MicroBio Unit 2

Exam prep for Microbiology Unit 2

In an E. coli cell that has a non-functioning NDH-1 enzyme, the electrons from the oxidations shown here would likely end up where?

HINT

In Organic Acids. In the absence of a functioning electron transport chain, an E. coli cell has the option of "dumping" electrons onto the end product of glycolysis (pyruvate) or one of its derivatives. This alternative to respiration is referred to as fermentation. E. coli conducts mixed acid fermentations during which NAD⁺ is recycled in the generation of organic acids such as succinate and lactate. 

For the electron carrier nicotinamide adenine dinucleotide, NAD⁺ is a/an ____ form that gets ____ to NADH. 

oxidized, reduced NAD⁺ is the oxidized form because it is electron deficient compared to NADH. NADH is the reduced form because it is more electron rich than NAD⁺.

How is citrate created, and at what point in metabolism does this event take place?

Acetyl-CoA reacts with oxaloacetate in the TCA cycle.

The electron transport system is located in the ___ of the prokaryotic cell, and the O₂ that is involved in the process must be ___

cell membrane, intracellular

Which of the following is/are correct for O₂ and its involvement in the electron transport system?

Molecular oxygen is the electron acceptor of the transport system.

The biology of the electron transport system eventually converts O2 into H2O.

Molecular oxygen becomes reduced by the electron transport system.

Rank each of the following in terms of their appearance in the cell during carbohydrate catabolism.

1. Glucose

2. Fructose-1,6-bisphosphate

3. Glyceraldehyde-3-phosphate

4. Pyruvate (Final product of glycolysis)

5. Citric acid (First intermediate of the citric acid cycle)

6. Succinyl-CoA

The oxidoreductase pumps transport electrons and then:

pump protons out of the cell, establishing a proton motive force.

When a cell internalizes energy, that energy can then be converted from one form to another; this statement is ___. Unusable energy is released from the cell in the form of ___.

True, heat

To biosynthesize large macromolecules such as lipids, polysaccharides, polypeptides (protein), and nucleic acid (DNA), what must the cell do?

Fix nitrogen, sulfur, and phosphorus

Spend energy

Assemble carbon skeletons

Reduce carbon skeletons

For every molecule of glucose that enters glycolysis, molecules of ATP are consumed and ___ molecules of ATP are produced, for a net of ___ ATP molecules.

2, 4, 2

Both ATP and NADH are generated during which of the following?

Glycolysis, Krebs Cycle

Chemical potential energy that was initially contained within C-C bonds of glucose is conserved in which molecule(s)? 

Both ATP and NADH

___ has more chemical potential energy than ___.

___-1,6-bisphosphate contains about the ___ chemical potential energy as both glyceraldehyde-3-phosphate molecules

glucose, two pyruvates, fructose, same

Which of the following best relates entropy to the life of the microbial cell?

Cells generally decrease internal entropy and increase external entropy levels.

Which of the following represent(s) a lithotrophic reaction?

CO₂ + 4H₂  → 2H₂O + CH₄

4Fe²⁺ + O₂ + 4H⁺ → 4Fe³⁺ + 2H₂O

FeS₂ + 14Fe³⁺ + 8H₂O → 15Fe²⁺ + 2SO₄^2– + 16H⁺

O₂ + 2H₂ → 2H₂O

Probiotics are live microorganisms that provide health benefits when consumed. Students in a food microbiology class are investigating the practice of making yogurt with Lactobacillus bulgaricus and Streptococcus thermophilus. At which bacterial growth stage would it be best to consume yogurt in order to maximize the health benefits? 

log phase

Anaerobically growing bacteria can grow in which type of medium?

Reduced

Halophilic organisms need high concentrations of which of the following to grow?

Salt

The phases of microbial growth.

Lag, log, stationary, death

What is the difference between facultative anaerobes and aerotolerant anaerobes?

Facultative anaerobes can both respire and ferment, whereas aerotolerant anaerobes only ferment.

If an experiment starts with 6 bacteria cells and ends with 96 bacteria cells, how many generations did the cells go through?

4

What is the name of the process in which bacteria respond to the density of other bacteria in their environment?

Quorum sensing

How many endospores are produced by a vegetative cell?

1

Bacteria enter a cut on a person's hand. The infection will take some time to become noticeable because the bacteria are in which phase?

Lag phase

Haemophilus influenzae requires two growth factors, X (hemin) and V (NAD), which can be found inside red blood cells (RBCs). Optimal growth is obtained on chocolate agar, but H. influenzae grows on standard blood agar media only as satellites around bacterial colonies. Why?

The RBCs in the blood agar may be lysed during growth of other nonfastidious bacteria.

Why are barophiles a relatively newly discovered group of microorganisms?

Until recently, technology that withstands the enormous pressures found in the world’s deepest oceans was not available.

Fastidious microbes are grown on which type of medium?

Enriched

A cell that uses an organic carbon source and obtains energy from light would be called which of the following?

Photoheterotrophs

In which growth phase are bacteria susceptible to antibiotics?

Log

How will the enzymes of thermophilic bacteria fare at human body temperature (37ºC)?

The enzymes will function more slowly than usual. 

A bacterium is grown at temperatures slightly below optimum. How will this change the shape of the growth curve?

The slope of log phase will be less steep.

Human pathogens are considered which of the following?

Mesophiles

Many Gram-negative bacteria can grow on MacConkey agar, but the growth of most Gram-positive bacteria is inhibited. What ingredient in MacConkey agar prevents the growth of Gram-positive bacteria?

Bile salts

___ are associated with the lagging strand. The discontinuous replication is needed due to the required "directionality" of nucleotide polymerization.

Okazaki fragments

Okazaki fragments are synthesized in the ___ direction.

5' → 3'

A  ___ mutation occurs within the coding sequence of a gene, and it results in the identity of the amino acid corresponding to the codon being changed to a different amino acid in that single location.

missense

A ___ mutation is one that occurs within the coding sequence of a gene but does NOT alter the identity of the amino acid that corresponds to the codon.

Silent

Which of the following is/are needed for elongation of RNA synthesis?

RNA polymerase

Bacterial cells replicate DNA using a method called bidirectional semiconservative replication. Part of the replication process is a “proofreading” step in which the new daughter strand is checked against the original parent strand. What is the function of proofreading?

Proofreading prevents mutations in daughter strands.

Which of the following enzymes is responsible for adding deoxyribonucleotides to a growing nucleotide strand during DNA replication?

Polymerase

During DNA replication,

both leading and lagging daughter DNA strands are synthesized in the 5′ to 3′ direction.

A ___ mutation is one that occurs within the coding sequence of a gene and involves the insertion or deletion of a nucleotide. This disrupts codon assignment, so the protein will likely be nonfunctional. 

frameshift

When do genetic mutations occur?

During DNA replication

Why do certain viruses benefit from mutations within their genome, whereas mutations in humans tend to have a negative result?

Viruses have high mutation rates, which help them evade the immune system.

Which of the following enzymes is responsible for creating a short RNA molecule during DNA replication?

Primase

Which of the following RNA species is/are involved either directly or in a regulatory role during translation?

mRNA, rRNA, and tRNA are regularly involved in translation, and sRNA plays a regulatory role.

All types of RNA are created during a process called ___, but only one kind is interpreted as codons by the ribosome to make a protein. 
Which type of RNA is used as a template for protein synthesis?

transcription, mRNA

Which of the following is true of mutations?


They always cause a change to an organism’s genotype.


The production of RNA complementary to a DNA template is known as________________.


transcription

Bacterial chromosomes are

usually circular.

Which of the following is/are considered "reactive oxygen species" (ROS) that tend to react with DNA and induce damage?

H₂O₂ (hydrogen peroxide), •O₂^– (superoxide radical)

Which of the following is the model of DNA replication that best accounts for our current understanding of the genetic replicative process?

Semiconservative

Which repair pathway removes a normal base that was incorrectly paired with the template base during DNA synthesis?

Methyl mismatch repair

plasmids are circular extrachromosomal DNA constructs that are usually smaller than the bacterial chromosome. Usually, a plasmid encodes genetics involved in conferring a survival advantage (e.g., antibiotic resistance). 

when plasmids are transferred from one cell to another, horizontal (or lateral) gene transfer takes place: one cell simply exchanges genetics with another.

Which of the following enzymes is responsible for breaking the hydrogen bonding of the parental double helix during DNA replication?

Helicase

Mutations come in several different physical and structural forms. How do point mutations occur?

They occur spontaneously as well as when bacteria are exposed to radiation or chemicals.