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 B
Explanation
Choice A rationale: High power is incorrect because high power is the second highest magnification objective lens, not the highest. High power is also called the 40x objective lens because it magnifies the specimen by 40 times. When combined with the 10x eyepiece lens, the total magnification is 400x.
Choice B rationale: Oil immersion is correct because oil immersion is the highest magnification objective lens. Oil immersion is also called the 100x objective lens because it magnifies the specimen by 100 times. When combined with the 10x eyepiece lens, the total magnification is 1000x. Oil immersion requires oil to be applied between the slide and the lens to reduce the refraction of light and increase the clarity of the image.
Choice C rationale: Low power is incorrect because low power is the second lowest magnification objective lens, not the highest. Low power is also called the 10x objective lens because it magnifies the specimen by 10 times. When combined with the 10x eyepiece lens, the total magnification is 100x.
Choice D rationale: Scanning is incorrect because scanning is the lowest magnification objective lens, not the highest. Scanning is also called the 4x objective lens because it magnifies the specimen by 4 times. When combined with the 10x eyepiece lens, the total magnification is 40x. Scanning is used to scan the whole slide and find the specimen.
Correct Answer is A
Explanation
Choice A rationale: The rate of diffusion is the speed at which particles move from an area of high concentration to an area of low concentration. This depends on the temperature, the size of the particles, and the medium they are in. Temperature affects the kinetic energy and the speed of the particles, which in turn affects the frequency and intensity of their collisions. Higher temperatures mean higher kinetic energy and faster particles, which leads to faster diffusion. ³
Choice B rationale: The change in rate of diffusion is not unaffected by temperature. Temperature is one of the main factors that influences the rate of diffusion, as explained above. Therefore, this choice is incorrect.
Choice C rationale: Diffusion does not halt when temperature is increased. On the contrary, diffusion becomes faster when temperature is increased, as explained above. Therefore, this choice is incorrect.
Choice D rationale: The change in rate of diffusion is not unpredictable when temperature is increased. There is a clear relationship between temperature and diffusion, as explained above. Therefore, this choice is incorrect.
Choice E rationale: The rate of diffusion does not decrease when temperature is increased. On the contrary, diffusion becomes faster when temperature is increased, as explained above. Therefore, this choice is incorrect..
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