Which of the following functions does the myelin sheath perform for a nerve cell?
Insulation
Regeneration
Sensory perception
Nutrition
Correct Answer : A
The myelin sheath is a protective membrane that wraps around parts of certain nerve cells.
Its fatty-protein coating provides protective insulation for your nerve cell like the plastic insulation covering that encases the wires of an electrical cord ².
This allows the electrical impulses to travel quickly and efficiently between one nerve cell and the next. The other options are incorrect because they do not describe the functions of the myelin sheath.
Regeneration, sensory perception, and nutrition are not functions performed by the myelin sheath for a nerve cell.
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Correct Answer is A
Explanation
A genetic mutation that results in uncontrolled division of a single cell within the body describes cancer ¹. Cancer is a disease of uncontrolled cell division ¹. Its development and progression are usually linked to a series of changes in the activity of cell cycle regulators ¹. In most cases, these changes in activity are due to mutations in the genes that encode cell cycle regulator proteins ¹.
The other options are not correct because they do not accurately describe a genetic mutation that results in uncontrolled division of a single cell within the body. Gene therapy, stem cells, and translation are not processes that result in uncontrolled cell division.
Correct Answer is B
Explanation
A change that takes place as a solid turns to a liquid is that particles become less ordered ¹. When a solid is heated, its particles gain energy and begin to vibrate more rapidly ². As the temperature increases, the particles gain enough energy to overcome the forces holding them in place and begin to move more freely
². This results in a loss of order as the solid melts and becomes a liquid.
The other options are not correct because they do not accurately describe a change that takes place as a solid turns to a liquid. Particles do not have a decrease in mobility, move closer together, or experience stronger intermolecular forces between them as a solid turns to a liquid.
Correct Answer is B
Explanation
The relaxation of the chambers of the heart during the cardiac cycle is called diastole ¹. The cardiac cycle is a sequence of events that occurs when the heart beats ². It consists of two phases: systole, when the heart contracts and pumps blood into circulation, and diastole, when the heart relaxes and fills with blood ².
The other options are not correct because they do not accurately describe the relaxation of the chambers of the heart during the cardiac cycle. Tachycardia is a rapid heart rate, bradycardia is a slow heart rate, and systole is the contraction of the heart chambers.
Correct Answer is A
Explanation
The correct answer is a. Nuclei. Genetic information describing the characteristics of an organism is found in the nuclei of its cells. The nucleus contains the organism's DNA, which carries the genetic information that determines its traits.
b. Membranes are structures that surround and enclose cells and organelles, but they do not contain genetic information.
c. Cilia are hair-like structures that protrude from the surface of some cells and are involved in movement, but they do not contain genetic information.
d. Ribosomes are organelles that are involved in protein synthesis, but they do not contain genetic information.
Correct Answer is B
Explanation
Emphysema is a lung condition that is caused by damage to the alveoli, the tiny air sacs in the lungs where gas exchange occurs. When the alveoli are damaged, the body has difficulty exchanging oxygen and carbon dioxide. This can lead to shortness of breath and other respiratory problems. The other options are not directly related to the function of the alveoli or the effects of emphysema.
Correct Answer is D
Explanation
An oxidation reaction occurs when there is a removal of electrons ¹. Oxidation is the loss of electrons during a reaction by a molecule, atom or ion ¹. When oxidation occurs, the oxidation state of the chemical species increases ¹.
The other options are not correct because they do not accurately describe what occurs in an oxidation reaction. Removal of oxygen, addition of carbon, and addition of neutrons are not processes that occur in an oxidation reaction.
Correct Answer is A
Explanation
Perforins are immune system molecules that create holes in the cell membranes of their target cells in order to destroy the cell. Perforins are proteins that are released by cytotoxic T cells and natural killer cells
They form pores in the target cell membrane, allowing water and ions to enter the cell and causing it to swell and burst.
The other options are not correct because they do not accurately describe the immune system molecules that create holes in the cell membranes of their target cells. Interferons, cytokines, and lymphotoxins do not create holes in cell membranes.
Correct Answer is A
Explanation
The thylakoid membrane of chloroplasts is where the light-dependent reactions of photosynthesis take place, while the mitochondrial inner membrane is where the electron transport chain and ATP synthesis occur during cellular respiration.
The tonoplast is the membrane that surrounds the central vacuole in plant cells. It is not involved in cellular respiration or photosynthesis.
The other options, epithelial and nuclear, are not related to these processes.
Correct Answer is A
Explanation
The function of a totipotent cell is to develop into any kind of cell ¹. Totipotent cells have the capacity to produce all adult cell types and can enter the germ line, contributing genetic material to succeeding generations ?. They have the ability to self-replicate, producing daughter cells that are identical to the parent ?.
The other options are incorrect because they do not accurately describe the function of a totipotent cell. Fighting infectious diseases, aiding in the maturation of sex cells, and carrying electrical impulses are not functions performed by totipotent cells.
Correct Answer is B
Explanation
Given the new findings that worm infestation can relieve the effects of certain autoimmune disorders, the hypothesis should be modified to state that worm infestation reduces the severity of certain autoimmune disorders.
This option best reflects the new information and suggests a potential benefit of worm infestation in relation to autoimmune disorders. The other options do not accurately reflect the new findings and do not provide a clear modification to the hypothesis.
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