I want to refresh you somewhat concerning the chemistry you will need to know to understand biology. Also, we use a "short-hand" notation when drawing organic molecules (molecules including carbon and hydrogen). This blog introduces you to that system, and some of the functional groups we will use consistently.

A common theme in biology is how large "macromolecules" from subunits, usually known as monomers. Really, I'm underselling this point. You will see it over and over for the next several months.
Two linked together is a "dimer," three is a trimer...you get the idea. We usually get lazy after "tetramer" and start calling them "oligomer" for groups that are in the range of 5-10 and then "polymer," when you get to many units…hundreds or thousands…even more. Hey…one common organic compound we will get to know is known as an "ester." What do you think we call a fiber made of many of these linked together?

In some sense, all science comes down to understanding energy. If someone ever asks you why something happens, you can answer: "The second law of thermodynamics." It's never wrong, but also may not be very helpful unless you can make the connection to more local causes. This is the beginning of the discussion, with a biological theme.

Introduction to a new and fun form of isomer!

As I said earlier, a common theme in biology is how large "macromolecules" from subunits, usually known as monomers.
Proteins are arguably the most important and, inarguably, the most diverse of all the macromolecules.
Each protein begins as a long strand of hundreds (or thousands) of amino acids. Since there are 20 different amino acids commonly used, 100 amino acids would have 20¹⁰⁰ possible sequences.
In practice, you won't see all possible ones and they are not randomly put together. Instead, the information in the DNA is used to specify what sequence is made (through a process we will learn about).
These chains then fold into complex structures you have seen.