Macromolecules and Their Biological Functions: Study Notes

5.1 Macromolecules are Polymers, Built from Monomers

Introduction to Macromolecules

Macromolecules are large biological molecules essential for life, constructed from smaller units called monomers. These polymers play critical roles in cellular structure and function.

• Macromolecules: Large polymers made from monomers; examples include carbohydrates, proteins, and nucleic acids.

• Monomers: The building blocks of polymers.

• Polymerization: The process of linking monomers to form polymers.

• Enzymes: Specialized macromolecules that speed up chemical reactions, such as those that build or break down polymers.

Hydrolysis and Dehydration Reactions

• Dehydration Reaction: Monomers are joined by removing water.

• Hydrolysis: Polymers are broken down into monomers by adding water.

• Functional Groups: Specific groups of atoms that participate in chemical reactions and give molecules their properties.

5.2 Carbohydrates are Sugars and Their Polymers

Structure and Classification of Carbohydrates

Carbohydrates are the most abundant biomolecules, serving as energy sources and structural materials.

• Monosaccharides: Simple sugars (e.g., glucose, fructose).

• Disaccharides: Two monosaccharides joined by a glycosidic linkage.

• Polysaccharides: Long chains of monosaccharides; serve storage and structural roles.

Types of Monosaccharides

• Aldose (Aldehyde sugar): Carbonyl group at the end of the carbon chain.

• Ketose (Ketone sugar): Carbonyl group in the middle of the carbon chain.

Polysaccharides and Their Functions

• Starch: Storage polysaccharide in plants; composed of glucose monomers.

• Glycogen: Storage polysaccharide in animals; highly branched.

• Cellulose: Structural polysaccharide in plant cell walls; provides rigidity.

• Chitin: Structural polysaccharide in arthropods and fungi.

Polysaccharide	Function	Organism
Starch	Energy storage	Plants
Glycogen	Energy storage	Animals
Cellulose	Structural support	Plants
Chitin	Structural support	Fungi, Arthropods

5.3 Lipids are a Diverse Group of Hydrophobic Molecules

Types and Functions of Lipids

Lipids are hydrophobic molecules that include fats, phospholipids, and steroids. They are not true polymers but are essential for energy storage, membrane structure, and signaling.

• Fats (Triglycerides): Composed of glycerol and three fatty acids; used for energy storage.

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

• Steroids: Lipids with a carbon skeleton of four fused rings; include cholesterol and hormones.

Saturated vs. Unsaturated Fats

• Saturated Fats: No double bonds; solid at room temperature.

• Unsaturated Fats: One or more double bonds; liquid at room temperature.

5.4 Proteins Include a Diversity of Structures, Resulting in a Wide Range of Functions

Structure and Function of Proteins

Proteins are polymers of amino acids and perform a vast array of functions in cells, including catalysis, transport, and structural support.

• Amino Acids: Organic molecules with an amino group and a carboxyl group; 20 different types.

• Peptide Bond: Covalent bond joining amino acids in a polypeptide.

• Primary Structure: Sequence of amino acids in a polypeptide chain.

• Secondary Structure: Local folding into alpha helices and beta sheets.

• Tertiary Structure: Overall 3D shape of a polypeptide.

• Quaternary Structure: Association of multiple polypeptide chains.

Protein Structure Level	Description
Primary	Sequence of amino acids
Secondary	Alpha helix, beta sheet
Tertiary	3D folding of polypeptide
Quaternary	Multiple polypeptides

Protein Functions

• Enzymatic: Catalyze biochemical reactions (e.g., digestive enzymes).

• Structural: Provide support (e.g., collagen, keratin).

• Transport: Move substances (e.g., hemoglobin).

• Defensive: Protect against disease (e.g., antibodies).

• Storage: Store amino acids (e.g., casein).

• Hormonal: Coordinate activities (e.g., insulin).

• Receptor: Respond to signals (e.g., nerve cell receptors).

• Contractile: Movement (e.g., actin, myosin).

5.5 Nucleic Acids Store, Transmit, and Help Express Hereditary Information

Structure and Function of Nucleic Acids

Nucleic acids (DNA and RNA) are polymers that store and transmit genetic information. They are composed of nucleotides, each consisting of a nitrogenous base, a pentose sugar, and a phosphate group.

• Nucleotide: Monomer of nucleic acids; contains a nitrogenous base, a sugar, and a phosphate group.

• DNA: Deoxyribonucleic acid; stores genetic information; double helix structure.

• RNA: Ribonucleic acid; involved in protein synthesis; single-stranded.

Nitrogenous Bases

• Pyrimidines: Cytosine, thymine, uracil; single-ring structure.

• Purines: Adenine, guanine; double-ring structure.

DNA Structure

• Double helix with antiparallel strands.

• Base pairing: Adenine with thymine, guanine with cytosine.

5.6 Genomics and Proteomics Have Transformed Biological Inquiry and Applications

Genomics and Proteomics

Advances in genomics and proteomics have revolutionized biological research, enabling the study of entire genomes and protein sets.

• Genomics: Study of whole sets of genes and their interactions.

• Proteomics: Study of entire sets of proteins expressed by a cell or organism.

• Applications include disease research, evolutionary studies, and biotechnology.

Key Equations and Concepts

• Dehydration Reaction: $\text{Monomer}_1 + \text{Monomer}_2 \rightarrow \text{Polymer} + \text{H}_2\text{O}$

• Hydrolysis: $\text{Polymer} + \text{H}_2\text{O} \rightarrow \text{Monomer}_1 + \text{Monomer}_2$

Additional info: Some explanations and examples have been expanded for clarity and completeness.