Astudent designs an experiment to test substances x, y, and z, to determine which one is a catalyst for the reaction: a + b ® c. only one of the unknown substances is a catalyst, and the others are nonreactive with a, b, or c.
when 10 ml of a is added to 10 ml of b, the reaction takes twenty seconds. bubbles form when the product c is created.
the student prepares three test tubes, each containing both reactants a and b. she adds unknowns x, y, and z to test tubes 1, 2, and 3, respectively. she then times the reaction in each test tube from the point when the unknown is added until bubbling stops.

Mouse liver cells were homogenized and the homogenate subjected to equilibrium density-gradient centrifugation with sucrose gradients. fractions obtained from these gradients were assayed for marker molecules (i.e., molecules that are limited to specific organelles). the results of these assays are shown in the figure. the marker molecules have the following functions: cytochrome oxidase is an enzyme involved in the process by which atp is formed in the complete aerobic degradation of glucose or fatty acids; ribosomal rna forms part of the protein-synthesizing ribosomes; catalase catalyzes decomposition of hydrogen peroxide; acid phosphatase hydrolysis monophosphoric esters at acid ph; cytidylyltransferase is involved in phospholipid biosynthesis; and amino acid permease aids in transport of amino acids across membranes. a) name the marker molecule and give the number of the fraction that is most enriched for each of the following cell components: lysosomes; peroxisomes; mitochondria; plasma membrane; rough endoplasmic reticulum; smooth endoplasmic reticulum.