This will be pretty basic chemistry but I need memorization techniques for knowing what monomers and polymers are in carbohydrates, proteins, nucleic acid, and lipid. Can anyone help? 

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caledon's profile pic

caledon | High School Teacher | (Level 3) Senior Educator

Posted on

Proteins are probably the easiest, because they're so complex that your teacher (in a basic chemistry class) is probably not going into detail about their structure. The monomer for proteins is the amino acid. There are 21 amino acids, and the average protein contains dozens to hundreds of copies of them. Thus, you probably won't be asked to do much more than recognize that amino acid = monomer for protein. You might be asked what an amino acid looks like; it looks like this. What you need to know is that this is the basic template for an amino acid, and that letter R represents the variations that make each of the 21 different types.

Carbohydrates are pretty easy too. I'm not sure why, but we use a separate name for the monomers and polymers of carbohydrates: monosaccharides and polysaccharides. "Saccharide" is pretty much just a name for sugar, so it literally means "one sugar" and "many sugars". Monosaccharides include glucose, fructose, galactose; the key thing here is that they end in "-ose", which is your clue that it's a sugar. The only polymers we typically discuss are starch and cellulose, both of which are made of glucose monomers, they're just linked together in different ways.

Nucleic acids can be kind of a pain. Their monomer is the nucleotide, which has three components; a phosphate group, a 5-carbon sugar, and a nitrogenous base. Fortunately there aren't many variations in this one; DNA uses deoxyribose as its sugar, and RNA uses ribose sugar. Otherwise they're pretty much the same.

Lipids are probably the worst, and personally I treat them as a whole separate thing when teaching macromolecules because their structure is so weird, and because the words lipid, fat, oil etc. are used so interchangeably and incorrectly by most people. What most classes teach is a lipid is a triglyceride; a glycerol molecule with three fatty acids attached. This isn't really the same sort of thing as the other macromolecules, because you can't polymerize the triglycerides to each other. What you should look for is the fact that three long chains of carbons and hydrogens will be involves (the fatty acids) bound to a single "head" molecule (the glycerol) and the fatty acids may all be identical to one another, or completely different.

So to summarize:

Amino acids combine to form proteins

Monosaccharides combine to form polysaccharides; all of them are carbs

nucleotides combine to form nucleic acids, which can be DNA or RNA

glycerol and three fatty acids combine to form triglycerides, aka lipids.

Normally I would give you something like a mnemonic that makes memorization and association easier, but I've never found one for macromolecules that doesn't make things even more complicated. I would really suggest that you do practice quizzes, like making flashcards of the different vocab words and putting them with the associated polymer, or making a flowchart like this.

gurviji's profile pic

gurviji | High School Teacher | (Level 1) Adjunct Educator

Posted on

The picture below describes polymers and each doll represents a monomer.

In Proteins the monomer is an aminoacid

In carbohydrates (polysaccharides) the monomer is a monosaccharide

In nucleic acids the monomer is a nucleotide

Fatty acids are different in that they are not a polymer, how ever lipids can vary in length based on the three fatty acids that combine with one glycerol.

"paa c'mon noontide is here"

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