General Biology: Biomolecules, Protein Structure, and Nucleic Acids Study Guide

Study Guide - Smart Notes

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Biomolecules and Their Functions

Definition and Types of Biomolecules

Biomolecules are organic molecules that are essential for life. They include carbohydrates, proteins, lipids, and nucleic acids. Each type of biomolecule has unique structures and functions within living organisms.

Carbohydrates: Serve as energy sources and structural components (e.g., glucose, cellulose).
Proteins: Function as enzymes, structural elements, and signaling molecules.
Lipids: Provide energy storage, insulation, and make up cell membranes (e.g., fats, oils).
Nucleic Acids: Store and transmit genetic information (DNA and RNA).

Hydrophobic vs. Hydrophilic

Biomolecules can be classified based on their affinity for water:

Hydrophobic: Molecules that repel water (e.g., oils, fats).
Hydrophilic: Molecules that interact well with water (e.g., sugars, salts).
Examples: Cell membranes have hydrophobic lipid tails and hydrophilic phosphate heads.

Functional Groups in Amino Acids

Amino acids, the building blocks of proteins, contain specific functional groups:

Amino group (-NH2): Acts as a base, accepting protons.
Carboxyl group (-COOH): Acts as an acid, donating protons.
R group (side chain): Determines the unique properties of each amino acid.

Be able to identify these groups in amino acid structures.

Peptide Bond Formation

Proteins are formed by linking amino acids via peptide bonds. This occurs through a dehydration synthesis reaction:

Dehydration/Condensation: Removal of a water molecule to form a new bond.
Peptide Bond: Covalent bond between the carboxyl group of one amino acid and the amino group of another.

Carbohydrates: Structure and Classification

Types of Carbohydrates

Carbohydrates are classified based on the number of sugar units:

Monosaccharides: Single sugar units (e.g., glucose, fructose).
Disaccharides: Two monosaccharides linked together (e.g., sucrose, lactose).
Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).

Bond Types in Carbohydrates

Glycosidic Bond: Covalent bond that joins carbohydrate molecules together.
Hydrolysis: The process of breaking glycosidic bonds using water.

Example: Starch and glycogen can be broken down by hydrolysis, while cellulose cannot be digested by humans due to the type of glycosidic bond present.

Protein Structure and Levels of Organization

Levels of Protein Structure

Proteins have four levels of structural organization, each contributing to the protein's final shape and function:

Level	Description	Types of Bonds
Primary	Sequence of amino acids in a polypeptide chain	Peptide bonds
Secondary	Local folding into alpha-helices and beta-sheets	Hydrogen bonds
Tertiary	Three-dimensional folding of a single polypeptide	Hydrogen bonds, ionic bonds, disulfide bridges, hydrophobic interactions
Quaternary	Association of multiple polypeptide chains	Same as tertiary (between subunits)

Protein Domains and Motifs

Proteins may contain distinct regions called domains, each with specific functions. Motifs are recurring structural elements within proteins.

Nucleic Acids: DNA and RNA

Structure of Nucleotides

Nucleotides are the building blocks of nucleic acids. Each nucleotide consists of:

Pentose Sugar: Deoxyribose in DNA, ribose in RNA.
Nitrogenous Base: Adenine (A), Thymine (T, in DNA), Uracil (U, in RNA), Cytosine (C), Guanine (G).
Phosphate Group

Comparison of DNA and RNA

	DNA	RNA
Pentose Sugar	Deoxyribose	Ribose
Nitrogenous Bases	A, T, C, G	A, U, C, G
Strandedness	Double-stranded	Single-stranded
Function	Genetic information storage	Protein synthesis, gene regulation

Base Pairing Rules

DNA: Adenine pairs with Thymine (A-T), Cytosine pairs with Guanine (C-G).
RNA: Adenine pairs with Uracil (A-U), Cytosine pairs with Guanine (C-G).

Lipids: Saturated vs. Unsaturated Fats

Differences Between Saturated and Unsaturated Fats

Saturated Fats: No double bonds between carbon atoms; solid at room temperature (e.g., butter).
Unsaturated Fats: One or more double bonds; liquid at room temperature (e.g., olive oil).
Health Implications: Diets high in saturated fats are linked to heart disease, while unsaturated fats are considered healthier.

Summary Table: Key Biomolecule Features

Biomolecule	Monomer	Bond Type	Main Function
Carbohydrate	Monosaccharide	Glycosidic bond	Energy, structure
Protein	Amino acid	Peptide bond	Enzymes, structure, signaling
Lipid	Fatty acid, glycerol	Ester bond	Energy storage, membranes
Nucleic Acid	Nucleotide	Phosphodiester bond	Genetic information

Additional info: Some explanations and examples were expanded for clarity and completeness based on standard General Biology curriculum.