Water Flashcards
What are the two structures of water?
Water is polar and water is hydrogen bonded.
Explain water being polar
- Each hydrogen atom is slightly positive as it shares electrons in a covalent bond with oxygen
- The unshared negative electrons in oxygen give it a slightly negative charge
- This makes a polar molecule as the charges are unequal
Explain water being hydrogen bonded
- Bonds between slightly positively charged hydrogen atoms and slightly negatively charged oxygen atoms
- Occur as the slightly negatively charged oxygen atoms of water is attracted to the slightly positively charged hydrogen atoms of other water molecules
- Hydrogen bonds are weak on its own and strong as a collective
- Represented by dotted lines
What are the 5 properties of water?
- Important metabolite
- Good solvent
- High latent heat of vaporisation
- High specific heat capacity (buffer)
- Very cohesive
Explain why water is an important metabolite?
- Involved in many metabolic reactions which require hydrolysis and condensation reactions
What is a condensation reaction?
A reaction that releases a molecule of water as a new bond is formed
What is an example of a condensation reaction?
Amino acids joined together make polypeptides which are proteins
What is a hydrolysis reaction?
A reaction that requires a molecule of water to break a bond
What is released through a hydrolysis reaction?
Energy from ATP is released through a hydrolysis reaction
Explain why water is a good solvent?
- Lots of important substances in biological reactions are ionic (eg. Salt)
- As water is polar, the slightly positively charged end of a water molecule is attracted to a negatively charged ion and the slightly negatively charged end of a water molecule is attracted to positively charged ion
- So ions will be completely surrounded by water molecules and dissolve
What is an example of water being a good solvent?
1.The transport of inorganic ions around the body in blood plasma
2. Dissolves monosaccharides and inorganic ions as water is dipolar
Explain why water has a high latent heat of vaporisation?
- Water vaporises when hydrogen bonds holding water molecules together are broken
- This allows water molecules on the surface of water to escape into the air as gas
- Takes a lot of heat energy to break hydrogen bonds between water molecules so water has a high latent heat of vaporisation
- When water evaporates, it carries away the heat energy from the surface so cools and lowers the temperature
What is an example of latent heat vaporisation?
Organisms use water loss through evaporation to cool down without losing excessive amounts of water
Explain why water has a high specific heat capacity (can buffer temperature)?
- Hydrogen bonds give water a high specific heat capacity (energy needed to raise the temperature of 1g of a substance by 1°c)
- Large amount of energy needs to be lost before water freezes (large latent heat of fusion)
- When water is heated, lots of energy to break hydrogen bonds are needed
- Less heat energy is available to actually increase temperature of water
What is specific heat capacity?
The energy needed to raise the temperature of 1g of a substance by 1°c