Nokea
Which of the following is a function of bone?
- A. Detoxification of alcohol
- B. Production of otoliths
- C. Storage of minerals
- D. Secretion of hormones
Correct Answer: C
Rationale: Bones serve as a crucial storage site for essential minerals like calcium and phosphorus. These minerals are indispensable for various physiological functions in the body, such as muscle contraction, nerve transmission, and blood clotting. Bones act as a reservoir for these minerals, releasing them into the bloodstream as needed to maintain appropriate mineral levels. Therefore, the correct answer is C, storage of minerals.
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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.
Why is nitrogen gas an extremely stable molecule?
- A. resonance bonds
- B. ionic bonds
- C. triple covalent bonds
- D. hydrogen bonds
Correct Answer: C
Rationale: The correct answer is C - triple covalent bonds. Nitrogen gas (N2) is composed of two nitrogen atoms held together by a triple covalent bond. This bond is very strong and requires a significant amount of energy to break, making nitrogen gas a stable molecule. Triple covalent bonds involve the sharing of three pairs of electrons, resulting in a very stable configuration. Resonance bonds, ionic bonds, and hydrogen bonds are not present in the structure of nitrogen gas, hence they do not contribute to its stability.
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 types of cells stimulates other immune cells to attack and destroy foreign agents?
- A. Cytotoxic T-cells
- B. Natural killer cells
- C. Helper T-cells
- D. Plasma cells
Correct Answer: C
Rationale: Helper T-cells play a crucial role in coordinating the immune response by activating and directing other immune cells, such as cytotoxic T-cells and macrophages, to attack and eliminate foreign invaders. They achieve this through the release of signaling molecules called cytokines, which regulate the immune system's response to infections and other challenges. Helper T-cells are also involved in activating B-cells to produce antibodies. Natural killer cells, on the other hand, are part of the innate immune system and can directly kill infected or abnormal cells without prior activation.
Which of the following organic molecules contains both an amine and a carboxyl group?
- A. Lipids
- B. Cellulose
- C. Chitin
- D. Proteins
Correct Answer: D
Rationale: Proteins are composed of amino acids, which contain both an amine (NH2) and a carboxyl (COOH) functional group. The amine group is found at one end of the amino acid molecule, while the carboxyl group is located at the other end. When amino acids join together through peptide bonds, the amine of one amino acid reacts with the carboxyl group of another, forming a protein chain. Therefore, the correct answer is proteins.