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Which term means a group of similar cells combined to perform a common function?
- A. Tissue
- B. System.
- C. Organism.
- D. Organ.
Correct Answer: A
Rationale:
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Which of the following cell types lacks a nucleus?
- A. platelet
- B. red blood cell
- C. white blood cell
- D. phagocyte
Correct Answer: B
Rationale: The correct answer is red blood cell (choice B). Red blood cells, also known as erythrocytes, lack a nucleus at maturity in humans. The absence of a nucleus allows these cells to carry oxygen more efficiently by maximizing space for hemoglobin, the oxygen-carrying protein. Platelets (choice A), white blood cells (choice C), and phagocytes (choice D) all have nuclei. Platelets are involved in blood clotting, white blood cells are part of the immune system, and phagocytes specialize in engulfing and digesting cellular debris and pathogens.
What term describes the process of producing the RNA strand from a DNA template?
- A. Metabolism.
- B. Transcription.
- C. Synthesis.
- D. Replication.
Correct Answer: B
Rationale: The correct answer is B: Transcription. Transcription is the process where RNA is synthesized from a DNA template by RNA polymerase. During transcription, the DNA double helix unwinds, and one strand is used as a template to create a complementary RNA molecule. This process occurs in the cell nucleus and is essential for gene expression.
Choice A, Metabolism, refers to the chemical reactions that occur in living organisms to maintain life and is not directly related to RNA synthesis. Choice C, Synthesis, is a general term that does not specifically describe the process of RNA production from a DNA template. Choice D, Replication, is the process of copying DNA to create an identical DNA molecule, not RNA synthesis. Therefore, the correct term for producing an RNA strand from a DNA template is Transcription.
Which of the following is always true about molecules?
- A. They can travel through all cell membranes
- B. They move from low concentration to high concentration without using energy
- C. They move from high concentration to low concentration without using energy
- D. They cannot move
Correct Answer: C
Rationale: The correct answer is C: 'They move from high concentration to low concentration without using energy.' This statement aligns with the concept of passive transport, where molecules naturally move from areas of higher concentration to lower concentration to reach equilibrium. This process does not require energy input. Option A is incorrect because not all molecules can freely pass through all cell membranes due to factors like size and charge. Option B describes active transport, which involves the movement of molecules against their concentration gradient, requiring energy. Option D is incorrect as molecules are in constant motion.
Which of the following statements about antibiotics is not true?
- A. They can interfere with the bacteria's ability to survive
- B. They can affect how bacteria multiply
- C. They can cause more bacteria to grow
- D. They only work on bacteria
Correct Answer: C
Rationale: Antibiotics are medications used to treat bacterial infections by either killing the bacteria or inhibiting their growth. Options A and B correctly describe the mechanisms of action of antibiotics, making them true statements. Option C is incorrect as antibiotics are meant to reduce bacterial growth, not cause more bacteria to grow. Option D is also true as antibiotics specifically target bacterial infections and do not work on viruses or other pathogens.
What are the two catabolic pathways that lead to cellular energy production?
- A. Fermentation and cellular respiration
- B. Fermentation and external respiration
- C. Fermentation and anaerobic respiration
- D. Fermentation and internal respiration
Correct Answer: A
Rationale: The correct answer is A: Fermentation and cellular respiration. Fermentation and cellular respiration are two catabolic pathways that lead to cellular energy production. Fermentation occurs in the absence of oxygen and involves glycolysis followed by the conversion of pyruvate to various byproducts. Cellular respiration, on the other hand, occurs in the presence of oxygen and involves glycolysis, the citric acid cycle, and the electron transport chain to produce ATP. While fermentation and anaerobic respiration involve partial breakdown of glucose without the complete utilization of oxygen, the term 'internal respiration' is not a commonly used concept in the context of cellular energy production.