Lehninger: Chapter Two Flashcards
What does it mean to be polar?
Polar molecules are those that have a separation of charge. For example, the interaction between nitrogen and hydrogen is polar but we don’t consider carbon and hydrogen to be polar.
What is the association between these four words: non polar, polar, hydrophobic, hydrophilic.
Non-polar molecules are hydrophobic and polar molecules are hydrophilic.
What does it mean for a molecule to be amphipathic? Give an example
These are molecules that contain BOTH polar and non polar groups. The amino acid phenylalanine in its charged state is amphipathic as it has the (NH3+) group and the (COO-) group.
Is water a polar molecule? Why?
Water is a polar molecule because of the interactions between the electronegative O atom and the 2 H atoms.
How do we apply like-with-like?
In the case of water, it can readily dissolve macromolecules like sugar and protein because both are polar and hydrophilic
Do lipids and waxes dissolve in water?
No they don’t, they don’t because they are are hydrophobic substances
Can you describe a clathrate structure?
A clathrate structure is one in which water molecules form an ordered cage around non-polar molecules.
How do hydrophobic areas like to present themselves?
For example, hydrophobic alkyl groups like to keep themselves inside a molecule and they arrange polar molecules all around them kind of like bodyguards so that the polar molecules can maximize their interaction with water.
why are h-bonds broken in water molecules when they come into contact with bodygaurded hydrophobic molecules?
Water molecules are forced to cage around the hydrophobic tail which produces an unfavorable reaction. Which is why lipids have a low solubility in water.
What does it mean when delta S is negative/positive.
Delta S explains the total change in entropy in a system, so for the case in which water dissolved NaCl, because NaCl is a polar substance so the water was able to hydrate and stabilize the ions. Therefore, it was a favorable reaction which gives us a positive delta s. For the case of the hydrophobic molecule the water molecules are FORCED to bind to them instead of working to dissolve them which gives us a negative delta s because it is an UNFAVORABLE reaction.
What doe enzymes and substrates have around them?
They have a shell of water that hydrates and surrounds them
What happens to the entropy when enzymes bind to substrates and release some of the bound water.
The entropy increases
What forces result in a decrease in enthalpy?
A negative delta h describes a situation in which the products have less energy than the reactants so the reaction has lost energy which makes sense slide number 35 in the first pp. Hydrogen bonds, ionic interactions, VDW forces and hydrophobic interactions result in a decrease in enthalpy.
