Question

84. ________ was the first to describe microorganisms, while ________ was the first person to see bacteria.

a. Antoni van Leeuwenhoek / Robert Hook

b. Antoni van Leeuwenhoek / Robert Koch

c. Robert Hooke / Antoni van Leeuwenhoek

d. Robert Koch / Antoni van Leeuwenhoek

85. Archaea and Bacteria are unified as prokaryotes in lacking ________ which Eukarya contain, such as golgi.

a. membranes

b. nuclei

c. membrane-enclosed organelles

d. nuclei and membrane-enclosed organelles

86. A bacterial species has a generation time of 20 minutes and is growing exponentially. If there are 10 cells initially how many cells are there after 80 minutes?

a. 30

b. 80

c. 160

d. 200

e. none of the above

87. The growth of almost all bacteria in the environment

a. is limited by cool temperatures

b. is limited by high pH

c. is limited by the availability of one or more nutrients

d. is unlimited because bacteria are metabolically versatile

88. According to Koch’s postulates a microorganism thought to cause a disease in one species of animal.

a. must be seen in samples of blood using a microscope

b. must be isolated in pure culture and then used to cause the same disease in healthy animals

c. must never be found in healthy individuals

d. answers (b) and (c) are correct

89. Antoni van Leeuwenhoek developed and used

a. the first compound microscope

b. the first vaccine to prevent an infectious disease

c. a microscope with a single lens

d. pasteurization to prevent the spoilage of food

90. Gram positive bacteria

a. have a thick cell wall, which retains the crystal violet dye when cells are Gram stained

b. contain teichoic acid in their cell walls

c. appear purple when Gram stained

d. all the above e. none of the above

91. The cell envelope of Gram negative bacteria

a. includes a thick cell wall

b. includes both an inner and outer membrane

c. includes a peptidoglycan layer

d. always includes a capsule made of polysaccharides

e. answers (b) and (c) are correct

92. The cell membrane of bacteria

a. is semi-permeable

b. is usually a lipid bilayer

c. prevents cell lysis due to high intracellular osmotic pressure

d. answers (a) and (b) are correct

e. answers (a) and (c) are correct

93. Regarding early life on Earth,

a. microbial life existed for hundreds of millions of years before plant and animal life

b. microbial life existed long before animals but has been around for about the same amount of time as plants

c. microbial life, plant life, and animal life all appeared at about the same time

d. it is impossible to determine which type of life first appeared.

94. The structure that confers structural strength on bacterial cells is known as the

a. cytoplasmic membrane

b. cell wall

c. ribosome

d. cytoplasm

95. Archaea and Bacteria are unified as prokaryotes in lacking ______________

a. membranes

b. nuclei

c. membrane-enclosed organelles

d. nuclei and membrane-enclosed organelles

96. When a bacterial culture contains only one type of organism, it is called a ______________.

a. mixed culture

b. liquid culture

c. environmental culture

d. pure culture

97. Prokaryotes and eukaryotes

a. have the same kinds of metabolic pathways, but little else in common

b. have nothing in common

c. have many things in common because they share a common ancestor

d. are identical to each other

98. Which of the following statements is true?

a. peptidoglycan is comprised of cross-linked fatty acids

b. the cell walls of most bacteria are composed of peptidoglycan

c. Gram-negative bacteria have a relatively thick layer of peptidoglycan

d. peptidoglycan is found mainly in the cell walls of fungi, algae and plants

e. answers (a) and (b) are both correct

99. The cell membrane of bacteria

a. is semi-permeable.

b. is usually a lipid bilayer

c. prevents cell lysis due to high intracellular osmotic pressure

d. answers (a) and (b) are correct

e. answers (a) and (c) are correct

100. A bacterial species has a generation time of 15 minutes and is growing exponentially. If there are 2 cells initially how many cells are there after 90 minutes?

a. 256

b. 128

c. 64

d. 32

e. none of the above

101. Most bacterial cells reproduce by

a. the budding of daughter cells from a mother cell

b. forming spores that later germinate

c. binary fission

d. production of gametes and sexual reproduction  

102. Which of these are routinely used to obtain a pure culture of bacteria?

a. swan necked flasks

b. agar streak plates

c. dilution plates

d. microscopes

103. The cells of all species of Bacteria and Archaea are very small, and:

a. must be stained before they can be seen using light microscopy

b. can only be seen using electron microscopy

c. can only be seen if they are first Gram stained

d. none of the above

104. Prokaryotes evolved early on in the history of the Earth:

a. so their physiology has little in common with Eukaryotes

b. so many aspects of their physiology also occur in Eukaryotes, which evolved much later in in the history of the Earth

c. and Eukaryotes evolved independently at a much later time in the history of the Earth

d. at about the same time that Eukaryotes first appeared on Earth

Answer 1

84. Robert Hook was the first to describe microorganisms, while Antoni van Leeuwenhoek was the first person to see bacteria.

Antonie Van Leeuwenhoek is known as the father of microbiology. He was the first to discover and observe microorganism in 1673 and scientific experiments was performed with microoorganisms by using single-lensed simple microscopes, designed of his own. Robert Hooke, a peer of Leeuwenhoek, observe microbial life (with microscope) in the form of moulds i.e. a fruiting body.

85. Archaea and Bacteria are unified as prokaryotes in lacking nuclei and membrane-enclosed organelles which Eukarya contain, such as golgi.

Prokaryotic cells are divided into the domains Bacteria and Archaea.

Archaea: ether linkages present in cell membrane contains ; genes and enzymes function more like Eukaryotes; cell wall lacks peptidoglycan; have three RNA polymerases like eukaryotes; and extremophiles

Bacteria: ester bonds present in cell membrane ; cell wall consist of peptidoglycan; have single RNA polymerase.

86. A bacterial species has a generation time of 20 minutes and is growing exponentially. If there are 10 cells initially how many cells are there after 80 minutes?

given that, generation time = 20 min, time = 80 min

therefore we know, generation time = t/n, where n = number of generation

hence, n = 80/20 = 4

Now, n = 3.3 log N/N₀ , N₀= initial population = 10 cells ( given) and N = final population ( to be calculated)

4 = 3.3 (logN - log10) 4/ 3.3 = log N - 1 [ log10 = 1]

log N = 1.212 + 1 = 2.212   log N = 2.212

N = 160 cells

87. The growth of almost all bacteria in the environment is limited by the availability of one or more nutrients.

According to Koch’s postulates a microorganism thought to cause a disease in one species of animal.

answers (b) and (c) are correct

Koch's postulates state that:

• In any disease condition the same pathogen must be present
• The pathogen must be grow in pure culture after isolating from the diseased host.
• The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal.

89. Antoni van Leeuwenhoek developed and used

answer c. a microscope with a single lens

90. Gram positive bacteria

answer d. all the above

Gram-positive bacteria consist of thick cell wall that is made up of thick peptidoglycan layer, which stains purple. Peptidoglycan is a polysaccharide that have two subunits are N-acetyl glucosamine & N-acetyl muramic acid. Gram-positive bacteria are allow to retain the complex of crystal violet-iodine due to the presence of thick peptidoglycan layer, and stains the cells as purple. Gram-positive cell wall composed of high percentage of teichoic acids that are important for integrity of cell wall.Teichoic acids provide the cell wall of gram-positive bacteria an overall negative charge because of the presence of phosphodiester bonds between  monomers of teichoic acid

91. The cell envelope of Gram negative bacteria

e. answers (b) and (c) are correct  

Gram-negative bacteria consists of thin layer of peptidoglycan and lose the complex of crystal violet and iodine during decolorization with the alcohol, and retain the counter stain Safranin, that appear as reddish or pink.

In the Gram-negative Bacteria, the cell wall contains thin peptidoglycan layer surrounded structure by theouter membrane. The outer membrane of Gram-negative bacteria always have a uniquelipopolysaccharide (LPS or endotoxin) component, that is toxic for animals. Presence of outer membrane makes gram negative bacteria more resistance to antibiotic as compared to gram positive.

92. The cell membrane of bacteria

d. answers (a) and (b) are correct

The bacterial plasma membrane is consist of a phospholipid bilayer and hence has all of the essential functions of a cell membrane is acting as a permeability barrier.

93. Regarding early life on Earth,
answer a) microbial life existed for billions of years before plant and animal life.

94. The structure that confers structural strength on bacterial cells is known as the

answer b. cell wall

A cell wall, of not only bacteria but for every organisms, is present outside of the cell membrane. It's an additional layer that provides few strength that lack in cell membrane, due to a semi-rigid structure

96. When a bacterial culture contains only one type of organism, it is called a ______________.

answer d. pure culture

Pure culture, consist of a single species of organism i.e. derived from the mixed culture.