A store sells a variety of sets for building molecular models. The sets are described by the diagram below. Each circled letter represents a box of 6 model atoms of one element. For example, the circled letter "P" represents a box with 6 model phosphorous atoms. Set 1 has 12 carbon, 12 oxygen, and 18 hydrogen atoms. Set 2 has 12 carbon, 12 oxygen, and 24 hydrogen atoms. Set 3 has 6 carbon, 12 oxygen, 12 hydrogen, 6 nitrogen, and 6 phosphorous atoms. Set 4 has 6 carbon, 6 oxygen, 6 hydrogen, and 6 phosphorous atoms.

Kendra wishes to build a model of a carbohydrate molecule, ideally containing as many monomers as possible. Which set should she choose?

A. Set 1
B. Set 2
C. Set 3
D. Set 4

B. Set 2

Explanation:

Carbohydrate is one of the four biological molecules in living systems (others are proteins, lipids and nucleic acid). The carbohydrate molecule consists of a long chain of carbon, hydrogen and oxygen elements in a ratio 1:2:1. Hence, the simplest unit of a carbohydrate has an empirical formula of (CH2O)n where n is the number of chains.

According to the question, a store sells a variety of sets for building molecular models and Kendra wishes to build a model of a carbohydrate molecule. Since carbohydrate monomers have a CH2O formula, Kendra needs a set in which the ratio of carbon: hydrogen: oxygen is 1:2:1. SET 2 fits this description by containing 12 carbon, 12 oxygen, and 24 hydrogen atoms

That is, carbon (12/12) : hydrogen (24/12) : oxygen (12/12), which is 1:2:1. Therefore, SET 2 is the best choice for Kendra in order to build her model of carbohydrate molecule containing as many monomers as possible.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.