Nitrogen Cycle MCQs

Ans: d) Gram-negative chemolithotrophs

Explanation: Both the ammonia oxidizers and the nitrite oxidizers that are used in the oxidizing of ammonia to the nitrite ammonia-oxidizing bacteria and oxidizing the nitrite to nitrate using the nitrite-oxidizing bacteria respectively are Gram-negative chemolithotrophs. Gram-negative chemolithotrophs belong to large bacterial groups used in the process of oxidation.

Ans: a) 1-4 months

Explanation: Nitrifying bacteria takes a duration of 1 to 4 months to grow at the temperature of 250 to 300 degrees Celsius at incubation. For the growth of the particular bacteria, the inoculum which tends to be relatively large is taken into consideration. The incubation process to an extent occurs in the dark.

Ans: a) True

Explanation: Deamination is the process of eliminating the amino group from the amino acids. Alanine yields pyruvic acid and ammonia as the product in the presence of alanine deaminase as its deamination reaction products. The enzyme which is responsible for converting the alanine to pyruvate is alanine aminotransferase. The pyruvate has four metabolic fates.

Ans: b) Denitrification

Explanation: Denitrification is the process of converting nitrates into nitrogen that tends to be in the gaseous state. For successful completion, this process requires several species of bacteria including pseudomonas, agrobacterium, bacillus, and many others.

Ans: c) Rhizobium trifolii

Explanation: The genus Rhizobium bacteria along with the legumes such as the Rhizobium trifolii successfully execute the symbiotic nitrogen fixation process. The nitrogen-fixing bacteria is responsible for converting the atmospheric nitrogen gas into ammonia or fixed nitrogen compounds.

Ans: a) Nitrospina gracilis

Explanation: Nitrospina gracilis falls under the category of nitrite-oxidizing bacteria that are used in the process of oxidizing nitrite into the nitrate. The ammonia-oxidizing bacteria are the ones that are used to oxidise the bacteria in the nitrogen cycle and remove the nitrogen in the marine sediments.

Ans: c) Component II is called the MoFe protein

Explanation: Component II is a smaller molecule of the nitrogenase enzyme complex that acts as a nitrogenase reductase. It is also designated the Fe protein and both of the molecules can’t activate without the presence of each other. Sulphur is present in both molecules.

Ans: c) Acidic pH

Explanation: As the soil contains the organic matter in abundance, in higher temperatures, in alkaline or neutral pH, the denitrification process is enhanced in the soil. Denitrification depicts the dual effect when exposed to oxygen. The process of converting the nitrates into nitrogen is known as Denitrification using bacteria.

Ans: b) False

Explanation: Nitrosococcus nitrosus comes under the category of ammonia-oxidizing bacteria. These bacteria tend to have an extensive system of membranes in the cytoplasm. They also form cysts and zooglea frequently. Nitrite-oxidizing bacteria are the bacteria that are used to oxidise nitrite. It is used in the second step of nitrification.

Ans: a) Nitrification

Explanation: The process of converting ammonia to nitrite and then back to the nitrate is known as nitrification which is completed through the specialised bacteria and the ammonia is obtained when the organic nitrogen sources get a breakdown. NH3(ammonia) first tends to produce NO₃^- (nitrite) and yields NO₃^- (nitrate).

Ans: d) Denitrification

Explanation: The process of converting nitrates into nitrogen is known as Denitrification. It is one of the microbial processes which tend to reduce both the nitrates and the nitrites into the nitrogen in the gaseous state. This process requires denitrifying bacteria like pseudomonas and thiobacillus for successful conversion.

Answer: c) 16

Explanation: The amount of ATP molecules that are used in fixing one nitrogen molecule is 16 moles. ATP refers to adenosine triphosphate which uses 16 moles for the reduction of every mole of nitrogen.

Ans: b) Nitrobacter

Explanation: The process of converting the nitrites into nitrates is done with the help of Nitrobacter. Nitrobacter is one of the chemoautotrophic bacteria which is rod-shaped and is gram-negative. They are found in soil and water and help in the oxidation of ammonium to nitrite followed by nitrite to nitrates.

Ans: a) Ammonia from amino acids

Explanation: Ammonification is the process of generating ammonia from amino acids. In this process, the bacteria are responsible for yielding ammonia from the amino acids using the process of decomposition. These bacteria act on the dead organisms that have nitrogen-containing chemicals.

Ans: c) N₂ to NH₃

Explanation: Nitrogen fixation is a process that converts the nitrogen gas into ammonia or NH₃ with the help of the nitrogenase protein complex or Nif or it can be said that Nitrogen fixation is the procedure of fixing N₂ (nitrogen) to NH₃ (ammonia). This process takes place with the help of two enzymes namely Nitrogenase and hydrogenase.

Ans: b) Atmosphere acts as a major reservoir for the plants

Explanation: The correct statement is that the Atmosphere acts as a major reservoir for the plants. Plants need carbon dioxide, phosphate, and other inorganic substances. These necessities of the plants cannot be fulfilled without the atmosphere. The atmosphere tends to be the most important reservoir for the survival of the plants and acts as one of the most found nutrients for the plants.

Ans: c) Gnetum

Explanation: Gnetum in general, does not have symbiotic nitrogen-fixing cyanobacteria. Cyanobacteria are bacteria commonly found in freshwater, marine, and terrestrial environments and are also called oxygenic photosynthetic bacteria. They can be used in fixing atmospheric nitrogen.

Ans: b) Nitrogenase and hydrogenase

Explanation: The important enzymes which are responsible for the process of nitrogen fixation are Nitrogenase and hydrogenase. Microbes tend to have the nitrogenase enzyme. It is one of the ATP-dependent enzymes that help in the conversion of dinitrogen to ammonia.

Ans: d) All of the above

Explanation: Plants absorb nitrogen in the form of nitrates, ammonium, and nitrites. Nitrate is one of the most used forms when it comes to absorbing the nitrogen in plants as it can be lost to groundwater easily. Proteins consist of the ammonium that a plant consumes and cannot be lost by the soil easily.