n metabolism

Question 1

What is nitrogen fixation?

Answer 1

The process of converting atmospheric nitrogen (N₂) into ammonia (NH₃) or ammonium (NH₄⁺), which can be incorporated into organic molecules like amino acids.

Question 2

Why is nitrogen fixation biochemically challenging?

Answer 2

Nitrogen (N₂) has a very strong triple bond (N≡N), making it inert and difficult to break, requiring high energy to fix it into usable forms for organisms.

Question 3

What are the primary natural sources of nitrogen fixation?

Answer 3

Microorganisms (67%), lightning (10%), and industrial processes (23%).

Question 4

How is nitrogen fixed in microorganisms?

Answer 4

By nitrogenase, an enzyme complex that reduces N₂ to NH₄⁺ using electrons from reduced ferredoxin and ATP.

Question 5

What are root nodules, and how are they involved in nitrogen fixation?

Answer 5

Root nodules are structures in legume plants where nitrogen-fixing bacteria live symbiotically, fixing nitrogen and providing NH₄⁺ to the plant in exchange for carbohydrates.

Question 6

What is the Haber process?

Answer 6

An industrial process for fixing nitrogen, where N₂ is combined with hydrogen (H₂) under high pressure and temperature to produce ammonia (NH₃).

Question 7

How is nitrogen incorporated into amino acids in plants and microorganisms?

Answer 7

Plants and microorganisms reduce nitrate (NO₃⁻) to NH₄⁺ via nitrate reductase and nitrite reductase enzymes.

Question 8

What is the role of glutamate in nitrogen assimilation?

Answer 8

Glutamate is synthesized from NH₄⁺ and α-ketoglutarate via glutamate dehydrogenase and is a key precursor for the synthesis of other amino acids.

Question 9

What enzyme is involved in the conversion of NH₄⁺ to glutamate?

Answer 9

Glutamate dehydrogenase.

Question 10

What is transamination?

Answer 10

The transfer of an amino group (–NH₂) from glutamate to α-keto acids to form other amino acids, a crucial process in amino acid metabolism.

Question 11

What is the primary nitrogen donor for most amino acids?

Answer 11

Glutamate is the main nitrogen donor for other amino acids via transamination.

Question 12

What are some examples of amino acids that are derived from glutamate?

Answer 12

Glutamine, proline, and arginine.

Question 13

How does nitrogen fixation in microorganisms differ from industrial nitrogen fixation?

Answer 13

Microorganisms use the nitrogenase enzyme and ATP to reduce N₂ to NH₄⁺ in an energy-intensive, anaerobic process, while industrial nitrogen fixation (Haber process) uses high pressure, temperature, and an iron catalyst to produce ammonia.

Question 14

What is the role of leghaemoglobin in nitrogen-fixing plants?

Answer 14

Leghaemoglobin maintains anaerobic conditions in root nodules, protecting the nitrogenase enzyme from oxygen, which would inhibit its function.

Question 15

What role does the citric acid cycle (TCA cycle) play in amino acid biosynthesis?

Answer 15

The intermediates of the citric acid cycle, such as α-ketoglutarate and oxaloacetate, are key precursors in the synthesis of amino acids like glutamate, aspartate, and others.

Question 16

How is nitrogen utilized in protein metabolism?

Answer 16

Nitrogen is incorporated into amino acids, which are then used to synthesize proteins in animals, playing a crucial role in cellular functions.

Question 17

What are the main steps in amino acid biosynthesis?

Answer 17

The incorporation of ammonia (NH₄⁺) into amino acids involves initial steps by enzymes like glutamate dehydrogenase and glutamine synthetase, followed by transamination and other modifications to form various amino acids.

Question 18

What are the major metabolic precursors for amino acids in bacteria and plants?

Answer 18

The major metabolic precursors include intermediates from glycolysis and the citric acid cycle, such as 3-phosphoglycerate, pyruvate, α-ketoglutarate, and oxaloacetate.

Question 19

Which enzyme is responsible for the incorporation of NH₄⁺ into glutamine?

Answer 19

Glutamine synthetase.

Question 20

What are some examples of essential amino acids that must be obtained from the diet?

Answer 20

Examples include leucine, valine, lysine, and tryptophan.

Question 21

What is the role of cofactors in amino acid biosynthesis?

Answer 21

Cofactors like ATP, NADPH, and vitamins play essential roles in the enzymes involved in amino acid biosynthesis, supporting reactions like transamination and reductive processes

Question 22

What are feedback inhibitors in amino acid biosynthesis?

Answer 22

Feedback inhibitors are molecules, often the end products of biosynthetic pathways, that inhibit enzymes in the pathway to regulate the amount of amino acid being produced.

Question 23

What is the importance of nitrogen fixation in the global nitrogen cycle?

Answer 23

Nitrogen fixation is a key process in the nitrogen cycle, as it converts inert atmospheric nitrogen into a form (NH₄⁺) that can be utilized by plants and microorganisms for growth.

Question 24

How does the nitrogen cycle impact agricultural practices?

Answer 24

Nitrogen fixation, through both natural (microbial) and industrial processes, provides essential nitrogen compounds (like ammonium and nitrates) used in fertilizers to support crop growth.

Question 25

Why is nitrogen fixation important for feeding the world’s population?

Answer 25

Nitrogen fixation is crucial for producing ammonia, which is then used to make fertilizers. Fertilizers are essential for growing crops and feeding a large portion of the global population.