An important way to think about the biological macromolecules is to think about the roles they play.
The vast majority of the machines in your body are proteins; they come in all shapes and sizes. One very common saying in biology is 'structure is function'. To do these many (many, MANY) jobs, proteins must therefore come in a dizzying array of shapes, sizes and 'feels' (positive, negative, neutral). This gives you an insight into why there are TWENTY amino acids--this (relatively) diverse 'toolkit' allows you to assemble strings that 'fold' into the huge diversity of shapes that are proteins.
DNA, on the other hand, is meant to sit there be easy to copy without error. So it has a very simple, stereotyped structure. It has only 4 components that fit ( or do NOT fit) with each other in a simple, unambiguous way.
RNA is made as a 'disposable copy' of DNA, so looks much like it (actually, we think that DNA evolved as an 'improved descendant' of RNA, but the principle still holds).
Carbohydrates often play the role of water-soluble 'energy' so they have a fair number of 'energy rich' C-H bonds but enough -OH groups to make water happy.
lipids are also energy-dense, but must also 'knit together' to form the long, double-layered structures that are biological membranes. Here, the key task is to limit the movement of water and charged or large molecules, so a 'hydrophobic' core is a key.
