BIOLOGY! WHY are nucleotides a good molecule to make DNA out of, while amino acids are a good molecule to make proteins out of?

Question

Hello everyone! I was wondering if you could help me answer this question. I have an upcoming quiz next week and this question will be on it - I am not asking for you to answer this completely, I just need some guidance. For the parts I know the answers to, I have put an asterisk.

WHY are nucleotides a good molecule to make DNA out of, while amino acids are a good molecule to make proteins out of?
A COMPLETE and well structured answer will include the following:
How many nucleotides there are? * There are four major nucleotides: A,G,C, and T (Guanine and Adenine and purines, and Cytosine and Thymine are pyrimidines)
How many amino acids there are * There are 20 amino acids
How nucleotides compare to amino acids in terms of diversity of shape and ‘feel’. * nucleotides are not really diverse in shape - there are two basic forms, a double-ringed purine structure and a single-ringed pyrimidine structure. In terms of feel, nucleotides don't have diverse charges - they are primarily negative due to their phosphate groups. Amino acids have a huge variety of shapes and charges. While they have the same properties like a central carbon atom, a carboxyl group, and amino group, and a H atom, they each have extremely different side chains that lead to their sizes and charges. In terms of charges, amino acids can be polar or nonpolar (hydrohphilic/hydrophobic), or acidic and basic. 

 

In what ways are all nucleotides identical? Different? 

I dont know how they are different besides the fact guanine and cytosine form 3 H-bonds and A and T form two. (and that they are pyrimidines or purines)

How many complementary interactions can nucleotides have with one another?

I don't know. ....

How the structure and function of DNA compares to the structure and function of proteins. *The structure of DNA is a double helix. The function of DNA is to store and transport genetic information, and have the ability to be replicated (and serve as a template for complementary RNA strands). Proteins have a huge variety of structures that allow them to carry out countless different functions (structural support, enzymatic actions, do the work of the cell, etc.)
Tie it all together:
What is the ‘job’ of DNA? Why are nucleotides good for allowing DNA to carry out its function? What is the job of proteins? How does being built out of amino acids help proteins function?

 

I am having a hard time putting together why nucleotides are good for DNA. I know that hydrogen bonding(while weak) between the nucleotides helps stabilize the DNA molecule and the phosphodiester bonds between the 5'phophates and 3' OHs helps the DNA molecule resist changes in pH/temp etc, but I ccan't think of many other reasons for why NUCLEOTIDES are good. Is it because they are built to pair with COMPLEMENTARY nucleotides? And that is what allows for replication?

 

*In terms of proteins, I think that amino acids are necessary for proteins because there is no limitation to how proteins can be stringed together, unlike DNA. Peptide bonds can form between any sequence of amino acids I also think that proteins are good because their R groups help proteins fold into a wide variety of shapes (the hydrophilic r groups go outside and the hydrophobic fold inside). I think this is why amino acids are good for creating proteins with countless different functions.

 

 

I guess I am mainly stumped on:

In what ways are all nucleotides identical? Different?
How many complementary interactions can nucleotides have with one another?

 

Are the rest of my ideas pretty solid though? I really appreciate any help I can get!!!

Answer 1

Hi!

"Is it because they are built to pair with COMPLEMENTARY nucleotides? And that is what allows for replication?"

 

This is the key to the whole question. You described amino acids very thoroughly but you didn't give nucleotides the same treatment. All nucleotides contain a phosphate group, five carbon sugar (deoxyribose in the case of DNA) and a nitrogenous base.

As you stated, "A,G,C, and T (Guanine and Adenine and purines, and Cytosine and Thymine are pyrimidines)... there are two basic forms, a double-ringed purine structure and a single-ringed pyrimidine structure." 

 

The reason the nucleotides are suited for DNA is because they form complementary base pairs, as you correctly stated. Because A only pairs with T and G only pairs with C, this insures that the two strands of DNA are complementary and held together by hydrogen bonds. Complementary base pairing is the key to  both replication and protein synthesis. 

 

As far as proteins go, I think you got it pretty much covered. 

"Amino acids have a huge variety of shapes and charges. While they have the same properties like a central carbon atom, a carboxyl group, and amino group, and a H atom, they each have extremely different side chains that lead to their sizes and charges. In terms of charges, amino acids can be polar or nonpolar (hydrohphilic/hydrophobic), or acidic and basic. 

 

In terms of proteins, I think that amino acids are necessary for proteins because there is no limitation to how proteins can be stringed together, unlike DNA. Peptide bonds can form between any sequence of amino acids I also think that proteins are good because their R groups help proteins fold into a wide variety of shapes (the hydrophilic r groups go outside and the hydrophobic fold inside). I think this is why amino acids are good for creating proteins with countless different functions."

 

It's all about form and function. The order of amino acids and the interaction of the R groups determines the shape of the protein and thus its function.