What role does the liver play in metabolism?

Correct Answer: D

Rationale: The correct answer is D: Producing enzymes. The liver is involved in metabolism by producing enzymes that are essential for regulating various metabolic processes in the body. While the liver does store glucose, secrete bile, and detoxify harmful substances, its primary role in metabolism is producing enzymes that facilitate biochemical reactions necessary for energy production, nutrient breakdown, and waste elimination. Choices A, B, and C are incorrect because although the liver performs these functions, they are not directly related to its primary role in metabolism, which is producing enzymes.

Correct Answer: B

Rationale: The correct answer is B: Hinge. A hinge joint, such as the one found at the elbow, allows for movement primarily in one plane, enabling flexion and extension similar to the movement of a door hinge. This joint structure permits bending and straightening of the arm, controlling the range of motion in a specific direction. Choices A, C, and D are incorrect. A ball and socket joint allows for multi-axial movement like the hip joint, a pivot joint allows for rotation around an axis like the joint between the first and second cervical vertebrae, and a saddle joint allows for movement in two planes at right angles to each other like the joint at the base of the thumb.

Correct Answer: C

Rationale: Platelets, also known as thrombocytes, play a crucial role in blood clotting. When there is an injury, platelets adhere to the site and release substances that form a clot, preventing excessive bleeding. This function is vital for maintaining hemostasis and preventing blood loss. Choice A is incorrect because red blood cells, not platelets, are responsible for transporting oxygen. Choice B is incorrect as white blood cells are primarily responsible for fighting infections. Choice D is incorrect as nutrients are mainly transported by plasma and red blood cells, not platelets.

Correct Answer: A

Rationale: Vitamin A is the correct answer. It is crucial for maintaining healthy vision and skin. Vitamin A plays a vital role in supporting normal vision, skin health, and immune function. Specifically, it is important for the health of the retina and is essential for the formation of rhodopsin, a protein in the retina necessary for low-light and color vision. Vitamin C (Choice B) is important for collagen synthesis and immune function, but it is not primarily associated with vision health. Vitamin D (Choice C) is crucial for bone health and immune function, while Vitamin E (Choice D) acts as an antioxidant, protecting cells from damage, but neither are primarily linked to vision and skin health like Vitamin A.

Correct Answer: A

Rationale: The primary function of the hypothalamus is to regulate body balance and thermoregulation. It plays a crucial role in maintaining overall body equilibrium by controlling functions such as body temperature and water balance. While the hypothalamus is also involved in hunger and thirst regulation, its main role is to ensure homeostasis by monitoring and adjusting body balance and temperature. Choices B, C, and D are incorrect because hunger and thirst regulation, sleep and circadian rhythm regulation, and control of voluntary movements are secondary functions of the hypothalamus compared to its primary role in maintaining body balance and thermoregulation.

Correct Answer: B

Rationale: The cerebrum, specifically the motor cortex located within it, is responsible for controlling voluntary movements such as walking, writing, and speaking. This region of the brain plays a crucial role in coordinating and executing voluntary muscle actions, making it the correct answer in this context. The cerebellum (Choice A) primarily coordinates balance, posture, and coordination of voluntary movements but does not control voluntary movement itself. The brainstem (Choice C) is responsible for basic life functions like breathing and heart rate, not voluntary movements. The medulla oblongata (Choice D) controls vital functions like blood pressure and breathing, not voluntary movement.

Correct Answer: B

Rationale: The correct answer is B: Ribosome. Ribosomes, the cellular structures located in the cytoplasm or on the endoplasmic reticulum, are responsible for protein synthesis in the cell. They are the sites where mRNA is translated into proteins, making them essential for the synthesis of proteins in all living cells. The other choices, such as the nucleus (choice A), endoplasmic reticulum (choice C), and Golgi apparatus (choice D), are not directly involved in protein synthesis. The nucleus contains DNA and is responsible for housing the genetic material, the endoplasmic reticulum is involved in protein folding and transport, and the Golgi apparatus is responsible for modifying, sorting, and packaging proteins.

Correct Answer: B

Rationale: The correct answer is B: Occipital lobe. The occipital lobe, situated at the back of the brain, is specifically responsible for processing visual information received from the eyes. It plays a crucial role in interpreting and making sense of visual stimuli, allowing individuals to perceive and comprehend the world around them. The Temporal lobe (Choice A) is involved in processing auditory information and memory, not visual processing. The Parietal lobe (Choice C) is responsible for processing sensory information from various parts of the body, but not specifically visual information. The Frontal lobe (Choice D) is involved in functions such as decision-making, problem-solving, and voluntary movement, but not processing visual stimuli.

Correct Answer: C

Rationale: The correct answer is C: To store urine. The main function of the urinary bladder is to store urine produced by the kidneys before it is excreted from the body. It acts as a reservoir for urine until it is expelled during urination. Choices A, B, and D are incorrect because the urinary bladder does not filter blood, store or concentrate bile, or absorb nutrients. It is solely responsible for storing and releasing urine.