Which of the following statements is true about an allergic reaction?

Correct Answer: C

Rationale: The correct answer is C. Mast cells are responsible for releasing histamine and other chemicals during an allergic response. Choice A is incorrect because hives and wheezing are symptoms of an allergic reaction, not the causes. Choice B is incorrect as B-cells are not directly involved in allergic reactions. Choice D is incorrect as keratin and collagen are not typically involved in allergic reactions, and histamine is released by mast cells.

Correct Answer: B

Rationale: The correct answer is the Medulla oblongata. This region of the brain is located in the brainstem and is responsible for controlling vital autonomic functions such as breathing, heart rate, and blood pressure. The Cerebellum (Choice A) is primarily involved in coordination and balance. The Cerebrum (Choice C) is responsible for higher brain functions like thinking and voluntary muscle movement. The Thalamus (Choice D) acts as a relay station for sensory information but is not primarily responsible for controlling involuntary actions like breathing and heart rate.

Correct Answer: B

Rationale: The correct answer is B: ATP energy. During cellular respiration, glucose is broken down to produce ATP, which is the primary energy currency of cells. While oxygen is required for cellular respiration to occur, it is not an end product but rather a reactant. Carbon dioxide and water are byproducts of cellular respiration, alongside ATP. Therefore, options A, C, and D are incorrect as they are not end products of cellular respiration.

Correct Answer: C

Rationale: The correct answer is C, the Lymphatic System. The lymphatic system is responsible for draining clear fluid, known as lymph, throughout the body to protect it from infection. The other choices are incorrect because the pulmonary loop specifically refers to circulation between the heart and lungs, the systemic loop refers to circulation between the heart and the rest of the body, and the immune system is responsible for fighting infections and diseases rather than draining clear fluid.

Correct Answer: B

Rationale: Thyroxine, also known as T4, is produced by the thyroid gland and plays a vital role in regulating the body's metabolism. Insulin is not responsible for regulating metabolism; instead, it helps regulate blood sugar levels. Melatonin is involved in regulating sleep-wake cycles, not metabolism. Adrenaline, also known as epinephrine, is a stress hormone that prepares the body for fight or flight responses, not primarily involved in metabolic regulation.

Correct Answer: B

Rationale: Vitamin D is the correct answer. When the skin is exposed to sunlight, it triggers a process where a form of cholesterol in the skin is converted into vitamin D. This vitamin plays a crucial role in aiding calcium absorption in the gut, which is essential for maintaining strong and healthy bones. Vitamin A (Choice A) is important for vision and immune function but is not produced by sunlight exposure. Vitamin K (Choice C) is known for its role in blood clotting and bone metabolism, but it is not produced by sunlight. Vitamin E (Choice D) is an antioxidant that protects cells from damage but is not synthesized in the skin through sunlight exposure.

Correct Answer: B

Rationale: The correct answer is B: Sebaceous gland. Sebaceous glands are responsible for producing oil (sebum) that keeps the skin and hair moisturized. Sudoriferous glands produce sweat, not oil, and are involved in temperature regulation. Hair follicles are responsible for hair growth and do not produce oil directly. Melanocytes are cells responsible for producing melanin, the pigment that gives skin its color, and are not involved in oil production.

Correct Answer: B

Rationale: The correct answer is B: "To fight infection." White blood cells are primarily responsible for fighting infections and foreign invaders in the body, making them a critical component of the immune system. Choice A, "To carry oxygen," is incorrect as red blood cells are responsible for oxygen transport. Choice C, "To transport nutrients," is incorrect as this function is mainly attributed to blood plasma and other specialized cells. Choice D, "To transport waste," is also incorrect as waste removal is primarily handled by the kidneys and the lymphatic system, not white blood cells.

Correct Answer: C

Rationale: The correct answer is the humerus. The humerus is the long bone located in the upper arm, between the shoulder and elbow. Option A, Femur, is incorrect as it is the long bone found in the thigh. Option B, Tibia, is incorrect as it is a long bone found in the lower leg. Option D, Radius, is incorrect as it is a bone located in the forearm, not the upper arm.