Overview
This lecture covers naturally occurring polymers, focusing on polypeptides, DNA, and carbohydrates, explaining their monomer units and how they form larger structures.
Polypeptides and Proteins
- Polypeptides are polymers made from linking many amino acids in a chain.
- Proteins are made when polypeptides fold or combine; different sequences lead to many types of proteins.
- Proteins serve various functions, such as catalyzing reactions (enzymes) and providing structure in tissues.
- Amino acids have two key functional groups: a carboxyl (carboxylic acid) group and an amino group, joined by a central carbon.
- The "R group" differs between amino acids, giving each its unique properties.
- Amino acids link via condensation reactions, forming bonds between the carbon of one and the nitrogen of another, releasing water.
- The linkage formed is called a peptide bond, amide bond, or amide link.
- The polymerization process can be represented by a general equation showing amino acids joining and producing water.
DNA
- DNA is a polymer whose monomers are nucleotides.
- Each nucleotide contains a base (T, A, G, or C) and a sugar-phosphate backbone.
- There are four types of nucleotides, one for each base.
- The sequence of nucleotides encodes genetic information as genes.
- DNA consists of two polymer chains connected together, forming a double helix.
Carbohydrates
- Carbohydrates include a variety of polymers (polysaccharides) and monomers (sugars), made from carbon, hydrogen, and oxygen.
- Polysaccharides include starch, cellulose, and glycogen.
- Monosaccharides (sugars) include glucose and fructose.
- Polymers form by joining many monosaccharides, like making starch from multiple glucose units.
Key Terms & Definitions
- Polymer — a long chain molecule made from repeating smaller units called monomers.
- Monomer — the basic repeating unit that joins to form a polymer.
- Amino Acid — the monomer unit of polypeptides and proteins, containing amino and carboxyl groups.
- Peptide Bond (also called amide bond or amide link) — the bond joining amino acids in a polypeptide.
- Nucleotide — the monomer of DNA, containing a base, a sugar, and a phosphate group.
- Polysaccharide — a carbohydrate polymer made from many monosaccharide units.
- Monosaccharide — a single sugar unit, such as glucose or fructose.
Action Items / Next Steps
- Review the structure of amino acids and practice drawing peptide bond formation.
- Learn the basic structure of nucleotides and how DNA strands pair up.
- Memorize examples of polysaccharides and monosaccharides.