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What is the approximate threshold value for mammalian neurons?
- A. -80 mV
- B. -55 mV
- C. 0 mV
- D. +35 mV
Correct Answer: B
Rationale: The approximate threshold value for mammalian neurons is around -55 mV. At this membrane potential, the neuron becomes more excitable and is more likely to generate an action potential. If the membrane potential reaches this level or depolarizes beyond it, it triggers the opening of voltage-gated ion channels, leading to the initiation of an action potential. Values below this threshold are considered subthreshold and do not usually result in action potential generation. Understanding the threshold potential is crucial in assessing the excitability and firing properties of neurons, as it represents the critical point at which the neuron transitions from a resting state to an active state, enabling the transmission of electrical signals.
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If A represents atomic mass and Z represents atomic number, which of the following describes an atom after a proton is emitted from its nucleus?
- A. A+1, Z-1
- B. A-1, Z+1
- C. A+1, Z+1
- D. A-1, Z-1
Correct Answer: D
Rationale: When a proton is emitted from the nucleus of an atom, the atomic mass (A) remains the same while the atomic number (Z) decreases by 1. This is because a proton carries a positive charge and has a mass of 1 atomic mass unit. Therefore, the correct description after the emission of a proton is A-1, Z-1. The atomic mass decreases by 1 because a proton is lost, and the atomic number decreases by 1 since the nucleus loses a positively charged particle.
Which of the following organs filters excess solutes from the blood?
- A. Stomach
- B. Kidney
- C. Gallbladder
- D. Spleen
Correct Answer: B
Rationale: The correct answer is B: Kidney. The kidneys are vital organs responsible for filtering excess solutes, wastes, and toxins from the blood to produce urine. The stomach's primary function is digestion, the gallbladder stores bile, and the spleen aids in blood filtration and fighting infections. However, it is the kidneys that specifically filter solutes from the blood, making them crucial for maintaining proper fluid and electrolyte balance in the body.
Where is genetic information that describes the characteristics of an organism found?
- A. Ribosomes
- B. Membranes
- C. Cilia
- D. Nuclei
Correct Answer: D
Rationale: The genetic information that describes the characteristics of an organism is found in the nuclei. The nucleus contains the organism's DNA, which carries the genetic information responsible for determining the organism's traits and characteristics. Ribosomes are involved in protein synthesis, membranes form boundaries of cells, and cilia are hair-like structures used for movement or sensory functions, but they do not house genetic information.
Which of the following statements is correct regarding the pH scale?
- A. A substance with a pH of 3 is more acidic than a substance with a pH of 4.
- B. A substance with a pH of 3 is two times more alkaline than a substance with a pH of 4.
- C. A substance with a pH of 3 is 10 times more alkaline than a substance with a pH of 4.
- D. A substance with a pH of 3 is 10 times more acidic than a substance with a pH of 4.
Correct Answer: D
Rationale: The correct answer is D. The pH scale measures the acidity or basicity of a substance on a scale of 0 to 14. Each whole pH value below 7 is ten times more acidic than the next higher value. Therefore, a substance with a pH of 3 is 10 times more acidic than a substance with a pH of 4. The difference in pH values indicates the concentration of hydrogen ions in the substance, with lower pH values representing higher acidity and higher pH values representing higher basicity.
A researcher writes a grant proposal to replicate an experiment recently published by another researcher. Which statement best supports the grant proposal?
- A. Funding this critical research will benefit science in the long term.
- B. Replicating the published work will provide independent confirmation of the results.
- C. Funding this grant proposal will allow this laboratory to further study this topic.
- D. Replicating published work with altered variables will extend the previous results.
Correct Answer: B
Rationale: Choice B is the correct answer as it emphasizes the significance of independent verification of research findings through replication. Replicating experiments is a fundamental part of the scientific method to ensure the credibility and accuracy of results. It plays a crucial role in validating the original outcomes and contributes to establishing a strong scientific knowledge base. By replicating the published work, the researcher aims to confirm the validity and reliability of the initial findings, which is essential for building upon existing knowledge and advancing scientific understanding.