obsidianvault/biology/Chemistry of Life/Proteins.md

Macromolecules

General Overview

first thing to think of when hearing proteins is "everything"

1. carry out most cellular functions
2. unlike the other macromolecules, proteins use all of chnops

Structure of Amino Acids:

monomers are called amino acids, polymers are polypeptides ! structure of proteins is pretty similar, the have an alpha carbon, a hydrogen, an amino group, a carboxyl group, and a r group. the r group differs and is what determines a proteins function, r groups can be hydrophobic, hydrophilic, or ionic

Structure of Polypeptides:

proteins have 4 structural levels, primary secondary tertiary and quaternary, describes order of which proteins formed

! amino end has a presence of ammonia, carboxyl end has a carboxyl group

the primary structure is a long chain of amino acids that determine the overall shape of the protein. each amino acid in a protein is connected by a covalent bond, called peptide bonds

long chains of amino acids first form in one of two shapes through hydrogen bonding in the peptide backbone, a spiral or a folded sheet, called alpha helices and beta pleated sheets, and represent the proteins secondary structure.

" Interactions (such as hydrogen bonds, disulfide bridges, ionic bonds, and hydrophobic interactions) between the polypeptide’s R-groups cause the helices and sheets to fold into a new shape, which is called the tertiary structure."

for some proteins, tertiary is their final structure, meaning that once it's achieved the protein is fully functional, some more complex proteins require multiple tertiary structures to combine, called a quaternary structure. ! first step to making a protein is creating appropriate amino acid sequence. amino acids fold into alpha helices or beta pleated sheets which come together to form a tertiary structure. some proteins require multiple tertiaries/polypeptides to come together to form a quaternary structure.

"Key Takeaway: Proteins are responsible for most cellular functions. All proteins have a central alpha carbon with a hydrogen, an amino group, and a carboxyl group. Where they differ is the R-group. Proteins cycle through three to four structures before becoming fully functional."

although proteins have multiple structures, they're dependent on the previous one. the protein structures are derived from the folding of the primary structure. proteins can fold back into the primary structure, called denaturation ! denaturation can be caused by:

1. heat
2. ph changes
3. mechanical agitation (stirring, shaking)

renaturation can also occur. eg pepsin enzyme. pepsin is one of the enzymes of the stomach, if ph is too high, it denatures, if it's brought back down, it renatures.

Function

Proteins have a bunch of different functions

1. Enzymes: speed up chemical reactions
2. Defensive proteins: antibodies help the immune system recognize viruses
3. Transport proteins: facilitate transport of large/polar molecules across cell membranes
4. Storage proteins: store amino acids, such as in milk
5. Receptor proteins: used in cell signaling
6. Contractile/ Motor proteins: helps muscles contract and cells with tails move
7. Structural proteins: makes up hair, nails, and scars

Summary

Structure	Monomer / Polymer Name	Function
All proteins have a central alpha carbon with a hydrogen, an amino group, and a carboxyl group. However, they have different R-groups, which lead to structural and functional differences.	Monomer: Amino Acid Polymer: Polypeptide	Most cellular and body functions