Which organelle is responsible for energy production in the cell?

Correct Answer: B

Rationale: Mitochondria are the organelles responsible for energy production in the cell. They generate energy through cellular respiration, producing ATP, which is the primary energy currency of the cell. Known as the powerhouse of the cell, mitochondria play a vital role in meeting the energy demands of various cellular processes. The nucleus is responsible for storing genetic material, not energy production. Ribosomes are involved in protein synthesis, not energy production. The endoplasmic reticulum is involved in protein and lipid synthesis, as well as detoxification, but it is not primarily responsible for energy production.

Correct Answer: A

Rationale: The correct answer is A: 'To filter blood and remove waste.' The kidneys play a crucial role in the urinary system by filtering blood to remove waste products and excess fluids, which are then excreted as urine. This process helps maintain the body's internal balance by regulating electrolyte levels and controlling blood pressure. Choices B, C, and D are incorrect because the kidneys do not produce red blood cells (bone marrow does), regulate blood pressure directly (although they indirectly influence it through the renin-angiotensin-aldosterone system), or absorb water (they regulate water balance but do not absorb water).

Correct Answer: B

Rationale: The thyroid gland is responsible for regulating the body's metabolic rate by producing hormones such as thyroxine (T4) and triiodothyronine (T3). These hormones play a crucial role in controlling the body's metabolism, affecting processes like growth, energy production, and temperature regulation. The pituitary gland is known as the 'master gland' but primarily regulates other endocrine glands by releasing hormones that stimulate their function. The adrenal gland is responsible for producing hormones like adrenaline and cortisol, which are involved in the body's response to stress. The pineal gland secretes melatonin, a hormone that regulates sleep-wake cycles and circadian rhythms, but is not directly involved in regulating metabolic rate.

Correct Answer: D

Rationale: The hypothalamus is the part of the brain responsible for regulating body temperature, along with controlling other autonomic functions like hunger, thirst, and sleep. It acts as the body's internal thermostat, helping to maintain a stable internal environment despite external temperature changes. The cerebrum is mainly associated with functions like thinking, perception, and voluntary movements, making it unrelated to regulating body temperature. The cerebellum is involved in coordination and balance, not in regulating body temperature. The brainstem is essential for basic life functions like breathing and heart rate, but it is not primarily responsible for regulating body temperature.

Correct Answer: A

Rationale: Vitamin A is the correct answer. It is crucial for maintaining healthy skin as it supports skin cell growth, repair, and overall skin health. Additionally, vitamin A plays a role in vision and immune function. Deficiency in vitamin A can lead to skin issues such as dryness and poor wound healing. Vitamin C is known for its role in collagen synthesis and antioxidant properties, while Vitamin D is important for bone health and immunity. Vitamin K is essential for blood clotting, but it is not primarily associated with skin health.

Correct Answer: A

Rationale: Melatonin, produced by the pineal gland, regulates the sleep-wake cycle by responding to light and darkness in the environment. It plays a crucial role in signaling the body when it's time to sleep and wake up, helping to establish and maintain a healthy circadian rhythm. Thyroxine, Insulin, and Cortisol do not directly regulate the sleep-wake cycle, making them incorrect choices for this question.

Correct Answer: A

Rationale: The primary function of the respiratory system is to facilitate the exchange of oxygen and carbon dioxide between the air and the bloodstream. Oxygen is taken in during inhalation and transported to cells, while carbon dioxide is removed during exhalation as a waste product of cellular metabolism. Choices B, C, and D are incorrect as they do not reflect the primary function of the respiratory system. Regulating body temperature is mainly controlled by the thermoregulatory system, fighting infections is a function of the immune system, and producing energy is primarily done by the metabolic system.

Correct Answer: A

Rationale: Oxytocin is the correct answer. It is released by the posterior pituitary gland and plays a vital role in childbirth and lactation. Oxytocin promotes uterine contractions during labor and milk ejection during breastfeeding. Choice B, Thyroxine, is incorrect as it is produced by the thyroid gland. Choice C, Insulin, is incorrect as it is produced by the pancreas. Choice D, ADH (Antidiuretic Hormone), is also released by the posterior pituitary gland, but it is not the hormone primarily associated with childbirth and lactation.

Correct Answer: A

Rationale: Insulin is the hormone that regulates blood sugar levels by promoting the uptake of glucose into cells. It is produced by the pancreas and helps to lower blood sugar levels when they are too high. Glucagon, on the other hand, works in opposition to insulin by raising blood sugar levels when they are too low. Cortisol and thyroxine play different roles in the body and are not primarily responsible for regulating blood sugar levels.