Water and its properties Flashcards
Why are weak bonds beneficial for life?
Weak bonds permit dynamic interactions that forms the basis of biochemistry and life itself.
What is Brownian motion a function of?
random motion in aqueous solution based on thermal input.
Describe the relationship between Brownian motion and temperature.
The higher the temperature, the higher the Brownian motion
What initiates many biochemical interactions?
Brownian motion of water (movement of molecules powered by random fluctuations of environmental energy)
Describe the features of water? is it polar or nonpolar?
Water is a POLAR molecule with an e-negative oxygen atom carrying a slightly negative charge and Hydrogen atoms carry slightly positive charges (form dipoles).
water also has asymmetric distribution of e- (can be transient)
Describe how the polarity of water provides more important properties.
The polarity of water allows for the formation of H-Bonds between water molecules and accounts for COHESIVENESS of water.
Polarity of water also accounts for ability to DISSOLVE many important biochemicals.
Why does the hydrophobic effect occur?
Due to inability of water to dissolve nonpolar molecules.
What are electrostatic interactions? What are other names used to describe the equation? What is the formula for energy of electrostatic equation?
attraction between oppositely charged ions. These interactions also called ionic bonds or salt bridges.
Formula for energy of electrostatic attraction (coulomb’s law) : E= kq1q2/Dr (E is energy, k is proportionality constant, q- charge on ions, D is dielectric constant, r is distance between 2 ions)
What is the Dielectric constant (D) ?
used to determine how well a solvent can weaken or strengthen the electrostatic interaction. D =1 in vaccum. D= 2 in hexane and D=80 in water.
How does water affect electrostatic interactions (ionic bonds)?
water has a high dielectric constant of 80 and therefore WEAKENS electrostatic interactions (able to dissolve ions)
How do Hydrogen bonds form?
H- bonds can occur whenever hydrogen is covalently bonded to an electronegative atom. (h-bonds are not unique to water molecules)
How does h-bonds play a role in protein strucuture?
H-bond puts alpha helixes together and bet sheets during secondary structure of making proteins.
How to identify the h-bond acceptor vs H-bond donor?
when three atoms are linked together for instance: N-H——–N the h-bond donor is the atom on left side of H as it is pulling e-. The h-bond acceptor is the atom on right of H as it has lone pair of e that form bond with hydrogen.
How does water affect hydrogen bonds?
Water disrupts hydrogen bonds between 2 molecules by competing for hydrogen bonding capability.
how do Van Der Waals interactions occur?
Van Der Waals- attraction of repulsion of molecules due to unequal distribution of e- between bound atoms (intermolecular forces)
allow for nonpolar and uncharged molecules to interact electrostatically.
Describe the interaction of molecules
In Van der waal attractions.
transient symmetry in one molecule will induce complementary asymmetry in nearby molecule. VDW have lower energy than H-bonds.
How does distance of molecules affect van der waals interactions?
As molecules move closer to each other, steric factors push them apart, allow for more repulsion. (further they are, the higher attraction).
What kind of forces allow for Gecko to stick to smooth surfaces?
Van der waals forces. The spatulae on the bottom of the gecko’s feet allow them to form van der waals with surface and foot will stick to surface.
Compare and contrast covalent and noncovalent bonds. List examples. Which of two bonds require more energy ?
Covalent bonds (C-C bonds, or phosphodiester linkage in DNA) are stronger than noncovalent bonds, require more energy to break bonds. Noncovalent bonds (ionic bonds, h-bonds, van der waals) weaker than covalent bonds. for ionic bonds- need more energy to break bonds when ion is in hexane vs, water. among noncovalent bonds, strongest to weakest: ionic, h-bonds, van der waals.
What is the distinction between ionic bonds, hydrogen bonds and van der waals interactions?
the ability to break bonds.
Why are weak bonds beneficial for life?
Weak bonds permit repeated interactions.
H-bonds contribute to stability of DNA double helix, But bonds are weak enough to be broken by enzymes of DNA metabolism (allowing access to genetic information)
What is the hydrophobic effect? what is it powered by? How does it benefit bio systems?
Describes the clustering of hydrophobic molecules (benzene) in water. It is powered by INCREASE IN ENTROPY of water that occurs when hydrophobic molecules come together. Hydrophobic effect is powerful ORGANIZING force in bio systems.
What thermodynamic property drives the hydrophobic process? why is the property lower in solution where molecules are separted?
Entropy. In image A, molecules are separated, hence why entropy is low. Entropy will only increase when hydrophobic molecules cluster together in water because less ordered water molecules surround nonpolar molecules and allow for increase in disorder or entropy.
What happens when a membrane is exposed to hexane?
Form compartmentalization of cell? Phospholipids have hydrophilic and hydrophobic properties (amphipathic or amphiphilic) Membrane formation powered by hydrophobic effect. Van der waals promote stability of lipid bilayer and increase in entropy.
