If a patient presents with fatigue and pallor several weeks after starting a strict vegan diet, which mechanism explains why vitamin B12 deficiency can cause macrocytic anemia?

💡 Explanation

Vitamin B12 is essential for DNA synthesis in rapidly dividing cells, including erythroblasts. In B12 deficiency, DNA synthesis is impaired, and erythroblasts cannot divide properly, resulting in large, immature red blood cells (macrocytes) being released into the circulation; therefore, impaired DNA synthesis explains macrocytic anemia rather than increased apoptosis or accelerated erythropoiesis.

• An individual undergoes chemotherapy, which affects rapidly dividing cells, including those in bone marrow and hair follicles. Which consequence related to cellular aging becomes most prominent following treatment?
• Why does ingesting a large amount of indigestible fiber, such as cellulose, lead to reduced absorption of certain medications in the small intestine?
• A weightlifter experiences muscle fatigue during a maximal lift. Which mechanism explains why lactate accumulation contributes to this phenomenon in anaerobic conditions?
• What happens to mean arterial pressure (MAP) when the cardiac muscle's contractility diminishes due to prolonged ischemia?
• A woman undergoing IVF treatment experiences premature luteinization during ovarian stimulation. Which risk increases as progesterone levels rise too early?
• Why does intense, prolonged exposure to jet engine noise potentially lead to permanent hearing loss?