Acid-Base Chemistry and Protein Function

A chemical compound that donates a proton (H+) to another molecule, increasing the concentration of hydrogen ions (H+) in solution. Examples include hydrochloric acid (HCl) and sulfuric acid (H2SO4).

A chemical compound that accepts a proton (H+) from another molecule, decreasing the concentration of hydrogen ions (H+) in solution. Examples include sodium hydroxide (NaOH) and ammonia (NH3).

A process where a proton (H+) rapidly moves from one molecule to another. This occurs in aqueous solutions. The transfer happens through a series of hydrogen bonds.

A pair of molecules that differ by the presence or absence of a single proton (H+). For example, water (H2O) and hydroxide (OH-) are a conjugate acid-base pair.

A measure of the acidity or alkalinity of a solution. It is the negative logarithm (base 10) of the hydrogen ion concentration ([H+]). A lower pH indicates higher acidity, while a higher pH indicates higher alkalinity.

Ketone bodies are produced during fat metabolism, particularly during fasting or diabetes, when the body utilizes fat instead of glucose for energy. These include acetoacetic acid and beta-hydroxybutyric acid, which are acidic and can lead to ketoacidosis if produced in excess.

Phosphoric acid is released from the breakdown of phospoproteins or nucleotides. It is a vital component of ATP and plays a crucial role in energy metabolism.

Sulfuric acid is produced from the metabolism of sulfur-containing amino acids, such as cysteine and methionine. These amino acids release sulfur, which is oxidized to sulfate in the liver.

Ammonia is generated during protein metabolism, specifically amino acid deamination. This basic compound combines with H+ to form ammonium, which is less toxic and excreted by the kidneys.

Bicarbonate, also known as HCO3-, is produced in metabolic processes or ingested. It plays a crucial role in neutralizing acids to maintain a stable blood pH. It effectively neutralizes both acids and hydroxide ions.

The bicarbonate buffer system is the primary buffering system in blood plasma. It involves an equilibrium between carbonic acid (H2CO3) and bicarbonate (HCO3-), effectively buffering against changes in blood pH.

Acidosis is a condition characterized by a decrease in blood pH below 7.35. This can result from various causes, including respiratory issues or metabolic disturbances.

Alkalosis is a condition characterized by an increase in blood pH above 7.45, often caused by respiratory or metabolic factors, leading to a decrease in acidity.

When hemoglobin (Hb) releases oxygen to tissues, it readily binds to hydrogen ions (H+) to prevent blood from becoming too acidic.

Hemoglobin binds to carbon dioxide (CO2) to form carboxyhemoglobin, which helps transport CO2 to the lungs for exhalation.

Cells can also transport hydrogen ions (H+) out by exchanging them with sodium ions (Na+) to maintain balance.

Red blood cells (RBCs) can transport bicarbonate ions (HCO3-) out into the plasma, exchanging with chloride ions (Cl-) to maintain electrostatic cell balance.

The phosphate buffer system plays a crucial role within cells and in urine, but also contributes to blood buffering, with a pKa of 7.2, meaning it is ionized at typical intracellular pH.

Dihydrogen phosphate (H2PO4-) and monohydrogen phosphate (HPO42-) are the key players in the phosphate buffer system, maintaining a balance between them.

Proteins like albumin in the blood help buffer pH by their ability to bind or release hydrogen ions (H+) as needed.

Amino acid side chains within proteins, particularly histidine, act as pH buffer sites, accepting or donating H+ depending on the changes in the blood pH.

The tendency of a substance to donate protons (H+). A strong acid readily gives up protons, while a weak acid holds onto them more tightly.

The negative logarithm (base 10) of the hydrogen ion concentration ([H+]) in a solution. It indicates the acidity or alkalinity of a solution.

A measure of the tendency of a substance to lose a proton (H+). A lower pKa indicates a stronger acid, while a higher pKa indicates a weaker acid.

The form of a drug that can easily pass through cell membranes. It is usually the uncharged form.

The form of a drug that is unable to pass through cell membranes. It is usually the charged form.

The process where a drug's absorption is influenced by the pH of the environment. Drugs are more readily absorbed in their uncharged form.

The process where a drug is concentrated in a specific organ before it is absorbed into the bloodstream. The stomach acts as a depot for aspirin, but not the main site of absorption.

The movement of a drug from its depot to the site of absorption, primarily the intestines.

Cysteine and Glycine are amino acids involved in producing glutathione, a powerful antioxidant crucial for protecting mitochondria.

Gamma-aminobutyric Acid (GABA) is a neurotransmitter and an amino acid but cannot be used to build proteins because it is a gamma amino acid.

Cystinuria is a genetic disorder that affects the reabsorption of cysteine in the kidneys, leading to high cysteine levels in urine and the formation of kidney stones.

Protein malnutrition occurs when the body lacks essential amino acids needed for protein synthesis, impacting health and hindering the body's ability to produce necessary proteins.

Kwashiorkor is a severe form of protein malnutrition primarily affecting children who are weaned too early and lack adequate protein intake.

Individuals with cystinuria have a defective amino acid transporter that reabsorbs cysteine in the kidneys.

Cysteine can spontaneously oxidize and form cystine, which is poorly soluble in water, especially in acidic urine, leading to kidney stone formation in individuals with cystinuria.

Hospital patients who are hypercatabolic, meaning their bodies rapidly break down nutrients for protein synthesis and repair, are at risk for protein malnutrition and may require IV administration of nutrients.

Amino acids are amphoteric, meaning they can either donate protons (acids) or accept protons (bases). This is due to their carboxyl (-COOH) and amino (-NH2) groups, which can exist in protonated or deprotonated forms based on the pH.

At a pH below its pKa, a group tends to be protonated.

At a pH above its pKa, a group tends to be deprotonated.

The carboxyl group (COOH) has a pKa around 2. At physiological pH (7.4) it is deprotonated to COO⁻.

The amino group (NH2) has a pKa around 9-10. At physiological pH (7.4), it is protonated to NH3⁺.

Certain amino acids have acidic side chains (like aspartate and glutamate) and basic side chains (like lysine, arginine, and histidine). These side chains contribute to the overall charge of the amino acid.

At physiological pH, most amino acids exist as zwitterions, which have both a positive and negative charge. However, the overall charge depends on the side chains.