Nokea
Which type of immune cell does the human immunodeficiency virus (HIV) target and destroy?
- A. Neutrophils
- B. Macrophages
- C. Helper T cells
- D. Memory B cells
Correct Answer: C
Rationale: HIV targets and destroys Helper T cells, which are vital for coordinating the immune response against infections. The destruction of Helper T cells weakens the immune system, leading to acquired immunodeficiency syndrome (AIDS). Neutrophils (Choice A) are primarily involved in acute inflammatory responses and fighting bacterial infections. Macrophages (Choice B) play a role in phagocytosis and antigen presentation but are not the primary target of HIV. Memory B cells (Choice D) are responsible for mounting a quicker and more robust antibody response upon re-exposure to a pathogen, but they are not the main target of HIV infection.
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What protein complex controls the progression of mitosis through its activation and degradation?
- A. Ribosome
- B. Cyclin-dependent kinase (CDK)
- C. Centriole
- D. Microtubule
Correct Answer: B
Rationale: A) Ribosome: Ribosomes are cellular organelles responsible for protein synthesis and are not directly involved in controlling the progression of mitosis.
B) Cyclin-dependent kinase (CDK): CDKs are a family of protein kinases that regulate the cell cycle, including the progression of mitosis. CDK activity is controlled by cyclins, which bind to CDKs to activate them at specific points in the cell cycle. The activation and degradation of cyclins regulate the activity of CDKs, which in turn control the progression of mitosis.
C) Centriole: Centrioles are involved in organizing the microtubules of the mitotic spindle but do not directly control the progression of mitosis.
D) Microtubule: Microtubules are structural components of the cytoskeleton and are involved in various cellular processes, including mitosis, but they do not control
What is the function of ribosomal RNA (rRNA)?
- A. Carries amino acids to the ribosomes
- B. Reads the genetic code on mRNA
- C. Forms the structural framework of ribosomes
- D. Controls the rate of protein synthesis
Correct Answer: C
Rationale: Ribosomal RNA (rRNA) plays a crucial role in forming the structural framework of ribosomes. Ribosomes are the cellular organelles responsible for protein synthesis and consist of both protein and rRNA components. The primary function of rRNA is to provide the structural support necessary for ribosomes to function properly. This structural framework allows the ribosome to interact with messenger RNA (mRNA) and transfer RNA (tRNA) during translation, where genetic information encoded in mRNA is used to assemble proteins from amino acids. Therefore, rRNA's main role is in contributing to the structure and function of ribosomes, rather than directly carrying amino acids, reading the genetic code, or controlling the rate of protein synthesis. Choices A, B, and D are incorrect because rRNA does not carry amino acids to the ribosomes (tRNA does this), read the genetic code (this is the role of ribosomes and tRNA), or control the rate of protein synthesis (this is regulated by various factors but not directly by rRNA).
When a car brakes to a stop, friction between the tires and the road acts as:
- A. A balanced force
- B. An unbalanced force causing deceleration
- C. An unbalanced force causing the car to remain at rest
- D. No force at all
Correct Answer: B
Rationale: When a car brakes to a stop, friction between the tires and the road acts as an unbalanced force causing deceleration. This friction force opposes the motion of the car, resulting in a decrease in speed until the car comes to a complete stop. Choice A is incorrect because if the forces were balanced, the car would not experience any deceleration. Choice C is incorrect because if the force were unbalanced in the direction of motion, the car would continue to move instead of coming to a stop. Choice D is incorrect because friction between the tires and the road does exert a force, causing deceleration.
Where does fertilization, the fusion of sperm and egg, typically occur in the human body?
- A. Ovary
- B. Uterus
- C. Fallopian tube
- D. Vagina
Correct Answer: C
Rationale: Fertilization typically occurs in the fallopian tube. This is where the sperm and egg meet and fuse to form a zygote. The fallopian tube provides the optimal environment for fertilization as it helps in the transportation of the egg and provides a suitable site for fertilization before the resulting embryo travels to the uterus for implantation. Choices A, B, and D are incorrect. The ovary is where eggs are produced, the uterus is where the fertilized egg implants and develops into a fetus, and the vagina is the canal that leads to the cervix, but fertilization itself does not occur in these locations.
What is the largest lymphatic vessel in the body?
- A. Jugular vein
- B. Thoracic duct
- C. Subclavian vein
- D. Aorta
Correct Answer: B
Rationale: The thoracic duct is the largest lymphatic vessel in the body, responsible for draining lymph from most parts of the body except for the right upper quadrant. The jugular vein, subclavian vein, and aorta are not part of the lymphatic system; they are blood vessels and do not serve as lymphatic vessels. Therefore, choices A, C, and D are incorrect as they are not associated with the lymphatic system's transport of lymph.