Nokea
What is the small repeating unit in the contractile apparatus of skeletal muscle?
- A. Myofibril
- B. Actin
- C. Sarcomere
- D. Myosin
Correct Answer: C
Rationale: The correct answer is 'Sarcomere.' The sarcomere is the smallest repeating unit within myofibrils and is responsible for muscle contraction in skeletal muscle. It consists of overlapping actin and myosin filaments arranged in a highly organized structure that allows for the sliding of filaments during muscle contraction. 'Myofibril' (choice A) is incorrect because it is a larger structure composed of sarcomeres. 'Actin' (choice B) and 'Myosin' (choice D) are incorrect as they are individual proteins that are components of the sarcomere, not the smallest repeating unit itself.
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Which of the following is NOT a major function of the respiratory system in humans?
- A. It provides a large surface area for gas exchange of oxygen and carbon dioxide.
- B. It helps regulate the blood's pH.
- C. It helps cushion the heart against jarring motions.
- D. It is responsible for vocalization.
Correct Answer: C
Rationale: Option C, 'It helps cushion the heart against jarring motions,' is NOT a major function of the respiratory system in humans. The primary functions of the respiratory system include gas exchange, regulation of blood pH, and vocalization. The respiratory system does not play a role in cushioning the heart; that function is primarily carried out by the pericardium and other protective structures around the heart. Choices A, B, and D are major functions of the respiratory system in humans. Choice A refers to the respiratory system's role in gas exchange, Choice B highlights its involvement in regulating blood pH, and Choice D points out its responsibility for vocalization.
What is bile, where is it produced, where is it stored, and what is its function?
- A. Produced in the pancreas, stored in the liver, aids in digestion
- B. Produced in the liver, stored in the gallbladder, aids in fat digestion
- C. Produced in the stomach, stored in the pancreas, neutralizes acid
- D. Produced in the gallbladder, stored in the liver, breaks down proteins
Correct Answer: B
Rationale: Bile is a digestive fluid produced in the liver, stored in the gallbladder, and it aids in the digestion of fats by emulsifying them. Emulsification helps to break down fats into smaller particles, facilitating their digestion by enzymes in the small intestine. Choice A is incorrect because bile is not produced in the pancreas, and it is not stored in the liver. Choice C is incorrect as bile is not produced in the stomach, and it does not neutralize acid. Choice D is also incorrect as bile is not produced in the gallbladder, and its primary function is not to break down proteins.
Which organ's primary role is the production of bile and other metabolic functions such as blood sugar regulation and detoxification?
- A. Gallbladder
- B. Pancreas
- C. Liver
- D. Stomach
Correct Answer: C
Rationale: The correct answer is the liver. The liver is responsible for producing bile, regulating blood sugar levels, and detoxifying the blood. Bile produced by the liver is stored in the gallbladder. The pancreas primarily functions in digestion by producing enzymes and insulin, while the stomach is mainly involved in breaking down food through the secretion of gastric juices.
Which two types of elements are most likely to form an ionic bond?
- A. Two elements that are in the same period.
- B. Two elements that are non-metals and have p orbitals.
- C. One element that is a transition metal with d orbitals and one element that is a metal with s orbitals.
- D. One element that is a metal with s orbitals and one element that is a nonmetal with p orbitals.
Correct Answer: D
Rationale: Ionic bonds typically form between a metal, which donates electrons from its s orbital, and a nonmetal, which accepts electrons into its p orbital. This transfer of electrons leads to the formation of an ionic bond. Choice A is incorrect as elements in the same period may vary significantly in their properties. Choice B is incorrect because ionic bonds are usually formed between a metal and a nonmetal, not two nonmetals. Choice C is incorrect because transition metals generally form complex ions through the sharing of electrons, not typical ionic bonds.
Which of the following types of stem cells can differentiate into any cell type, including forming an entire organism?
- A. Totipotent stem cells
- B. Multipotent stem cells
- C. Pluripotent stem cells
- D. Hematopoietic stem cells
Correct Answer: A
Rationale: Totipotent stem cells possess the unique ability to differentiate into any cell type, including forming an entire organism. These cells have the highest potency level and can give rise to both embryonic and extraembryonic cell types, allowing them to develop into a complete organism. Multipotent stem cells (Choice B) can differentiate into a limited range of cell types within a specific tissue or organ. Pluripotent stem cells (Choice C) can differentiate into any cell type in the body except for those needed to support and develop a fetus. Hematopoietic stem cells (Choice D) are a type of multipotent stem cell that can differentiate into various blood cell types.