Which of the following immune system molecules creates holes in the cell membranes of their target cells in order to destroy the cell?
Perforins
Interferons
Cytokines
Lymphotoxins
Correct Answer : A
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.
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Related Questions
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 C
Explanation
The statement "Experiments cannot validate hypotheses, only falsify them" can be restated as "A hypothesis that has not been falsified remains provisional." This means that a hypothesis is considered valid until it is disproved by experimental evidence. However, even if a hypothesis has not been falsified, it is still considered provisional and subject to further testing and scrutiny.
a."Until disproved, an explanation for an observation is valid" is similar to the correct answer but does not capture the provisional nature of a hypothesis.
b."Certain concepts cannot be subjected to direct experimentation" is not a restatement of the original statement.
d. "Proving a hypothesis exempts it from further testing" is incorrect because no hypothesis can be definitively proven and all hypotheses are subject to further testing and scrutiny.
Correct Answer is A
Explanation
The correct answer is a. Soap’s dual polar and nonpolar nature helps bond oil and water. Soap is an emulsifier, which means that it has both polar and nonpolar regions. The polar regions of soap molecules are atracted to water, while the nonpolar regions are atracted to oil and grease. This allows soap to bond with both water and oil, helping to remove dirt and grime from surfaces.
B. Soap’s acidity does not cause grime to precipitate into the water.
C. Soap does not have enzymatic action that helps to dissolve grime into small particles.
D. Soap’s texture does not physically scour grime off surfaces.
Correct Answer is C
Explanation
When a muscle cell is stimulated by a nerve impulse, calcium ions are released from the sarcoplasmic reticulum into the cytoplasm. The calcium ions bind to the troponin complex, which is a protein that regulates the interaction between actin and myosin filaments. The binding of calcium to troponin causes a conformational change that exposes the binding sites for myosin on the actin filaments. This allows the myosin heads to attach to the actin and pull the filaments past each other, resulting in muscle contraction.
Correct Answer is D
Explanation
Enzymes are a type of protein that catalyze chemical reactions in the body. Proteins are one of the four main classes of biological molecules, along with lipids, carbohydrates, and nucleic acids.
The other options are not classes of biological molecules that include enzymes.Lipids are a class of molecules that includes fats and oils, vitamins are organic compounds that are essential for normal growth and nutrition, and carbohydrates are a class of molecules that includes sugars and starches.
Correct Answer is D
Explanation
Air resistance could be greater for A than for B.
Since both objects have the same mass but different times of fall, it suggests that there could be differences in air resistance affecting their fall rates. Object A took longer to fall, indicating that it might have experienced more air resistance compared to Object B.
Correct Answer is C
Explanation
The correct answer is c. Atoms, cells, tissues, organs. This is the correct order of structures from simple to complex. Atoms are the smallest and simplest units of mater. Cells are made up of atoms and are the basic units of life.
Tissues are groups of similar cells that work together to perform a specific function. Organs are made up of different types of tissues and perform more complex functions.
A. Cells, tissues, atoms, organs is not the correct order from simple to complex.
B. Atoms, organs, tissues, cells is not the correct order from simple to complex.
D. Organs, tissues, cells, atoms is not the correct order from simple to complex.
Correct Answer is B
Explanation
The structure that is present in both prokaryotic and eukaryotic cells is the cell membrane ². The cell membrane is a thin layer that surrounds the cell and separates its internal environment from the external environment ². It is composed of a lipid bilayer and proteins and regulates the movement of substances into and out of the cell ².
The other options are not correct because they are not present in both prokaryotic and eukaryotic cells. The endoplasmic reticulum, chloroplast, and Golgi apparatus are organelles that are only found in eukaryotic cells ².
Correct Answer is A
Explanation
To accurately measure the density of a series of small irregular solids made of plastic, wood, fiberglass, and glass, a student will need a graduated cylinder, water, and a weighing balance. The student can use the water displacement method to determine the volume of each solid by measuring the volume of water displaced when the solid is submerged in a graduated cylinder filled with water. The mass of each solid can be measured using a weighing balance. The density can then be calculated by dividing the mass by the volume.
The other options are not correct because they do not provide the necessary tools to accurately measure the density of the solids. A spectrophotometer is used to measure light absorption and is not necessary for measuring density. A graduated beaker is less accurate than a graduated cylinder for measuring volume. A Bunsen burner is used for heating and is not necessary for measuring density.
Correct Answer is D
Explanation
D. The opening of potassium channels allowing potassium to leave the neuron
The correct answer is d. The opening of potassium channels allowing potassium to leave the neuron. Repolarization of a neuron occurs after an action potential, when the neuron's membrane potential returns to its resting state. This is achieved by the opening of potassium channels, which allows potassium ions to flow out of the neuron. This movement of positively charged ions out of the neuron helps to restore the negative membrane potential.
A. The inhibition of sodium and potassium pumps would not allow for repolarization because these pumps are necessary for maintaining the resting membrane potential.
B. The opening of sodium channels would cause depolarization, not repolarization.
C. The closing of both sodium and potassium channels would restrict ion movement, but it would not allow for repolarization.
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