Nokea
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.
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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.
Which type of joint is the hip an example of?
- A. Hinge
- B. Gliding
- C. Ball-and-socket
- D. Pivot
Correct Answer: C
Rationale: The correct answer is C: Ball-and-socket. The hip joint is a ball-and-socket joint, allowing for a wide range of motion in multiple directions. This joint type permits flexion, extension, abduction, adduction, and rotation. Hinge joints, like the knee, allow movement in one plane, similar to a door hinge. Gliding joints permit limited sliding movements. Pivot joints allow rotation around a single axis.
Where is genetic information that describes the characteristics of an organism found?
- A. Ribosomes
- B. Membranes
- C. Cilia
- D. Nuclei
Correct Answer: D
Rationale: The genetic information that describes the characteristics of an organism is found in the nuclei. The nucleus contains the organism's DNA, which carries the genetic information responsible for determining the organism's traits and characteristics. Ribosomes are involved in protein synthesis, membranes form boundaries of cells, and cilia are hair-like structures used for movement or sensory functions, but they do not house genetic information.
To accurately measure the density of a series of small irregular solids made of plastic, wood, fiberglass, and glass, which of the following laboratory tools will a student need?
- A. Graduated cylinder, water, weighing balance
- B. Weighing balance, Bunsen burner, metric ruler
- C. Graduated cylinder, spectrophotometer, water
- D. Graduated beaker, metric ruler, water
Correct Answer: A
Rationale: To accurately measure the density of irregular solids made of various materials, a student needs specific laboratory tools. Firstly, a graduated cylinder is required to measure the volume of the irregular solids using the water displacement method, which allows for precise volume determination. Secondly, a weighing balance is necessary to measure the mass of the irregular solids accurately. Density is calculated by dividing the mass by the volume, hence the need for both mass and volume measurements. Therefore, the essential tools for this task are a combination of a graduated cylinder, water, and weighing balance (Choice A). These tools together provide the necessary measurements for calculating the density of the irregular solids accurately.
Which of the following chemicals is released by one type of immune cell to directly activate another immune cell?
- A. lysozymes
- B. cytokines
- C. perforin
- D. granzymes
Correct Answer: B
Rationale: The correct answer is B: cytokines. Cytokines are signaling molecules released by immune cells to regulate the immune response. They play a crucial role in coordinating and communicating between different immune cells. By releasing cytokines, immune cells can directly activate other immune cells, enhancing the immune response. Lysozymes are enzymes that break down bacterial cell walls, perforin is a protein involved in cell-mediated immune responses, and granzymes are enzymes that induce apoptosis in target cells, mainly used by cytotoxic T cells and natural killer cells, not for directly activating other immune cells.