Which of the following forms of Hb molecule has the lowest affinity for oxygen?

Correct Answer: A

Rationale: The correct answer is A: Tense. In the tense form of the hemoglobin (Hb) molecule, the binding of oxygen is hindered, leading to low oxygen affinity. This form occurs in tissues where oxygen is needed, promoting oxygen release. The relaxed form (choice B) has higher oxygen affinity, favoring oxygen binding. Arterial (choice C) and venous (choice D) refer to the oxygen saturation levels in blood, not directly related to the oxygen affinity of Hb molecules.

Correct Answer: D

Rationale: The correct answer is D: Liver. During midfetal life, the liver is the primary source of blood cells. The rationale behind this is that the liver is the major site of hematopoiesis during this developmental stage, producing red blood cells, white blood cells, and platelets. The liver's hematopoietic function gradually declines as the bone marrow takes over this role postnatally. Explanation for why other choices are incorrect: A: Bone marrow - While bone marrow becomes the primary site of hematopoiesis in adults, during midfetal life, it is not the main source of blood cells. B: Spleen - The spleen plays a role in blood filtration and immune response, but it is not the primary source of blood cells during midfetal life. C: Lymph Nodes - Lymph nodes are important for immune function and lymphocyte production, but they do not serve as the primary source of blood cells during midfetal life.

Correct Answer: C

Rationale: The correct answer is C: Glycoprotein. Glycoproteins are the most common type of protein found in the cell membrane because they play crucial roles in cell signaling, adhesion, and recognition. They have sugar molecules attached to them, which help in cell-cell interactions. Lipoproteins (choice A) have lipids attached to them and are found in cell membranes but are not as common as glycoproteins. Mucoproteins (choice B) are proteins with carbohydrate chains but are not as prevalent in cell membranes. Nucleoproteins (choice D) are proteins associated with nucleic acids and are not typically found in the cell membrane.

Correct Answer: C

Rationale: The correct answer is C (70+). Chronic lymphoblastic leukemia typically affects older adults, with the median age of diagnosis around 70 years old. This is due to the gradual accumulation of genetic mutations over time. Older patients are more likely to develop this type of leukemia compared to younger individuals. Choices A, B, and D are incorrect because they suggest younger age groups, which are less commonly associated with chronic lymphoblastic leukemia. Additionally, younger individuals are more likely to be affected by acute lymphoblastic leukemia rather than the chronic form.

Correct Answer: B

Rationale: The correct answer is B: slow-reacting substance A (leukotrienes). In severe asthma, leukotrienes are potent inflammatory mediators that cause bronchoconstriction, mucus production, and airway inflammation. Antihistamines target histamine, which is not the primary mediator in asthma. Interleukin-2 is involved in immune response modulation, not asthma symptoms. Serotonin plays a role in smooth muscle contraction, but it is not a major player in asthma pathophysiology. Bradykinin is a potent vasodilator and increases vascular permeability, but it is not the primary mediator in asthma. Therefore, the lack of relief from antihistamines suggests that leukotrienes are likely the cause of the symptoms in this patient with severe asthma.