General Biology: Biomolecules, Proteins, and Nucleic Acids Study Guide

Biomolecules and Their Functions

Definition and Types of Biomolecules

Biomolecules are organic molecules that are essential for life and are found in all living organisms. The four major types are carbohydrates, proteins, lipids, and nucleic acids.

• Carbohydrates: Provide energy and structural support. Examples: glucose, cellulose.

• Proteins: Serve as enzymes, structural components, and signaling molecules. Examples: hemoglobin, collagen.

• Lipids: Store energy, form cell membranes, and act as signaling molecules. Examples: fats, phospholipids.

• Nucleic Acids: Store and transmit genetic information. Examples: DNA, RNA.

Hydrophobic vs. Hydrophilic: Hydrophobic molecules repel water (e.g., oils), while hydrophilic molecules attract water (e.g., sugars).

Functional Groups in Amino Acids: Amino acids contain an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable R group.

Amino Acids and Proteins

Structure and Properties of Amino Acids

Amino acids are the building blocks of proteins. Each amino acid has a unique R group that determines its properties and function.

• Peptide Bond: The bond formed between the amino group of one amino acid and the carboxyl group of another, releasing water (condensation reaction).

• Polymers: Proteins are polymers of amino acids.

• Variation: The R group makes each amino acid different.

Example: Glycine has a hydrogen as its R group, while alanine has a methyl group.

Levels of Protein Structure

Proteins have four levels of structure, each contributing to their function.

Level of Folding	Description	Types of Bonds
Primary	Sequence of amino acids	Peptide bonds
Secondary	Local folding into alpha helices and beta sheets	Hydrogen bonds
Tertiary	Three-dimensional folding due to side chain interactions	Hydrogen, ionic, disulfide, hydrophobic interactions
Quaternary	Association of multiple polypeptide chains	Same as tertiary

Carbohydrates

Monomers and Polymers

Carbohydrates are composed of monosaccharides (simple sugars), which can form disaccharides and polysaccharides.

• Monosaccharide: Single sugar unit (e.g., glucose).

• Disaccharide: Two sugar units (e.g., sucrose).

• Polysaccharide: Many sugar units (e.g., starch, cellulose).

Bond: Glycosidic bond links monosaccharides.

Example: Starch and cellulose are both polymers of glucose, but differ in their glycosidic linkages.

Lipids

Saturated vs. Unsaturated Fats

Lipids are hydrophobic molecules that include fats, oils, and phospholipids.

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

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

Example: Butter is saturated; olive oil is unsaturated.

Nucleic Acids

Structure of Nucleotides

Nucleic acids are polymers of nucleotides. Each nucleotide consists of three components:

• Pentose Sugar

• Nitrogenous Base

• Phosphate Group

They belong to the "Nucleic Acid" category of biomolecules.

DNA vs. RNA

DNA and RNA differ in their sugar, bases, and structure.

	DNA	RNA
Pentose Sugar	Deoxyribose	Ribose
Nitrogenous Bases	Adenine, Thymine, Cytosine, Guanine	Adenine, Uracil, Cytosine, Guanine
Strandedness	Double-stranded	Single-stranded
Function	Genetic information storage	Protein synthesis, gene regulation

Base Pairing Rules

Base pairing in DNA and RNA follows specific rules:

• DNA: Adenine (A) pairs with Thymine (T); Cytosine (C) pairs with Guanine (G).

• RNA: Adenine (A) pairs with Uracil (U); Cytosine (C) pairs with Guanine (G).

Example: In DNA, the sequence ATCG pairs with TAGC.

Additional Info

• Equation for Peptide Bond Formation:

$\text{Amino acid}_1 + \text{Amino acid}_2 \rightarrow \text{Dipeptide} + H_2O$

• Equation for Glycosidic Bond Formation:

$\text{Monosaccharide}_1 + \text{Monosaccharide}_2 \rightarrow \text{Disaccharide} + H_2O$

• General Structure of a Nucleotide:

$\text{Nucleotide} = \text{Pentose sugar} + \text{Phosphate group} + \text{Nitrogenous base}$