ati teas 7 science

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: One layer. Simple epithelium consists of a single layer of cells. This arrangement allows for efficient diffusion and absorption due to the short distance between cells and the underlying tissues. Option A is incorrect because epithelial tissue always has at least one layer. Option C is incorrect as it describes stratified epithelium, which has two or more layers. Option D is incorrect as it refers to stratified squamous epithelium, not simple epithelium.

Correct Answer: C

Rationale: The myelin sheath is derived from nervous tissue, specifically glial cells. Glial cells, also known as neuroglia, support and protect nerve cells. They produce the myelin sheath, which insulates nerve fibers and allows for faster transmission of nerve impulses. Epithelial tissue (choice A) primarily covers and lines body surfaces, muscle tissue (choice B) is responsible for movement, and connective tissue (choice D) provides support and structure to the body. None of these tissues are involved in the production of the myelin sheath, making them incorrect choices.

Correct Answer: C

Rationale: The correct answer is C: Nephron. The nephron is the functional unit of the kidney responsible for filtering blood and reabsorbing essential substances like water, salts, and nutrients back into the body. It consists of various components like the glomerulus, proximal tubule, loop of Henle, and distal tubule, each playing a specific role in the reabsorption process. The renal artery brings blood to the kidney for filtration by the nephron, while the renal vein carries filtered blood away from the kidney. The glomerulus is a part of the nephron responsible for initial filtration of blood. Thus, the nephron is the correct structure for reabsorption, making choices A, B, and D incorrect.

Correct Answer: B

Rationale: The correct answer is B: Peptide bond. A peptide bond is a covalent bond that connects amino acids in a protein chain. During protein synthesis, the carboxyl group of one amino acid reacts with the amino group of another amino acid, forming a peptide bond. This bond is crucial for the structural integrity and function of proteins. A: Covalent bonds are generic chemical bonds that can occur between any atoms, not specifically between amino acids in proteins. C: Ionic bonds involve the transfer of electrons between atoms with opposite charges, which is not how amino acids are connected in proteins. D: Hydrogen bonds are weak interactions between hydrogen and electronegative atoms, not the primary bond connecting amino acids in proteins.