Which of the following best describes transcriptional regulation of the lac operon in e. coli?
a. on in the presence of lactose
b. on in the presence of lactose and presence of glucose
c. off in the presence of glucose
d. on in the absence of lactose and presence of glucose
e. on in the presence of lactose and absence of glucose

How do you transfer mrna into codons ? i'm so confused : (

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.

The table lists the observations students made about four specimens under a microscope. based on these observations, what specimens did the students examine? animal plant virus prokaryote cell membrane present ribosomes present lysosomes present nuclear membrane present cell wall present ribosomes present nuclear membrane absent cell wall present ribosomes present nucleus present large vacuole present reproduces inside of a cell nucleus absent rna present 2019 edmentum all rights reserved intl