MCAT Biochemistry Syllabus

Biochemistry syllabus: all 13 chapters

Expand any chapter to see its topics and sub-topics.

1. 1

   Amino Acids and Proteins

   4 topics

   • Amino Acid Structure and Properties
     • Side Chains (Hydrophobic, Hydrophilic, Acidic, Basic)
     • Peptide Bonds
   • Protein Structure
     • Primary, Secondary (Alpha Helices, Beta Sheets), Tertiary, and Quaternary Structures
     • Protein Folding and Stability
   • Enzyme Structure and Function
     • Active Sites
     • Substrate Specificity
     • Catalysis Mechanisms
   • Enzyme Kinetics
     • Michaelis-Menten Equation
     • Vmax and Km
     • Lineweaver-Burk Plot
     • Inhibition Types (Competitive, Non-competitive, Uncompetitive)
2. 2

   Carbohydrates

   4 topics

   • Monosaccharides
     • Structure (Glucose, Fructose, Galactose)
     • Ring and Linear Forms
   • Disaccharides
     • Structure (Sucrose, Lactose, Maltose)
     • Glycosidic Bonds
   • Polysaccharides
     • Storage Polysaccharides (Starch, Glycogen)
     • Structural Polysaccharides (Cellulose, Chitin)
   • Carbohydrate Metabolism
     • Glycolysis
     • Glycogenesis and Glycogenolysis
     • Gluconeogenesis
3. 3

   Lipids

   5 topics

   • Fatty Acids
     • Saturated and Unsaturated
     • Essential Fatty Acids
   • Triglycerides
     • Structure and Function
     • Saponification
   • Phospholipids
     • Structure and Role in Cell Membranes
   • Steroids
     • Cholesterol and Steroid Hormones
   • Lipid Metabolism
     • Beta-Oxidation
     • Ketogenesis
     • Lipogenesis
4. 4

   Nucleic Acids

   2 topics

   • DNA and RNA Structure
     • Nucleotides (Adenine, Thymine, Cytosine, Guanine, Uracil)
     • Double Helix Structure of DNA
     • RNA Types and Structures
   • Nucleotide Metabolism
     • Purine and Pyrimidine Synthesis and Degradation
5. 5

   Enzyme Structure and Function

   2 topics

   • Catalytic Mechanisms
   • Cofactors and Coenzymes
     • Metal Ions
     • Organic Molecules
6. 6

   Enzyme Kinetics and Regulation

   3 topics

   • Enzyme Inhibition
   • Allosteric Regulation
   • Feedback Inhibition
7. 7

   Metabolism of Carbohydrates

   5 topics

   • Glycolysis
     • Key Enzymes and Regulation
   • Citric Acid Cycle (Krebs Cycle)
     • Steps and Enzymes
     • Regulation Points
   • Electron Transport Chain and Oxidative Phosphorylation
     • Proton Gradient and ATP Synthase
   • Gluconeogenesis
     • Key Steps and Regulation
   • Pentose Phosphate Pathway
     • Oxidative and Non-Oxidative Phases
8. 8

   Metabolism of Lipids

   4 topics

   • Fatty Acid Oxidation (Beta-Oxidation)
     • Steps and Enzymes
   • Ketogenesis
     • Conditions for Ketone Body Production
   • Lipid Synthesis
     • Fatty Acid Synthase
     • Triglyceride Synthesis
   • Cholesterol Metabolism
     • Synthesis Pathway
     • Regulation
9. 9

   Metabolism of Proteins and Amino Acids

   3 topics

   • Transamination and Deamination
     • Enzymes Involved
   • Urea Cycle
     • Steps and Regulation
   • Amino Acid Catabolism
     • Glucogenic and Ketogenic Amino Acids
10. 10

    DNA Replication Mechanisms

    6 topics

    • Helicase
    • DNA Polymerase
    • Primase
    • Ligase
    • Leading and Lagging Strands
    • Proofreading and Repair Mechanisms
11. 11

    RNA Transcription Processes

    3 topics

    • RNA Polymerase
    • Promoters, Enhancers, and Transcription Factors
    • Post-Transcriptional Modifications
      • Capping
      • Polyadenylation
      • Splicing
12. 12

    Protein Translation and Post-Translational Modifications

    4 topics

    • Ribosome Structure and Function
    • tRNA and Codon-Anticodon Interaction
    • Steps of Translation (Initiation, Elongation, Termination)
    • Post-Translational Modifications (Phosphorylation, Glycosylation, Proteolytic Cleavage)
13. 13

    Regulation of Gene Expression

    3 topics

    • Operons in Prokaryotes
      • Lac Operon
      • Trp Operon
    • Epigenetics
      • DNA Methylation
      • Histone Modification
    • Transcription Factors and Regulatory Elements in Eukaryotes

MCAT Biochemistry flashcards — 51 questions with answers

1. What are the four components attached to the central (alpha) carbon of a standard amino acid?

   An amino group ($\ce{-NH2}$), a carboxyl group ($\ce{-COOH}$), a hydrogen atom, and a variable R (side chain) group.

2. Which amino acid is the only one that is achiral, and why?

   Glycine. Its R group is a single hydrogen atom, so the alpha carbon is bonded to two identical hydrogens and is not a stereocenter.

3. Name the three nonpolar, aromatic-ring-containing or unique amino acids that absorb UV light at 280 nm.

   Tryptophan, tyrosine, and phenylalanine (aromatic side chains); tryptophan and tyrosine are the strongest absorbers at 280 nm.

4. At physiological pH ($\approx 7.4$), what is the charge state of a typical amino acid, and what is this form called?

   It exists as a zwitterion: the amino group is protonated ($\ce{-NH3+}$) and the carboxyl group is deprotonated ($\ce{-COO-}$), giving a net charge of $0$.

5. How is the isoelectric point (pI) calculated for an amino acid with a nonionizable side chain?

   $$\text{pI} = \frac{\text{p}K_{a1} + \text{p}K_{a2}}{2}$$ where $\text{p}K_{a1}$ is the carboxyl group and $\text{p}K_{a2}$ is the amino group.

6. Which three amino acids have basic (positively charged at physiological pH) side chains?

   Lysine, arginine, and histidine. Histidine (p$K_a \approx 6$) is often partially protonated near physiological pH.

7. Which two amino acids have acidic (negatively charged) side chains, and what are their amide counterparts?

   Aspartate and glutamate (acidic); their neutral amide forms are asparagine and glutamine, respectively.

8. What type of bond links amino acids in a protein, and what type of reaction forms it?

   A peptide bond (an amide linkage) formed by a condensation (dehydration) reaction that releases a molecule of water.

9. Distinguish the alpha-helix and beta-pleated sheet in terms of hydrogen bonding.

   In the alpha-helix, H-bonds form between backbone groups within the same chain (intra-strand, parallel to the helix axis). In the beta-sheet, H-bonds form between backbone groups of adjacent strands (inter-strand, perpendicular to strand direction).

10. Define primary, secondary, tertiary, and quaternary protein structure.

    Primary: the linear sequence of amino acids. Secondary: local backbone folding (alpha-helices, beta-sheets) from H-bonds. Tertiary: overall 3D shape of a single chain from side-chain interactions. Quaternary: assembly of multiple polypeptide subunits.

11. Which amino acids are most important for stabilizing tertiary structure, and what bond do two cysteines form?

    Cysteine forms disulfide bonds (covalent $\ce{-S-S-}$ bridges); hydrophobic residues drive the hydrophobic core; also involved are H-bonds, ionic (salt) bridges, and van der Waals forces.

12. Why is proline known as a 'helix breaker'?

    Its side chain forms a rigid ring with the backbone nitrogen, so it lacks an amide hydrogen for H-bonding and its cyclic structure kinks the chain, disrupting alpha-helices.

13. By how much do enzymes affect the equilibrium constant ($K_{eq}$) and the activation energy ($E_a$) of a reaction?

    Enzymes lower the activation energy $E_a$ but do NOT change $K_{eq}$, $\Delta G$, or the position of equilibrium; they speed both forward and reverse reactions equally.

14. Contrast the lock-and-key model with the induced-fit model of enzyme-substrate binding.

    Lock-and-key: the active site is already perfectly complementary to the substrate's shape. Induced-fit: the active site changes conformation upon substrate binding to achieve optimal fit.

15. Match each enzyme class to its function: oxidoreductase, transferase, hydrolase, lyase, isomerase, ligase.

    Oxidoreductase: redox (electron transfer). Transferase: move a functional group. Hydrolase: cleave bonds with water. Lyase: cleave/form bonds without water or redox (often forming double bonds). Isomerase: rearrange within a molecule. Ligase: join two molecules using ATP.

16. Write the Michaelis-Menten equation and define its terms.

    $$v_0 = \frac{V_{max}[S]}{K_m + [S]}$$ where $v_0$ is initial velocity, $V_{max}$ is maximum velocity, $[S]$ is substrate concentration, and $K_m$ is the Michaelis constant.

17. What does $K_m$ equal, and what does a low $K_m$ indicate about enzyme-substrate affinity?

    $K_m$ equals the substrate concentration at which $v_0 = \tfrac{1}{2}V_{max}$. A low $K_m$ indicates high affinity (less substrate is needed to reach half-maximal velocity).

18. Write the Lineweaver-Burk equation and state what the axis intercepts represent.

    $$\frac{1}{v_0} = \frac{K_m}{V_{max}}\cdot\frac{1}{[S]} + \frac{1}{V_{max}}$$ The y-intercept is $\frac{1}{V_{max}}$ and the x-intercept is $-\frac{1}{K_m}$; the slope is $\frac{K_m}{V_{max}}$.

19. How does a competitive inhibitor affect $K_m$ and $V_{max}$?

    It increases the apparent $K_m$ (lower apparent affinity) but leaves $V_{max}$ unchanged, because the inhibition can be overcome by high substrate concentrations.

20. How does a noncompetitive inhibitor affect $K_m$ and $V_{max}$?

    It decreases $V_{max}$ but leaves $K_m$ unchanged. It binds equally to enzyme and enzyme-substrate complex at an allosteric site, and cannot be overcome by adding substrate.

MCAT Biochemistry FAQ