S01 - Water and Noncovalent Bonds

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

What is a hydrogen bond?

A bond between an electron-rich atom with a lone pair (N or O) and an electron-deficient hydrogen

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

What atoms commonly provide the lone pair of electrons in a hydrogen bond?

Nitrogen (N) and Oxygen (O).

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

How many hydrogen bonds can a Nitrogen atom accept?

One hydrogen bond

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

How many hydrogen bonds can an Oxygen atom accept?

Two hydrogen bonds

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

What range of strength can a hydrogen bond exhibit?

Weak to moderate in strength

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

What unique characteristic takes place during hydrogen bonding?

An interaction of orbitals

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

What is a hydrogen bond donor (HBD)?

A group in which a hydrogen atom is covalently bound to a more electronegative atom (X-H).

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

What charge does the bound hydrogen atom in a hydrogen bond donor gain?

partially positive charge.

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

What is a hydrogen bond acceptor (HBA)?

A functional group that provides an electron-rich atom to participate in the hydrogen bond.

Learning Objective 1: Define hydrogen bonding, hydrogen bond donors and hydrogen bond acceptors

Which functional groups can act as both a hydrogen bond donor and acceptor?

Hydroxyl (-OH) and amino (-NH2) groups.

Learning Objective 2: Define the terms: amphipathic, hydrophilic (lipophobic), hydrophobic (lipophilic) and hydrophobic effect

What does the term hydrophilic mean?

Water loving or lipophobic

Learning Objective 2: Define the terms: amphipathic, hydrophilic (lipophobic), hydrophobic (lipophilic) and hydrophobic effect

What does the term lipophobic mean?

Lipid hating or hydrophilic.

Learning Objective 2: Define the terms: amphipathic, hydrophilic (lipophobic), hydrophobic (lipophilic) and hydrophobic effect

What does the term hydrophobic mean?

Water hating or lipophilic

Learning Objective 2: Define the terms: amphipathic, hydrophilic (lipophobic), hydrophobic (lipophilic) and hydrophobic effect

What does the term lipophilic mean?

Lipid loving or hydrophobic

Learning Objective 2: Define the terms: amphipathic, hydrophilic (lipophobic), hydrophobic (lipophilic) and hydrophobic effect

What is an amphipathic molecule?

A molecule containing both hydrophobic and hydrophilic regions.

Learning Objective 2: Define the terms: amphipathic, hydrophilic (lipophobic), hydrophobic (lipophilic) and hydrophobic effect

What is the hydrophobic effect?

The separation of non-polar, hydrophobic molecules from water because water excludes them to form hydrogen bonds with itself.

Learning Objective 3: List the factors that affect water solubility of biological molecules and describe how the properties of water affect the interactions among biomolecules

What dipolar property of water allows it to act as a solvent?

Uneven distribution of electrons between hydrogen and oxygen atoms.

Learning Objective 3: List the factors that affect water solubility of biological molecules and describe how the properties of water affect the interactions among biomolecules

What is the first factor that affects the water solubility of a biological molecule?

The ability to form hydrogen bonds with water.

Learning Objective 3: List the factors that affect water solubility of biological molecules and describe how the properties of water affect the interactions among biomolecules

What is the second factor that affects the water solubility of a biological molecule?

Ionization of one or more functional groups.

Learning Objective 3: List the factors that affect water solubility of biological molecules and describe how the properties of water affect the interactions among biomolecules

Why do oil molecules separate when mixed with water?

Oils lack ionic groups or dipoles to interact with water, so water excludes them to form hydrogen bonds with other water molecules.

Learning Objective 4: Define covalent bonds, ionic bonds and Van der Waals bonds and describe how they occur

What is a covalent bond?

A bond formed when two atoms with half-filled orbitals overlap and their electrons align with opposite spins.

Learning Objective 4: Define covalent bonds, ionic bonds and Van der Waals bonds and describe how they occur

What effect does orbital overlap in covalent bonding have on the energy of the system?

Energy stabilization.

Learning Objective 4: Define covalent bonds, ionic bonds and Van der Waals bonds and describe how they occur

What type of bond restriction is caused by a double bond (sigma + pi)?

Restricted rotation.

Learning Objective 4: Define covalent bonds, ionic bonds and Van der Waals bonds and describe how they occur

What is an ionic bond?

An electrostatic attraction between two oppositely charged ions.

Learning Objective 4: Define covalent bonds, ionic bonds and Van der Waals bonds and describe how they occur

What are Van der Waals interactions?

Very weak forces occurring between hydrophobic regions of different molecules.

Learning Objective 4: Define covalent bonds, ionic bonds and Van der Waals bonds and describe how they occur

How do temporary dipoles form in non-polar molecular regions?

Electronic distribution is never completely even, creating transient areas of high and low electron density.

Learning Objective 4: Define covalent bonds, ionic bonds and Van der Waals bonds and describe how they occur

How do Van der Waals interactions occur between two molecules?

A transient dipole in one molecule induces a dipole in a neighboring molecule, attracting areas of opposite electron density.

Learning Objective 4: Define covalent bonds, ionic bonds and Van der Waals bonds and describe how they occur

What physical condition is required for Van der Waals interactions to be significant?

The molecules/drug must be in close distance to the binding site.

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

What does chemical thermodynamics study?

The spontaneity, direction, and extent to which a chemical reaction proceeds.

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

What does chemical kinetics study?

The speed or rate at which a reaction takes place.

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

What equation defines Gibbs Free Energy (G)?

G = H - TS

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

In the Gibbs free energy formula, what does H represent?

Enthalpy, or the heat of the reaction.

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

In the Gibbs free energy formula, what does S represent?

Entropy, or randomness

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

In the Gibbs free energy formula, what unit is used for temperature (T)?

Degrees Kelvin

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

What thermodynamic conditions characterize a favorable reaction?

Heat is given off (lower energy products) and products are more random (higher entropy).

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

What does a negative change in free energy (Delta G < 0) indicate?

The reaction is exergonic and proceeds spontaneously to the right.

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

What does a positive change in free energy (Delta G > 0) indicate?

The reaction is endergonic and proceeds to the left.

Learning Objective 5: Define the important parameters of thermodynamics (enthalpy, entropy and free Gibbs energy) describe How Delta G can be used to predict whether a reaction will occur spontaneously or not

What does Delta G = 0 indicate about a reaction?

The reaction is at equilibrium.