BIOC 300A, I Flashcards
(122 cards)
What key property of water emerges from its high melting & boiling points and heat of vaporization?
Cohesiveness between water molecules in solution.
Which is the strongest type of chemical bond?
Covalent.
What functional group promotes solubility in water?
-OH (hydroxyl).
What is the consequence of H-bonding between water molecules?
Each molecule of water forms 4 H-bonds to other water molecules, creating water’s characteristic lattice structure.
Under what circumstances can H-bonding occur?
When a H atom attached to an electronegative atom approaches another electronegative particle.
Define van der Waals forces.
Very weak attractions created by transient dipole moments between uncharged molecules.
How do weak intermolecular attractive forces contribute to bonding?
Abundance - many weak bonds together can form one stronger bond.
What is the significance of weak nonpolar molecular interactions in biology?
The ability to easily form and break bonds allows for fluid, dynamic biological processes and contributes to the constant ebb & flow of macromolecules.
Define metabolite.
Low-molecular-weight molecules (such as glucose & glycerol) that are chemically transformed in biological processes.
Define protein.
A biological macromolecule made of a linear array of amino acids joined by peptide bonds.
What is the basic structure of all life processes?
The interplay between macromolecules and metabolites, with members of both classes common to all living things.
What is the basic structure of DNA?
A linear polymer consisting of a fixed sugar-phosphate backbone with attached bases (A, T, G, C) oriented to give the whole strand directionality with a distinct head and tail end.
What is indicated by similar 3D structures between proteins in different organisms?
They likely perform similar functions.
Define hydrophobic interaction.
The tendency of nonpolar molecules in water to interact with one another; interactions are driven by an increase in the entropy of water when water molecules in contact with nonpolar molecules are released into bulk water.
What are the 4 fundamental noncovalent bond types?
Ionic interactions, hydrogen bonds, van der Waals forces, and hydrophobic interactions.
What 2 features of water make it an especially versatile solvent?
The asymmetric distribution of charge between H and O makes it polar, and H-bonding between water molecules makes water highly cohesive.
Define dielectric constant.
A quantity measuring the ability of a substance to store electrical energy in an electric field, giving a rough measure of a solvent’s polarity; a higher constant means greater polarity.
What is the significance of water’s high dielectric constant?
A high dielectric constant means greater polarity, so ionic compounds are more likely to dissolve in water than in less polar solvents as it is more energetically favourable for its component ions to associate with water molecules than with each other.
What makes for the strongest hydrogen bonds?
A straight, linear configuration of all atoms involved.
How does water break ionic compounds apart?
Water’s high dielectric constant means it can store a large amount of electrical energy in its electrical field, which it can use to cancel out some of the electric bond strength between ionic molecules and make ionic compounds less likely to stick together.
What is the difference between H-bond acceptors and H-bond donors?
The H-bond donor is the molecule containing the H and is thus more tightly linked to the H atom; the acceptor is the electronegative atom that becomes less tightly linked to the H atom on the donor.
How do H-bonding and ionic interactions affect surface complementarity?
When complementary surfaces meet, H-bond donors align with H-bond acceptors, and nonpolar surfaces come together via the hydrophobic effect to maximize van der Waals interactions between each other and to minimize the surface area exposed to the aqueous environment.
In the hydrophobic effect, why is it favourable for some water molecules to be released from their shells when two nonpolar molecules come together in solution?
Molecules in the water shells are highly ordered, so release of some results in an increase in entropy, which is energetically favourable (2nd Law of Thermodynamics).
In the hydrophobic effect, why do water molecules form ordered shells around nonpolar molecules?
Nonpolar molecules can’t participate in H-bonding or ionic interactions, so it is easier for water molecules to bond with each other.
