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Which of the following organs removes nitrogenous waste from the body?
- A. Gallbladder
- B. Liver
- C. Kidneys
- D. Large intestines
Correct Answer: C
Rationale: The correct answer is C, Kidneys. The kidneys are essential organs responsible for filtering waste products, including nitrogenous wastes like urea and creatinine, from the blood to form urine. The other organs listed have different primary functions. The gallbladder stores bile produced by the liver, which aids in digestion. The liver has various metabolic functions but is not primarily involved in removing nitrogenous waste. The large intestines mainly absorb water and electrolytes from feces, not nitrogenous waste. Therefore, the kidneys are the specific organs designed to remove nitrogenous waste from the body.
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Which of the following is an efferent neuron responsible for releasing a neurotransmitter that stimulates a muscle?
- A. Neuron
- B. Motor neuron
- C. Nephrons
- D. Neurotransmitter
Correct Answer: B
Rationale: The correct answer is B, 'Motor neuron.' Motor neurons are efferent neurons that carry signals from the central nervous system to muscles or glands. These neurons release neurotransmitters, such as acetylcholine, at the neuromuscular junction to stimulate muscle contraction. Choice A, 'Neuron,' is a broad term for a nerve cell and does not specifically describe the function mentioned. Choice C, 'Nephrons,' are structural components of the kidney and are not related to muscle stimulation. Choice D, 'Neurotransmitter,' refers to the chemical messenger released by neurons to communicate with other cells and is not the specific neuron type responsible for muscle stimulation.
Through which of the following transport mechanisms do water molecules enter cells?
- A. Facilitated diffusion
- B. Electrochemical gradients
- C. Gated channels
- D. Proton pumps
Correct Answer: A
Rationale: Water molecules enter cells through facilitated diffusion. Facilitated diffusion is the passive movement of molecules across a cell membrane with the help of specific transport proteins. In the case of water, it moves through specialized channels called aquaporins using this mechanism, allowing it to cross the membrane more efficiently than by simple diffusion. While electrochemical gradients, gated channels, and proton pumps play roles in transporting other substances and ions, they are not directly involved in the transport of water molecules into cells.
To accurately measure the density of a series of small irregular solids made of plastic, wood, fiberglass, and glass, which of the following laboratory tools will a student need?
- A. Graduated cylinder, water, weighing balance
- B. Weighing balance, Bunsen burner, metric ruler
- C. Graduated cylinder, spectrophotometer, water
- D. Graduated beaker, metric ruler, water
Correct Answer: A
Rationale: To accurately measure the density of irregular solids made of various materials, a student needs specific laboratory tools. Firstly, a graduated cylinder is required to measure the volume of the irregular solids using the water displacement method, which allows for precise volume determination. Secondly, a weighing balance is necessary to measure the mass of the irregular solids accurately. Density is calculated by dividing the mass by the volume, hence the need for both mass and volume measurements. Therefore, the essential tools for this task are a combination of a graduated cylinder, water, and weighing balance (Choice A). These tools together provide the necessary measurements for calculating the density of the irregular solids accurately.
A researcher writes a grant proposal to repeat an experiment that was recently published by another researcher. Which of the following statements best supports the grant proposal?
- A. Funding this grant proposal will allow for the continuation of studying this topic.
- B. Repeating the published work will provide independent confirmation of the results.
- C. Repeating published work with altered variables will extend the previous findings.
- D. Supporting this important research will be beneficial for science in the long term.
Correct Answer: B
Rationale: The best support for the grant proposal is that repeating the published work will provide independent confirmation of the results. This is crucial for scientific research as it strengthens the validity and reliability of the original findings. Independent confirmation is essential for verifying the reproducibility and credibility of the study. Options A, C, and D, though somewhat relevant, do not directly address the primary purpose of repeating the experiment for validation and verification in scientific research.
Which of the following substances is excreted by the sweat glands in response to the breakdown of proteins and the formation of ammonia?
- A. Lysozymes
- B. Water
- C. Urea
- D. Sebum
Correct Answer: C
Rationale: The correct answer is Urea. Sweat glands excrete urea in response to the breakdown of proteins and the formation of ammonia. Urea is a waste product formed in the liver by the breakdown of amino acids. It is then excreted by the kidneys in urine and by sweat glands through perspiration. Urea plays a vital role in the excretory process by helping eliminate nitrogenous wastes from the body and maintaining proper physiological balance.