Nokea
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 measure the density of irregular solids, a student needs a graduated cylinder to measure the volume of the solids by water displacement, water for the displacement method, and a weighing balance to measure the mass of the solids. Density is calculated by dividing the mass by the volume.
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Which of the following nucleotides is only found in RNA?
- A. Adenine
- B. Uracil
- C. Guanine
- D. Thymine
Correct Answer: B
Rationale: The correct answer is B: Uracil. Uracil is a nucleotide base that is specifically found in RNA. In DNA, thymine replaces uracil. Adenine, guanine, and cytosine are nucleotides present in both RNA and DNA. Understanding the unique nucleotide composition of RNA and DNA is essential in molecular biology to comprehend the genetic information flow and transcription processes accurately. RNA uses uracil instead of thymine, which is a key distinction between the two nucleic acids.
What is the atomic number of an atom that has 12 protons and 12 neutrons?
- A. 1
- B. 144
- C. 12
- D. 24
Correct Answer: C
Rationale: The atomic number of an element is determined by the number of protons in its nucleus. In this case, the atom has 12 protons, which directly corresponds to its atomic number. Neutrons have no impact on the atomic number; they contribute to the atomic mass. The atomic number uniquely identifies an element based on the number of protons in its nucleus. Therefore, the correct answer is 12, as it represents the number of protons in the nucleus and defines the element, regardless of the presence of neutrons.
In a specific scenario, red flowers are dominant over white flowers. A plant heterozygous for red flowers and a plant with white flowers are crossed. What is the expected proportion of phenotypes in the next generation?
- A. 2 red, 2 white
- B. 3 red, 1 white
- C. 4 red, 0 white
- D. 1 red, 3 white
Correct Answer: A
Rationale: When a plant heterozygous for red flowers (Rr) is crossed with a plant having white flowers (rr), according to Mendelian genetics, the Punnett square predicts a 1:1 ratio of red (Rr) to white (rr) flowers in the offspring. This means that the expected proportion in the next generation would be 2 red flowers and 2 white flowers.
The triple point of a substance is the temperature and pressure at which the substance exists as which of the following?
- A. As a gel with solid and liquid trapped in gas
- B. Simultaneously in sol, gel, and plasma phases
- C. Simultaneously in solid, liquid, and gas phases
- D. As a sol with gas and solid trapped in liquid
Correct Answer: C
Rationale: The triple point is a specific condition where a substance can exist simultaneously in all three phases: solid, liquid, and gas. The other options do not accurately describe this state.
Which of the following blood vessels is affected by a myocardial infarction?
- A. coronary
- B. vena cava
- C. pulmonary
- D. aorta
Correct Answer: A
Rationale: A myocardial infarction affects the coronary arteries, not the vena cava, pulmonary, or aorta. The coronary arteries supply blood to the heart muscle, and blockages in these arteries can result in a heart attack. The vena cava is a large vein that carries deoxygenated blood back to the heart, the pulmonary arteries carry deoxygenated blood from the heart to the lungs for oxygenation, and the aorta is the main artery that carries oxygenated blood from the heart to the rest of the body. These vessels are not typically associated with myocardial infarctions as they perform different functions within the circulatory system.