Biochemistry ACS Exam Questions and Answers 2024

structures and properties of amino acids Nonpolar, Aliphatic (Hydrophobic): Glycine (Gly, G) Alanine (Ala, A) Valine (Val, V) Leucine (Leu, L) Isoleucine (Ile, I) Proline (Pro, P) Aromatic (Hydrophobic): Phenylalanine (Phe, F) Tyrosine (Tyr, Y) Tryptophan (Trp, W) Polar, Uncharged (Hydrophilic): Serine (Ser, S) Threonine (Thr, T) Cysteine (Cys, C) Methionine (Met, M) Asparagine (Asn, N) Glutamine (Gln, Q) Positively Charged (Basic, Hydrophilic): Lysine (Lys, K) Arginine (Arg, R) Histidine (His, H) Negatively Charged (Acidic, Hydrophilic): Aspartic Acid (Asp, D) Glutamic Acid (Glu, E) protein structure 1. Primary Structure: Definition: The primary structure of a protein is the linear sequence of amino acids that make up the polypeptide chain. Importance: The specific order of amino acids determines the protein's unique identity and influences its folding and function. 2. Secondary Structure: Definition: Secondary structure refers to the local folding patterns within a polypeptide chain. The two most common secondary structures are alpha helices and beta sheets. Alpha Helix: A helical structure where the polypeptide chain coils like a spring. Stabilized by hydrogen bonds between the carbonyl oxygen of one amino acid and the amide hydrogen of an amino acid four residues away. Beta Sheet: A sheet-like structure where adjacent strands are connected by hydrogen bonds. Can be parallel or antiparallel, depending on the direction of neighboring strands. 3. Tertiary Structure: Definition: Tertiary structure refers to the overall three-dimensional arrangement of the entire polypeptide chain, including its secondary structures. Stabilizing Forces: Tertiary structure is stabilized by various interactions, including hydrogen bonds, disulfide bridges, hydrophobic interactions, and electrostatic attractions. Folded Domains: Proteins often consist of distinct folded domains, each with a specific function. Domains are independently folded units within a protein. 4. Quaternary Structure: Definition: Quaternary structure arises when multiple polypeptide chains (subunits) come together to form a functional protein complex. Examples: Hemoglobin is a tetrameric protein with four subunits. Collagen is a fibrous protein with a triple helix quaternary structure. Stabilizing Interactions: The interactions stabilizing quaternary structure are similar to those in tertiary structure, including hydrogen bonds, disulfide bridges, and hydrophobi enzyme kinetics the study of the rates at which enzymes catalyze chemical reactions. Understanding enzyme kinetics is crucial for elucidating the mechanisms of enzyme action, optimizing reaction conditions, and designing drugs that target specific enzymes. michaelis menten assumptions Substrate Binding: The enzyme (E) binds to the substrate (S) to form the enzyme-substrate complex (ES). Enzyme-Substrate Complex Formation: The enzyme-substrate complex undergoes a transition state to form the product (P) and release the enzyme. enzyme inhibition types competitive inhibitor, noncompetitive inhibitor, and mixed inhibitor allosteric enzymes and cooperative binding Allosteric Enzymes: Allosteric enzymes have multiple binding sites and exhibit cooperativity. Binding of one substrate molecule can affect the enzyme's affinity for other substrate