Biology Chapter 2: Water as Life's Medium

A substance that produces hydrogen ions (H+) when dissolved in water.

A substance that produces hydroxide ions (OH-) when dissolved in water.

A substance that can donate a proton (H+) to another substance.

A substance that can accept a proton (H+) from another substance.

A substance that forms when an acid loses a proton.

A substance that forms when a base gains a proton.

The reaction involving the transfer of a proton between an acid and a base.

A solution where the concentration of H+ ions is greater than the concentration of OH- ions.

A solution where the concentration of OH- ions is greater than the concentration of H+ ions.

A reaction where both forward and reverse reactions occur simultaneously.

The chemical reaction between an acid and a base, where the acid donates a proton (H+) and the base accepts it, forming a conjugate acid-base pair.

Acids that ionize 100% in solution, dissociating completely into their ions. Represented by a single arrow.

Acids that only partially ionize in solution, creating an equilibrium between the ionized and non-ionized forms. Represented by double arrows.

Acids that donate all of their protons (H+) when dissolved in water.

Hydroxides of Group I and Group II metals that completely dissociate in water, releasing hydroxide ions (OH-).

A measure of the hydrogen ion concentration [H3O+] in a solution. Calculated using the formula: pH = -log[H3O+]

The process of nonpolar molecules dissolving in water is driven by entropy. When nonpolar molecules dissolve, they force water molecules into more ordered arrangements, decreasing the overall entropy of the system. This decrease in entropy is offset by the increase in entropy of the water molecules surrounding the nonpolar solute. In simpler terms, the water molecules become more disordered around the nonpolar solute, making the overall system less ordered.

Amphiphilic molecules possess both polar and nonpolar components. These molecules can self-assemble into structures like micelles to minimize contact between their nonpolar tails and the water environment. This self-assembly is driven by entropy.

Colligative properties are physical properties of a solution that depend on the concentration of solute particles, but not the type of solute. These properties include freezing point depression, boiling point elevation, vapor pressure lowering, and osmotic pressure.

Freezing point depression is the phenomenon where the freezing point of a liquid is lowered when a solute is dissolved in it. This occurs because the solute particles disrupt the ordered arrangement of water molecules in the liquid state, making it more difficult for the water to transition into the solid state. The solute creates local order, making it more difficult for water molecules to assume their crystalline lattice.

Boiling point elevation is the phenomenon where the boiling point of a liquid is raised when a solute is dissolved in it. This occurs because the solute particles increase the intermolecular forces in the liquid, making it more difficult for the water molecules to escape into the gas phase. The solute's effect on water's local order makes it harder for water to escape.

Vapor pressure lowering is the phenomenon where the vapor pressure of a liquid is lowered when a solute is dissolved in it. This occurs because the solute particles decrease the number of water molecules at the surface of the liquid that are able to escape into the gas phase. The solute makes water less free to evaporate.

Osmotic pressure is the pressure that must be applied to a solution to prevent the inward flow of water across a semipermeable membrane. This pressure is proportional to the concentration of solute particles in the solution. The higher the solute concentration, the greater the osmotic pressure, making it harder for water to flow through the membrane.

By storing substances like amino acids and sugars in polymeric form, cells can minimize osmotic pressure within their cytosol. Polymers exert less osmotic pressure than the same number of free monomers because they contribute fewer particles to the solution. This strategy helps cells maintain osmotic balance and avoid swelling or shrinking.

The primary base in the body that is regulated by the kidneys. The kidneys maintain the appropriate levels of HCO3- in the blood.

The process by which the kidneys regenerate bicarbonate (HCO3-) to maintain the body's buffering capacity.

An enzyme found in the renal tubule cells that catalyzes the conversion of carbonic acid (H2CO3) into carbon dioxide (CO2) and water (H2O). This is crucial for bicarbonate regeneration.

An abnormal state where the body's pH is too acidic.

The renal response to acidosis is a three-step process, involving: 1) increased reabsorption of filtered bicarbonate, 2) increased excretion of titratable acids, and 3) increased ammonia production.

Acidosis is a state where the body's pH is too low. The kidneys play a crucial role in regulating the body's pH by reabsorbing filtered bicarbonate, excreting acids, and generating ammonia.

The process of actively moving substances from the renal tubules back into the bloodstream. This is essential for conserving valuable nutrients and maintaining proper blood composition.

The phosphate buffer is effective but not found in high concentrations in extracellular fluid. It plays a role in intracellular fluid (ICF) and renal tubules where phosphates are more concentrated and function closer to their optimum pH of 6.8.

Free and terminal amino acids in proteins respond to pH changes by either accepting or releasing hydrogen ions (H+). They can neutralize acids by accepting H+ and bases by releasing H+.

Hemoglobin, a protein found in red blood cells, acts as a buffer by binding to carbon dioxide (CO2) and transporting hydrogen ions (H+) and oxygen. Its ability to switch between oxyhemoglobin and deoxyhemoglobin helps maintain blood pH.

The lungs are part of the body's pH regulation system. They remove carbon dioxide (CO2) through exhalation, which helps to control the bicarbonate buffering system. The rate and depth of breathing can adjust blood pH by changing CO2 levels.

Increased ventilation rate leads to the removal of CO2 and H2O, driving the reaction between CO2 and water to the left, resulting in the removal of H+ and an increase in pH. Hyperventilation raises blood pH.

Decreased ventilation rate leads to an accumulation of CO2, driving the reaction between CO2 and water to the right, resulting in the production of H+ and a decrease in pH. Hypoventilation lowers blood pH.

The kidneys are the most powerful regulators of pH. They eliminate fixed acids, conserve and produce bicarbonate ions, and excrete base. Their failure can disrupt blood pH balance.

Fixed (“nonvolatile”) acids are those that cannot be eliminated by the lungs, and must be removed by the kidneys. Examples include lactic acid and sulfuric acid.

Volatile acids are those that can be eliminated by the lungs. They can be converted into gases, such as carbon dioxide, which can be exhaled.

The process by which the kidneys can produce new bicarbonate ions, which act as a base to neutralize excess acid in the blood. This is an important mechanism for maintaining blood pH balance.