Nokea
After infecting host cells, how does the AIDS virus, which contains RNA, insert viral DNA into the host T-cell?
- A. Receptor proteins located on the surface of the virus
- B. Reverse transcriptase, an enzyme encoded by the virus
- C. The phospholipids found on the envelope of the virus
- D. The protein that makes up the capsid of the virus
Correct Answer: B
Rationale: Reverse transcriptase is an essential enzyme unique to retroviruses like the AIDS virus. It catalyzes the conversion of viral RNA into DNA through a process known as reverse transcription. The newly formed viral DNA is then integrated into the host cell's genome, enabling the virus to replicate and establish a persistent infection within the host.
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When a volcano erupts, its actions are similar to which of the following events?
- A. A tree root pushing up through the pavement
- B. A can of soda fizzing when it is opened
- C. A building burning to the ground
- D. A flood eroding the banks of a stream
Correct Answer: B
Rationale: When a volcano erupts, it releases built-up pressure, gases, and magma explosively, similar to the fizzing action of a can of soda when it is opened. Just like how gas in a soda can causes pressure and fizz when released, the pressure within a volcano causes an explosive release of material during an eruption. This makes choice B the most analogous event to a volcanic eruption among the options provided. The other options do not capture the sudden, forceful, and explosive nature of a volcanic eruption.
Which of the following organs removes nitrogenous waste from the body?
- A. Gallbladder
- B. Liver
- C. Kidneys
- D. Large intestines
Correct Answer: C
Rationale: The correct answer is C, Kidneys. The kidneys are essential organs responsible for filtering waste products, including nitrogenous wastes like urea and creatinine, from the blood to form urine. The other organs listed have different primary functions. The gallbladder stores bile produced by the liver, which aids in digestion. The liver has various metabolic functions but is not primarily involved in removing nitrogenous waste. The large intestines mainly absorb water and electrolytes from feces, not nitrogenous waste. Therefore, the kidneys are the specific organs designed to remove nitrogenous waste from the body.
Which of the following synthesizes antidiuretic hormone?
- A. Pancreas
- B. Thymus
- C. Hypothalamus
- D. Pineal gland
Correct Answer: C
Rationale: The correct answer is C: Hypothalamus. The hypothalamus, located in the brain, synthesizes antidiuretic hormone (ADH), also known as vasopressin. ADH is crucial in regulating water balance by controlling the reabsorption of water in the kidneys. This action reduces urine production, helping to maintain proper fluid levels in the body and prevent dehydration. While the pancreas, thymus, and pineal gland play important roles in the endocrine system, they are not responsible for synthesizing antidiuretic hormone.
Why do chloride ions have a negative charge?
- A. It lost a proton.
- B. It gained a proton.
- C. It gained an electron.
- D. It lost an electron.
Correct Answer: C
Rationale: Chloride ions (Cl-) have a negative charge because they gained an electron. When an atom gains an electron, it increases the number of negative charges relative to positive charges, resulting in a net negative charge, as seen in chloride ions. In the case of chloride ions, a chlorine atom gains an extra electron to achieve a stable electron configuration, turning it into a chloride ion with a negative charge.
Which of the following substances is responsible for donating H+ ions to act as a buffer when blood pH rises?
- A. Carbon Monoxide
- B. Oxygen
- C. Carbon Dioxide
- D. Carbonic Acid
Correct Answer: D
Rationale: Carbonic acid is a pivotal buffer in blood that plays a key role in maintaining pH balance. When blood pH rises, indicating increased alkalinity, carbonic acid releases hydrogen ions (H+) to counterbalance the excess base, thereby preventing significant changes in pH levels. This mechanism highlights the essential function of carbonic acid in regulating the acid-base equilibrium in the blood.