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

True or False?

Tonicity is the ability of a solution to cause water movement across a semi-permeable membrane, such as the cell membrane. In the lab, tonicity can be tested by observing the effects of different solutions on cells, such as red blood cells or plant cells. However, the items that have been contaminated with blood, such as slides, pipettes, or gloves, cannot be thrown away in the regular trash can, because they pose a biohazard risk. Biohazardous waste is any material that contains or has been exposed to infectious agents, such as blood, bacteria, viruses, or parasites. Biohazardous waste must be handled and disposed of according to specific safety protocols, such as using autoclaves, incinerators, or biohazard bags. Therefore, after testing tonicity in the lab, the items that have been contaminated with blood cannot be disposed of in the trash can.

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.