Question 1

Inorganic nitrogen must be converted to ammonia to be used by a cell.

Accepted Answer

Inorganic nitrogen, such as nitrate or nitrite, needs to be converted to ammonia through a process called nitrogen fixation before it can be used by cells. Ammonia is then incorporated into organic molecules, such as amino acids and nucleotides, which are essential building blocks for various cellular processes.

Question 2

Whether an organism is a phototroph or a chemotroph depends on its source of energy.

Accepted Answer

This statement is true. A phototroph obtains energy from sunlight, while a chemotroph obtains energy from chemical compounds.

Question 3

The methanogens, producers of methane gas, require environments that

Accepted Answer

Methanogens are strictly anaerobic, meaning they cannot survive in the presence of oxygen. They require hydrogen gas (H2) and/or carbon dioxide (CO2) as electron donors and carbon sources, and produce methane gas (CH4) as a waste product. Therefore, the only option that describes the correct environmental conditions for methanogens is E: are anaerobic with hydrogen gas and CO2.

Question 4

Whether an organism is an autotroph or heterotroph depends on its source of nitrogen.

Accepted Answer

Whether an organism is an autotroph or heterotroph depends on its source of energy, not nitrogen. Autotrophs produce their own energy from sunlight or other inorganic sources, while heterotrophs rely on consuming organic matter for energy. The source of nitrogen is important for life, but does not determine whether an organism is an autotroph or heterotroph.

Question 5

Phosphorus is one of the major elements needed in larger quantities by microorganisms.

Accepted Answer

Phosphorus is an essential macronutrient for microorganisms and is required in larger quantities for their growth and survival. It plays a crucial role in various cellular processes such as energy transfer, DNA synthesis, and signal transduction.

Question 6

This microbe is photosynthetic, but in the absence of light it can use organic compounds as an energy source.Its carbon source is an organic compound.The appropriate classification for this organism would be ______.

Accepted Answer

This microbe is still photosynthetic, but can also use organic compounds as an energy source in the absence of light. Since its carbon source is organic compounds, it cannot be a photoautotroph or chemoautotroph. Therefore, the best choice would be photoheterotroph.

Question 7

Which of the following is not a major element of a microbial cell?

Accepted Answer

Oxygen, carbon, hydrogen, and nitrogen are major elements present in microbial cells. However, copper is not a major element and is only required in trace amounts for some microbial processes.

Question 8

An important mineral ion found in the cytochrome pigments of cellular respiration is ______.

Accepted Answer

Iron is an important mineral ion found in the cytochrome pigments of cellular respiration. It is a crucial component of heme, which is part of the cytochrome molecule and is responsible for transporting electrons during cellular respiration.

Question 9

Lithoautotrophs use inorganic nutrients for carbon and energy sources.

Accepted Answer

Lithoautotrophs are organisms that can use inorganic compounds (such as carbon dioxide and nitrogen gas) as their source of carbon and energy. They do not require organic nutrients like heterotrophs do. This process is known as chemosynthesis. Examples of lithoautotrophs include certain types of bacteria that can live in extreme environments such as deep sea vents and hot springs.

Question 10

Many lakes in the United States are suffering from periodic algae blooms, which can be thought of as an infection of the lake.Although the algae are naturally-occurring in the lake, when adjacent farm fields are over-fertilized with diammonium phosphate, the run-off deposits these nutrients in the lake, allowing the algae to grow without limit.Which of the following statements is incorrect regarding the overgrowth of algae?

Accepted Answer

The algae are actually autotrophs, meaning they can produce their own food through photosynthesis. Heterotrophs rely on consuming other organisms for energy.

Question 11

Growth factors

Accepted Answer

Growth factors cannot be synthesized by the organism, and therefore must be obtained through the diet or environment.

Question 12

An important mineral ion that is a component of chlorophyll and serves as a stabilizer of membranes and ribosomes is ______.

Accepted Answer

Magnesium is an important mineral ion that is a component of chlorophyll and serves as a stabilizer of membranes and ribosomes. Zinc, iron, calcium, and potassium are important minerals but do not have these specific functions in the cell.

Question 13

An organic nutrient that cannot be synthesized by the organism and must be provided is called a(n) ______.

Accepted Answer

Growth factors are organic nutrients that cannot be synthesized by the organism and must be provided. Elements are the basic building blocks of all matter and can include both organic and inorganic substances. Trace elements are required in small amounts but are still considered elements. Macronutrients are required in large amounts and can be both organic and inorganic compounds. Compounds refer to any substance made up of two or more elements.

Question 14

A saprobe differs from a parasite in that

Accepted Answer

A saprobe obtains nutrients from dead organic matter, while parasites rely on living hosts for nutrients. Therefore, a saprobe differs from a parasite in that a saprobe derives nutrients from dead plants and animals, but a parasite derives nutrients from living plants and animals. The other choices are incorrect.

Question 15

An organism that uses CO₂ for its carbon needs and sunlight for its energy needs would be called a ______.

Accepted Answer

The organism described is a photoautotroph since it uses sunlight for energy and CO₂ for carbon, which means it can produce its own organic compounds through photosynthesis. A chemoheterotroph obtains both its energy and carbon from organic compounds, while a halotroph obtains its energy from inorganic compounds and a saprobe obtains its nutrients from dead or decaying matter.

Question 16

Most of the dry weight of a microbial cell is from ______.

Accepted Answer

The majority of a microbial cell's dry weight comes from organic compounds, such as proteins, lipids, and nucleic acids. Water typically makes up a large portion of a cell's weight overall, but once it is removed to get to the "dry weight," the organic compounds make up the bulk of the remaining weight. Minerals, inorganic compounds, and salts usually make up a smaller fraction of the cell's dry weight.

Question 17

Which compound has the highest concentration in a cell?

Accepted Answer

Water (H2O) is the most abundant compound in cells, making up about 70-90% of a cell's mass, thus having the highest concentration.

Question 18

Following the Deepwater Horizon accident in the Gulf of Mexico in 2010, bioremediation was used to eliminate much of the oil from the contaminated water.To encourage the growth of oil-degrading microbes, "fertilizer" including iron and nitrogen was added to the water.Which of the following statements regarding the growth of these microbes is incorrect?

Accepted Answer

Iron is a micronutrient, not a macronutrient, for oil-degrading microbes, so large amounts are not needed.

Question 19

Calcium is required for bacteria because it

Accepted Answer

Calcium is required to stabilize the cell wall in many bacteria. It helps in maintaining the structural integrity of the cell wall and preventing damage to the bacterial cell. Calcium may also be involved in the synthesis of certain components of the cell wall, such as the peptidoglycan layer.

Question 20

Microorganisms require large quantities of ______ for use in cell structure and metabolism.

Accepted Answer

D

Quiz 7: Microbial Nutrition, Ecology, and Growth