LC3- WATER AND ACID BASE EQUILIBRIA

What is the predominant chemical component of living organisms?

Water

What term describes water's ability to solvate a wide range of organic and inorganic molecules?

Universal solvent

What feature of water contributes to its ability to act as a universal solvent?

Dipolar structure and hydrogen bond formation

What geometry does the water molecule have?

Tetrahedral geometry

What hypothalamic mechanism controls thirst?

Hypothalamic mechanisms that control thirst

What hormone affects water balance by promoting renal water retention?

Antidiuretic hormone (ADH)

What renal processes affect water balance?

Renal water retention or excretion

What type of loss of water occurs from the body through evaporation?

Evaporative loss

Which atom in water is more electronegative?

Oxygen

Why does oxygen attract electrons more strongly than hydrogen?

Oxygen is more electronegative

What type of attraction occurs between the oxygen of one water molecule and the hydrogen of another?

Hydrogen bond

At room temperature and atmospheric pressure, water molecules are in what state of molecular arrangement?

Disorganized and in continuous motion

On average, how many other molecules does each liquid water molecule hydrogen-bond with?

3.4 other molecules

Compared with the covalent O-H bond, how strong are hydrogen bonds?

Relatively weak

What is bond dissociation energy?

Energy to break a bond

In ice, how many other water molecules does each water molecule form hydrogen bonds with?

Four

What type of structure is formed by hydrogen bonding in ice?

Regular lattice structure

Why is ice less dense and able to float in liquid water?

Its crystal lattice structure

What contributes to water's high melting point?

Hydrogen bonding

What term describes molecules that are easily dissolved in water?

Hydrophilic

What does hydrophilic literally mean?

Water-loving

What type of molecules are usually hydrophilic?

Polar molecules

What term describes substances that do not easily dissolve in water?

Hydrophobic

What are hydrophobic substances soluble in?

Other hydrophobic molecules

Give one example of a hydrophobic substance.

Chloroform, benzene, or wax

What term describes molecules containing charged/polar and non-polar regions?

Amphiphatic

What biological structure is given as an example of an amphiphatic structure?

Phospholipid bilayer

What is required for hydrogen bonding with polar solutes?

A hydrogen donor and a hydrogen acceptor

What atoms can act as hydrogen acceptors?

Oxygen or nitrogen

What is a hydrogen donor?

Another electronegative atom

What does water do to crystalline salts?

Dissolves them by hydrating their component ions

What happens to the NaCl crystal lattice when water molecules cluster around Na+ and Cl-?

The crystal lattice is disrupted

What happens to the ionic charges during hydration?

They are partially neutralized

What is the effect of partial neutralization of ionic charges on lattice attractions?

Electrostatic attractions are weakened

What are the four types of non-covalent interactions among biomolecules in an aqueous solvent?

Hydrogen bonds, ionic interactions, hydrophobic effect, and Van der Waals forces

What type of non-covalent interaction can occur between neutral groups?

Hydrogen bonds

What type of non-covalent interaction can occur between peptide bonds?

Hydrogen bonds

What are the two forms of ionic interactions?

Attraction and repulsion

What effect involves nonpolar groups in an aqueous environment?

Hydrophobic effect

What forces occur when two uncharged atoms are brought very close together?

Van der Waals forces

What is the Van der Waals radius?

A measure of how close an atom will allow another atom to approach

How do the four non-covalent interactions compare individually with covalent bonds?

They are weaker

Why can non-covalent interactions still be significant?

Their cumulative effect can be significant

What type of binding between biomolecules is given as an example of non-covalent interaction?

Non-covalent binding of an enzyme to its substrate

What molecular process is stabilized by non-covalent interactions in polypeptides?

Folding of a polypeptide chain into its three-dimensional shape

What type of biological binding between immune molecules is an example of non-covalent interaction?

Binding of an antigen to an antibody

What type of receptor interaction is an example of non-covalent interaction?

Binding of a hormone or neurotransmitter to its receptor

What do concentrated solutes produce?

Osmotic pressure

What are the four colligative properties?

Vapor pressure, boiling point, melting/freezing point, and osmotic pressure

What does the term colligative mean?

Tied together

Why are the four properties called colligative properties?

Their effects have the same basis: the concentration of water is lower in solutions than in pure water

What determines osmotic pressure?

The number of solute particles, molecules, or ions in a given amount of water

Is osmotic pressure dependent on the chemical properties of the solute?

No

What happens to NaCl when it dissolves in water?

It dissociates into Na+ and Cl- ions

Does glucose dissociate in solution?

No

Compared with glucose, how does NaCl affect osmotic pressure?

NaCl has twice the effect

In what direction do water molecules move in the colligative-property explanation?

From higher water concentration to lower water concentration

What is osmosis?

Water movement across a semipermeable membrane driven by differences in osmotic pressure

Why is osmosis important?

It is an important factor in the life of most cells

What is a semipermeable membrane?

A membrane that allows passage of water but not solutes

What is osmotic pressure (π)?

The force necessary to resist water movement or diffusion of water from a higher concentration to a lower concentration

Why are plasma membranes more permeable to water?

Because protein channels or aquaporins selectively permit passage of water

What are aquaporins?

Proteins that facilitate water transport across cell membranes

What are protein channels that selectively permit the passage of water called?

Aquaporins

What is the water movement in an isotonic solution compared with the cytosol?

No net movement

What happens to a cell in an isotonic solution?

No changes

What happens to water in a hypertonic solution?

Water moves out of the cell

What happens to a cell in a hypertonic solution?

The cell shrinks

What happens to water in a hypotonic solution?

Water moves into the cell

What happens to a cell in a hypotonic solution?

The cell swells

What is osmotic lysis?

Bursting of the cell due to distention of the plasma membrane from inward movement of water

What is the slight tendency of water molecules to undergo reversible ionization called?

Ionization of water

What two ions are produced by water ionization?

Hydrogen ion (proton) and hydroxide ion

What form do hydrogen ions immediately take in water?

Hydronium ions (H3O+)

Is water ionization reversible?

Yes

Why is water ionization important in cellular function?

It allows water to act as an acid or base

What does the equilibrium constant (Keq) describe?

The position of equilibrium of a chemical reaction

How is Keq defined?

In terms of the concentrations of reactants and products at equilibrium

At a specified temperature, what is true of the equilibrium constant for a given reaction?

It is fixed and characteristic of that reaction

What does the equilibrium constant define?

The composition of the final equilibrium mixture

Does the final equilibrium mixture depend on the starting amounts of reactants and products?

No

What does the pH scale designate?

The concentrations of H+ and OH- ions in an aqueous solution

What does the prefix 'p' denote in pH?

Negative logarithm of

What is the equation for pH?

pH = - log [H+]

What can a small change in pH cause to a protein?

A large change in its structure and function

Where are pH measurements commonly used in medical diagnosis?

Blood and urine

What can extreme acidosis or alkalosis be?

Life-threatening

What is the neutral blood pH?

7.4

What blood pH is classified as acidosis?

Less than 7.4

What blood pH is classified as alkalosis?

Greater than 7.4

What condition can lead to lactic acidosis?

Uncontrolled diabetes mellitus

What can cause alkalosis by vomiting acidic gastric contents?

Vomiting of acidic gastric contents

What is the Brønsted-Lowry definition of an acid?

A proton donor

What is the Brønsted-Lowry definition of a base?

A proton acceptor

What acid-base pair is illustrated by acetic acid?

Acetic acid and acetate

What happens to a strong acid?

It is completely ionized

What is the tendency of a stronger acid?

A greater tendency to lose a proton

Give one strong acid listed in the lecture.

Sulfuric acid (H2SO4) or hydrochloric acid (HCl)

What is characteristic of a weak acid?

It is not completely ionized

What weak acid species is listed in the lecture?

Monohydrogen phosphate (HPO4²-)