Topic 1- Lipids + Water + Inorganic ions Flashcards
What are lipids?
Lipids are biological molecules that are composed of carbon, hydrogen and oxygen.
What are the 2 groups of lipids?
Triglycerides
Phospholipids
How are triglycerides formed?
The condensation of one molecule of glycerol and three molecules of fatty acid.
What is the bond formed between the glycerol molecule and each fatty acid chain?
A condensation reaction between glycerol and a fatty acid (RCOOH) form an ester bond.
What are the two types of fatty acids called?
Saturated fatty acids
Unsaturated fatty acids
What is the difference between saturated and unsaturated fatty acid chains?
Saturated fats do not have double bonds between their carbon atoms.
Unsaturated fats do have double bonds between carbon atoms.
What does the double bonds cause the fatty acid chain to do?
It causes the fatty acid chain to kink/bend, causing the chain to not be able to pack together tightly and therefore are liquids in room temperature (oils).
How does triglyceride’s structure relate to their properties?
- High ratio of energy storing carbon-hydrogen bonds to carbon atoms and therefore are excellent source of energy.
- Low mass to energy ratio, meaning that they are a good storage molecules as much energy can be stored in a small space.
- Insolubility (due to being large and non-polar) in water means that their storage does not affect the water potential of cells.
- High ratio of H to O atoms so release water when oxidised, and therefore provides an important source of water, especially for organisms living in dry deserts.
How does the structure of a phospholipid molecule look like?
One of the fatty acids of a triglyceride is substituted by a phosphate-containing group. So has two fatty acids attached to a glycerol and a phosphate group.
Fill in the gap: The phosphate group is _______________ to water and therefore is ______________________.
The phosphate group is attracted to water and therefore is hydrophilic.
Fill in the gap: The fatty acid chains _______________ water and therefore are ________________.
The fatty acid chains repels water and therefore are hydrophilic.
How does phosholipid’s structure relate to their properties?
- Since phospholipids have a hydrophilic and hydrophobic side, the molecule is polar meaning that when placed in water, they form a bilayer. The hydrophilic head to hold at the surface of the cell membrane.
- This phospholipid bilayer is what forms the cell membranes, which controls what enters and leaves the cell.
- The centre of the bilayer is hydrophobic, meaning water soluble substances cannot enter easily.
What is the test for lipids?
- Add test sample with ethanol in a test
tube. - Shake it thoroughly
- Pour the solution in water
- If there is a cloudy white emulsion then this indicates that a lipid is present
Describe the structure of a water molecule?
A water molecule is made up of two atoms of hydrogen and one of oxygen.
Water molecules are dipolar since hydrogen has a slightly positive side and the oxygen has a slightly negative side. Therefore water molecules can form hydrogen bonds with each other.
State the properties of water.
- Water is an important metabolite that is used in many important metabolic reactions, including condensation and hydrolysis.
- Water has a high specific heat capacity as water takes a lot of heat energy to heat it up due to the presence of the hydrogen bonds. This allows water to buffer changes in temperature.
- Water has a large latent heat of vaporisation as it takes a lot of energy to break the hydrogen bonds between water molecules, allowing water to evaporate.
- Water has a strong cohesion and high surface tension due to their polarity, which helps water molecules to stick together.
- Water is also a place where solutes can be separated out and dissolved based on their charge. This is due to the polarity of water.
