Lecture 18

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What is the capital of France? (example question)

Paris (correct)

London

Berlin

Madrid

What does pH measure?

The concentration of hydroxide ions

The concentration of hydrogen ions (correct)

The concentration of carbon dioxide

The concentration of ammonia

What is the formula for calculating pH?

pH = log [H+]

pH = -log [H+] (correct)

pH = [H+] × 10

pH = 1/[H+]

Which of the following groups is NOT part of an amino acid?

Hydroxyl group Signup and view all the answers

What type of structure do L and D amino acids represent?

Stereoisomers Signup and view all the answers

What happens to the charge of amino acids when the pH is increased?

They become more negatively charged. Signup and view all the answers

What is the significance of the equilibrium constant (K) in chemical reactions?

It represents the ratio of products to reactants at equilibrium. Signup and view all the answers

Which statement is true for strong acids?

They fully dissociate in solution. Signup and view all the answers

What does a high acid dissociation constant (Ka) indicate?

Strong acid Signup and view all the answers

What is a zwitterion?

A molecule with both positive and negative charges Signup and view all the answers

Which equation can be used to calculate the pH of a buffer solution?

Henderson-Hasselbalch equation Signup and view all the answers

Which of the following is a common biological buffer?

Bicarbonate Signup and view all the answers

Which form of an amino acid predominates at a low pH?

Protonated form Signup and view all the answers

What is the effect of increasing temperature on chemical equilibrium?

It shifts the equilibrium to favor products, depending on the reaction. Signup and view all the answers

What do you call the species that forms when an acid donates a proton?

Conjugate base Signup and view all the answers

Which of the following amino acids is classified as polar?

Serine Signup and view all the answers

What happens to the protonation state of amino acids when pH increases above their pKa?

They become deprotonated. Signup and view all the answers

Which amino acid has a side chain that can form hydrogen bonds?

Glutamine Signup and view all the answers

Which of the following statements is true regarding weak acids?

They partially dissociate in solution. Signup and view all the answers

What is the primary function of buffers in biological systems?

To maintain stable pH levels Signup and view all the answers

At which pH do amino acids typically exist as zwitterions?

Varies depending on the amino acid Signup and view all the answers

What is the relationship between the pKa of an acid and its strength?

Lower pKa indicates stronger acids. Signup and view all the answers

What happens to the equilibrium constant (K) if the concentration of products increases?

K remains the same. Signup and view all the answers

Which property of water makes it an excellent solvent for polar substances?

Its ability to form hydrogen bonds Signup and view all the answers

What is the effect of a buffer when an acid is added to a solution?

The pH remains relatively stable. Signup and view all the answers

Which amino acid is known for its unique cyclic structure?

Proline Signup and view all the answers

How does pH affect enzyme activity?

Extreme pH can denature enzymes and alter their activity. Signup and view all the answers

Lecture 18 – Protein structure: Amino acids, Equilibrium and pH

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