Nokea
What is the primary function of centrosomes in animal cells?
- A. Pathogen digestion
- B. Cytoplasm formation
- C. Organelle trafficking
- D. Microtubule organization
Correct Answer: D
Rationale: Centrosomes play a crucial role in animal cells by organizing microtubules. They act as the main microtubule organizing center (MTOC) and are essential for various cellular processes such as cell division, cell shape maintenance, and intracellular transport. Correctly organized microtubules are vital for maintaining cell structure and function, making option D, 'Microtubule organization,' the correct answer.
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Which class of biological molecules includes enzymes?
- A. Carbohydrates
- B. Vitamins
- C. Lipids
- D. Proteins
Correct Answer: D
Rationale: Enzymes are proteins that serve as biological catalysts, accelerating chemical reactions in living organisms. Proteins, a class of biological molecules crucial for the structure and function of cells, tissues, and organs, include enzymes. While carbohydrates, vitamins, and lipids are essential biomolecules, they do not encompass enzymes. Therefore, the correct answer is Proteins (Choice D).
Which of the following macromolecules forms the cytoskeleton of a cell?
- A. Proteins
- B. Carbohydrates
- C. Nucleic acids
- D. Lipids
Correct Answer: A
Rationale: The correct answer is Proteins (Choice A). The cytoskeleton of a cell is primarily composed of proteins. Proteins such as actin, tubulin, and intermediate filaments form the structural framework of the cytoskeleton, providing support, shape, and aiding in cellular movement. Carbohydrates, nucleic acids, and lipids do not constitute the cytoskeleton; instead, they serve various functions within the cell. Therefore, understanding the composition of the cytoskeleton is crucial for comprehending cellular structure and function.
Which of the following substances is excreted by sweat glands in response to the breakdown of proteins and the formation of ammonia?
- A. Sebum
- B. Water
- C. Urea
- D. Lysozymes
Correct Answer: C
Rationale: Urea is the correct answer. Sweat glands excrete urea in response to the breakdown of proteins and the formation of ammonia. Urea is a waste product resulting from the breakdown of proteins in the liver and is excreted in urine as well as through sweat. Sebum is an oily substance produced by the skin's sebaceous glands, water is excreted by various means but is not specifically a result of protein breakdown, and lysozymes are enzymes that help protect the body against bacterial infections.
Which laboratory method is most useful for separating genomic DNA fragments by size?
- A. Titration
- B. Spectrophotometry
- C. Electrophoresis
- D. Filtration
Correct Answer: C
Rationale: Electrophoresis is the most suitable method for separating genomic DNA fragments by size. In electrophoresis, DNA fragments are separated based on their size through an electric field. The smaller fragments move faster towards the positive electrode, while the larger fragments move slower, allowing for differentiation based on size. Titration is a technique used to determine the concentration of a substance in a solution, not for separating DNA fragments. Spectrophotometry is a method used to measure how much a substance absorbs light at different wavelengths, not for separating DNA fragments. Filtration is a process of separating solids from liquids using a filter, not commonly used for separating DNA fragments by size.
What is the function of the myelin sheath for a nerve cell?
- A. Sensory perception
- B. Insulation
- C. Nutrition
- D. Regeneration
Correct Answer: B
Rationale: The myelin sheath functions as an insulator for nerve cells, enabling the rapid transmission of electrical impulses along the nerve fiber. This insulation is essential for maintaining the speed and efficiency of nerve signal conduction. Sensory perception involves detecting sensory stimuli, nutrition involves the supply of nutrients, and regeneration is the process of regrowth or repair, which are distinct functions from what the myelin sheath provides.