Diffusion continues to occur until there is an equal concentration of particles on both sides of a semi-permeable membrane.

True or False?

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.

Choice A rationale: H2O is a reactant or input for the light reaction of photosynthesis. In the light reaction, water is split by the energy from sunlight in photosystem II, releasing electrons, protons, and oxygen. The electrons and protons are used to reduce NADP+ to NADPH and to synthesize ATP from ADP and Pi. The oxygen is either used for respiration or released into the air¹².

Choice B rationale: Oxygen is not a reactant or input for the light reaction of photosynthesis, but a product or output. Oxygen is released as a by-product of the splitting of water in photosystem II. Oxygen is either used for respiration or released into the air¹².

Choice C rationale: NADPH is not a reactant or input for the light reaction of photosynthesis, but a product or output. NADPH is an electron carrier that is reduced by the electrons from water in photosystem I. NADPH provides electrons and hydrogen for the dark reaction, which uses CO2 to produce glucose¹².

Choice D rationale: ATP is not a reactant or input for the light reaction of photosynthesis, but a product or output. ATP is an energy molecule that is synthesized by the enzyme ATP synthase using the proton gradient created by the electron transport chain. ATP provides energy for the dark reaction, which uses CO2 to produce glucose¹².

Choice E rationale: Carbon dioxide is not a reactant or input for the light reaction of photosynthesis, but a reactant or input for 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 require light and can occur in the day or night¹².