What is the purpose of cholesterol?

a. raw material for steroid hormones

b. structural component of cell membranes

c. raw material for myelin sheaths

d. all of these

e. a and b?

According to the animation, how do the repressor proteins block the transcription of the structural genes?

which step in rock cycle occurs immediately befor sediments are laid down a. layers form b. heat and pressher are applided. c lava cools d. erosion breaks down rock

Which is not a factor in a fossil organism being useful as an index fossil?

Primates lack the enzyme needed to complete the conversion of simple sugars into vitamin C, yet their DNA contains the gene that controls this conversion. It has been "turned off" due to a mutation.

Which of the following provides the best evidence that organ systems in the human body interact with one another? A-Shivering in response to sensing of cold environment. B-Storing waste products for later elimination.

Why is it necessary to do a spinal tap when you suspect a bacterial infection of the central nervous system? why can't you use a blood test?

Name the major greenhouse gasses and how they get into the atmosphere

Which type of cell goes through the determination process?

What organic molecule is the basis of enzymes.?

Which transport mechanisms require the formation of a vesicles to transport material into or out of the cell? A: diffusion and osmosis B: exocytosis and calcium pumps C: exocytosis and endocytosis D: diffusion and facilitated diffusion