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Positron emission tomography (PET) scans utilize a key property of positrons for medical imaging. What is this property?
- A. High mass
- B. Positive charge
- C. Extreme stability
- D. Identical behavior to electrons
Correct Answer: B
Rationale: Positron emission tomography (PET) scans utilize the property of positrons having a positive charge. Positrons are the antimatter counterpart of electrons, having the same mass but opposite charge. When a positron collides with an electron, they annihilate each other, producing gamma rays that can be detected by the PET scanner to create images of the body's internal structures and functions. Choice A is incorrect because positrons have the same mass as electrons. Choice C is incorrect as positrons are not extremely stable due to their tendency to annihilate when they encounter electrons. Choice D is incorrect as positrons exhibit different behavior than electrons due to their opposite charges.
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Which of the following blood vessels carries oxygenated blood away from the heart?
- A. Pulmonary artery
- B. Aorta
- C. Superior vena cava
- D. Inferior vena cava
Correct Answer: B
Rationale: The aorta is the correct answer because it is the main artery in the body that carries oxygenated blood away from the heart to the rest of the body. The pulmonary artery carries deoxygenated blood from the heart to the lungs for oxygenation. The superior and inferior vena cava are veins that carry deoxygenated blood from the body back to the heart. Therefore, choices A, C, and D are incorrect as they do not carry oxygenated blood away from the heart.
What is the technical term for the involuntary muscular contractions that move food through the digestive tract?
- A. Segmentation
- B. Peristalsis
- C. Chylification
- D. Emulsification
Correct Answer: B
Rationale: Peristalsis is the term used to describe the involuntary muscular contractions that move food through the digestive tract. This process involves rhythmic contractions and relaxations of the muscles in the digestive system, which help propel food from the esophagus to the stomach and through the intestines for digestion and absorption of nutrients. Segmentation refers to the mixing movements in the intestines that aid in the absorption of nutrients but is not the term for the movement of food through the digestive tract. Chylification is not a recognized term in digestive physiology. Emulsification is the process of breaking down fat globules into smaller droplets to aid in digestion, not the movement of food through the digestive tract.
What is the process of converting simple sugars into complex carbohydrates called?
- A. Glycolysis
- B. Gluconeogenesis
- C. Krebs cycle
- D. Oxidative phosphorylation
Correct Answer: B
Rationale: Gluconeogenesis is the correct answer. It is the process of synthesizing glucose from non-carbohydrate sources, such as amino acids or glycerol. A) Glycolysis is the process of breaking down glucose into pyruvate to produce energy. C) The Krebs cycle, also known as the citric acid cycle, generates energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. D) Oxidative phosphorylation is the final stage of cellular respiration where ATP is produced using energy derived from the electron transport chain. Therefore, choices A, C, and D are not the processes involved in converting simple sugars into complex carbohydrates.
How does an increase in surface area affect the force of friction between two surfaces?
- A. Increases friction
- B. Decreases friction
- C. Has no effect on friction
- D. Causes unpredictable changes in friction
Correct Answer: A
Rationale: An increase in surface area typically increases the force of friction between two surfaces. This is because with a larger surface area in contact, there are more points of contact between the surfaces, leading to a greater frictional force resisting motion. As a result, the correct answer is that an increase in surface area increases the force of friction between two surfaces. Choice B is incorrect because a greater surface area increases the frictional force. Choice C is incorrect because an increase in surface area results in more contact points and greater friction. Choice D is incorrect as the relationship between surface area and friction is predictable - an increase in surface area generally leads to an increase in frictional force.
How do vaccines work?
- A. By directly killing pathogens
- B. By introducing weakened or inactive versions of pathogens to trigger an immune response
- C. By stimulating the immediate production of specific antibodies
- D. None of the above
Correct Answer: B
Rationale: Vaccines work by introducing weakened or inactive versions of pathogens to trigger an immune response in the body. This exposure helps the immune system recognize and remember the pathogen, enabling a faster and more effective response upon future exposure. Vaccines do not directly kill pathogens but prepare the immune system for a potential encounter, enhancing protection. They also do not stimulate the immediate production of specific antibodies as the immune response takes time to develop upon vaccination. Choice A is incorrect because vaccines do not kill pathogens directly; they prime the immune system to recognize and respond to them. Choice C is incorrect because while vaccines lead to the production of specific antibodies, it is not immediate, as it takes time for the immune response to develop and produce these antibodies.