Tap. 31e

One last group of Organic (carbon and hydrogen-containing) molecules that is extremely important to

the body are Nucleic Acids

You have probably heard of the nucleic acid called DNA – Deoxyribonucleic Acid, and maybe even its

close partner molecule called RNA – Ribonucleic Acid.

Both DNA and RNA are extremely long macromolecules that perform very complex crucial processes in each of our trillions of cells. But

despite being so long and so important, their structure is quite simple. They are built by joining several NUCLEOTIDE monomers together via

Dehydration Synthesis.

Each nucleotide, whether it be a DNA nucleotide or a RNA nucleotide will consist of three key components:

1.A Phosphate group –consisting of phosphorous and oxygen2.A 5-carbon sugar –classified as being a PENTOSE (penta = 5) sugar.

3.A Nitrogen-containing base (alkali-basic in pH) –which may have a single ring structure or may be a double ringed structure.

General Structure Detailed Structure

Tap. 40

In this DNA nucleotide the single-ringed base is called

CYTOSINE

Just like the other organic macromolecules (polymers) we studied in this chapter; an “H” is taken off of one of the monomers and an “OH” off the other to link the two monomers together. The “H” and “OH” then

join together to form a “H2O” water. As illustrated in the “Dehydration Synthesis” A.K.A. “Condensation Synthesis” reaction shown below.

We will be looking at DNA structure in more detail when we hit Unit D –Chapter 25. But for now, we should at least know that there are four

different DNA nucleotides found in a DNA molecule. Each of the four DNA nucleotides have the same phosphate group, and the same 5-carbon

sugar (Deoxyribose). The thing that distinguishes the four DNA nucleotides is what type of base is found coming off of the Deoxyribose

sugar.

The four different bases are Adenine, Guanine, Cytosine and Thymine. A helpful Mnemonic for DNA is “Any Geek Can

Teach”. As you are witnessing!

Fig. 2.28DNA is also unique in that it is a double stranded molecule. Two strands form then link together with weak Hydrogen bonding between the bases

Fig. 2.28ab

Fig. 2.28c

Table 2.3

We will be comparing DNA and RNA structurally and functionally in greater depth in the next unit. But when it comes to bases, recall that “Any Geek Can Teach”, yah,

“Any Geek Can U?”

Nucleotide monomers are used to build nucleic acids like DNA and RNA (we will study RNA later on). But the cells of your body will also take a RNA nucleotide and modify to make it into an energy rich molecule that

is used universally by life forms to release energy. This modified Nucleotide is called – A.T.P. = Adenosine Triphosphate.

Note that this molecule posseses the base called Adenine, a 5-carbon pentose sugar

called “Ribose” (found in RNA nucleotides). But instead of a single

phosphate group like a typical nucleotide, it possesses three phosphate groups. There are very high energy bonds between each

phosphate group.

Fig. 2.29Cells in life forms, build this ATP molecule then they quickly

perform a hydrolysis reaction on the bond between the second and third phosphate groups. When this happens, energy is released to perform processes in the body and

within the cell.

Then the life form will burn carbs and fats to acquire caloric energy to run a dehydration synthesis reaction to rebuild the

ATP molecule from the ADP (adenosine diphosphate) and the free phosphate group.

Tap. 43

The diagram below illustrates the process of building various polymers from their respective monomers. For Example – “a” could be

GLUCOSE, then “c” could be STARCH. “b” represents dehydration synthesis, while “d” represents hydrolysis of the polymer back down to

its monomers.