Which of the following is a non-carbohydrate precursor available for gluconeogenesis in the cell?
malate
fatty acids
pyruvate
phosphoenolpyruvate
The Correct Answer is C
Gluconeogenesis is the metabolic pathway that generates glucose from non-carbohydrate substrates during periods of fasting or intense exercise. This process occurs mainly in the liver and kidneys to maintain blood glucose levels. Key substrates include glucogenic amino acids, lactate, and glycerol. It essentially reverses glycolysis but must bypass three irreversible enzymatic steps using specific mitochondrial and cytosolic enzymes.
Rationale:
A. Malate is an intermediate in the citric acid cycle and is used as a shuttle to transport oxaloacetate out of the mitochondria. While it is part of the gluconeogenic pathway, it is an intermediate rather than a primary starting "precursor" like lactate or amino acids. It is a transitional molecule in the carbon flux.
B. Fatty acids are generally not precursors for gluconeogenesis in humans because the pyruvate dehydrogenase reaction is irreversible. The acetyl-CoA produced from fatty acid oxidation cannot be converted back into pyruvate. Only the glycerol backbone of triacylglycerols can be converted into glucose, while the fatty acid chains cannot.
C. Pyruvate is the primary non-carbohydrate precursor that enters the gluconeogenic pathway. It can be derived from the deamination of alanine or the oxidation of lactate via the Cori cycle. Pyruvate is carboxylated to oxaloacetate, marking the commencement of the bypass reactions necessary to synthesize new glucose molecules.
D. Phosphoenolpyruvate (PEP) is a high-energy intermediate in both glycolysis and gluconeogenesis. It is the product of the PEP carboxykinase reaction during the bypass of the pyruvate kinase step. Because it is an intermediate formed during the process, it is not considered a primary external non-carbohydrate precursor.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Step 1. Calculate the duration of the infusion.
Time = Total Volume / Rate
Time = 150 mL / 25 mL/hr = 6 hours.
Step 2. Determine the completion time.
Start time: 8 am
8 am + 6 hours = 2 pm.
Correct Answer is D
Explanation
Allergic rhinitis is a common inflammatory condition of the nasal mucosa triggered by an IgE-mediated response to inhaled allergens. This hypersensitivity reaction leads to the release of histamine and other pro-inflammatory mediators from mast cells. It is often categorized as seasonal or perennial depending on the trigger. Effective management involves allergen avoidance and the use of antihistamines or intranasal corticosteroids to control the inflammatory cascade.
Rationale:
A. A cold, or viral upper respiratory infection, typically presents with a sore throat, low-grade fever, and thick, discolored mucus. While sneezing and congestion occur, itchy watery eyes are less characteristic of a viral infection than an allergic one. Colds usually resolve within 7 to 10 days, whereas allergic symptoms persist as long as the trigger is present.
B. Sinusitis is an inflammation of the paranasal sinuses often characterized by facial pain, pressure, and purulent nasal discharge. It is frequently associated with a diminished sense of smell and a cough that worsens at night. It does not typically present with the "itchy" symptoms that define an allergic profile, and the discharge is usually opaque rather than clear.
C. Influenza is a systemic viral infection characterized by sudden onset of high fever, myalgia, headache, and severe malaise. While respiratory symptoms are present, the systemic toxicity and exhaustion are far more prominent than the localized itching and sneezing found in rhinitis. It is a more severe illness that involves the lower respiratory tract more frequently than simple allergies.
D. Allergic rhinitis is the most likely diagnosis given the constellation of symptoms, particularly the pruritic (itchy) eyes and clear rhinorrhea. The sneezing and congestion are classic responses to allergen exposure, such as pollen or dust mites. The absence of fever and the presence of "itchy" markers strongly suggest a hypersensitivity reaction rather than an infectious process.
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