Nokea
What is the name of the sheath of connective tissue that surrounds a skeletal muscle?
- A. Epimysium
- B. Perimysium
- C. Endomysium
- D. Myofibril
Correct Answer: A
Rationale: The correct answer is Epimysium. The epimysium is the outermost layer of connective tissue that surrounds a skeletal muscle, providing protection and support to the muscle as a whole. Perimysium, which surrounds bundles of muscle fibers known as fascicles, is not the sheath that surrounds the entire muscle. Endomysium surrounds individual muscle fibers, not the entire muscle. Myofibril is a structure within muscle fibers that contains the contractile proteins responsible for muscle contraction, but it is not the sheath of connective tissue surrounding the muscle.
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Which of the following is an example of a fibrous protein?
- A. Insulin
- B. Keratin
- C. Hemoglobin
- D. Collagen
Correct Answer: D
Rationale: A) Insulin is a hormone, not a fibrous protein. It is produced in the pancreas and regulates blood sugar levels.
B) Keratin is a fibrous structural protein found in hair, nails, and the outer skin layer, providing strength and protection.
C) Hemoglobin is a globular protein in red blood cells responsible for oxygen transport; it is not fibrous.
D) Collagen is a fibrous protein found in tendons, ligaments, and skin, offering strength and structure to connective tissues. Therefore, the correct answer is collagen, making it the main component of various connective tissues.
What is the term for the gradual loss of topsoil due to wind or water erosion?
- A. Desertification
- B. Leaching
- C. Salinization
- D. Acidification
Correct Answer: A
Rationale: A) Desertification is the correct term for the gradual loss of topsoil due to wind or water erosion. It refers to the process by which fertile land becomes desert, usually due to factors like drought, deforestation, or inappropriate agriculture practices. This process can lead to the degradation of land and contribute to the expansion of deserts. B) Leaching is the process in which minerals are washed out of the soil by water moving downwards through it. This is different from the loss of topsoil due to erosion. C) Salinization occurs when salt accumulates in the soil, typically as a result of irrigation in arid regions. While salinization affects soil quality, it is not specifically related to the gradual loss of topsoil due to erosion. D) Acidification refers to the decrease in soil pH, often caused by factors like acid rain or the use of acidic fertilizers. This process is distinct from the gradual loss of topsoil due to erosion.
An uncharged atom has an electron configuration of 1s² 2s² 2pⶠ3s² and a mass number of 14. How many protons does it have?
- A. 14
- B. 6
- C. 8
- D. 12
Correct Answer: B
Rationale: The number of protons in an atom is determined by the atomic number, which is equal to the number of protons in the nucleus. The electron configuration given corresponds to carbon (C) with 6 protons. The atomic number of an element is the same as the number of protons in its nucleus, so in this case, the atom has 6 protons. Choices A, C, and D are incorrect because they do not correspond to the correct number of protons for an atom with the given electron configuration and mass number. Therefore, option B, 6 protons, is the correct answer.
What are the constituents of an atomic nucleus?
- A. Electrons and protons only
- B. Protons and neutrons only
- C. Electrons, protons, and neutrons
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B: Protons and neutrons only. Electrons are located outside the nucleus in electron shells. Protons and neutrons are the subatomic particles found within the nucleus of an atom. Protons carry a positive charge, while neutrons are neutral. These particles contribute to the mass and stability of the nucleus. Choice A is incorrect because electrons are not part of the nucleus. Choice C is incorrect as electrons are not found within the nucleus, only protons and neutrons. Choice D is incorrect as protons and neutrons are indeed constituents of an atomic nucleus.
In nuclear physics, the term 'magic number' refers to specific numbers of protons or neutrons that contribute to:
- A. Increased nuclear instability
- B. Enhanced radioactive decay rates
- C. Exceptional stability of the nucleus
- D. All of the above
Correct Answer: C
Rationale: In nuclear physics, the term 'magic number' refers to specific numbers of protons or neutrons that lead to exceptional stability of the nucleus. These 'magic numbers' correspond to completely filled nuclear energy levels, resulting in increased stability rather than instability. Choice A, 'Increased nuclear instability,' is incorrect as magic numbers actually contribute to stability. Choice B, 'Enhanced radioactive decay rates,' is also incorrect as magic numbers do not affect decay rates but rather stability. Therefore, the correct answer is choice C, as magic numbers contribute to the exceptional stability of the nucleus.