Nokea
Which of the following organelles is the site of intracellular digestion?
- A. Ribosomes
- B. Lysosomes
- C. Centrosomes
- D. Mitochondria
Correct Answer: B
Rationale: Lysosomes are the organelles responsible for intracellular digestion within the cell. These specialized vesicles contain various enzymes that break down different molecules, such as old cell components or foreign substances. This breakdown process aids in cellular maintenance, recycling of materials, and waste elimination. Ribosomes are primarily involved in protein synthesis, centrosomes are essential for cell division processes, and mitochondria are the powerhouses of the cell, producing energy in the form of ATP. Therefore, the correct answer is B, Lysosomes, as they are specifically designed for intracellular digestion.
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The breakdown of lactose in the small intestine is mediated by the enzyme lactase, and the products are galactose and glucose. Galactose and glucose are which of the following?
- A. Disaccharides
- B. Oligosaccharides
- C. Polysaccharides
- D. Monosaccharides
Correct Answer: D
Rationale: Galactose and glucose are both simple sugars consisting of single sugar units. Therefore, they are classified as monosaccharides. This makes option D the correct answer.
Which of the following vessels carries oxygenated blood?
- A. Pulmonary vein
- B. Superior vena cava
- C. Pulmonary artery
- D. Inferior vena cava
Correct Answer: A
Rationale: The correct answer is A, the pulmonary vein. The pulmonary vein carries oxygenated blood from the lungs back to the heart. It is crucial to differentiate between the pulmonary vein, which carries oxygenated blood, and the pulmonary artery, which carries deoxygenated blood. This understanding is fundamental in comprehending the flow of oxygen-rich and oxygen-poor blood within the cardiovascular system.
Which laboratory method is most useful to separate genomic DNA fragments by size?
- A. Titration
- B. Spectrophotometry
- C. Electrophoresis
- D. Filtration
Correct Answer: C
Rationale: Electrophoresis is the most suitable laboratory method for separating genomic DNA fragments by size. It works by subjecting DNA fragments to an electric field, causing them to migrate through a gel matrix based on size differences. Smaller fragments move faster and travel farther than larger ones, allowing for separation and analysis based on size. Titration is a technique used to determine the concentration of a solution, not to separate DNA fragments by size. Spectrophotometry is used to measure the amount of light absorbed by a substance at different wavelengths, not for DNA fragment size separation. Filtration is a method used to separate solid particles from a liquid or gas by passing it through a filter medium, not for separating DNA fragments by size.
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.
In a specific scenario, red flowers are dominant over white flowers. A plant heterozygous for red flowers and a plant with white flowers are crossed. What is the expected proportion of phenotypes in the next generation?
- A. 2 red, 2 white
- B. 3 red, 1 white
- C. 4 red, 0 white
- D. 1 red, 3 white
Correct Answer: A
Rationale: When a plant heterozygous for red flowers (Rr) is crossed with a plant having white flowers (rr), according to Mendelian genetics, the Punnett square predicts a 1:1 ratio of red (Rr) to white (rr) flowers in the offspring. This means that the expected proportion in the next generation would be 2 red flowers and 2 white flowers.