Nokea
Which of the following is the primary physical barrier the body uses to prevent infection?
- A. mucus membranes
- B. stomach acid
- C. skin
- D. urine
Correct Answer: C
Rationale: The correct answer is 'C: skin.' The skin is the primary physical barrier the body uses to prevent infection. It acts as a protective shield that prevents harmful microorganisms from entering the body. The outer layer of the skin, known as the epidermis, acts as a tough physical barrier that blocks the entry of pathogens. Additionally, the skin has special immune cells that can help fight off invaders that manage to breach the physical barrier. Choices A, B, and D are incorrect. While mucous membranes, stomach acid, and urine play important roles in the body's defense against pathogens, the primary physical barrier is the skin, which covers the entire body and provides a robust protective barrier.
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What type of reaction is represented by the following equation: 2C₆Hâ‚â‚„ + 19Oâ‚‚ → 12CO + 14Hâ‚‚O?
- A. Substitution reaction
- B. Acid-base reaction
- C. Enzyme reaction
- D. Combustion reaction
Correct Answer: D
Rationale: The given chemical equation represents a combustion reaction. Combustion reactions involve the burning of a hydrocarbon (C₆Hâ‚â‚„) in the presence of oxygen (Oâ‚‚) to produce carbon monoxide (CO) and water (Hâ‚‚O). Combustion reactions typically release heat and light energy. In this case, the reactants are a hydrocarbon and oxygen, resulting in the formation of carbon monoxide and water. Choices A, B, and C are incorrect because the reaction does not involve substitution, acid-base reactions, or enzyme catalysis. Combustion reactions are characterized by the rapid combination of a substance with oxygen, leading to the production of heat and light energy.
Neurotransmitters send chemical messages across the gap between one neuron and another through which of the following structures?
- A. Schwann cell
- B. ganglion
- C. synapse
- D. axon
Correct Answer: C
Rationale: Neurotransmitters send chemical messages across the gap between one neuron and another through a structure called the synapse. The synapse is a specialized junction where the axon of one neuron meets the dendrite or cell body of another neuron. Neurotransmitters are released from the axon terminal of the presynaptic neuron and travel across the synaptic cleft to bind to receptors on the postsynaptic neuron, transmitting the signal between the two neurons.
Choice A, Schwann cell, is incorrect as Schwann cells are responsible for producing myelin sheath around axons in the peripheral nervous system, not for transmitting neurotransmitters between neurons.
Choice B, ganglion, is incorrect as ganglia are clusters of nerve cell bodies outside the central nervous system and do not directly participate in the transmission of chemical messages between neurons.
Choice D, axon, is incorrect as the axon is a long, slender projection of a neuron that conducts electrical impulses away from the cell body and towards the axon terminals, where neurotransmitters are released into the synapse, but it is not the structure across which neurotransmitters travel to communicate between neurons.
What is the function of fascia in muscle tissue?
- A. to enclose, protect, support, and separate muscle tissue
- B. to connect muscle tissue to bone
- C. to serve as the contractile unit of muscle
- D. to slide past the actin protein cells in muscle to create contraction
Correct Answer: A
Rationale: The correct answer is A: 'to enclose, protect, support, and separate muscle tissue.' Fascia is a connective tissue that surrounds muscles, providing structural support, protecting them from friction and injury, and helping in movement. Choice B is incorrect as tendons are responsible for connecting muscle tissue to bone. Choice C is incorrect as the contractile unit of muscle is the sarcomere, not fascia. Choice D is incorrect as the process described relates to muscle contraction mechanisms involving actin and myosin, not the function of fascia.
How many neutrons are in an atom of the following element with a mass number of 50?
- A. 38
- B. 88
- C. 50
- D. 126
Correct Answer: C
Rationale: Neutrons are found in the nucleus of an atom along with protons. To determine the number of neutrons in an atom, subtract the atomic number (number of protons) from the mass number. In this case, the mass number given is 50. Since the atomic number is not specified, we can infer it from the choices provided. The mass number of an element represents the total sum of protons and neutrons in the nucleus. Therefore, the number of neutrons in this atom would also be 50, as the mass number is equivalent to the combined number of protons and neutrons, making choice C the correct answer. Choices A, B, and D are incorrect as they do not match the given mass number of 50.
Chromatids divide into identical chromosomes and migrate to opposite ends of the cell in which of the following phases of mitosis?
- A. metaphase
- B. anaphase
- C. prophase
- D. telophase
Correct Answer: B
Rationale: During anaphase of mitosis, the sister chromatids detach from each other and migrate to opposite poles of the cell. This process ensures that each daughter cell ultimately receives an identical set of chromosomes, as the chromatids separate and become individual chromosomes again. This is a crucial step in ensuring accurate distribution of genetic material during cell division. In metaphase, the chromosomes align at the cell's equator but do not separate yet. Prophase is the phase where chromatin condenses into chromosomes and the nuclear envelope breaks down. Telophase is the final phase where the nuclear envelope reforms around the separated chromosomes.