Biochemistry Core Concepts

Biomolecules & Enzymes

Biochemistry focuses on the structure and function of biomolecules, including amino acids, proteins, and enzymes. Understanding their properties and mechanisms is essential for grasping metabolic pathways and cellular processes.

• Amino Acids: Building blocks of proteins, each with a central carbon (alpha carbon), amino group, carboxyl group, and unique R-group.

• Zwitterion: Amino acids exist as neutral dipolar ions at their isoelectric point (pI).

• Protein Structure:

  • Primary: Sequence of amino acids linked by peptide bonds.

  • Secondary: Hydrogen bonding forms alpha-helices and beta-sheets.

  • Tertiary: Three-dimensional folding driven by hydrophobic collapse.

• Enzymes: Biological catalysts that lower activation energy but do not alter the free energy change () of reactions.

• Enzyme Inhibition:

  Type	Mechanism	Kinetics
  Competitive	Binds active site	same, increases
  Non-competitive	Binds allosteric site	decreases, same
  Uncompetitive	Binds ES complex	decreases, decreases

Metabolism: The Energy Pathways

Glycolysis, Citric Acid Cycle, and Electron Transport Chain

Cellular metabolism involves a series of interconnected pathways that convert glucose into usable energy. These include glycolysis, the citric acid cycle (Krebs), and the electron transport chain.

• Glycolysis: Occurs in the cytoplasm; converts glucose to 2 pyruvate, producing 2 ATP and 2 NADH.

• Citric Acid Cycle: Takes place in the mitochondrial matrix; generates NADH, FADH2, and GTP from pyruvate.

• Electron Transport Chain: Located in the inner mitochondrial membrane; uses electron carriers (NADH, NADPH, FADH2, ubiquinone) to drive oxidative phosphorylation and generate the proton motive force.

Biology: Central Dogma & Genetics

DNA, RNA, and Protein Synthesis

The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein. This process is fundamental to understanding gene expression and inheritance.

• Replication: DNA is copied in a semi-conservative manner.

• Transcription: DNA is transcribed into RNA.

• Translation: RNA is translated into protein.

Cell Division

• Mitosis: Produces identical somatic cells (2n → 2n).

• Meiosis: Generates gametes with genetic diversity (2n → n).

Genetics Equations

• Mendelian Inheritance: Dominant/recessive traits.

• Hardy-Weinberg Equilibrium: ; (genotype frequency).

Chemistry Foundations

Atomic Structure & Periodic Trends

Chemistry underpins biochemistry by explaining atomic structure, periodic properties, and chemical reactions.

• Atomic Structure:

  • Protons determine identity ().

  • Neutrons determine isotope ().

  • Electrons determine reactivity.

• Periodic Trends:

  • Ionization energy and electronegativity increase across a period.

  • Atomic radius decreases across a period.

Stoichiometry & Equilibrium

• Mole: entities.

• Molarity (M): Moles solute per liter solution.

• Limiting Reagent: Consumed first, determines yield.

• Equilibrium Constant: (exclude pure solids and liquids).

Thermodynamics vs. Kinetics

Thermodynamics determines whether a reaction is spontaneous, while kinetics determines the rate.

• Free Energy Change:

• : Exergonic (spontaneous)

• : Endergonic (non-spontaneous)

• Activation Energy (): Determines reaction rate.

• Ideal Gas Law:

Organic Chemistry Foundations

Functional Groups

Organic chemistry is essential for understanding biomolecules. Functional groups define the chemical properties and reactivity of organic compounds.

• Common Functional Groups:

  • Formaldehyde

  • Acetaldehyde

  • Acetone

  • Formic Acid

  • Benzoic Acid

  • Acetophenone

Spectroscopy

Spectroscopy is used to identify functional groups and molecular structure in organic compounds.

• IR Spectroscopy: O-H stretch (broad), C=O stretch (sharp).

• NMR: Chemical shifts for carboxylic acids and aldehydes.

• Mass Spectrometry: Base peak and molecular ion peak.

MCAT Foundational Concepts Overview

Bio/Biochem Foundations

The MCAT covers foundational biochemistry concepts, including amino acids, proteins, metabolism, cell structure, and organ systems. These topics are directly relevant to college biochemistry courses.

• Amino Acids & Proteins

• Metabolism (Glycolysis/Krebs)

• The Cell & Genetics

• Organ Systems

Additional Relevant Topics

Control Systems: Nervous & Endocrine

Understanding the biochemical basis of nervous and endocrine systems is important for signal transduction and metabolic regulation.

• Action Potential: All-or-nothing, Na+ influx (depolarization), K+ efflux (repolarization).

• Synapse: Neurotransmitter release.

• Hormones:

  • Peptide: Fast, surface receptors.

  • Steroid: Slow, intracellular receptors.

• Insulin vs. Glucagon: Insulin promotes storage; glucagon mobilizes energy during fasting.

Organ Systems: Heart & Oxygen

Biochemistry is integral to understanding oxygen transport and cardiovascular physiology.

• Heart Anatomy: Chambers, valves, conduction system.

• Oxygen Transport:

  • Hemoglobin: Cooperative binding.

  • Myoglobin: High affinity for O2.

  • Bohr Effect: Low pH, high CO2 decreases O2 affinity.

Summary Table: Biochemistry-Related MCAT Topics

Additional info:

• Some topics (e.g., physics, psychology, sociology) are included for MCAT completeness but are not directly relevant to biochemistry college courses.

• All included images are directly relevant to the biochemistry topics discussed.