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: 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.
Correct Answer is A
Explanation
Choice A rationale: A cover slip is correct because 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.
Choice B rationale: Clear paper is incorrect because clear paper is not suitable for covering a wet mount specimen. Clear paper is a type of paper that is transparent or translucent, but it is not thin or flat enough to fit over the specimen on the slide. Clear paper can also interfere with the passage of light or distort the image of the specimen.
Choice C rationale: Transparent tape is incorrect because transparent tape is also not suitable for covering a wet mount specimen. Transparent tape is a type of adhesive tape that is clear or see-through, but it is sticky and can damage the specimen or the slide. Transparent tape can also affect the quality of the image or the focus of the microscope.
Choice D rationale: Another glass slide is incorrect because another glass slide is too thick and heavy to cover a wet mount specimen. Another glass slide is a thin, flat piece of glass or plastic that can be used to place the specimen on, but not over it. Another glass slide can also crush the specimen or block the light source of the microscope.
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