Vernon is using the diagram shown below to develop a model of photosynthesis. The letters A, B, and C each represent a reactant or product of the process. In the light-dependent reactions, light strikes the oval thylakoids. Compound A enters the thylakoid, and compound B leaves it. In the light-independent reactions, compound C enters a cycle in the stroma, and sugars leave the cycle. ATP and NADPH cycle between the two sets of reactions.

Vernon wonders whether NADPH and ATP should be classified as reactants or as products of photosynthesis. How should these compounds be classified?

A. as reactants, because they are used up by photosynthesis
B. as products, because they are generated by photosynthesis
C. as either reactants or products, depending on the rate that photosynthesis occurs
D. as neither reactant nor product, because they are recycled instead of made or used up

the answer is c) abandoned properties that are contaminated with hazardous materials.

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation: