Why do proteins not pass through plasma membranes?
They contain nitrogen.
They cause emulsification.
The membrane is made of protein.
They are very large molecules.
They bind to the phospholipids.
The Correct Answer is D
Choice A rationale: Proteins contain nitrogen, but this is not the reason why they cannot pass through plasma membranes. Nitrogen is a common element in many organic molecules, including nucleic acids and amino acids, which can cross the membrane under certain conditions.
Choice B rationale: Proteins do not cause emulsification, which is the process of breaking down large fat droplets into smaller ones. Emulsification is facilitated by bile salts, which are amphipathic molecules that have both hydrophilic and hydrophobic regions. Proteins are not amphipathic, and they do not interact with fats in this way.
Choice C rationale: The membrane is made of protein, but this does not prevent proteins from passing through it. The membrane is composed of a phospholipid bilayer with embedded proteins, which can act as channels, carriers, receptors, or enzymes for various substances. Some proteins can cross the membrane by using these transport proteins, or by endocytosis or exocytosis.
Choice D rationale: Proteins are very large molecules, and this is the main reason why they cannot pass through plasma membranes. The size of a molecule determines its permeability across the membrane, and proteins are too big to diffuse through the small gaps between the phospholipids or the pores of the transport proteins. Proteins can only cross the membrane by vesicular transport, which requires energy and specific signals.
Choice E rationale: Proteins do not bind to the phospholipids, which are the main components of the membrane. Phospholipids are also amphipathic molecules, with a hydrophilic head and a hydrophobic tail. Proteins are generally hydrophilic, and they do not associate with the hydrophobic core of the membrane. Proteins can bind to other proteins or carbohydrates on the surface of the membrane, but this does not affect their ability to cross it.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is ["A","B","E","F"]
Explanation
Choice A rationale: Transfer pipette is correct because you need a transfer pipette to transfer a drop of water or a liquid specimen onto the center of the slide. A transfer pipette is a plastic or glass tube with a bulb at one end that can suck up and release liquids.
Choice B rationale: Clean slide is correct because you need a clean slide to place the specimen on. A slide is a thin, flat piece of glass or plastic that can be viewed under a microscope. A clean slide ensures that there is no contamination or interference from other substances.
Choice C rationale: Bunsen burner is incorrect because you do not need a Bunsen burner to make a wet mount. A Bunsen burner is a device that produces a flame by mixing gas and air. A Bunsen burner is used for heating, sterilizing, or burning substances, not for making a wet mount.
Choice D rationale: Timer is incorrect because you do not need a timer to make a wet mount. A timer is a device that measures or indicates the passage of time. A timer is used for timing experiments, not for making a wet mount.
Choice E rationale: Tweezers is correct because you need tweezers to pick up and place the specimen on the slide. Tweezers are a pair of metal or plastic pincers that can grasp and hold small objects. Tweezers are useful for handling delicate or microscopic specimens.
Choice F rationale: Cover slip is correct because you need a cover slip to cover the specimen on the slide. A cover slip is a thin, transparent piece of glass or plastic that can be placed over the specimen on the slide. A cover slip protects the specimen from drying out, dust, or damage, and creates a flat surface for viewing under the microscope.
Correct Answer is D
Explanation
Choice A rationale: CO2 is not the source of oxygen produced by a plant, but a reactant of the dark reaction. The dark reaction uses CO2 and energy intermediates from the light reaction to produce glucose, a type of sugar. The dark reaction does not release any oxygen¹.
Choice B rationale: C6H12O6 is the chemical formula for glucose, which is the product of the dark reaction. Glucose is synthesized from CO2 and energy intermediates from the light reaction. Glucose does not produce any oxygen, but can be used by the plant for respiration or storage².
Choice C rationale: Glyceraldehyde-3-phosphate is an intermediate molecule in the dark reaction. It is formed from CO2 and energy intermediates from the light reaction, and then converted into glucose. Glyceraldehyde-3-phosphate does not produce any oxygen³.
Choice D rationale: H2O is the source of oxygen produced by a plant. In the light reaction, water is split by the energy from sunlight in photosystem II, releasing electrons, protons, and oxygen. The oxygen is either used for respiration or released into the air⁴.
Choice E rationale: O2 is the product of oxygen produced by a plant, not the source. O2 is released as a by-product of the splitting of water in photosystem II. O2 is either used for respiration or released into the air⁴.
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