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Chapter 32: Problem 23

The urea cycle is also referred to as the _____ cycle. a. Krebs b. ornithine c. citric acid d. uric acid

Short Answer

Expert verified
b. ornithine

Step by step solution

01

Understand the Urea Cycle

The urea cycle is a series of biochemical reactions that produce urea (NH2)2CO from ammonia (NH3). This cycle is essential for removing excess nitrogen from the body.
02

Review Choices

Given the options, identify which cycle is most directly associated with the removal of excess nitrogen and the production of urea. The choices are: a. Krebs, b. ornithine, c. citric acid, d. uric acid.
03

Eliminate Irrelevant Options

Eliminate options that do not pertain to the nitrogen removal process or urea production. The Krebs cycle and citric acid cycle are related to energy production. Uric acid is a different nitrogenous waste compound.
04

Identify the Correct Cycle

The correct cycle involved in the production of urea is the ornithine cycle. The ornithine cycle is another name for the urea cycle because ornithine is one of the key intermediates in this process.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

ornithine cycle
The ornithine cycle, also known as the urea cycle, is a critical metabolic pathway in the liver. This cycle helps detoxify ammonia by converting it into urea, which can be safely excreted by the kidneys. The cycle includes several steps and key intermediates like ornithine, citrulline, arginine, and aspartate. Each intermediate plays a crucial role in converting toxic ammonia into the less harmful urea.
Understanding the ornithine cycle gives insights into how the body processes and eliminates nitrogen waste.
This cycle not only helps in nitrogen removal but also avoids ammonia toxicity, which can be fatal.
nitrogen removal
Nitrogen removal from the body is essential for maintaining metabolic balance. Excess nitrogen is primarily produced when proteins are broken down into amino acids. The body can't store excess amino acids, so they get deaminated to form ammonia, which is highly toxic.
Through the urea cycle, the liver converts ammonia into urea, which is far less toxic. This urea is then transported to the kidneys and excreted in urine. Efficient nitrogen removal is crucial for sustaining life and ensuring that cellular processes aren't disrupted by toxic compounds.
Any disruption in the nitrogen removal process can lead to a buildup of ammonia, resulting in conditions like hyperammonemia.
biochemical reactions
Biochemical reactions are fundamental to the urea cycle. Here's a breakdown of key steps:
  • Ammonia and carbon dioxide combine to form carbamoyl phosphate.
  • Carbamoyl phosphate reacts with ornithine to form citrulline.
  • Citrulline moves to the cytoplasm and reacts with aspartate to form argininosuccinate.
  • Argininosuccinate is then split into arginine and fumarate.
  • Arginine is cleaved to form urea and regenerate ornithine, allowing the cycle to continue.
Each of these steps is catalyzed by specific enzymes, ensuring efficiency and regulation of the cycle.
This series of reactions exemplifies the body's ability to keep harmful substances in check through intricate biochemical pathways.

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Most popular questions from this chapter

Describe the urea cycle. a. The urea cycle is the mechanism of conversion of urea to ammonia involving five intermediate steps catalyzed by five different enzymes. Of the five steps, the first two occur in the mitochondria and the last three in the cytosol. b. The urea cycle is the mechanism of conversion of ammonia to urea involving five intermediate steps catalyzed by five different enzymes. Of the five steps, the first two occur in the mitochondria and the last three in the cytosol. c. The urea cycle is the mechanism of conversion of ammonia to urea involving five intermediate steps catalyzed by five different enzymes. Of the five steps, the first two occur in the cytosol and the last three in the mitochondria. d. The urea cycle is the mechanism of conversion of ammonia to urea involving five intermediate steps all catalyzed by one enzyme. Of the five steps, the first two occur in the mitochondria and the last three in the cytosol.

Would an organism that is constantly in a hypertonic environment likely be an osmoregulator or an osmoconformer? Why? a. osmoconformer, because it would need to prevent water from leaving its body to remain alive b. osmoregulator, because it would need to prevent solutes from leaving its body to remain alive c. osmoconformer, because it would need to prevent solutes from leaving its body to remain alive d. osmoregulator, because it would need to prevent water from leaving its body to remain alive.

Patients with kidney illnesses use dialysis machines to remove harmful urea from their blood. The blood is separated from a solution, called the dialysate, that is designed to remove wastes by diffusion through a semipermeable membrane. How does the concentration of solutes likely differ between the upper component of the dialyzer and the lower compartment, containing the fresh dialysate, for the dialysis to successfully remove wastes from the blood? a. In the upper component, the dialysate has a higher solute concentration than the blood, which allows the urea to diffuse to the lower dialysate down its concentration gradient. b. In the upper component, the dialysate has a lower solute concentration than the blood, which allows the urea to be separated via active transport down the concentration gradient. c. In the upper component, the dialysate has a higher solute concentration than the blood, which allows the urea to utilize facilitated diffusion in order to diffuse to the lower dialysate. d. In the upper component, the dialysate has a lower solute concentration than the blood, which allows the urea to diffuse to the lower dialysate down its concentration gradient.

What is given to a dehydrated human patient when he or she needs to be given fluids intravenously? a. Water, which is hypotonic with respect to body fluids. b. Saline at a concentration that is isotonic with respect to body fluids. c. Glucose because it is a non-electrolyte. d. blood

Birds and reptiles convert toxic ammonia to uric acid or the closely related compound guanine (guano), reflecting the close evolutionary ancestry of these groups. However, terrestrial arthropods also convert ammonia to uric acid. This is as opposed to fish, which excrete ammonia directly, without converting it to another substance. However, the conversion of ammonia to uric acid requires more energy and is much more complex than the conversion of ammonia to urea. What do these findings suggest about why these organisms evolved the conversion of ammonia to uric acid? a. To evolve the ability to switch between uric acid and ammonia excretion b. To conserve water to allow them to persist on land c. For reduction in excretion of ammonia d. For excretion of higher concentrations of ammonia
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