram-positive cell wall

The peptidoglycan cell wall of bacteria is most analogous to _____

a chain-link fence

Peptidoglycans are composed of sugars and _____

amino acids

Which of the following organisms is a prokaryote? fungus protozoa algae archaea both archaea and protozoa

archaea

Which of the following processes requires a channel protein?

both facilitated diffusion and active transport

Hydrophobic molecules move across a membrane

by passive transport directly across the membrane

Which of the following is NOT a characteristic of a eukaryotic cell? A) can undergo transcription and translation simultaneously B) presence of membrane-bound organelles C) presence of a nuclear envelope D) contain chromosomes composed of DNA and histones

can undergo transcription and translation simultaneously

If a eukaryotic cell suffers damage to its mitochondria, which of the following processes of life would be most immediately affected?

energy production

A glycoprotein

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

Which of the following is NOT a characteristic of all living things? motility reproduction metabolism growth responsiveness

motility

The process of bringing a solid substance into a eukaryotic cell is known as __________

phagocytosis

Eukaryotic cells use a process known as (pinocytosis/phagocytosis/exocytosis) to obtain liquids from their environment

pinocytosis

Which of the following statements concerning the characteristics of life is FALSE? A) organisms may not exhibit all of the characteristics of life at all times. B) reproduction is defined as an increase in the size of an organism. C) viruses have some, but not all, of the characteristics of living things. D) living things store metabolic energy in the form of chemicals such as ATP. E) reproduction can occur asexually or sexually in living things.

reproduction is defined as an increase in the size of an organism.

Using a microscope, you observe an amoeba moving toward a food source. This is an example of

responsiveness

As a bacterium approaches a food source, one would expect

runs to become more frequent

Which of the following is NOT a basic process of life? A) metabolism B) growth C) responsiveness D) sexual reproduction

sexual reproduction

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

Axial filaments are found on

spirochetes

One chain of alternating NAGs and NAMs is connected to another chain via _____

tetrapeptides

Tumbles occur when

the flagella rotate clockwise.

Peritrichous bacteria make a run when

the flagella turn counterclockwise and become bundled.

One of the main differences between a Gram-positive and a Gram-negative bacterial cell wall is that the peptidoglycan portion of a Gram-positive cell wall is _____ as compared to a Gram-negative cell wall

thicker

Integral proteins are mostly involved in

transport function

Within the peptidoglycan layer, the crossbridges that connect the chains of alternating sugar molecules extend between _____

two N-acetylmuramic acid molecules

A positively charged sodium ion

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