A student performed an experiment to see if water temperature affects the level of activity
in aquatic snails. The student set up four tanks with five snails in each tank. All four of the
setups were identical in every way, except for the temperature of the water. In order to
make the conclusions more valid, the student could
A.
alter the pH of the water
B.
change the size of the tank
C.
carry out the experiment for a shorter period of time
D.
use a larger number of snails

How many cells are our body made of ? ♡

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.

About how much of the cell mass is watet