Water Flashcards
(33 cards)
Define solubility
A substance’s relative capability of being dissolved.
Define dissociation
The splitting up of a salt by water to form the separate ions
Define electrolyte
The ions dissolved in the water in the body
What are the most important electrolytes? (5)
Sodium Potassium Calcium Chloride Magnesium
Why must the correct concentration of electrolytes be maintained?
An imbalance of electrolytes causes severe illness or death
What is hyponatremia?
When the salt concentration is too low
What is hypernatrenia?
When the salt concentration is too high
What often causes hypernatrenia?
Dehydration
Define osmolarity
The concentration of electrolytes (might be different to the concentration of the dissolved salt)
What is the intermolecular force that occurs between water molecules?
Hydrogen bonding
Why can water molecules hydrogen bond to each other?
The oxygen atom is more electronegative than the hydrogen atoms, so is slightly negative (𝛿-). Hydrogen atoms (𝛿+) associate with the oxygen atom on another molecule.
What properties does hydrogen bonding give water?
- Ice is less dense than water, meaning ice can float
- Water has a very high melting and boiling point for its size
Why is the fact that ice is less dense that water essential for life on Earth?
Polar ice-caps insulate the water beneath them, keeping it liquid. Otherwise most water on Earth would be ice
Why is water’s high melting and boiling point essential for life on Earth?
It means that life can exist at the Earth’s temperature
What other element can take part in hydrogen bonding?
Nitrogen: N-H .... N N-H .... O O-H .... O O-H .... N
Which other biological molecules does hydrogen bonding occur in?
Complementary base pairing in DNA requires H-bonds. H-bonds form the secondary structure of proteins.
Why can polar molecules dissolve in water?
They are able to make hydrogen bonds with water, making them hydrophilic
Why are non-polar molecules unable to dissolve in water?
They don’t contain electronegative atoms, so they can’t form hydrogen bonds with water.
Describe the hydrophobic effect
In order to minimise interactions with water, hydrophobic molecules tend to stick together in solution.
Why is the hydrophobic effect useful?
It’s important in forming the structure of biological membranes and proteins
Why are ions able to dissolve in water?
They form electrostatic interactions with the dipoles in water
How does [Na+] inside cells compare to outside cells?
[Na+] is higher outside cells than inside cells
How does [K+] inside cells compare to outside cells?
[K+] is higher inside cells than outside cells
Where is [Ca2+] very low?
In the cytosol of cells
