ati teas 7 science

Correct Answer: A

Rationale: The correct answer is A: Nucleosome. Nucleosomes are the basic units of DNA packaging in eukaryotic cells, consisting of DNA wrapped around histone proteins. This structure helps in compacting the DNA to fit inside the nucleus. Choice B (Chromatin) is a broader term for DNA and associated proteins, not a specific packaging structure. Choice C (Histone) refers to the protein component of nucleosomes, not the packaging structure itself. Choice D (Centromere) is a region on a chromosome where the kinetochore forms during cell division, not involved in DNA packaging.

Correct Answer: B

Rationale: The correct answer is B: Humoral immunity. B-cells produce antibodies that circulate in bodily fluids to combat pathogens. This is a key aspect of humoral immunity. A: Cell-mediated immunity involves T-cells directly attacking infected cells, not antibody secretion by B-cells. C: Innate immunity is non-specific and does not involve B-cells producing antibodies. D: Phagocytic immunity involves phagocytes engulfing and destroying pathogens, not antibody secretion by B-cells.

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 because the main function of the pancreas is to produce enzymes that help digest food. These enzymes are released into the small intestine to break down carbohydrates, proteins, and fats. Choice A is incorrect as the pancreas does not store or break down food. Choice B is incorrect as nutrient absorption primarily occurs in the small intestine, not the pancreas. Choice D is incorrect as regulating blood sugar levels is primarily the role of the endocrine portion of the pancreas, not its main function.

Correct Answer: B

Rationale: The correct answer is B: Insulin. Insulin is responsible for regulating blood sugar levels by facilitating the uptake of glucose into cells for energy production and storage. It helps lower blood sugar levels by promoting glucose utilization. Thyroxine (A) regulates metabolism, adrenaline (C) is involved in the fight-or-flight response, and cortisol (D) regulates stress response and metabolism, but they do not directly regulate blood sugar levels like insulin does.