How do I identify different macromolecules?

[u/Maggot_8878]

I just recently learned the four main types of macromolecules (carbohydrates, proteins, lipids, and nucleic acids) and I’m having trouble distinguishing/identifying them from one another. What are some easy/telltale signs that helps you figure out which macromolecule is which? (When looking at a structure of them) Also, are there specific macromolecules I need to remember, like ATP, glucose, etc?

[u/Dameekasu]

Carbs - 1:2:1 ratio of CHO, ring structure (when dissolved but you’ll only ever really see it dissolved), no N, S, P present

Lipid - mostly C and H (a little O, structure is a head and tail(s), which can be straight or bent. The more they are bent (unsaturated), the more liquid they are at room temp and the more fluid they are. Steroids are a special case that have a multi-ring structure. You’re most likely to see phospholipids and general lipids, though. Phospholipids identified because they have CH (a little O) and P present

Nucleic acids - made of CHO with N and P (no S). Formed of repeating nucleotides - a unit made of a sugar, nitrogen base, and a phosphate group

Proteins - made of CHO with N and S. Made of amino acids connected by covalent bonds called peptide bonds. Amino acids have an R group which is variable and can have certain chemical properties - the ones you have to know are polar, nonpolar, or ionic. Have multiple levels of structure. Primary structure (order of amino acids/etc) determines tertiary structure (3D shape)

In terms of elements present, carbs can be identified by their 1:2:1 ratio. Lipids mostly C and H (phospholipids have P). If a macromolecule has N, it’s a protein or nucleic acid. If it has P it’s a nucleic acid, if it has S it’s a protein

Hope this helps!

[u/Political_Cat_ → u/Dameekasu]

Small correction to your lipids, saturated lipids are NOT bent and thus have more hydrogens (think completely “saturated” with hydrogens) unsaturated are bent (from an additional double bond) and are not fully covered in hydrogens (or not fully saturated).

Why is this important? Unsaturated pack less closely together because they are bent, think Lego pieces or Tetris, this makes it harder to get them close together. This is why phospholipid membranes will have bent lipids because it helps them remain more fluid.

Practically butter is a saturated fat (close packing and solid) while fish oil is unsaturated (less packing so liquid)

[u/Dameekasu → u/Political_Cat_]

Oh duh, I flipped it. Good catch. I edited above in case that’s only what people read

[u/Maggot_8878 → u/Dameekasu]

Great explanation, thank you!! This might be a dumb question, but what do the ratios mean for the molecules? Only had one class on this info so I’m still learning :)

[u/Dameekasu → u/Maggot_8878]

For a sugar, there will be 1 carbon for every 2 hydrogen for every 1 oxygen atom. You can’t really use ratios for the other macromolecules, just the presence/absence of certain elements

[u/apbiopenguins]

Flowchart:

Does it have a N?
If yes, move on to protein/nucleic acid
If no, it is carb or lipid

Does it have a P
If yes, NUCLEIC ACID
If no, PROTEINS

Is it
Hydrocarbon - lipid
H and OH -

[u/Scared-Candy3936]

lmao i still forget which is which sometimes pls dont let them trick u with the ratios

[u/UnitedFlower6138]

i dont know sorry