Course Overview

This study guide summarizes the foundational topics in introductory biochemistry, focusing on the molecular basis of life, the major classes of biomolecules, and the unique properties of water as the solvent of life. The content is structured to provide a clear, academic overview suitable for college-level biochemistry students.

Course Structure and Objectives

• Scope: One-term overview of biochemistry, emphasizing molecular explanations of life processes.

• Objectives:

  • Introduce biochemistry terminology and concepts.

  • Highlight relevance to medicine, nutrition, and related fields.

  • Prepare students for advanced study in life sciences.

• Textbooks: "Biochemistry" (Voet & Voet) or "Fundamentals of Biochemistry" (Voet, Voet & Pratt).

Major Topics Covered

• Biomolecules

• Amino acids

• Protein structure and function

• Protein purification

• Enzymes

• Nucleic acids

• Transcription & Translation

• Biological membranes

• Carbohydrates

• Metabolism & Bioenergetics

• Glycolysis & Fates of Pyruvate

• Oxidative phosphorylation

1. Introduction to Biochemistry

Definition and Scope

• Biochemistry is the study of the molecular basis of living systems.

• All biomolecules and processes in living organisms obey the same physical and chemical laws as inanimate matter.

• Life emerges from the interaction of inanimate biomolecules.

• Applications include medicine, disease treatment, nutrition, and industry.

Levels of Organization in Organisms

• Organism → Organ → Cell → Organelle → Molecule (e.g., DNA, proteins, metabolites)

• Each level represents increasing complexity and specialization.

2. Biomolecules

Elements in Biological Systems

• Major elements: C, H, O, N, P, S

• Trace elements: Fe, Mg, Zn, Cu, etc.

• These elements form the backbone of biomolecules.

Major Classes of Biomolecules

• Amino acids – building blocks of proteins

• Carbohydrates – sugars and polysaccharides

• Nucleotides – building blocks of nucleic acids

• Lipids – fats, oils, and related molecules

Functional Groups and Linkages

• Functional groups: amino, hydroxyl, sulfhydryl, carbonyl, carboxyl, phosphate

• Linkages:

  • Esters: between carboxyl and hydroxyl groups

  • Amides: between carboxyl and amino groups (peptide bonds)

  • Phosphodiester: between phosphate and hydroxyl groups (in nucleic acids)

Monomers and Polymers

• Monomers: Small molecules that serve as building blocks (e.g., amino acids, nucleotides, monosaccharides)

• Polymers: Large molecules formed by covalent linkage of monomers (e.g., proteins, nucleic acids, polysaccharides)

• Directionality: Polymers have a defined start and end, with all covalent bonds oriented in the same direction.

3. Water and Basic Chemistry

Importance of Water

• Life occurs exclusively in aqueous solution.

• Water is the solvent for all biological reactions.

Properties of Water

• Polarity: Water is a highly polar molecule, enabling it to dissolve polar and ionic substances.

• Hydrogen bonding: Each water molecule can form up to four hydrogen bonds (two as donor, two as acceptor).

• Structure: Liquid water forms a dynamic network of hydrogen bonds; ice forms a regular lattice.

Water as a Solvent

• Excellent solvent for hydrophilic (polar and ionic) substances.

• Poor solvent for hydrophobic (non-polar) substances.

• Biological molecules often have both polar and non-polar regions, affecting their solubility and structure.

Acids, Bases, and pH

• Water acts as a weak acid and base, participating in proton transfer reactions.

• Bronsted acids: Proton donors

• Bronsted bases: Proton acceptors

• pH: Measure of hydrogen ion concentration:

• pKa: ; when ,

Buffer Systems

• Buffers resist changes in pH near their pKa values.

• Biological systems use buffers (e.g., phosphate, bicarbonate) to maintain stable pH.

• Henderson-Hasselbalch equation:

Ionization of Amino Acids

• Amino acids have ionizable groups (carboxyl and amino) with characteristic pKa values.

• At low pH, amino acids are fully protonated; at high pH, they are deprotonated.

• At physiological pH (~7), most amino acids exist as zwitterions (both positive and negative charges).

Summary Table: Key Functional Groups

Key Equations

• Acid dissociation constant:

• pH definition:

• Henderson-Hasselbalch:

Study Tips

• Keep up with readings and practice questions.

• Attend lectures and Q&A sessions.

• Form study groups and ask questions early.