Which of the following is a problem with using solar power as a main source of energy?
a.) people do not yet have the technology to use solar power
b.) the sun is not close enough to provide solar energy
c.) power from solar energy contains a large amount of harmful ultraviolet rays
d.) solar powers is not available at night or when it is cloudy

hormones in blood stream

image: dtc.ucsf.edu

endocrine glands secrete hormones into the blood stream near them; the hormones then travel in our bloodstream until it reaches its destination, called a target cell, in distance parts of the body. in the target tissue, hormones lock onto the target’s plasma membrane, called the receptor site.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.