Identify two structural features of purines and pyrimidines.

purines

__contain two heterocyclic rings.
__contain only two ring nitrogen atoms.
__contain four ring nitrogen atoms.
__contain one heterocyclic ring.
__contain only three ring nitrogen atoms.

pyrimidines

__contain one heterocyclic ring.
__contain four ring nitrogen atoms.
__contain only three ring nitrogen atoms.
__contain two heterocyclic rings.
__contain only two ring nitrogen atoms.

Asolution of an enzyme and a substrate was placed in a water bath and the temperature of the reaction was raised gradually. the graph shown was plotted at the end of the experiment. what can be concluded from the graph? a) temperature has no effect on the activity of the enzyme. b) the effect of temperature on the enzyme is unpredictable. c) the enzyme shows increased activity up to a certain temperature. d) the activity of the enzyme is inversely proportional to the temperature.

Aresearcher designed an investigation to test what effect eating different types of food would have on blood insulin levels. she selected 10 male subjects who were all 25 years of age and in good health. the experiment took place over 3 days. at 8: 00 a.m. on each day, the subjects ate a meal consisting of only 1 type of food. they had their blood insulin levels measured after consuming the meal. on day 1 they ate a high fat diet, on day 2 they ate a high protein diet, and on day 3 they ate a high sugar diel what is the independent variable in this experiment? a the age of the subjects b the blood insulin level c the type of food consumed d the time of day the meal was consumed

What type of pollution does household garbage cause