Nokea
During inhalation, which muscle contracts to increase the volume of the thoracic cavity, allowing air to flow into the lungs?
- A. Diaphragm
- B. Intercostal muscles
- C. Abdominal muscles
- D. Pectoral muscles
Correct Answer: A
Rationale: The diaphragm is the primary muscle responsible for inhalation. When it contracts, it moves downward, increasing the volume of the thoracic cavity and creating a pressure gradient that allows air to flow into the lungs. While the intercostal muscles also play a role in expanding the chest cavity during inhalation, the diaphragm is the main muscle involved in this process. Abdominal muscles and pectoral muscles are not directly involved in the process of inhalation.
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What are the differences between RNA and DNA?
- A. Both have the same structure and function.
- B. RNA is single-stranded, while DNA is double-stranded.
- C. RNA contains ribose sugar, while DNA contains deoxyribose sugar.
- D. RNA has adenine and guanine, while DNA has thymine and cytosine.
Correct Answer: B
Rationale: A) This statement is incorrect. RNA and DNA have different structures and functions. RNA is involved in protein synthesis and other cellular processes, while DNA stores genetic information. B) This statement is correct. RNA is typically single-stranded, while DNA is double-stranded, forming a double helix structure. C) This statement is correct. RNA contains ribose sugar in its backbone, while DNA contains deoxyribose sugar. D) This statement is incorrect. RNA contains adenine, guanine, cytosine, and uracil, while DNA contains adenine, guanine, cytosine, and thymine. Choice B is the correct answer as it accurately describes one of the key differences between RNA and DNA, emphasizing their structural disparity in terms of single-strandedness for RNA and double-strandedness for DNA. Choices A, C, and D contain inaccuracies regarding the structural and compositional distinctions between RNA and DNA, making them incorrect choices.
Which property of a wave remains constant when the wave enters a different medium?
- A. Frequency
- B. Wavelength
- C. Amplitude
- D. Speed
Correct Answer: A
Rationale: When a wave enters a different medium, its frequency remains constant. Frequency is an intrinsic property of the wave determined by its source, and it does not change when transitioning between different mediums. On the other hand, wavelength, amplitude, and speed of the wave can all be altered when the wave moves from one medium to another. Wavelength is dependent on the speed of the wave and can change when entering a different medium due to differences in propagation speed. Amplitude can also change as it is influenced by factors like energy loss or gain at the boundary of the mediums. Speed, determined by the medium's properties, typically changes when a wave transitions between different mediums due to variations in the medium's density and elasticity.
Unlike the circulatory system, the lymphatic system does not have a pump. How does lymph move through the lymphatic vessels?
- A. By the pumping action of the heart
- B. Due to muscle contractions and breathing movements
- C. Through one-way valves within the vessels
- D. All of the above
Correct Answer: C
Rationale: Lymph moves through the lymphatic vessels primarily due to muscle contractions and breathing movements and also with the help of one-way valves within the vessels. The lymphatic system lacks a central pump like the heart; hence, it relies on the contraction of surrounding muscles and breathing movements to propel lymph fluid. One-way valves within the lymphatic vessels prevent backflow and ensure the unidirectional flow of lymph. Option A is incorrect as the lymphatic system does not rely on the pumping action of the heart. Option D is incorrect as the correct answer is the combination of muscle contractions, breathing movements, and one-way valves, not all the options provided.
What is the process of making copies of RNA from DNA called?
- A. Replication
- B. Transcription
- C. Translation
- D. DNA repair
Correct Answer: B
Rationale: Transcription is the correct answer. Transcription is the process of making copies of RNA from DNA. During transcription, the enzyme RNA polymerase binds to a specific region of DNA and synthesizes a complementary RNA strand based on the DNA template. This process is essential for gene expression and protein synthesis in cells. Replication (option A) refers to the process of making copies of DNA, not RNA. Translation (option C) is the process of synthesizing proteins from mRNA, not making copies of RNA from DNA. DNA repair (option D) involves mechanisms that cells use to repair damaged DNA, not the process of making RNA copies from DNA.
What happens to the work done on an object when the angle between the force and displacement is 90 degrees?
- A. Maximum work is done
- B. No work is done
- C. Minimum work is done
- D. Work is infinite
Correct Answer: B
Rationale: When the angle between the force and displacement is 90 degrees, the work done is given by the formula W = F * d * cos(theta), where theta is the angle between the force and displacement vectors. Since cos(90 degrees) = 0, the work done becomes zero. This means that no work is done on the object when the angle between the force and displacement is 90 degrees. Choice A is incorrect because maximum work is done when the force and displacement are in the same direction (theta = 0 degrees). Choice C is incorrect as minimum work is done when the force and displacement are parallel (theta = 0 degrees), not perpendicular. Choice D is incorrect because work cannot be infinite; it depends on the force, displacement, and the cosine of the angle between them.