Biological Macromolecules: Lipids, Nucleic Acids, and Proteins

Lipids

Triglycerides

Triglycerides are a type of lipid composed of one glycerol molecule and three fatty acid chains. They are the main constituents of body fat in humans and other animals, as well as vegetable fat.

• Glycerol: A three-carbon alcohol that forms the backbone of triglycerides.

• Fatty Acids: Long hydrocarbon chains with a carboxyl group at one end.

• Formation: Triglycerides are formed by the condensation of glycerol and three fatty acids, releasing three molecules of water.

Equation:

$\text{Glycerol} + 3\ \text{Fatty Acids} \rightarrow \text{Triglyceride} + 3\ \text{H}_2\text{O}$

Types of Triglycerides

• Saturated: Fatty acids with only single bonds between carbon atoms. Solid at room temperature. Common in the animal kingdom (e.g., bacon).

• Unsaturated: Fatty acids with one or more double bonds. Liquid at room temperature. Common in the plant kingdom (e.g., vegetable oil).

Type	Bond Type	State at Room Temp	Example
Saturated	Single	Solid	Bacon
Unsaturated	Double	Liquid	Vegetable oil

Hydrogenation: The process of converting unsaturated fats to saturated fats by adding hydrogen, often used in making margarine.

Phospholipids

Phospholipids are major components of cell membranes. They contain a phosphate functional group and are amphipathic, meaning they have both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

• Structure: Two fatty acid tails (hydrophobic) and a phosphate group head (hydrophilic).

• Function: Form bilayers in cell membranes, with hydrophobic tails facing inward and hydrophilic heads facing outward.

Steroids

Steroids are lipids characterized by a carbon skeleton with four fused rings. They serve various functions in the body, including acting as hormones.

• Examples: Sex hormones (e.g., testosterone, estrogen), adrenal cortical hormones (e.g., aldosterone).

• Function: Regulatory (hormones), structural (cell membrane), and defense.

Nucleic Acids

Functions of Nucleic Acids

Nucleic acids are polymers of nucleotide monomers and are essential for storing, transferring, and expressing genetic information.

• Information Storage: DNA stores genetic information.

• Information Transfer: RNA transfers genetic information.

• Energy Transfer: ATP transfers energy within cells.

Structure of Nucleic Acids

• Nucleotide: The monomer unit of nucleic acids, consisting of a five-carbon sugar, a nitrogenous base, and a phosphate group.

• Polymerization: Nucleotides bond together to form long chains (nucleic acids).

Components of a Nucleotide

• Five-carbon sugar: Deoxyribose in DNA, ribose in RNA.

• Nitrogenous base: Can be a single or double ring structure, contains nitrogen (e.g., adenine, thymine, cytosine, guanine, uracil).

• Phosphate group: Provides the acidic character and links nucleotides together.

Proteins

Functions of Proteins

Proteins are polymers of amino acids and perform a wide variety of functions in living organisms.

• Structural: Provide support (e.g., collagen in cartilage, tendons, skin, cornea).

• Mechanical: Involved in movement (e.g., actin and myosin in muscle contraction).

• Receptor: Serve as receptors for signals (e.g., receptor proteins in taste).

• Regulatory: Many hormones are proteins (e.g., insulin, growth hormone).

• Defense: Antibodies are proteins that defend against pathogens.

• Transport: Hemoglobin transports oxygen; channel proteins transport ions and molecules across membranes.

• Venomous: Some proteins act as venoms, immobilizing prey.

• Catalysts: Enzymes are proteins that catalyze biochemical reactions.

Levels of Protein Structure

• Primary Structure: The sequence of amino acids in the polypeptide chain.

• Secondary Structure: Local folding patterns such as alpha helix and beta pleated sheet.

• Alpha Helix: Resembles a coiled telephone cord; held together by hydrogen bonds.

• Beta Pleated Sheet: More wavy and folded structure.

Amino Acids

• General Structure: Central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and an R group (side chain).

• Functional Groups: Amino group ($\text{-NH}_2$), carboxyl group ($\text{-COOH}$).

• R Group: Determines the properties and identity of each amino acid.

• Polarity: Amino acids can be polar, nonpolar, or ionic.

• Number: There are 20 standard amino acids used in protein synthesis.

Equation:

$\text{Amino Acid}_1 + \text{Amino Acid}_2 \rightarrow \text{Dipeptide} + \text{H}_2\text{O}$

Peptide Bond: A strong covalent bond formed between the amino group of one amino acid and the carboxyl group of another.

Level	Description
Primary	Sequence of amino acids
Secondary	Alpha helix, beta sheet

Key Fact: All living things use the same 20 amino acids to make proteins, which is strong evidence for a common ancestor.

Example: Collagen is a structural protein found in cartilage, tendons, skin, and cornea.

Additional info: The notes reference further details and diagrams on other papers; standard textbook context has been added to ensure completeness.