Utilization of Inorganic Nitrogen

Why is nitrogen availability limited?

limited by the abilities of organisms to utilize different inorganic forms of nitrogen, All organisms can convert ammonia (NH₃) to organic nitrogen compounds that is, substances containing bonds. However, not all organisms can synthesize ammonia from the far more abundant forms of inorganic nitrogen dinitrogen gas (N₂),

diazotrophs

The reduction of N₂ to NH₄ carried out only by certain prokaryotes CALLED.

nitrogen economy

supply, demand, turnover, reuse, growth, and maintenance of a steady state.

leguminous plants

Plants that form symbiotic root nodules infected with nitrogen-fixing bacteria (diazotrophs), allowing them to grow without an exogenous nitrogen source.

Rhizobium

A notable genus of diazotrophs (bacteria) that infects the root nodules of leguminous plants to perform biological nitrogen fixation.

Leghemoglobin

An abundant protein found in root nodules that maintains an anaerobic environment by binding to stray oxygen (O₂).

Anaerobic Environment Requirement

Critical in root nodules because the nitrogen-fixing enzymes (like nitrogenase) are extremely sensitive to and damaged by oxygen.

Why rotate crops like clovers, soybeans, or alfalfa with non-nitrogen-fixing crops?

To replenish the soil with nitrogen.

Name three examples of nitrogen-fixing crops used in crop rotation.

Clovers, soybeans, and alfalfa.

Rotating crops like soybeans with non-nitrogen-fixing crops helps to __________ the soil with __________.

Replenish; nitrogen.

Why is N₂ difficult to reduce?

because of the triple bond

nitrogenase

Biological N₂ reduction is catalyzed by these enzymes

Protein turnover

Refers to the continuous cycle of breaking down (degradation) and rebuilding (biosynthesis) proteins within a cell.

Purpose of Protein turnover

It serves as a quality control system to remove and replace proteins that have been damaged by environmental factors (like reactive oxygen species). It is also a crucial biological regulation mechanism; by breaking down specific enzymes, the cell can control metabolic pathways.

do cells store nitrogen?

Unlike carbohydrates and lipids, organisms do not have specialized storage depots for polymeric nitrogen compounds. Because nitrogen is continually lost through catabolism and waste, animals must constantly replenish their nitrogen supply through their diet to maintain "nitrogen equilibrium".

nitrogen equilibrium

The Balance: A well-nourished adult maintains this equilibrium when the nitrogen they consume through their diet (primarily from protein) is equal to the nitrogen they excrete through urine, sweat, and other metabolic processes.

• Daily Target: To maintain nitrogen equilibrium, a healthy 70-kg adult needs to consume about 8 grams of nitrogen a day, which equates to roughly 52 grams of dietary protein.

Consequence of Nitrogen Imbalance

If dietary protein intake drops too low, the body still needs nitrogen. To survive, it begins breaking down existing functional proteins (mostly muscle tissue) to harvest the nitrogen, and these lost proteins are not replaced.