Life at a Cellular Level 4 Flashcards
(32 cards)
What does water do/
- Bathes our cells
- Dissolves and transports compounds
- Allows compounds to move within an between cells
- Participates in chemical reactions
- Dissipates heat
Describe the structure of water.
- Polar molecule
- Electrons of covalent bond attracted to O
What does the polarity of water allow?
Hydrogen bonding
Where can hydrogen bonds occur?
Between any electronegative atom and a H atom that is electropositive
When are hydrogen bonds strongest?
When the 3 atoms involved lie in a straight line
What are examples of hydrophilic substances that can dissolve in water?
- Sugars
- Alcohols
- Aldehydes
- Ketones
- Compounds with N-H groups
What happens when hydrophilic substances dissolve in water?
The water-water H bonding and solvent-solvent H bonding is replaced with more energetically favourable solute-water H bonding
How do O2 and CO2 dissolve if they have no polarity?
- The atoms lie in a straight line so the ends of the molecule are the same so a partial charge does not happen
- this makes O2 and CO2 relatively poorly water soluble
What happens to ionic compounds in water?
The water forms screens around each ion keeping the compound in solution once it has dissolved.
How do hydrophobic molecules arrange themselves in water?
- To minimise disruption of hydrogen bonding among surrounding water molecules
- This proves the most energetically favourable arrangement of the molecules
- This is the hydrophobic effecys
Describe lipids in water
- Lipid portions at the edge of the cluster force the ordering of water
- Fewer H2O molecules are ordered, and entropy is increased
What happens to phospholipids in water?
They minimise the disruption of water-water H-bonds by forming micelles or bilayers
What happens if you put lots of phospholipids in water?
They can form liposomes
What happens to proteins in water?
- Hydrophobic regions of the protein chain on the inside and hydrophilic regions on the outside
- This allows them to be water soluble
How are hydrophobic lipids transported in the blood?
-Transported as chlomicrons
How is the equilibrium of water described?
Keq= [H][OH]
———-
[H2O]
What is the ion product of water equal to?
1 × 10^-14 (mol/L)2
What is true in pure water?
[H]=[OH]=1 × 10^-7(mol/L)
What is a strong acid?
An acid which fully dissociates in water like HCl
What is a weak acid?
An acid which partially dissociates in water
How is optimal pH maintained?
Using buffer systems within cells and organisms
What are buffers?
Solutions of weak acids
What is a proton donor?
Acid
What is a proton acceptor?
Alkali
