Bio Chem 3630 - Exam 1

A buffering system that maintains blood pH using bicarbonate (HCO₃⁻) and carbonic acid (H₂CO₃).

What is the bicarbonate buffer system?

It prevents dangerous fluctuations in blood pH.

Why is the bicarbonate buffer system important for maintaining blood pH?

Bicarbonate (HCO₃⁻) and carbonic acid (H₂CO₃).

What chemical species make up the bicarbonate buffer system?

It accepts hydrogen ions when pH decreases.

How does bicarbonate (HCO₃⁻) function as a buffer?

It donates hydrogen ions when pH increases.

How does carbonic acid (H₂CO₃) function as a buffer?

CO₂ forms carbonic acid in blood

What role does CO₂ play in blood pH regulation?

Blood pH increases.

How does exhaling CO₂ affect blood pH?

Excess CO₂ is expelled, lowering carbonic acid levels.

Why does hyperventilation increase blood pH?

It decreases.

What happens to carbonic acid concentration when CO₂ is exhaled?

Blood pH decreases.

How does hypoventilation affect blood pH?

Because CO₂ can be eliminated through the lungs.

Why is the bicarbonate buffer system considered an “open” buffer system?

The lungs and kidneys.

What organs are primarily involved in regulating the bicarbonate buffer system?

By regulating CO₂ levels.

How do the lungs contribute to acid–base balance?

By excreting or conserving H⁺ and HCO₃⁻.

How do the kidneys contribute to bicarbonate regulation?

Because CO₂ can be rapidly adjusted via respiration.

Why is the bicarbonate buffer system especially effective in blood?

Blood pH would decrease (acidosis).

What would happen to blood pH if bicarbonate levels decrease?

Blood pH would decrease.

What would happen to blood pH if carbonic acid levels increase?

Because it forms carbonic acid in solution.

Why is CO₂ considered an acid in physiological systems?

It speeds up the conversion between CO₂ and carbonic acid.

How does carbonic anhydrase facilitate buffering?

To prevent acidosis.

Why is rapid CO₂ removal important for maintaining homeostasis?

An equation that relates pH to the ratio of conjugate base and acid.

What is the Henderson–Hasselbalch equation?

pH, bicarbonate concentration, and carbonic acid (CO₂).

What variables does the Henderson–Hasselbalch equation relate?

A higher ratio results in a higher pH.

How does the [HCO₃⁻]/[H₂CO₃] ratio affect pH?

pH increases

What happens to pH when bicarbonate concentration increases?

pH decreases

What happens to pH when carbonic acid concentration increases?

Buffering depends on balance between acid and base.

Why is the ratio more important than absolute concentrations?

Increased CO₂ lowers pH.

How does the equation explain respiratory acidosis?

Decreased CO₂ raises pH.

How does the equation explain respiratory alkalosis?

Decreased bicarbonate lowers pH.

How does metabolic acidosis affect the equation?

Increased bicarbonate raises pH.

How does metabolic alkalosis affect the equation?

It explains and predicts acid–base disorders.

Why is the Henderson-Hasselbach equation useful in clinical medicine?

Equilibrium conditions and constant temperature.

What assumptions does the Henderson–Hasselbalch equation make?

Because fewer free hydrogen ions are present.

Why does a higher [HCO₃⁻]/[H₂CO₃] ratio result in higher pH?

A condition where blood pH is abnormally low.

What is acidosis?

A condition where blood pH is abnormally high.

What is alkalosis?

It decreases enzyme efficiency.

How does acidosis affect enzyme activity?

Respiratory failure or COPD.

What are common causes of respiratory acidosis?

Diabetes and kidney failure.

What metabolic conditions can cause acidosis?

Loss of stomach acid.

How can vomiting cause alkalosis?

Excess acid or low bicarbonate.

What is metabolic acidosis?

Excess bicarbonate

What is metabolic alkalosis?

The disturbance may be too severe.

Why can compensation fail?

To guide treatment decisions.

Why is blood pH monitored clinically?

Organ failure or death.

What can happen if pH imbalance is untreated?

The pH at which a group is 50% protonated.

What is pKa?

Equal protonated and deprotonated forms.

What happens when pH equals pKa?

Active sites require specific charges.

Why does enzyme activity depend on pH?

Nearby charges shift ionization.

How can protein environment alter pKa?

They are adapted to their environments.

Why do digestive enzymes have different pH optima?

By changing charge.

How does pH affect protein binding?

Primary, secondary, tertiary, quaternary.

What are the four levels of protein structure?

Amino Acid sequence

What defines primary structure?

It determines folding and function.

Why is primary structure critical?

By dehydration reactions.

How are peptide bonds formed?

Partial double-bond character.

Why are peptide bonds rigid?

Resonance.

What causes this partial double-bond character?

A spiral secondary structure.

What is an α-helix?

Hydrogen bonds.

What stabilizes α-helices?

3.6

How many amino acids per α-helix turn?

An extended secondary structure.

What is a β-sheet?

Hydrogen Bonds

How are β-sheets stabilized?

Strand Direction

What is the difference between parallel and antiparallel β-sheets?

A β-sheet folding pattern.

What is a Greek key motif?

A cylindrical β-sheet structure.

What is a β-barrel?

Two β-strands connected by an α-helix.

What is a β–α–β (bab) motif?

They support flexible binding.

Why do oxygen-binding proteins often contain α-helices?

+1

What is the charge of lysine at pH 7.4?

-1

What is the charge of glutamate or aspartate at pH 7.4?

By summing all charges.

How is net charge of a protein calculated?

It affects solubility, binding, and localization.

Why is net charge important for protein function?

tertiary Structure

The Final 3D arrangement of all amino acids in a single protein is called the _____

pH > pK

Under what conditions would a carboxyl group be mostly charged

• pH > pK

• pH = pK

• pH < pK

carboxyl group and amino group

Adjacent amino acids in a polypeptide are joined together by peptide bonds form a:

• carboxyl group and amino group

• carboxyl group and hydrogen atom

• carboxyl group and R group

• R group and amino group

The Primary driving force for protein folding is the hydrophobic effect

When considering protein structure, which of the following

statements is true?

A. Peptide bonds that link amino acids most commonly occur in the cis configuration.

B. Disulfide bonds in proteins are between cysteine residues adjacent in the primary structure.

C. Denaturation of proteins leads to irreversible loss of secondary structural elements.

D. The primary driving force for protein folding is the hydrophobic effect.

Increased Respiration

An 18-year-old woman with a 15-year history of type 1 diabetes mellitus

is brought to the emergency department for evaluation of nausea,

vomiting, and altered consciousness. Her blood glucose is 560 mg/dL

(reference range for random glucose, <200 mg/dL). Her arterial blood pH

is 7.15 (reference range 7.35 to 7.45) and bicarbonate is 12 mEq/L (22 to

28 mEq/L). Which of the following would be the expected type of

compensation in her body in response to this acid-base imbalance?

A. Increased respiration

B. Decreased respiration

C. Increased renal release of acid

D. Increased renal retention of base

Lysine and Arginine

Which amino acids are positively charged at neutral pH

The pH at the mid-point of the charge between pronated and depronated forms

What does pK2 indicate

Compounds that interact with water and dissolve in it

What are hydrophilic compound

Nonpolar compounds that avoid water, such as oils and fats.

What are hydrophobic compounds?

Alanine, Isoleucine, Leucine, Methionine, Phenylalanine, Tryptophan, and Valine.

Which amino acids are considered nonpolar?

Its side chain cyclizes back to the amino group, forming a 5-membered ring.

What is unique about Proline among amino acids?

a strong attraction between a slightly positive hydrogen atom and a slightly negative lone pair on another electronegative

What are hydrogen bonds?

In bacterial cell walls and in antibiotics made by fungi.

Where can D-amino acids be found?

An acid is a molecule that behaves as a proton donor.

Define an acid in terms of proton donation.

A base is a proton acceptor.

Define a base in terms of proton acceptance.

A strong acid completely ionizes in solution, while a weak acid does not.

What distinguishes a strong acid from a weak acid?

Water can act as both a weak acid and a weak base.

What role does water play in acid-base chemistry?

The species that remains after an acid donates a proton.

What is a conjugate base?

HA + H2O ⇌ H3O+ + A- (where HA is the weak acid).

What is the reaction involving a weak acid and water?

Every acid has a conjugate base formed after it donates a proton.

What is the relationship between acids and their conjugate bases?

They tend to aggregate to avoid contact with water.

What happens to nonpolar amino acids in water?

It indicates the pH at which the group is 50% protonated and 50% deprotonated.

What is the significance of the pKa of weakly acidic or basic groups?

It helps in understanding the behavior of amino acids in proteins and their interactions with water.

What is the importance of understanding non-polar and polar atoms in amino acids?

pH = -log10[H+]

What is the formula for calculating pH?

It is the normal physiological pH of human blood.

What does a pH of 7.4 indicate?

Kw = [H+][OH-]

What is the dissociation constant (Kw) for water?

[OH-] decreases.

What happens to [OH-] when [H+] increases?

About 1 pH unit above and below the pKa of the weak acid.

What is the effective buffer range of a weak acid?

4.8

What is the pKa of acetic acid?

It gives pH relative to a reference point called pKa.

What does the Henderson-Hasselbalch equation relate?