Nokea
Fill in the blanks in the following sentence: Enzymes are ________ molecules that serve as _______ for certain biological reactions.
- A. complex; suppressors
- B. acidic; triggers
- C. small; targets
- D. large; catalysts
Correct Answer: D
Rationale: Enzymes are large molecules that act as catalysts, accelerating chemical reactions by lowering the activation energy required for the reactions to occur. In the context of biological reactions, enzymes function as catalysts, not suppressors, triggers, or targets. The use of 'large' and 'catalysts' accurately describes the nature and role of enzymes in facilitating biological processes.
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What function do ribosomes serve within the cell?
- A. Ribosomes are responsible for cell movement.
- B. Ribosomes aid in protein synthesis.
- C. Ribosomes help protect the cell from its environment.
- D. Ribosomes have enzymes that help with digestion.
Correct Answer: B
Rationale: Ribosomes serve a crucial role in protein synthesis by translating mRNA into proteins. They are not involved in cell movement, protecting the cell from the environment, or aiding in digestion. Choice A is incorrect because ribosomes are not responsible for cell movement. Choice C is incorrect because ribosomes do not primarily protect the cell from its environment. Choice D is incorrect because ribosomes do not have enzymes that aid in digestion.
Two isotopes of the same element have different numbers of:
- A. Electrons
- B. Protons
- C. Neutrons
- D. Nuclei
Correct Answer: C
Rationale: The correct answer is C: 'Neutrons.' Isotopes are variants of an element that have the same number of protons and electrons but differ in the number of neutrons they contain. This difference in neutron count is what distinguishes isotopes from each other while maintaining the same chemical properties. Choice A, 'Electrons,' is incorrect because isotopes of the same element have the same number of electrons. Choice B, 'Protons,' is incorrect because isotopes of the same element have the same number of protons. Choice D, 'Nuclei,' is incorrect as nuclei refer to the central part of an atom containing protons and neutrons, and the question specifically asks about differences between isotopes of the same element.
Which statement most accurately compares and contrasts the structures of DNA and RNA?
- A. Both DNA and RNA have 4 nucleotide bases. Three of the bases are the same, but the fourth base is thymine in DNA and uracil in RNA.
- B. Both DNA and RNA have the same 4 nucleotide bases. However, the nucleotides bond differently in DNA compared to RNA.
- C. Both DNA and RNA have different numbers of nucleotide bases. DNA is a double helix while RNA is a single strand.
- D. Both DNA and RNA have a double helix structure. However, DNA contains 6 nucleotide bases and RNA contains 4 nucleotide bases.
Correct Answer: A
Rationale: The correct answer is A because DNA and RNA both consist of 4 nucleotide bases, namely adenine, cytosine, and guanine, which are common in both. The key difference lies in the fourth base, which is thymine in DNA and uracil in RNA. This distinction is fundamental in understanding the structural variances between DNA and RNA. Choice B is incorrect as it incorrectly states that the nucleotides bond differently in DNA compared to RNA without specifying the crucial base differences. Choice C is inaccurate as it misrepresents the numbers of nucleotide bases in DNA and RNA, and incorrectly describes DNA as a double helix and RNA as a single strand, which is not related to the difference in bases. Choice D is incorrect as it inaccurately portrays DNA with 6 nucleotide bases and RNA with 4, which is not true; both DNA and RNA have 4 nucleotide bases, but with differences in one of the bases.
An atom has 2 protons, 4 neutrons, and 2 electrons. What is the approximate atomic mass of this atom?
- A. 2
- B. 4
- C. 6
- D. 8
Correct Answer: D
Rationale: The atomic mass of an atom is the sum of the protons and neutrons in its nucleus. In this case, the atom has 2 protons and 4 neutrons, totaling 6 particles in the nucleus. Therefore, the approximate atomic mass of this atom is 6, making choice C incorrect. The number of electrons does not significantly contribute to the atomic mass, as they are much lighter and located in the electron cloud surrounding the nucleus. Choices A, B, and C are incorrect as they do not reflect the correct calculation of atomic mass based on protons and neutrons only.
Which of the following statements accurately characterizes the relationship between genes and chromosomes?
- A. Each gene contains multiple chromosomes.
- B. Each chromosome contains multiple genes.
- C. Genes and chromosomes are two different things referring to the same entity.
- D. Genes and chromosomes are not interchangeable terms and do not always occur in equal numbers.
Correct Answer: B
Rationale: The correct answer is B: Each chromosome contains multiple genes. Genes, which are segments of DNA, are located on chromosomes and carry hereditary information. Chromosomes contain many genes, indicating that genes are part of the structure of chromosomes. Choice A is incorrect because genes do not contain chromosomes; rather, they are located on chromosomes. Choice C is incorrect as genes and chromosomes are distinct entities with different functions. Choice D is incorrect because genes and chromosomes are related but not in equal numbers; chromosomes contain multiple genes, but the number of genes can vary between chromosomes.