Nokea
Which statement is true regarding aromatic compounds?
- A. Contain a ring structure with alternating single and double bonds
- B. Readily undergo addition reactions
- C. Are easily broken down by water
- D. Do not contain any pi (π) bonds
Correct Answer: A
Rationale: Aromatic compounds contain a ring structure with alternating single and double bonds, known as a benzene ring. This alternating pattern of bonds gives aromatic compounds their stability and unique properties. Due to this resonance, aromatic compounds are less reactive towards addition reactions. Water does not easily break down aromatic compounds due to their stability from the delocalized electrons in the ring structure. Therefore, the correct statement is that aromatic compounds contain a ring structure with alternating single and double bonds, providing them with stability and unique properties. Choices B, C, and D are incorrect. Aromatic compounds do not readily undergo addition reactions (B), are not easily broken down by water (C), and do contain pi (π) bonds due to the presence of the alternating single and double bonds in the ring structure (D).
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What is the scientific name for the building blocks of proteins?
- A. Residues
- B. Monomers
- C. Macromolecules
- D. Peptides
Correct Answer: B
Rationale: Rationale:
- Proteins are made up of long chains of amino acids.
- Amino acids are the building blocks of proteins and are considered monomers.
- Monomers are the individual units that can be linked together to form larger molecules called polymers.
- In the context of proteins, amino acids are the monomers that are linked together through peptide bonds to form polypeptide chains, which then fold into functional proteins.
- Residues refer to the specific amino acids within a protein after certain modifications or cleavages have occurred, so it is not the correct term for the building blocks of proteins.
- Macromolecules are large molecules made up of smaller subunits, such as proteins, nucleic acids, and carbohydrates, but they are not the specific building blocks of proteins.
- Peptides are short chains of amino acids linked by peptide bonds, but they are not the fundamental building blocks of proteins.
Which of the following is NOT a characteristic of mitosis?
- A. The replication of DNA
- B. The condensation of chromosomes
- C. The separation of sister chromatids
- D. The formation of haploid cells
Correct Answer: D
Rationale: Rationale:
A) The replication of DNA is a characteristic of mitosis. Before cell division occurs, the DNA is replicated to ensure that each daughter cell receives a complete set of genetic information.
B) The condensation of chromosomes is a characteristic of mitosis. During mitosis, the chromosomes condense and become visible under a microscope as distinct structures.
C) The separation of sister chromatids is a crucial step in mitosis. During anaphase, the sister chromatids are pulled apart and move to opposite poles of the cell to ensure that each daughter cell receives a complete set of chromosomes.
D) The formation of haploid cells is NOT a characteristic of mitosis. Mitosis results in the formation of two identical diploid daughter cells, each containing the same number of chromosomes as the parent cell. Haploid cells are typically formed through the process of meiosis, not mitosis.
According to the theory of evolution by natural selection, which of the following statements is true?
- A. Organisms evolve towards perfection
- B. Traits are acquired through use and disuse
- C. Individuals with favorable traits survive and reproduce more
- D. All of the above
Correct Answer: C
Rationale: Rationale:
A) Organisms evolve towards perfection - This statement is incorrect. Evolution by natural selection does not suggest that organisms evolve towards perfection. Instead, it emphasizes the adaptation of organisms to their environment over time.
B) Traits are acquired through use and disuse - This statement reflects Lamarck's theory of evolution, not Darwin's theory of evolution by natural selection. Lamarck proposed that organisms could acquire traits during their lifetime and pass them on to their offspring, which has been largely discredited.
C) Individuals with favorable traits survive and reproduce more - This statement accurately reflects the central concept of Darwin's theory of evolution by natural selection. Individuals with traits that are advantageous in their environment are more likely to survive and reproduce, passing on those traits to future generations.
D) All of the above - This option is incorrect because not all of the statements are true. Only option C accurately represents the theory of evolution by natural selection.
Which of the following is the main organ responsible for producing antibodies?
- A. Thymus gland
- B. Spleen
- C. Bone marrow
- D. Lymph nodes
Correct Answer: C
Rationale: Antibodies are proteins produced by specialized white blood cells called B lymphocytes (B cells). These B cells mature in the bone marrow, where they undergo a process of differentiation and maturation to become plasma cells that secrete antibodies. The bone marrow is the primary site for the production of B cells and antibodies in the immune system. The thymus gland is responsible for the maturation of T lymphocytes (T cells), not antibody production. The spleen and lymph nodes play roles in filtering and trapping pathogens but are not the main organs responsible for producing antibodies.
Which of the following is NOT a common location for lymph nodes?
- A. Groin
- B. Armpit
- C. Neck
- D. Liver
Correct Answer: D
Rationale: The correct answer is 'D: Liver.' The liver is not a common location for lymph nodes. Lymph nodes are small, bean-shaped structures distributed throughout the body, including common sites like the groin, armpit, and neck. They play a crucial role in the immune system by filtering lymph fluid and trapping harmful substances, aiding the body in defending against infections and diseases. The liver, on the other hand, is an organ responsible for various functions like detoxification, metabolism, and storage, but it does not house lymph nodes.