Exam 2

Question 1

Walter Sutton was one of the first biologists to clearly propose the idea that:

Answer 1

the hereditary material of a cell resides in its chromosomes

Question 2

Nicotinamide adenine dinucleotide (NAD) is an important molecule in the overall metabolism of cells because it acts as a(an):

Answer 2

intracellular hydrogen-atom carrier molecule

Question 3

All of the following enzymes are essential participants in DNA replication at the replication forks in the E. Coli chromosomes except:

Answer 3

RNA polymerase

Question 4

A chemical compound that slows down an enzyme’s activity, and its effect can be reversed by adding more of the enzyme’s substrate, is called a(an):

Answer 4

competitive inhibitor

Question 5

In autotrophy, carbon dioxide is reduced to cellular material that is approximately at the oxidation-reduction level of carbohydrates. Given our discussion about heterotrophic metabolism in lecture, what unique problem would these organisms need to solve?

Answer 5

how to obtain extra hydrogen atoms (electrons) for CO2 reduction

Question 6

Ethylene oxide is most commonly used to sterilize:

Answer 6

plasticware

Question 7

Filters remove microbes from fluids (liquids and gases) due to:

Answer 7

Two or more are correct

Question 8

If a microbe (such as yeast) carries out an essentially pure ethanol fermentation through the Emden-Meyerhof pathway with glucose as the carbon and energy source, what is the other required end product in the fermentation?

Answer 8

Carbon Dioxide

Question 9

Why would CO2 be the required end product?

Answer 9

The breakdown of pyruvic acid to ethanol would necessarily also produce a one-carbon unit that is released as carbon dioxide.

Question 10

When the chemical composition of dried bacterial cells is determined, the element that will be found in the highest amount is:

Answer 10

Carbon

Question 11

What type of antimicrobial agent is a quaternary ammonium compound?

Answer 11

Surfactant

Question 12

Lack of the enzymes superoxide dismutase and catalase in some bacteria may explain:

Answer 12

the inability of a bacterial species to grow in the presence of oxygen

Question 13

A student finds mold growing on the surface of an orange in his refrigerator at home. Streaks the mold onto PDA plate then leaves the plate on a shelf in the walk-in incubator. Checks the plate and finds no growth. What has gone wrong?

Answer 13

The mold is psychrophilic and does not grow at 37 degrees Celsius.

Question 14

After a microorganism is shifter from anaerobic to aerobic conditions, the rate of its sugar catabolism decreases dramatically. This phenomenon was first reported by Louis Pasteur and is called the Pasteur effect. Based on discussion about metabolism, what is the best explanation for this observation?

Answer 14

The aerobically growing cells are able to obtain the same amount of ATP from far fewer sugar molecules.

Question 15

The enzyme that links the Emden-Meyerhof pathway with the citric acid cycle during aerobic respiration uses which of the following compounds as a substrate?

Answer 15

pyruvic acid

Question 16

What is the mode of action for tetracycline in controlling bacterial infections?

Answer 16

it inhibits protein synthesis

Question 17

In aerobic respiration, the electron transport chain ______ molecular oxygen (O2) and ______ NADH.

Answer 17

reduces; oxidizes

Question 18

The doubling (generation) time of a bacterial culture varies with the:

Answer 18

Two or more are correct (temperature and species)

Question 19

Why do concentrated sugar or salt solutions inhibit microbial growth?

Answer 19

They cause water to flow out of the cell, resulting in shrinkage of the cytoplasm.

Question 20

A certain bacterium, found in a playa lake, grows anaerobically only in the sunlight and assimilates pyruvic acid from the water as its source of carbon. This organism is best described as a:

Answer 20

photoheterotroph

Question 21

All of the following methods are effective ways to achieve sterilization except:

Answer 21

boiling

Question 22

Why is boiling not considered to be a sterilization method?

Answer 22

Boiling (at 100 degrees C) kills vegetative cells but does not destroy endospores.

Question 23

Doubling (or generation) time refers to:

Answer 23

the amount of time it takes for a bacterial population to double in number

Question 24

A sequence of enzyme-catalyzed reactions that is organized as a unit to make a required end product is called:

Answer 24

an enzyme pathway

Question 25

A bacterium produces the following fermentation end products from glucose: ….. The fermentation pattern of this bacterium is best described as a(an):

Answer 25

mixed acid fermentation

Question 26

The primer in DNA replication is:

Answer 26

and RNA starter sequence with a free 3’-OH group

Question 27

What is the mode of action for Penicillin G in controlling bacterial infections?

Answer 27

it inhibits cell wall synthesis

Question 28

Why is penicillin ineffective against fungal infections?

Answer 28

Eukaryotic cell walls do not contain peptidoglycan.

Question 29

The aerobic electron transport chain of E. Coli contains all of the following biochemical components except:

Answer 29

sterols

Question 30

The basic role of transfer RNA (tRNA) in translation is to:

Answer 30

deliver the appropriate amino acids to ribosome

Question 31

Asexual reproduction in yeast usually occurs via the process of:

Answer 31

budding

Question 32

Halogens kill microbial cells primarily by:

Answer 32

inactivating essential enzymes

Question 33

What is a sanitizer?

Answer 33

a chemical agent that reduces microbial populations to safe levels as defined by public health standards

Question 34

Under standardized test conditions, isopropyl alcohol has a phenol coefficient of 0.5 against S. aureus. This means that isopropyl alcohol:

Answer 34

is a less effective disinfectant than phenol against S. aureus

Question 35

The proton gradient represents a form of stored energy because:

Answer 35

Two or more are correct

Question 36

What role did Gerhard Domagk play in the history of antimicrobial chemotherapy?

Answer 36

He discovered the first sulfa drug.

Question 37

The type of metabolism in which the final hydrogen (electron) acceptor used by the cell is always generated by the cell’s endogenous metabolism is called:

Answer 37

fermentation

Question 38

The number of cells per milliliter in an E. coli culture is 1x10^6 when growth begins. The number of cells per milliliter reaches 2x10^9 at the end of growth. The doubling time of the culture is 30 min. How long is the total period growth?

Answer 38

320 minutes

Question 39

When the chromosome replicates, how is the newly made strand related to its template strand?

Answer 39

The two strands have complementary sequences and are antiparallel to each other.

Question 40

Plates of E. coli were irradiated with ultraviolet light to determine the rate of cell killing. No decrease was seen in the number of colonies on the irradiated plates compared to the non-irradiated plates. What mistake did this student make?

Answer 40

He left the lids on the spread plates, and the UV light was unable to penetrate the plastic barrier.