Question

buffin bio181 fall 25 - aurélie buffin

1. how does carbon contribute to the diversity of organic molecules? (give examples of molecules, their diversity and the role of carbon in generating the diversity)
2. name and describe the 4 levels of structure of proteins. differentiate the 3rd and 4th level in details, give examples. how does the 1st level of protein structure influence the 4th?
3. define dehydration/condensation synthesis and hydrolysis. why is this process central to cells and thus organisms?

Explanation:

1. Carbon can form four covalent bonds, allowing for diverse molecular shapes like straight - chains, branched - chains and rings. For example, carbohydrates like glucose ($C_6H_{12}O_6$) have different isomers due to carbon's bonding versatility. The ability of carbon to bond with itself and other elements such as hydrogen, oxygen, nitrogen etc. generates molecular diversity.
2. The four levels of protein structure are: primary (linear sequence of amino acids), secondary (local folding into alpha - helices or beta - sheets due to hydrogen bonding), tertiary (3 - D folding due to interactions like disulfide bridges, hydrophobic interactions etc.), and quaternary (association of multiple polypeptide chains). The tertiary structure is of a single polypeptide chain while the quaternary involves multiple chains. For example, hemoglobin has a quaternary structure with four polypeptide chains. The primary structure determines the final 3 - D shape including the quaternary structure as the sequence of amino acids dictates the interactions that lead to folding.
3. Dehydration/condensation synthesis is a reaction where two molecules combine with the loss of a water molecule, forming a covalent bond. Hydrolysis is the reverse, where a molecule is broken down by the addition of a water molecule. These processes are central to cells as they are involved in the synthesis and breakdown of macromolecules such as proteins, carbohydrates, and nucleic acids, which are essential for cell structure, function, and metabolism.

Answer:

1. Carbon forms four covalent bonds enabling diverse molecular shapes and bonding with various elements. Examples include glucose isomers.
2. Primary: amino - acid sequence; Secondary: local folding; Tertiary: 3 - D folding of single chain; Quaternary: multiple chain association. Tertiary is single - chain, quaternary is multi - chain (e.g., hemoglobin). Primary influences quaternary by dictating interactions for folding.
3. Dehydration/condensation synthesis combines molecules with water loss, hydrolysis breaks with water addition. Central for macromolecule synthesis and breakdown in cells.