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?

Strands below five cannot maintain hydrogen bonding. Signup and view all the answers

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

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

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

Leucine Signup and view all the answers

What is the significance of proline in protein structure?

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

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

Isoleucine Signup and view all the answers

Arginine is classified as essential in which context?

For infants Signup and view all the answers

Which amino acid has a non-chiral carbon atom?

Glycine Signup and view all the answers

What phrase can help remember essential amino acids?

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

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

Isoleucine Signup and view all the answers

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

Non-essential amino acids Signup and view all the answers

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

Container for food, nutrients, and waste products Signup and view all the answers

Which organelle is responsible for photosynthesis in plant cells?

Chloroplast Signup and view all the answers

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

Composed of cellulose Signup and view all the answers

What is the function of lysosomes in animal cells?

Intracellular digestion using hydrolytic enzymes Signup and view all the answers

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

Large ribosomal subunit Signup and view all the answers

What is the primary function of the mitochondrion?

Cellular respiration Signup and view all the answers

What do plasmodesmata allow between neighboring plant cells?

Exchange of small molecules Signup and view all the answers

What role do peroxisomes play in a cell?

Degradation of hydrogen peroxide Signup and view all the answers

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

Smooth ER and Rough ER; lipid and protein synthesis respectively Signup and view all the answers

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

Modification and sorting of proteins and lipids Signup and view all the answers

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

It is a tetravalent atom and can form 4 bonds Signup and view all the answers

What type of motion is primarily associated with a flagellum?

Locomotion Signup and view all the answers

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

Plant cells have a cell wall made of cellulose Signup and view all the answers

Which organelle is primarily involved in protein synthesis?

Ribosome Signup and view all the answers

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

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

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

Using the formula $C_iV_i = C_fV_f$. Signup and view all the answers

What is the significance of pKa values in buffer preparation?

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

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

60 mM NaH2PO4 and 75 mM Na2HPO4. Signup and view all the answers

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

Prepare the concentrated stock solution. 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?

1.90 L. Signup and view all the answers

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

Measure the pH to ensure it matches the target. Signup and view all the answers

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

Transfer 2.65 g of NaCH3COO. Signup and view all the answers

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

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

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

4.74 Signup and view all the answers

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

Weak acid, $CH_3COOH$ Signup and view all the answers

Which statement about buffers is true?

Buffers can resist changes in pH. 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?

pH = pKa Signup and view all the answers

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

The conjugate base predominates. Signup and view all the answers

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

$K_w = [H_3O^+][OH^-]$ 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?

The pKa of the weak acid. Signup and view all the answers

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

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

How can buffers be prepared?

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

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

The strength of the acid. Signup and view all the answers

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

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

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

The weak acid predominates over the conjugate base. 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.