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What is the difference between DNA and RNA?
- A. Both are double-stranded.
- B. DNA contains deoxyribose sugar, while RNA contains ribose sugar.
- C. RNA contains the nitrogenous base uracil, while DNA contains thymine.
- D. Both are identical molecules.
Correct Answer: B
Rationale: A) Incorrect. DNA is double-stranded, but RNA is typically single-stranded.
B) Correct. DNA contains deoxyribose sugar, which lacks an oxygen atom on the 2' carbon of the sugar ring, while RNA contains ribose sugar, which has an additional hydroxyl group on the 2' carbon.
C) Incorrect. RNA contains the nitrogenous base uracil, while DNA contains thymine.
D) Incorrect. DNA and RNA have distinct structures and functions, so they are not identical molecules.
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What is the main component that gives bones their rigidity and hardness?
- A. Collagen
- B. Calcium phosphate
- C. Cartilage
- D. Ligaments
Correct Answer: B
Rationale: Calcium phosphate is the main component that gives bones their rigidity and hardness. It combines with calcium hydroxide to form hydroxyapatite crystals, which provide strength and structure to bones. Collagen, on the other hand, provides flexibility and tensile strength. Cartilage is a type of connective tissue found in joints, and ligaments are fibrous tissues that connect bones to other bones, but they do not contribute to the rigidity and hardness of bones.
Which part of the brain is responsible for coordinating various sensory inputs, regulating sleep, and maintaining wakefulness?
- A. Cerebrum
- B. Hypothalamus
- C. Medulla oblongata
- D. Reticular formation
Correct Answer: D
Rationale: The reticular formation is a network of neurons located in the brainstem that plays a crucial role in regulating sleep-wake cycles, coordinating various sensory inputs, and maintaining wakefulness. It acts as a filter for incoming sensory information and helps in directing attention to important stimuli. The other options, the cerebrum, hypothalamus, and medulla oblongata, are important structures in the brain but are not primarily responsible for the specific functions mentioned in the question. The cerebrum is mainly involved in higher brain functions such as thinking and voluntary movements. The hypothalamus is responsible for regulating body temperature, hunger, and thirst, among other functions. The medulla oblongata is essential for controlling vital autonomic functions like breathing and heart rate.
Which law of motion states that for every action, there is an equal and opposite reaction?
- A. Newton's First Law
- B. Newton's Second Law
- C. Newton's Third Law
- D. Law of Universal Gravitation
Correct Answer: C
Rationale: The correct answer is Newton's Third Law of Motion. This law states that for every action, there is an equal and opposite reaction. It means that when one object exerts a force on a second object, the second object exerts an equal force in the opposite direction back on the first object. This fundamental law describes the relationship between the forces acting on two interacting objects. Newton's First Law (Choice A) is known as the law of inertia and states that an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an external force. Newton's Second Law (Choice B) relates the force acting on an object to its mass and acceleration. The Law of Universal Gravitation (Choice D) describes the force of gravity between two objects with mass and the distance between them.
Antidiuretic hormone (ADH) plays a crucial role in regulating water balance. When ADH levels are high, what happens to urine production?
- A. Urine production increases significantly
- B. Urine production decreases to conserve water
- C. There is no change in urine production
- D. The kidneys stop producing urine altogether
Correct Answer: B
Rationale: When ADH levels are high, urine production decreases to conserve water. ADH acts on the kidneys to increase water reabsorption, leading to the production of concentrated urine and conservation of water in the body. Choice A is incorrect as high ADH levels lead to increased water reabsorption, reducing urine output. Choice C is incorrect since high ADH levels do influence urine production. Choice D is incorrect as the kidneys do not stop producing urine entirely but rather adjust the reabsorption of water based on ADH levels.
What is the primary function of the mucous membrane lining the muscular tube connecting the mouth to the stomach?
- A. Secretion of digestive enzymes
- B. Absorption of nutrients
- C. Lubrication and protection
- D. Storage of bile
Correct Answer: C
Rationale: The primary function of the mucous membrane lining the muscular tube connecting the mouth to the stomach is to provide lubrication and protection. This mucous membrane serves to protect the esophageal lining from damage caused by the passage of food and liquids. It also aids in facilitating the smooth passage of food from the mouth to the stomach by lubricating it, ensuring easier movement. Choices A, B, and D are incorrect as the mucous membrane does not secrete digestive enzymes, absorb nutrients, or store bile. Its main role is primarily related to lubricating and protecting the lining of the tube.