When testing tonicity in Elodea cells, once Elodea cells were placed in distilled water, what did you observe? Select all that apply.
Cell membranes pressed tightly against the cell walls.
Many of the cells had burst.
Full central vacuoles.
Many of the cells had become crenated.
Correct Answer : A,C
Choice A rationale: Cell membranes pressed tightly against the cell walls is correct because this is what happens when a plant cell is placed in a hypotonic solution. A hypotonic solution has a higher concentration of water than the cell, so water moves into the cell and out of the solution by osmosis, causing the cell to swell and press against the cell wall. This is called turgor and it helps the cell maintain its shape and rigidity.
Choice B rationale: Many of the cells had burst is incorrect because plant cells do not burst in a hypotonic solution, unlike animal cells. Plant cells have a rigid cell wall that prevents them from bursting, even when they are full of water. The cell wall can withstand the pressure of water entering the cell.
Choice C rationale: Full central vacuoles is correct because this is also what happens when a plant cell is placed in a hypotonic solution. The central vacuole is a large organelle that stores water and other substances in the plant cell. When water enters the cell, the central vacuole expands and fills up the cell, increasing its turgor pressure.
Choice D rationale: Many of the cells had become crenated is incorrect because crenation is the opposite of what happens in a hypotonic solution. Crenation is the process by which a cell shrinks and becomes wrinkled due to water loss in a hypertonic solution. A hypertonic solution has a lower concentration of water than the cell, so water moves out of the cell and into the solution by osmosis, causing the cell to shrink.
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Naxlex Comprehensive Predictor Exams
Related Questions
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.
Correct Answer is B
Explanation
Choice A rationale: Plant pigments do not produce photon energy, but rather capture it from the sun. Photon energy is the energy carried by particles of light, called photons. Different types of electromagnetic radiation, such as visible light, have different amounts of photon energy depending on their wavelength¹.
Choice B rationale: Plant pigments absorb light energy and use it to initiate photosynthesis. Photosynthesis is the process by which plants convert light energy into chemical energy, stored in the bonds of sugar molecules. Plant pigments are specialized organic molecules, such as chlorophyll and carotenoids, that are found in the chloroplasts of plant cells. They absorb specific wavelengths of light and reflect others, giving plants their characteristic colors²³.
Choice C rationale: Plant pigments do not provide electrons, but rather transfer them to other molecules. Electrons are negatively charged subatomic particles that are involved in chemical reactions. In photosynthesis, plant pigments absorb light energy and use it to split water molecules, releasing electrons, protons, and oxygen. The electrons are then passed along an electron transport chain, generating a proton gradient that drives the synthesis of ATP, an energy molecule. The electrons are also used to reduce NADP+ to NADPH, an electron carrier⁴.
Choice D rationale: Plant pigments do not convert heat to electricity, but rather convert light to chemical energy. Heat and electricity are both forms of energy, but they are not directly involved in photosynthesis. Heat is the kinetic energy of molecules, while electricity is the flow of electrons or electric charge. Plant pigments absorb light energy and use it to drive the chemical reactions of photosynthesis, which produce sugar and oxygen as products⁵.
Choice E rationale: Plant pigments do not reduce NADP, but rather donate electrons to it. Reduction is a chemical reaction in which a molecule gains electrons, while oxidation is a chemical reaction in which a molecule loses electrons. NADP+ is an oxidized form of NADP, which stands for nicotinamide adenine dinucleotide phosphate. It is an electron carrier that accepts electrons from plant pigments in photosystem I, a complex of proteins and pigments in the thylakoid membrane of the chloroplast. The reduced form of NADP is NADPH, which carries electrons and hydrogen for the dark reaction of photosynthesis, which uses CO2 to produce glucose⁶.
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