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What primarily makes up the 'gray matter' of the brain?
- A. Meninges
- B. Neuron cell bodies
- C. Corpus callosum
- D. Neuron cell axons
Correct Answer: B
Rationale: The 'gray matter' of the brain primarily consists of neuron cell bodies. Gray matter is responsible for processing information in the brain as it contains the cell bodies of neurons, dendrites, and unmyelinated axons. Meninges are the protective membranes covering the brain and spinal cord, the corpus callosum is a structure connecting the two brain hemispheres, and neuron cell axons are part of the white matter in the brain.
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For the reaction below, which of the following would result from increasing the temperature of the environment? A + B ⇌ C + Heat
- A. The concentrations of A and B would increase, and the concentration of C would decrease.
- B. The reaction would remain at equilibrium, and there would be no change in the concentrations of A, B, or C.
- C. The concentrations of A and B would decrease, and the concentration of C would remain the same.
- D. The concentrations of A, B, and C would all increase.
Correct Answer: A
Rationale: Increasing the temperature shifts the equilibrium of an exothermic reaction (such as this one) to favor the reactants (A and B), causing their concentrations to increase and the concentration of the product (C) to decrease. This is due to Le Chatelier's principle, which states that if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance. In this case, by increasing the temperature, the system will shift the equilibrium position in the endothermic direction to absorb the excess heat. As a result, more reactants (A and B) will be produced, leading to an increase in their concentrations, while the concentration of the product (C) will decrease to counteract the temperature increase.
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.
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.
What summarizes a change that occurs as solids transition into liquids?
- A. Particles become less ordered
- B. Particles increase in mobility
- C. Particles move further apart
- D. Intermolecular forces between particles weaken
Correct Answer: A
Rationale: The correct answer is A. When solids transition into liquids, particles become less ordered. In a solid state, particles are arranged in a fixed, orderly pattern due to strong intermolecular forces. As the solid transitions into a liquid, these forces weaken, allowing the particles more freedom of movement. Consequently, the particles become less ordered in a liquid compared to a solid, where they have more mobility and are not bound in a fixed structure.
Among the following molecules, which one contains the fewest covalent bonds?
- A. Water molecule (H2O)
- B. Methane molecule (CH4)
- C. Chlorine molecule (Cl2)
- D. Ammonia molecule (NH3)
Correct Answer: C
Rationale: The correct answer is C. The chlorine molecule (Cl2) contains the fewest covalent bonds as it consists of two chlorine atoms sharing a single covalent bond. Water (H2O), methane (CH4), and ammonia (NH3) involve multiple atoms bonded together, leading to more covalent bonds compared to the chlorine molecule. Hence, among the options provided, the chlorine molecule has the least number of covalent bonds.