Copernicus and other astronomers before him thought that celestial bodies followed a orbital path.
circular
elliptical
square

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.

How can a geological time scale best be reconstructed? a) comparing vestigial structures in living species b) comparing homologous structures in living species c) examining homologous structures in fossil remains d) examining the written records of scientists from past cultures

Ras is a g-protein that is activated when a growth factor attaches to egfr. its activation results in the replacement of a gdp molecule with a gtp molecule, thus allowing a signal transduction pathway to be activated. considering the signal pathway illustrated on this page, what is one potential outcome of a mutation in the ras gene that leads to ras protein hyperactivity. be specific.