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 D
Explanation
Choice A rationale: An isotonic solution has the same solute concentration as the plant cells, which means it has the same water potential. Water will move in and out of the plant cells at the same rate, causing them to remain unchanged in size and shape. This will not help the lettuce to become less wilted.
Choice B rationale: A hypertonic solution has a higher solute concentration than the plant cells, which means it has a lower water potential. Water will move out of the plant cells by osmosis, causing them to shrink and become plasmolysed. This will make the lettuce more wilted and not crisper.
Choice C rationale: Soaking the lettuce in water would have an effect, depending on the relative solute concentration of the water and the plant cells. Water will move across the cell membrane by osmosis, either into or out of the plant cells, causing them to change in size and shape.
Choice D rationale: A hypotonic solution has a lower solute concentration than the plant cells, which means it has a higher water potential. Water will move into the plant cells by osmosis, causing them to swell and become turgid. This will make the lettuce crisper and more appealing.
Choice E rationale: A hypotonic solution will cause the plant cells to gain water and become turgid, not more wilted. Wilted lettuce is caused by the loss of water from the plant cells, which makes them flaccid and soft.
Correct Answer is D
Explanation
Choice A rationale: Only use lower power magnification is incorrect because this does not solve the problem of the dark field of view, but rather avoids it. Using lower power magnification means that you will not be able to see the details of the specimen that you want to observe under the 40x objective lens. Lower power magnification also has a larger field of view and a lower resolution than higher power magnification.
Choice B rationale: Add more immersion oil is incorrect because immersion oil is only used for the highest magnification objective lens, which is the 100x oil immersion objective lens, not the 40x objective lens. Immersion oil is a type of oil that has the same refractive index as glass, which means that it bends light in the same way as glass. Immersion oil is applied between the slide and the lens to reduce the refraction of light and increase the clarity of the image.
Choice C rationale: Adjust the fine adjustment knob is incorrect because the fine adjustment knob is used to fine-tune the focus of the specimen, not the brightness of the field of view. The fine adjustment knob is a small knob that is located on the side of the microscope, next to the coarse adjustment knob. The fine adjustment knob is used to make small changes in the distance between the objective lens and the specimen, which improves the sharpness of the image.
Choice D rationale: Increase the light intensity is correct because the light intensity is the amount of light that reaches the specimen and the objective lens, which affects the brightness of the field of view. The light intensity can be adjusted by using the rheostat, which is a dial that is located on the base of the microscope, next to the light source. The rheostat can increase or decrease the voltage of the light source, which changes the brightness of the light. Increasing the light intensity can make the field of view brighter and easier to see.
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