Biochemistry and Organic Chemistry

Introduction to Biochemistry

Biochemistry is the study of the chemical processes and substances that occur within living organisms. It is closely related to organic chemistry, which focuses on carbon-containing compounds.

• Biochemistry explores the structure, function, and interactions of biological macromolecules.

• Organic chemistry is the study of carbon compounds, which are fundamental to life.

Carbon's Versatility

Carbon is a versatile element due to its four valence electrons, allowing it to form four covalent bonds and a wide variety of structures.

• Carbon skeletons can vary in length, branching, and ring formation.

• Hydrocarbons are organic molecules containing only carbon and hydrogen.

Functional Groups in Organic Molecules

Organic molecules have unique properties due to attached functional groups, which influence their chemical behavior.

• Hydroxyl group (–OH): Found in alcohols and sugars.

• Carbonyl group (C=O): Found in sugars.

• Amino group (–NH2): Found in amino acids and urea.

• Carboxyl group (–COOH): Found in amino acids, fatty acids, and vitamins.

Elements Essential for Life

Major Elements in Living Organisms

Six elements make up 97% of the compounds present in living organisms: Phosphorus (P), Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), and Sulfur (S).

• These elements are often abbreviated as PCHONS.

• They are crucial for the structure and function of biological macromolecules.

Macromolecules: Structure and Terminology

Key Terms

• Monomer: Subunit or building block of a polymer.

• Polymer: Large molecule made of many monomers strung together.

• Macromolecule: Giant molecule of matter, such as proteins, nucleic acids, carbohydrates, and lipids.

• Carbon skeleton: Backbone of carbon atoms in organic molecules.

• Hydrocarbon: Organic molecule containing only carbon and hydrogen (e.g., methane, CH4).

Organic Compounds

To be considered organic, a molecule must contain both carbon and hydrogen. Other elements may be attached, such as oxygen, nitrogen, phosphorus, and sulfur.

• Carbon dioxide (CO2) is not organic because it lacks hydrogen.

• O2 and H2O are also not organic, as they lack carbon.

Polymer Formation and Breakdown

Building and Breaking Polymers

Polymers are built and broken down by specific chemical reactions:

• Dehydration reaction: Joins monomers by removing a molecule of water, forming a longer polymer.

• Hydrolysis: Breaks polymers into monomers by adding a molecule of water.

Carbohydrates

Structure and Function

Carbohydrates are organic molecules consisting of carbon, hydrogen, and oxygen in a ratio of 1:2:1 (e.g., glucose is C6H12O6). They serve as major immediate energy sources and are classified by the length of their carbon chain.

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

• Disaccharides: Two monosaccharides bonded together (e.g., maltose, sucrose, lactose).

• Polysaccharides: Several simple sugars bonded together, used for energy storage and structural components.

Isomers

Isomers are molecules with the same molecular formula but different structures, resulting in different properties (e.g., glucose and fructose).

Disaccharides Formation

Disaccharides are formed by dehydration reactions between two monosaccharides.

• Glucose + Glucose = Maltose + Water

• Glucose + Fructose = Sucrose + Water

• Glucose + Galactose = Lactose + Water

Polysaccharides

Polysaccharides are used for short-term energy storage and structural components.

• Starch: Storage polysaccharide in plants.

• Glycogen: Storage polysaccharide in animals, stored in liver or muscle cells.

• Cellulose: Structural component of plant cell walls.

• Chitin: Structural component in arthropod exoskeletons.

Hydrophilic Properties

Polysaccharides are hydrophilic, meaning they mix or dissolve in water and absorb water.

• This property is important for their biological functions, such as energy storage and structural support.

Lipids

Structure and Function

Lipids are organic molecules that serve two main functions: long-term energy storage (fats) and structural/hormonal roles (steroids).

• Always consist of carbon, hydrogen, and oxygen, but not in a fixed ratio.

• Are nonpolar and hydrophobic (do not dissolve in water).

Structure of Fats

Fats are composed of glycerol and fatty acids. A dehydration reaction joins three fatty acids to one glycerol, forming a triglyceride.

Types of Fatty Acids

• Saturated fatty acids: Single bonds join all carbon atoms; solid at room temperature.

• Unsaturated fatty acids: Double bonds join some carbon atoms; liquid at room temperature.

Steroids

Steroids are lipids made of four interconnected rings of carbon with different functional groups attached. Examples include cholesterol, estrogen, and testosterone.

Proteins

Structure and Function

Proteins are made of monomers called amino acids (aa). They provide support, facilitate growth, enable movement, transport substances, and speed up chemical reactions (enzymes).

• Always consist of carbon, hydrogen, oxygen, and nitrogen; some contain sulfur (cysteine and methionine).

• Each amino acid differs in its side/variable (R) group.

• Amino acids are joined by peptide bonds.

Protein Structure Hierarchy

Proteins have four levels of structure:

1. Primary structure: Sequence of amino acids.

2. Secondary structure: Folding into alpha helices or beta sheets.

3. Tertiary structure: 3D shape of a single polypeptide.

4. Quaternary structure: Association of multiple polypeptides.

Importance of Protein Structure

The type, number, and arrangement of amino acids make each protein unique. Even a single wrong amino acid can cause a protein to lose its proper function (e.g., sickle cell hemoglobin).

Denaturation

Denaturation is the unfolding of a protein from its proper 3D shape. It does not destroy the protein or break peptide bonds.

Nucleic Acids

Structure and Function

Nucleic acids are made of monomers called nucleotides. They always consist of phosphorus, carbon, hydrogen, oxygen, and nitrogen. Nucleic acids store genetic information and form genes passed from parent to child.

• DNA: Double-stranded, contains deoxyribose sugar, and bases adenine (A), thymine (T), cytosine (C), guanine (G).

• RNA: Single-stranded, contains ribose sugar, and bases adenine (A), uracil (U), cytosine (C), guanine (G).

Nucleotide Structure

Each nucleotide has three components:

1. Pentose sugar (ribose or deoxyribose)

2. Phosphate group

3. Nitrogen base (single or double ring of C, H, N)

DNA Structure Rules

• Nucleotide monomers are joined by covalent bonding (dehydration reactions).

• DNA consists of two chains of nucleotides connected at their nitrogen bases by hydrogen bonding.

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

• DNA has a double helix shape; strands are complementary and antiparallel.

RNA vs. DNA

• RNA contains uracil instead of thymine.

• RNA occurs as a single strand.

• RNA has three forms: tRNA, mRNA, rRNA.

Summary Table: Macromolecules

Macromolecule Comparison