Microbiology: MCB 3020 Ch 3 Smart Connect HW Flashcards


Set Details Share
created 1 year ago by c_mylinh
20 views
book cover
Microbiology
Chapter 3
updated 1 year ago by c_mylinh
Subjects:
microbiology, biology, science biology
show moreless
Page to share:
Embed this setcancel
COPY
code changes based on your size selection
Size:
X
Show:

1

The most abundant molecule in the cell is

Choose one:

A. proteins.

B. lipids.

C. DNA.

D. water.

D. water.

The model bacterium E. coli is about 70% water by weight.

2

The cell structure immediately external to the cytoplasm is the
Choose one:

A. outer membrane.

B. periplasm.

C. cell membrane.

D. cell wall.

C. cell membrane.

The cell membrane is in contact with the cytoplasm. All the other structures listed, if present, are external to the cell membrane.

3

The fatty acids found in bacterial phospholipids are
Choose one:

A. a mix of saturated and unsaturated fatty acids.

B. identical to fatty acids found in eukaryotic phospholipids.

C. all unsaturated fatty acids.

D. all saturated fatty acids.

A. a mix of saturated and unsaturated fatty acids.

Bacteria membranes may contain a mixture of saturated and unsaturated fatty acids. There are some phospholipids, such as cardiolipin, that are unique to bacteria.

4

Phospholipids with an ether link between glycerol and the fatty acids are found in
Choose one:

A. plants.

B. fungi.

C. bacteria.

D. archaea.

D. archaea.

Archaean phospholipids contain an ether link that strengthens the membrane. In bacteria and eukaryotes, such as plants and fungi, an ester link bridges the link between fatty acids and glycerol.

5

Which class of molecules can directly cross the cell membrane without the aid of transport proteins?
Choose one:

A. Uncharged gasses

B. Ions

C. Amino acids

D. Sugars

A. Uncharged gasses

Polar sugars and charged amino acids and ions cannot directly cross the cell membrane. Uncharged gasses can directly cross the cell membrane.

6

Which of the following is NOT a function of the cell membrane?
Choose one:

A. Production of proteins

B. Detection of environmental signals

C. Transport of molecules into and out of the cell

D. Separation of charge across the membrane

A. Production of proteins

The cell membrane has many functions but protein production is not one of them. Ribosomes are responsible for the production of proteins.

7

Aspirin, like many pharmaceutical drugs, can access the cell because it is a weak acid. This occurs because
Choose one:

A. it is carried by water during osmosis.

B. as a weak acid it can cross the membrane when in its uncharged form.

C. it disrupts the membrane enough to squeeze through.

D. it is a small uncharged molecule.

B. as a weak acid it can cross the membrane when in its uncharged form.

Weak acids and bases can occur in charged and uncharged forms. When charged they cannot cross the membrane, but they can when uncharged.

8

As temperatures drop, membrane fluidity decreases. Which of the following changes to phospholipids will help maintain correct bacterial membrane fluidity under cold temperatures?
Choose one:

A. An increase in the length of the fatty acid tails

B. A switch from ester linkages between fatty acids and glycerol to ether linkages

C. An increase in unsaturated fatty acids

D. Cyclization of part of the fatty acid chain to form a planar ring

C. An increase in unsaturated fatty acids

Unsaturated fatty acids can introduce kinks into the fatty acid tails that prevent tight packing and increase fluidity.

9

The bacterial cell wall is composed mainly of
Choose one:

A. lipopolysaccharides.

B. peptidoglycan.

C. chitin.

D. cellulose.

B. peptidoglycan.

Peptidoglycan is a major component of bacterial cell walls. Cellulose is found in plant cell walls and chitin in fungal cell walls. Lipopolysaccharides are found in the outer membrane of Gram-negative bacteria.

10

The major function of the cell wall is to
Choose one:

A. allow for bacterial motility.

B. serve as a barrier to prevent entry of molecules into the cytoplasm.

C. constrain bacterial cell growth.

D. serve as a rigid barrier to prevent cell lysis.

D. serve as a rigid barrier to prevent cell lysis.

The cell wall is highly porous to molecules and does not provide for bacterial mobility. It does help the bacterial cell withstand interior turgor pressure and thus helps prevent cell lysis. The cell wall continues to expand to accommodate bacterial cell growth.

11

The lipopolysaccharides are found in the
Choose one:

A. inner membrane.

B. cytoplasm.

C. periplasm.

D. outer membrane.

D. outer membrane.

The lipopolysaccharides are only found in the outer membrane of Gram-negative bacteria.

12

The surface layer (S-layer) of prokaryotes
Choose one:

A. is composed primarily of saccharin.

B. is found only in archaea.

C. may be lost from bacteria cultured in the lab.

D. is present all the time in all bacteria.

C. may be lost from bacteria cultured in the lab.

The S-layer is found in many free-living prokaryotic species. However, due to lack of selection pressure, the S-layer may be lost in cultured bacteria.

13

Which of the following cellular components is considered an endotoxin that is harmless as long as the pathogen remains intact but when released by a lysed cell overstimulates host defenses, which may result in a lethal endotoxic shock?
Choose one:

A. Inner membrane phospholipids

B. The cell wall

C. Periplasmic proteins

D. Lipopolysaccharides

D. Lipopolysaccharides

Lipopolysaccharides are of crucial medical importance because they act as an endotoxin.

14

Penicillin’s mode of action is to inhibit
Choose one:

A. cell wall cross-link formation.

B. DNA replication by allosterically binding to DNA polymerase.

C. translation by binding to the 30S ribosomal subunit.

D. translation by binding to the 50S ribosomal subunit.

A. cell wall cross-link formation.

Penicillin inhibits the transpeptidase that cross-links peptidoglycan peptides. Other antibiotics may target ribosomal subunits.

15

Which one of the following proteins would be found in the outer membrane of Gram-negative bacteria?
Choose one:

A. Amino acid transporters

B. ATP synthase

C. Amino acid synthetic enzymes

D. Peptide porins

D. Peptide porins

The outer membrane is not as selective as the inner membrane. It contains porins that admit larger molecules. Both ATP synthase and amino acid transporters are found in the inner membrane. Amino acid synthetic enzymes are cytoplasmic.

16

The idea that the bacterial genome is “loose” in the cytoplasm is incorrect because
Choose one:

A. the DNA is attached to the cell envelope and organized into domains through supercoiling and DNA-binding proteins.

B. bacterial cells have a nucleus.

C. the DNA is usually condensed into a chromosome.

D. attached ribosomes prevent tangling of the DNA.

A. the DNA is attached to the cell envelope and organized into domains through supercoiling and DNA-binding proteins.

Prokaryotic cells like bacteria are defined by not having a nucleus, but the DNA is organized in several ways, including attachment to the envelope, supercoiling, and DNA binding proteins arranging the genome into domains. The circular chromosome may be regionally condensed, but not the whole thing. Ribosomes bind mRNA during translation to produce proteins.

17

In bacterial cells,
Choose one:

A. transcription and translation occur together but not while DNA replication is occurring.

B. transcription, translation, and DNA replication can all occur at the same time in the same cell compartment.

C. transcription, translation, and DNA replication are all spatially separate.

D. transcription and DNA replication can occur together, but translation is spatially separate from transcription and replication.

B. transcription, translation, and DNA replication can all occur at the same time in the same cell compartment.

Bacteria have a single compartment, the cytoplasm, where transcription, translation, and replication can all take place at the same time.

18

Why do bacteria usually contain an even number of replisomes?
Choose one:

A. Bacteria need only one replisome; the other serves as a backup copy.

B. DNA is double-stranded and each single strand requires its own replisome.

C. Because replication is bidirectional, there are two replication forks emanating from the origin of replication.

D. There are two copies of the gene that codes for DNA polymerase, an important enzymatic protein component of replisomes.

C. Because replication is bidirectional, there are two replication forks emanating from the origin of replication.

As DNA unwinds at the origin of replication, replication proceeds in both directions around the genome. This bidirectional replication requires two replisomes, one for each replication fork. Each replisome contains two DNA polymerases, one for each strand of DNA.

19
card image

In the image below of a dividing bacterium, what structure is indicated by the arrows?

Choose one:

A. The flagellum

B. The septum

C. The replisome

D. The origin of replication

B. The septum

The septum forms the division between the two new cells.

20

The terms “peritrichous,” “lophotrichous,” and “monotrichous” describe the
Choose one:

A. distribution of flagella around a bacterium.

B. distribution of the nucleoid within a bacterium.

C. shape of bacterial cells.

D. means by which a bacterium obtains energy.

A. distribution of flagella around a bacterium.

Peritrichous bacteria have randomly distributed flagella, and lophotrichous bacteria have flagella at one or both ends. Monotrichous bacteria have a single flagellum.

21

Bacterial flagella
Choose one:

A. do not require any energy to move.

B. are identical in form and function to eukaryotic flagella.

C. can propel bacteria toward a food source.

D. move in a whip-like fashion.

C. can propel bacteria toward a food source.

Bacterial flagella can move the bacteria in a directed fashion termed “chemotaxis.” The energy for flagellar rotation is provided by the proton motive force. Bacterial flagella differ in structure from eukaryotic flagella. Bacterial flagella rotate while eukaryotic flagella move in a whip-like motion.

22

A bacterial species is discovered that contains thylakoids and carboxysomes. It can be assumed from the presence of these structures that this bacterium
Choose one:

A. can orient along Earth’s magnetic fields.

B. is pathogenic.

C. can attach to a nonliving substrate.

D. is capable of photosynthesis.

D. is capable of photosynthesis.

The presence of thylakoids (intracellular membranes containing photosynthetic pigments) and carboxysomes (containing carbon-fixation enzymes) suggests that the organism is photosynthetic.