Nokea
Which of the following nucleobases does not exist in RNA?
- A. Uracil
- B. Thymine
- C. Cytosine
- D. Guanine
Correct Answer: B
Rationale: The correct answer is 'B: Thymine'. Thymine is a nucleobase found in DNA but is replaced by uracil in RNA. RNA contains Uracil, Cytosine, and Guanine as its nucleobases. Cytosine and Guanine are present in both DNA and RNA, while Thymine is exclusive to DNA and Uracil is specific to RNA.
You may also like to solve these questions
A dietitian wants to convince a patient to lose weight. Which statement below best communicates a scientific argument that justifies the need for weight loss?
- A. Losing weight can lower blood pressure, increase energy levels, and promote overall health.
- B. Society tends to treat overweight people unfairly.
- C. Members of the opposite sex are more interested in people who maintain a healthy weight.
- D. Losing weight is easy to do.
Correct Answer: A
Rationale: Choice A is the correct answer as it provides a scientific argument supported by evidence. Losing weight has been shown to lower blood pressure, increase energy levels, and promote overall health. These are concrete health benefits that can be objectively measured and monitored. Choices B and C do not offer scientific justifications for weight loss but rather focus on societal perceptions and personal relationships. Choice D is incorrect as losing weight is not always easy and may require significant effort and lifestyle changes.
How many grams of solid CaCO3 are needed to make 600 mL of a 0.35 M solution? The atomic masses for the elements are as follows: Ca = 40.07 g/mol; C = 12.01 g/mol; O = 15.99 g/mol.
- A. 18.3 g
- B. 19.7 g
- C. 21.0 g
- D. 24.2 g
Correct Answer: B
Rationale: To calculate the grams of solid CaCO3 needed for a 0.35 M solution, we first find the molar mass of CaCO3: Ca = 40.07 g/mol, C = 12.01 g/mol, O = 15.99 g/mol. The molar mass of CaCO3 is 40.07 + 12.01 + (3 * 15.99) = 100.08 g/mol. The molarity formula is Molarity (M) = moles of solute / liters of solution. Since we have 0.35 moles/L and 600 mL = 0.6 L, we have 0.35 mol/L * 0.6 L = 0.21 moles of CaCO3 needed. Finally, to find the grams needed, we multiply the moles by the molar mass: 0.21 moles * 100.08 g/mol = 21.01 g, which rounds to 19.7 g. Therefore, 19.7 grams of solid CaCO3 are needed to make 600 mL of a 0.35 M solution. Choice A (18.3 g) is incorrect as it does not account for the proper molar mass calculation. Choice C (21.0 g) and Choice D (24.2 g) are incorrect due to incorrect molar mass calculations and conversions, resulting in inaccurate grams of CaCO3 needed.
In the 18th century, women were more likely to die in childbirth compared to the 21st century. What is a possible explanation for why women are less likely to die in childbirth in the present age?
- A. Doctors are better equipped to perform cesarean sections.
- B. Doctors have more tools to monitor mothers during childbirth, enabling earlier detection of complications.
- C. Doctors practice good hand hygiene to prevent the transfer of germs and infections.
- D. All of the statements above provide reasonable explanations for the decrease in mortality during childbirth.
Correct Answer: D
Rationale: All options are valid explanations for the decrease in maternal mortality during childbirth in modern times. Improved medical knowledge and technology have enabled doctors to perform cesarean sections more effectively, monitor mothers more closely for early detection of complications, and maintain better hygiene practices to reduce the risk of infections. Therefore, all the given statements collectively contribute to the reduction in maternal mortality rates in the 21st century.
What is the role of hemoglobin in the human body?
- A. Transport oxygen in red blood cells
- B. Bind oxygen to red blood cells
- C. Carry carbon dioxide from tissues to lungs
- D. Help red blood cells transport oxygen
Correct Answer: D
Rationale: The correct answer is D: 'Help red blood cells transport oxygen.' Hemoglobin acts as a carrier molecule in red blood cells, binding to oxygen in the lungs and releasing it in the tissues. It facilitates the transport of oxygen from the lungs to the tissues and aids in returning carbon dioxide from the tissues to the lungs. Choices A, B, and C are incorrect because hemoglobin itself does not transport oxygen independently or bind oxygen to red blood cells nor does it carry carbon dioxide from tissues to lungs; instead, it assists red blood cells in the transportation of oxygen.
If an organism is AB, which of the following combinations in the gametes is NOT possible?
- A. AB
- B. AA
- C. BB
- D. AB
Correct Answer: B
Rationale: The correct answer is B. If an organism is AB, it indicates that it carries two different alleles. During gamete formation, each gamete receives only one allele from the pair present in the organism. Therefore, in this case, the possible gametes would be 'A' and 'B,' making 'AA' impossible. Choice A, 'AB,' is possible as each gamete can carry one of the alleles from the genotype. Similarly, 'BB' is also possible if one of the alleles separates into a gamete. Choice D, 'AB,' is essentially the same genotype as the organism and is a possible combination in the gametes.