ati teas 7 science

Correct Answer: B

Rationale: The correct answer is B: Cytoplasm. Cytoplasm is the fluid-filled, jelly-like substance within the cell that suspends the organelles. It is where many cellular processes occur. The nucleus (A) contains genetic material, not the organelles. The plasma membrane (C) is the cell's outer boundary, not the internal fluid. The Golgi apparatus (D) is an organelle involved in processing and packaging proteins, not the cell's fluid. Therefore, the correct answer is cytoplasm.

Correct Answer: D

Rationale: The correct answer is D: tRNA. Transfer RNA (tRNA) carries amino acids to ribosomes during protein synthesis. tRNA has an anticodon that pairs with the mRNA codon, ensuring the correct amino acid is added to the growing polypeptide chain. A: DNA carries genetic information but does not directly participate in protein synthesis. B: mRNA carries the genetic information from DNA to the ribosomes but does not carry amino acids. C: rRNA is a structural component of ribosomes and helps in protein synthesis but does not carry amino acids to the ribosomes.

Correct Answer: C

Rationale: The correct answer is C: Control sleep-wake cycles. Melatonin is primarily responsible for regulating our sleep-wake cycles, also known as the circadian rhythm. This hormone is released by the pineal gland in response to darkness, signaling to the body that it is time to sleep. Melatonin helps to synchronize our internal body clock with the natural day-night cycle. Choice A (Regulate blood pressure) is incorrect because melatonin does not play a direct role in regulating blood pressure. Choice B (Stimulate the digestive system) is incorrect as melatonin is not involved in stimulating the digestive system. Choice D (Maintain bone density) is also incorrect as melatonin's primary function is not related to bone density regulation.

Correct Answer: B

Rationale: The correct answer is B: Alveoli. Alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide occurs during respiration. Oxygen from the air we breathe diffuses into the bloodstream, while carbon dioxide from the blood is released into the alveoli to be exhaled. The trachea (A) is a tube that carries air to and from the lungs, the bronchi (C) are branches of the trachea, and the diaphragm (D) is a muscle that helps with breathing but is not directly involved in gas exchange. Therefore, the alveoli are responsible for gas exchange in the respiratory system.

Correct Answer: D

Rationale: The correct answer is D, Collagen. Collagen is a fibrous protein known for its structural role in connective tissues. It has a triple helix structure, providing strength and support to tissues. Insulin (A) is a hormone, not a fibrous protein. Keratin (B) is a structural protein found in hair and nails. Hemoglobin (C) is a globular protein responsible for oxygen transport in red blood cells. Therefore, collagen is the only fibrous protein among the choices.