Henderson-Hasselbalch Equation Quiz
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Questions and Answers

What is the overall tendency of non-polar residues in protein structures?

  • To disperse randomly throughout the protein
  • To form hydrogen bonds with other residues
  • To collect in the interior of the protein (correct)
  • To remain at the surface of the protein

    • Which characteristic distinguishes antiparallel beta-pleated sheets from hydrophobic interactions?

  • Antiparallel sheets are more stable than hydrophobic interactions. (correct)
  • Antiparallel sheets do not involve side chain interactions.
  • Hydrophobic interactions strengthen hydrogen bonding.
  • Hydrophobic interactions occur only at the surface of proteins.

    • What interactions are primarily involved in stabilizing protein structures through charged side chains?

  • Van der Waals forces
  • Electrostatic interactions (correct)
  • Hydrogen bonding
  • Hydrophobic interactions

    • Why is it rare for beta-pleated sheets to have fewer than five strands?

    <p>Strands below five cannot maintain hydrogen bonding.</p> Signup and view all the answers

    What role do hydrogen bonds play in the formation of protein structures?

    <p>They form connections between side groups or peptide bonds.</p> Signup and view all the answers

    Which of the following amino acids is considered essential for adults?

    <p>Leucine</p> Signup and view all the answers

    What is the significance of proline in protein structure?

    <p>It limits structural flexibility due to its rigid ring.</p> Signup and view all the answers

    Which of the following amino acids cannot be synthesized by the human body?

    <p>Isoleucine</p> Signup and view all the answers

    Arginine is classified as essential in which context?

    <p>For infants</p> Signup and view all the answers

    Which amino acid has a non-chiral carbon atom?

    <p>Glycine</p> Signup and view all the answers

    What phrase can help remember essential amino acids?

    <p>Here lies the most famous versatile woman I’ve known.</p> Signup and view all the answers

    Which amino acid is known as the 'conformational isomer' of leucine?

    <p>Isoleucine</p> Signup and view all the answers

    Which category do amino acids like glycine and alanine fall into?

    <p>Non-essential amino acids</p> Signup and view all the answers

    What is the main function of the central vacuole in plant cells?

    <p>Container for food, nutrients, and waste products</p> Signup and view all the answers

    Which organelle is responsible for photosynthesis in plant cells?

    <p>Chloroplast</p> Signup and view all the answers

    What distinguishes the cell wall of plant cells from the cell walls of prokaryotic cells?

    <p>Composed of cellulose</p> Signup and view all the answers

    What is the function of lysosomes in animal cells?

    <p>Intracellular digestion using hydrolytic enzymes</p> Signup and view all the answers

    Which part of the ribosome is involved in the assembly of proteins?

    <p>Large ribosomal subunit</p> Signup and view all the answers

    What is the primary function of the mitochondrion?

    <p>Cellular respiration</p> Signup and view all the answers

    What do plasmodesmata allow between neighboring plant cells?

    <p>Exchange of small molecules</p> Signup and view all the answers

    What role do peroxisomes play in a cell?

    <p>Degradation of hydrogen peroxide</p> Signup and view all the answers

    What are the two types of endoplasmic reticulum and their main features?

    <p>Smooth ER and Rough ER; lipid and protein synthesis respectively</p> Signup and view all the answers

    What is the role of the Golgi complex in the cell?

    <p>Modification and sorting of proteins and lipids</p> Signup and view all the answers

    Why is carbon described as the most important atom for biomolecules?

    <p>It is a tetravalent atom and can form 4 bonds</p> Signup and view all the answers

    What type of motion is primarily associated with a flagellum?

    <p>Locomotion</p> Signup and view all the answers

    What is the main structural difference between animal cells and plant cells?

    <p>Plant cells have a cell wall made of cellulose</p> Signup and view all the answers

    Which organelle is primarily involved in protein synthesis?

    <p>Ribosome</p> Signup and view all the answers

    What is the purpose of using the Henderson-Hasselbalch equation in preparing a buffer solution?

    <p>To calculate the ratio of conjugate base to weak acid for the desired pH.</p> Signup and view all the answers

    How would you calculate the total volume of buffer solution derived from the given concentrations?

    <p>Using the formula $C_iV_i = C_fV_f$.</p> Signup and view all the answers

    What is the significance of pKa values in buffer preparation?

    <p>They represent the pH at which the acid and its conjugate base are in equal concentrations.</p> Signup and view all the answers

    Which components are used to prepare a phosphate buffer solution with a pH of 6.5?

    <p>60 mM NaH2PO4 and 75 mM Na2HPO4.</p> Signup and view all the answers

    When diluting a buffer solution to a specific final volume, which action should be performed first?

    <p>Prepare the concentrated stock solution.</p> Signup and view all the answers

    In preparing 2 L of a buffer, if 0.10 L of 1 M phosphate buffer is used, how much distilled water should be added?

    <p>1.90 L.</p> Signup and view all the answers

    Which of the following steps is essential after preparing the buffer solution?

    <p>Measure the pH to ensure it matches the target.</p> Signup and view all the answers

    What is the first measurement step when preparing a buffer solution using NaCH3COO and CH3COOH?

    <p>Transfer 2.65 g of NaCH3COO.</p> Signup and view all the answers

    What is the equilibrium constant expression for the dissociation of acetic acid?

    <p>$K_a = \frac{[CH_3COO^-][H_3O^+]}{[CH_3COOH]}$</p> Signup and view all the answers

    What is the pKa of acetic acid based on its theoretical value?

    <p>4.74</p> Signup and view all the answers

    If the pH of a solution is less than the pKa of acetic acid, which species predominates?

    <p>Weak acid, $CH_3COOH$</p> Signup and view all the answers

    Which statement about buffers is true?

    <p>Buffers can resist changes in pH.</p> Signup and view all the answers

    At what pH does the predominant species of acetic acid become both the weak acid and the conjugate base?

    <p>pH = pKa</p> Signup and view all the answers

    In a solution where pH is greater than the pKa of a weak acid, what occurs?

    <p>The conjugate base predominates.</p> Signup and view all the answers

    What is the relationship between $K_w$, $[H_3O^+]$, and $[OH^-]$ at 25°C?

    <p>$K_w = [H_3O^+][OH^-]$</p> Signup and view all the answers

    During a titration of a weak acid, what is indicated by the inflection point of the resulting titration curve?

    <p>The pKa of the weak acid.</p> Signup and view all the answers

    What occurs at physiological pH (6.4-7.6) concerning weak acids?

    <p>Both weak acids and their conjugate bases can be significant.</p> Signup and view all the answers

    How can buffers be prepared?

    <p>By combining a weak acid with its salt or a weak base with its conjugate acid.</p> Signup and view all the answers

    What does the $pK_a$ value indicate for a weak acid?

    <p>The strength of the acid.</p> Signup and view all the answers

    What is the value of water's ion product constant ($K_w$) at 25°C?

    <p>$1.0 \times 10^{-14}$</p> Signup and view all the answers

    If the pH of a solution is 4.50, which statement is true regarding acetic acid?

    <p>The weak acid predominates over the conjugate base.</p> Signup and view all the answers

    Study Notes

    Buffer Solutions

    • The Henderson-Hasselbalch equation relates the pH of a buffer solution to the ratio of conjugate base to weak acid:
      [ \frac{[A^-]}{[HA]} = 10^{(pH - pK_a)} ]
    • For a buffer with acetic acid and sodium acetate, combine 2.65 g NaCH3COO and 0.73 mL CH3COOH in 500 mL of distilled water.
    • Prepare a 2L 50 mM phosphate buffer at pH 6.5 using 60 mM NaH2PO4 and 75 mM Na2HPO4.

    Cell Organelles: Animal and Plant Cells

    • Lysosomes: Contain hydrolytic enzymes for intracellular digestion.
    • Centrioles: Essential for spindle apparatus formation during cell division.
    • Flagellum: Enables locomotion in certain cells.
    • Central Vacuole (Plant Cells): Functions as a reservoir for nutrients, waste, and pigments; larger than vacuoles in animal cells.
    • Cell Wall (Plant Cells): Composed of cellulose, providing rigidity unlike prokaryotic cell walls which are made of peptidoglycan.
    • Chloroplasts (Plant Cells): Site of photosynthesis, containing chlorophyll for light harvesting.

    Common Organelles in Animal and Plant Cells

    • Nucleus: Contains genetic material and is the site for DNA and RNA synthesis.
    • Ribosome: Site of protein synthesis, can be free in the cytoplasm or attached to the rough endoplasmic reticulum (Rough ER).
    • Endoplasmic Reticulum: Network of membranes; Rough ER is involved with ribosomes, while Smooth ER synthesizes lipids.
    • Golgi Complex: Sorts and transports molecules for cellular export.
    • Peroxisomes: Contain oxidative enzymes for digestion, including hydrogen peroxide degradation.
    • Mitochondrion: Powerhouse of the cell, involved in cellular respiration and has distinct membranes.

    Biomolecules and Key Elements

    • Carbon is essential in biomolecules due to its tetravalent nature, allowing it to form four bonds.
    • Biologically Important Elements: Include C, H, N, O, P, and S, required in grams daily.
    • Trace Elements: Required in milligrams or lesser amounts daily.

    Weak Acids and pKa

    • Acetic acid dissociation:
      [ CH3COOH + H2O ⇌ CH3COO^- + H3O^+ ]
    • Equilibrium constant for acetic acid, ( K_a ):
      ( K_a = \frac{[CH3COO^-][H3O^+]}{[CH3COOH]} = 1.8 \times 10^{-5} )
    • pKa = -log(K_a) = 4.74, with experimentally determined pKa varying slightly (4.76).
    • pH comparisons indicate predominant species based on pH relative to pKa.

    Amino Acids and Protein Structure

    • Essential Amino Acids: Cannot be synthesized by the body; includes tryptophan, isoleucine, phenylalanine, and others.
    • Non-essential Amino Acids: Can be synthesized by the body.
    • Zwitterionic Form: Exists in physiological pH, facilitating interactions in proteins.
    • Various interactions stabilize protein structures:
      • Hydrophobic Interactions: Non-polar residues aggregate within the protein.
      • Hydrogen Bonding: Occurs between side groups or peptide bonds.
      • Electrostatic Interactions: Involve charged side chains (e.g., aspartate, glutamate).

    Buffer Action

    • Buffers resist pH changes upon small additions of acid or base, maintaining physiological conditions.
    • Buffers can be composed of weak acid and its conjugate base or weak base and its conjugate acid.

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    Description

    Test your understanding of the Henderson-Hasselbalch equation. This quiz will challenge you to calculate the ratio of the conjugate base to a weak acid based on pH and pKa values. Prepare to apply your knowledge and work through examples for mastery.

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