Nokea
From which of the following germ layers does the nervous system develop?
- A. Ectoderm
- B. Endoderm
- C. Gastroderm
- D. Mesoderm
Correct Answer: A
Rationale: The correct answer is A: Ectoderm. The nervous system develops from the ectoderm, which is the outermost of the three germ layers. The ectoderm gives rise to structures such as the skin, hair, nails, and the entire nervous system. Choices B, C, and D are incorrect because the endoderm gives rise to the lining of the gut and associated organs, the gastroderm is not a recognized germ layer, and the mesoderm forms structures like muscles, bones, blood, and the circulatory system, but not the nervous system.
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Which structure in the lungs is the site of gas exchange?
- A. Trachea
- B. Alveoli
- C. Bronchioles
- D. Diaphragm
Correct Answer: B
Rationale: The correct answer is B: Alveoli. Alveoli are tiny air sacs in the lungs where gas exchange occurs. Oxygen from inhaled air diffuses into the bloodstream, while carbon dioxide from the blood is released into the alveoli to be exhaled. The trachea (Choice A) is the windpipe that carries air to and from the lungs, but it is not involved in gas exchange. Bronchioles (Choice C) are small air passages within the lungs that branch off from the bronchi, leading air to the alveoli but not directly involved in gas exchange. The diaphragm (Choice D) is a muscle below the lungs that helps in breathing by expanding and contracting the chest cavity, but it is not the site of gas exchange.
Which of the following hormones is responsible for regulating blood sugar levels?
- A. Insulin
- B. Adrenaline
- C. Cortisol
- D. Melatonin
Correct Answer: A
Rationale: Insulin is the hormone responsible for regulating blood sugar levels by facilitating the uptake of glucose into cells. Insulin helps lower blood sugar levels by promoting the storage of glucose in the liver, muscle, and fat cells. Adrenaline, cortisol, and melatonin do not directly regulate blood sugar levels. Adrenaline is involved in the fight-or-flight response, cortisol is a stress hormone that affects metabolism, immune response, and anti-inflammatory actions, while melatonin regulates sleep-wake cycles.
Which of the following is the space between the lungs?
- A. Mediastinum
- B. Pericardial cavity
- C. Pleural cavity
- D. Thoracic space
Correct Answer: A
Rationale: The correct answer is A, mediastinum. The mediastinum is the space between the lungs in the chest that contains the heart, major blood vessels, esophagus, trachea, and other structures. This area separates the lungs into right and left cavities. Choice B, pericardial cavity, is incorrect as it refers to the space that surrounds the heart. Choice C, pleural cavity, is not the correct answer as it is the space between the layers of the pleura surrounding each lung. Choice D, thoracic space, is a vague term and not specific to the space between the lungs.
Which of the following does not describe a general trait of macromolecules?
- A. They can exist as single chains.
- B. They can be branched.
- C. They all contain carbon, hydrogen, and phosphorus.
- D. They are all used by the body.
Correct Answer: C
Rationale: The correct answer is C. While many macromolecules contain carbon, hydrogen, and phosphorus, not all of them do. For example, lipids, a type of macromolecule, may not contain phosphorus. Choice A and B describe structural features that macromolecules can exhibit, whether as single chains or branched forms. Choice D is incorrect as not all macromolecules are used by the body, such as synthetic polymers or certain non-digestible fibers.
What is the ultimate end product of glucose breakdown in glycolysis?
- A. ATP
- B. NADPH
- C. Pyruvic acid
- D. Oxygen
Correct Answer: C
Rationale: The ultimate end product of glucose breakdown in glycolysis is pyruvic acid. During glycolysis, glucose is broken down into pyruvic acid through a series of enzymatic reactions. ATP is produced as an energy carrier during glycolysis, but it is not the final end product. NADPH is not a direct product of glycolysis; it is mainly produced in the pentose phosphate pathway. Oxygen is not a product of glycolysis but is used as an electron acceptor in the electron transport chain of cellular respiration.