3 - Water, pH, pK and buffers Flashcards
4 Important properties of water
Chemical stability
Remarkable solvent properties
Role as biochemical reactant
Hydration
What type of geometry does water have
Tetrahedral
Why is water a dipole? Why type of bond does this make between H and O?
Water is a dipole because its negative and positive charge are separate and this makes the bonds polar.
What elements can hydrogen form HYDROGEN BONDS with?
Oxygen, nitrogen and fluorine
What two characteristics do hydrogen bonds have
electrostatic (opposite charges) and covalent (electron sharing) properties
Bonds ranked by strength (4)
Covalent (strongest)
Ionic
Van der Waals forces
Hydrogen Bonds (weakest)
Noncovalent interactions are electrostatic, list two noncovalent interactions.
Van der Waals forces and ionic interactions. Hydrogen bonds are mixed covalent and electrostatic.
A Van der Waal force occurs between what three types of dipoles?
Neutral
Permanent
Induced
How many hydrogen bonds can a single water molecule form with other water molecules?
4, although this usually only occurs in ice
What two characteristics help maintain an organism’s internal temperature? How?
High heat of fusion and high heat of vaporization
These properties are due to waters abundance in organisms.
What are solvation shells?
shells of solvent molecules that form around a solute species. With water, a hydration shell is formed around ions.
What is the name for water surrounded molecules that have nonpolar tails sticking into core and polar head sticking into water?
Micelles, amphipathic molecules form micelles when mixed with water.
What is the role of turgor pressure in plants
It allows them to grow by using osmotic pressure
What is Kw at standard conditions?
1x10^-14. This is temperature dependent, and therefore pH is temp dependent as well
What is the equation for pH?
pH = -log[H+]
What is the equation for pKa?
-log[Ka]
What is Ka
The acid dissociation constant.
What is acidosis and alkalosis
Certain diseases that can cause changes in pH that can be disastrous
What do buffers do?
By following Le Chatelier’s principle buffers establish an equliibrium between buffers components. They shift the equilibrium in the direction that relieves stress
What does the Henderson-Hasselbalch Equation show? And what is it?
Establishes the relationship between the pH and pKa for selecting a buffer.
pH = pKa + log([A-]/[HA])
What is the enzyme responsible for bicarbonate buffer in the blood?
Carbonic Anhydrase
What is phosphate buffer for?
Important buffer for intracellular fluids
Can proteins act as buffers? If they can, what is an example?
Proteins are a significant source of buffering capacity (hemoglobin)
When does water have a maximum number of hydrogen bonds formed? (eg. what state is it in)
When water has frozen into ice. It has an open, less dense structure as ice.
What gives cytoplasm the properties of a gel? What is an advantage of this property?
It is a colloidal (evenly dispersed particles throughout)
Transition from gel to sol is important in cell movement. Converting an edge to sol makes the cell ‘flow’ that way.
What type of force stabilizes the hydrophobic effect?
van der Waals interactions
What is osmotic pressure?
The pressure required to stop the net flow of water across the membrane. It depends on solute concentration.
What is osmosis?
The diffusion of water across a membrane. Because it is water, it flows to where the concentration gradient is lesser than where it came from.
What is ionization?
The process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or ions.
Eg. converting H2O into H+ and -OH
