Which variables affect the rate of diffusion? (Select all that apply.)
Density of media
Size of molecules
Concentration gradient
Membrane permeability
pH
Correct Answer : A,B,C,D,E
Choice A rationale: Density of media affects the rate of diffusion because it influences the frequency of collisions between the diffusing molecules and the molecules of the medium. The denser the medium, the slower the diffusion rate, and vice versa.
Choice B rationale: Size of molecules affects the rate of diffusion because it determines how easily the molecules can move through the spaces between the molecules of the medium. The smaller the molecules, the faster the diffusion rate, and vice versa.
Choice C rationale: Concentration gradient affects the rate of diffusion because it is the difference in concentration of the diffusing molecules between two regions. The higher the concentration gradient, the faster the diffusion rate, and vice versa.
Choice D rationale: Membrane permeability affects the rate of diffusion because it is the ability of the membrane to allow the diffusing molecules to pass through it. The more permeable the membrane, the faster the diffusion rate, and vice versa.
Choice E rationale: pH affects the rate of diffusion because it is the measure of acidity or alkalinity of the medium. pH can affect the charge and shape of the diffusing molecules, which can affect their ability to cross the membrane or interact with the molecules of the medium. pH can also affect the membrane permeability by altering the charge and shape of the membrane proteins.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale: Diffusion is correct because it is the passive movement of molecules from an area of high concentration to an area of low concentration. Small lipid soluble molecules can easily cross the plasma membrane by diffusing through the hydrophobic core of the phospholipid bilayer.
Choice B rationale: Filtration is incorrect because it is the process of separating solid particles from a fluid by passing it through a porous medium. Filtration does not involve the plasma membrane, and it does not depend on the solubility of the molecules.
Choice C rationale: Osmosis is incorrect because it is the diffusion of water across a selectively permeable membrane. Osmosis does not apply to lipid soluble molecules, which are not water molecules.
Choice D rationale: Active transport is incorrect because it is the movement of molecules across a membrane against their concentration gradient, which requires energy and transport proteins. Active transport does not depend on the solubility of the molecules, and it is not a passive process.
Choice E rationale: Pumping is incorrect because it is a type of active transport that involves the use of specific pumps to move ions or molecules across a membrane. Pumping does not apply to lipid soluble molecules, which are not ions or polar molecules.
Correct Answer is B
Explanation
Choice A rationale: Up and down is incorrect because the mechanical stage upper knob does not control the vertical movement of the stage. The vertical movement of the stage is controlled by the coarse and fine adjustment knobs, which are located on the side of the microscope. The coarse adjustment knob is used to raise or lower the stage quickly, while the fine adjustment knob is used to fine-tune the focus of the specimen.
Choice B rationale: Right and left is correct because the mechanical stage upper knob controls the horizontal movement of the stage along the x-axis. The mechanical stage is a platform that holds the slide and the specimen, and it can be moved by two knobs that are located below the stage. The upper knob moves the stage right or left, while the lower knob moves the stage forward or backward.
Choice C rationale: Back and forth is incorrect because the mechanical stage upper knob does not control the horizontal movement of the stage along the y-axis. The horizontal movement of the stage along the y-axis is controlled by the mechanical stage lower knob, which is located below the stage and next to the upper knob. The lower knob moves the stage forward or backward, while the upper knob moves the stage right or left.
Choice D rationale: All of the answer choices are correct is incorrect because only one of the answer choices is correct. The mechanical stage upper knob only causes the stage to move right or left, not up and down or back and forth. The other movements of the stage are controlled by different knobs.
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