microbiology exam 2

What is needed for two bacterial cells to undergo conjugation?

To undergo conjugation, bacterial cells must be in close proximity to lead to direct, and they must have the F factor that codes for a pilus (duct).

Guanine is a purine and complementary base pairs with _____, which is a _____.

cytosine; pyrimidine

How are Petri dishes/ agar plates sterilized

Ethylene Oxide

The mRNA complement for the codon CGA would be:

GCU

What two classes of drugs disrupts cell walls.

1. Penicillin 2. Cephalosporins

10. Chemical energy for cellular activities in prokaryotes is provided by:

ATP

Briefly describe two methods, whereby bacteria attach to host tissues.

Bacteria can attach to host tissue with fimibriae, which have the tendency to stick to each other and surfaces, and because of their tight adhesion, they are able to infect host tissues. Bacteria can also attach by pili, which use conjugation to create a pilus to connect to another cell.

Ecoli placed in a environment with no glucose

Cyclic AMP (cAMP)

List four characteristics of exotoxins.

Exotoxins are toxic in small amounts, secreted from live cells, can be converted to toxoids, and have highly specific targets and physiological effects

antibiotic restistance mutations occur due to the antibiotic causing the mutation

False

What happens during the elongation stage of translation?

In elongation, 2 charged tRNAs carrying a single amino acid are present in the ribosome. Peptidyl transferase catalyzes the peptide bond between the amino acids, allowing the polypeptide chain to grow. One tRNA will leave the P site, triggering the tRNA on the A site to move to the open P site. Another tRNA will occupy the A site, restarting the process of forming a peptide bond.

What is an Okazaki fragment? How is it generated?

Okazaki fragments are produced when DNA polymerase adds nucleotides to the new strand in the 5' to 3' direction, creating short fragments of DNA. RNA primer must be added to make a new template, so this process is discontinuous.

Briefly describe two methods by which bacteria resist antibiotics.

One method bacteria resist antibiotics is by inactivating drugs by hydrolyzing enzymes in antibiotics, destroying or modifying their structure. Another method is through decreased permeability by controlling their porins. They mediate the passive diffusion of antibiotics in the outer membrane.

Describe peptidoglycan. Which bacterial cell type has a thicker wall: Gram-positive or Gram-negative?

Peptidoglycan consists of polysaccharides that are linked to peptide fragments. This structure provides the main source of structural support to a bacterium. The peptidoglycan is the thickest in a gram-positive cell.

What do we call operon that has against gene it spreads

Repressable

Describe how tetracyclines interfere with bacteria?

Tetracycline blocks the attachment of tRNA on the A site by binding to the 30S subunit, preventing further synthesis of protein.

How is transfer RNA synthesized

Transcription

For bacteria, why do we have to make a distinction between anaerobic respiration and fermentation?

We must be able to differentiate that anaerobic respiration doesn't use oxygen. In fermentation, oxygen is not required, organic molecules are used for the final electron receptor, and little ATP is produced.

Briefly describe negative control in the lac operon when glucose is present and lactose is absent.

When glucose is present and lactose is absent, transcription does not occur. The repressor protein interacts with the promoter, creating a loop configuration, blocking the RNA polymerase. This prevents further transcription.

The operator of an operon is:

a sequence of DNA that is non-coding

What binds at the single origin of replication site in bacterial DNA at the start of replication?

an enzyme complex

In bacteria, the ribosome:

binds to an mRNA even before transcription is completed

Bacterial capsules are typically organized:

carbohydrates

Peptidoglycan is: a. one, complex molecule. b. the principle component of bacterial cell walls. c. made partly of N-acetyl muramic acid (NAM) which is unique to prokaryotes. d. Each of these is true.

d. each of these is true

Which of the following pathways occurs in the bacterial cytosol? a. glycolysis b. Krebs cycle c. fermentation d. Each of these occurs in the cytosol

d. each of these occurs in the cytosol

Eukaryotic flagella have an internal motor that relies on microtubule sliding motion with the help of motor proteins. Prokaryotic flagella consists primarily of the protein ______ and functions more like a ______.

flagellin, rotor

Electrons that pass through the electron transport chain in bacterial membranes, initially come from:

glucose

Which of the following is not a product of gene expression? a. protein b. enzyme c. tRNA d. glucose

glucose

A fermentation pathway begins with:

glycolysis

The toxic portion of the lipopolysaccharide molecule is the:

lipid A

Transcription is regulated in prokaryotes by:

repressor proteins

DNA is compacted into a bacterial cell by:

supercoiling

Before glucose is broken down by the cell respiration pathway it must first be:

taken into the cell by glucose transporters

How are substances moved through the Gram negative outer membrane?

through highly regulated pores in the membrane

RNA polymerase catalyzes:

transcription

When pieces of DNA that leave one part of the genome and insert in another part, they are engaging in:

transposition