Introduction to Biomolecules: Carbohydrates, Lipids, Proteins, and Nucleic Acids

There are three major types of lipids you should distinguish:

1. Triglycerides: Composed of one glycerol molecule bonded to three fatty acid chains. These are the primary form of stored fat in the body.
2. Phospholipids: These molecules have a hydrophilic "head" and two hydrophobic "tails," making them the fundamental component of all cell membranes.
3. Steroids: Lipids characterized by a carbon skeleton consisting of four fused rings, such as cholesterol.

When studying fatty acids, pay close attention to their saturation. Saturated fatty acids have no double bonds between carbon atoms, resulting in straight chains. Unsaturated fatty acids contain one or more double bonds, which create "kinks" in the chain.

Proteins: The Functional Workhorses

Proteins are perhaps the most versatile biomolecules. They are polymers made of monomers called amino acids, which are linked together by peptide bonds.

A protein's ability to function is entirely dependent on its three-dimensional shape. This shape is organized into four hierarchical levels:

• Primary Structure: The linear sequence of amino acids in a polypeptide chain.
• Secondary Structure: Local folding patterns, such as $\alpha$-helices and $\beta$-pleated sheets, maintained by hydrogen bonds.
• Tertiary Structure: The overall three-dimensional folding of a single polypeptide chain.
• Quaternary Structure: The arrangement of multiple polypeptide subunits into a single functional complex.

Warning: Denaturation occurs when environmental factors like extreme pH or high temperature disrupt these structures. Once a protein is denatured, it loses its shape and, consequently, its biological function.

Nucleic Acids: The Genetic Blueprint

Nucleic acids, specifically DNA and RNA, are the molecules responsible for storing and transmitting genetic information. They are polymers composed of monomers called nucleotides.

Every nucleotide is made of three distinct parts:

1. A pentose sugar (ribose in RNA or deoxyribose in DNA).
2. A phosphate group.
3. A nitrogenous base (Adenine, Guanine, Cytosine, Thymine, or Uracil).

The specific pairing of nitrogenous bases (such as Adenine pairing with Thymine in DNA) is what allows for the accurate replication of genetic code during cell division.

Laboratory Identification: Chemical Indicators

In your lab practical, you will likely be asked to identify unknown substances using chemical indicators. Memorizing these specific reagents is critical for success:

By understanding the relationship between the molecular structure and these chemical tests, you will be well-prepared for both the written quiz and the hands-on laboratory component.