Nokea
What type of bond connects sugar and phosphate in DNA?
- A. hydrogen
- B. ionic
- C. covalent
- D. overt
Correct Answer: C
Rationale: The correct answer is covalent (Choice C). In DNA, the bond connecting the sugar and phosphate groups is a phosphodiester bond, which is a type of covalent bond. Covalent bonds involve the sharing of electrons between atoms, forming strong and stable connections. Hydrogen bonds are important in DNA structure but are not the primary bond connecting sugar and phosphate. Ionic bonds involve the transfer of electrons between atoms, which is not the case in sugar-phosphate bonds. 'Overt' is not a term used to describe the bond between sugar and phosphate in DNA.
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Among all the molecules that are significant to biology, which of the following are considered the most important?
- A. Carbohydrates, lipids, protein, and nucleic acids
- B. Carbohydrates, lipids, protein, and calcium
- C. Carbohydrates, lipids, protein, and sulfur
- D. Carbohydrates, lipids, protein, and iron
Correct Answer: A
Rationale: The correct answer is A: Carbohydrates, lipids, protein, and nucleic acids. These four types of molecules are essential for various biological processes. Carbohydrates provide energy, lipids are important for energy storage and cell membrane structure, proteins are involved in nearly all cell functions, and nucleic acids carry genetic information. While the other choices contain important components, nucleic acids play a crucial role in storing and transmitting genetic information, making them indispensable in biology.
During which phase is the chromosome number reduced from diploid to haploid?
- A. S phase
- B. interphase
- C. mitosis
- D. meiosis I
Correct Answer: D
Rationale: The correct answer is meiosis I. Meiosis is a specialized cell division process that occurs in sexually reproducing organisms to produce gametes (sperm and egg). In meiosis I, the chromosome number is reduced from diploid (2n) to haploid (n) by separating homologous chromosomes. This reduction in chromosome number is crucial for maintaining the correct chromosome count in sexually reproducing organisms and ensuring genetic diversity in offspring.
What type of bond bonds one molecule of water with another molecule of water?
- A. Ionic
- B. Covalent
- C. Hydrogen
- D. Molecular
Correct Answer: C
Rationale: Two molecules of water are bonded through hydrogen bonding. This type of bond forms between the slightly positive hydrogen atom in one water molecule and the slightly negative oxygen atom in another water molecule. Hydrogen bonds are weaker than covalent bonds but are essential in various biological processes and properties of water, contributing to its unique characteristics like high surface tension, cohesion, and adhesion.
Why is DNA important for metabolic activities of the cell?
- A. It initiates cellular mitosis.
- B. It provides cell wall stability.
- C. It increases glucose absorption.
- D. It controls the synthesis of enzymes.
Correct Answer: D
Rationale: DNA is crucial for metabolic activities as it contains the genetic information needed for the synthesis of enzymes, which are essential for various metabolic reactions within the cell. Enzymes are biological catalysts that regulate and speed up chemical reactions, allowing the cell to carry out necessary metabolic processes efficiently. Therefore, DNA's role in controlling enzyme synthesis directly impacts the cell's metabolic activities, making option D the correct answer.
Skin cells undergo what type of cellular division?
- A. Melosis.
- B. Binary fission.
- C. Sexual reproduction.
- D. Mitosis.
Correct Answer: D
Rationale: The correct answer is D: Mitosis. Skin cells undergo mitosis, a type of cellular division where a parent cell divides into two identical daughter cells. During mitosis, the genetic material is equally distributed between the daughter cells to ensure genetic stability. Melosis (A) is incorrect as it refers to the type of cell division that occurs during sexual reproduction to produce gametes. Binary fission (B) is incorrect as it is a form of asexual reproduction seen in prokaryotes. Sexual reproduction (C) is incorrect as it involves the fusion of gametes from two different parents to produce genetically diverse offspring, not the division of existing cells like in skin cells. In summary, mitosis is the correct choice for skin cell division as it maintains genetic continuity and ensures tissue growth and repair.