Biological Macromolecules and Chemical Reactions

Macromolecules are defined as large and complex molecules that are composed of many covalently connected atoms.
Biological structure and function are fundamentally inseparable; the architecture of a molecule directly dictates its functional properties.
All living organisms are composed of four main classes of large biological molecules:
- Carbohydrates
- Lipids
- Proteins
- Nucleic acids
A polymer is a long molecule consisting of many similar or identical building blocks linked together.
Monomers are the smaller, repeating molecules that serve as the chemical building blocks of polymers.
Out of the four primary classes of biological molecules, three are classified as polymers:
- Carbohydrates
- Proteins
- Nucleic acids
Lipids are distinguished from the other three classes as a diverse group of hydrophobic molecules rather than true polymers.

Carbohydrates:
- Serve as cellular fuel for energy requirements.
- Function as structural building material for cells and organisms.
Lipids:
- Form a diverse group of non-polar, hydrophobic molecules.
Proteins:
- Feature a high diversity of 3D molecular structures.
- Their structural variation results directly in a wide range of biological functions within organisms.
Nucleic Acids:
- Store genetic information.
- Transmit genetic information from one generation to the next.
- Help express hereditary information within living systems.
Systems Disciplines:
- Genomics and proteomics have fundamentally transformed biological inquiry and real-world applications.

The chemical mechanisms governing polymer synthesis and degradation rely on specific enzyme-catalyzed reactions.
Dehydration Reaction:
- A reaction in which two monomers become covalently bonded together.
- Involves the loss of a water molecule ( $H_2O$ ) as a new covalent bond is formed.
- Catalyzed by enzymes to facilitate the synthesis of polymers from monomer units.
Hydrolysis Reaction:
- A reaction in which polymers are disassembled into individual monomers.
- Operates as the direct reverse of a dehydration reaction.
- Involves the addition of a water molecule ( $H_2O$ ) to break the covalent bond between monomer units.

Macromolecules: Large, complex molecules composed of covalently connected atoms where architecture dictates function.
Classes of Molecules:
- Carbohydrates, Proteins, Nucleic acids (classified as polymers).
- Lipids (diverse, hydrophobic non-polymers).
Polymers and Monomers:
- Polymer: Long molecule consisting of similar or identical building blocks linked by covalent bonds.
- Monomer: Small repeating molecule serving as a chemical building block.

Carbohydrates: Function as cellular fuel and structural building materials.
Lipids: Form a diverse group of non-polar, hydrophobic molecules.
Proteins: Possess diverse 3D molecular structures resulting in a wide range of biological functions.
Nucleic Acids: Store, transmit, and express hereditary genetic information.
Systems Disciplines: Genomics and proteomics transform biological inquiry and applications.

Enzyme-catalyzed chemical reactions govern polymer assembly and degradation:
- Dehydration Reaction: Synthesizes polymers by covalently bonding two monomers together with the loss of a water molecule ( $H_2O$ ).
- Hydrolysis Reaction: Disassembles polymers into individual monomers by adding a water molecule ( $H_2O$ ) to break covalent bonds.