1) Brianna was a 2-month-old, formula-fed infant in a rural community in Nebrask
ID: 252450 • Letter: 1
Question
1) Brianna was a 2-month-old, formula-fed infant in a rural community in Nebraska. Brianna’s mother noticed signs of blueness around the baby’s mouth and fingers. One night after feeding, Brianna had trouble breathing, and her face had a peculiar lavender color. She became lethargic, salivated excessively, and had diarrhea and vomiting. An EMT came and took blood samples, which appeared brown and failed to turn pink when exposed to air. The EMT diagnosed methemoglobinemia, a condition in which toxic levels of nitrite oxidize hemoglobin and prevent it from receiving oxygen. The nitrite-oxidized hemoglobin is called methemoglobin; elevated levels can cause asphyxiation and death. A solution of methylene blue, a reducing agent, was administered by IV to reduce (add electrons to) the hemoglobin in Brianna’s blood.
Nitrite forms in the digestive tract by bacterial reduction of nitrate during anaerobic respiration. The well water from which Brianna’s formula was prepared was tested and found to contain high levels of nitrate, enough to cause methemoglobinemia. Brianna’s parents were surprised because they had felt no ill effect from the water. An infant’s stomach pH is high, however, allowing bacteria to reduce nitrate to nitrite, which may then oxidize hemoglobin.
Part 2: Under what pH condition do bacteria convert nitrate to nitrite. A. basic. B. neutral. C. Acid
Explanation / Answer
1 A. Methylene blue was added to Brianna's blood by injection into her vasculature; methylene blue donates electrons to hemoglobin, a blood protein.
2. A. Bacteria reduce the nitrate to nitrite anaerobically under basic conditions (high pH).
3 A. The fungal cell wall is made of chitin.
4 C. A parasite enetering a new host. Sexual reproduction helps to provide genetic variation which would give it an edge when facing the immune system of the host.
6 A. Mosquitoes carry and transmit for example the parasite plasmodium that causes malaria, but mosquitoes are technically not parasites because they dont live on us.
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