Biodiesel: used cooking oils and fats can be used as an alternative to fossil fuels to power vehicles.
In this post, Jayne gives examples of different types of lipids and explains what they are composed of and their corresponding functions in the human body.
There are different types of Lipid found in living organisms. Triglycerides, phospholipids and sterols are those you are likely to come across at A Level. A typical question may ask you to describe the structure and function of each.
From FATBERGS to FUEL !
This item from the BBC explains how lipids can cause a domestic waste disposal problem namely :
30 TONNES OF FATBERG per week from one treatment station in Birmingham.
It also shows how this waste product is now getting turned into a useful "green" fuel.
Olive oil is one example of a lipid.
Types of lipid:
Several different types of lipid exist. They have different properties because their molecules contain different functional groups.
- Each of the boxes below contains the name of one type of lipid which can be found in a living organism.
- Clicking on the box will reveal or hide an explanation of the structure and function of the lipid.
- Hide the content in all the boxes.
- Can you draw or describe the structure and function BEFORE you click for the answer?
Triglycerides
- Triglycerides are formed when a molecule of glycerol and three fatty acid molecules join up.
- The reaction is known as a condensation reaction as a small molecule (water) is released.
- A new (ester) bond is formed.
- There are three ester bonds in a molecule of triglyceride.
Saturated and Unsaturated Fatty acids
- In saturated fatty acids, all the carbon atoms are bonded to the maximum number of hydrogen atoms.
- All the carbon to carbon bonds are single bonds the chain (and therefore the fatty acid) is called "saturated" .
- saturated fats are semi-solid at body temperature so are good for energy storage, protection and insulation.
- Animal lipids often contain saturated fatty acids. They are linked with the formation of low density lipoproteins.
- These are liquid at room temperature and are called oils. Plant lipids are often unsaturated and are linked with the formation of high density lipoproteins.
Phospholipids
- Phospholipids are composed of 1 glycerol, 1 phosphate group and 2 fatty acids molecules.
- The glycerol and phosphate make up the 'head' end of the phospholipid
- the head is polar and hydrophilic.
- The 2 fatty acids molecules make up the 'tail' end and are non polar and hydrophobic.
- There are two layers of phospholipid molecules (the phospholipid bilayer) in plasma membranes.
- The tails are inside and the heads are on the outside.
Sterols
High levels of cholesterol can be linked with consumption of large amounts of saturated fats.
Cholesterol is a sterol. It is found in plasma membranes and functions to stabilise them. Cholesterol is also important in the production of some hormones and vitamins. Cholesterol is carried around the body by proteins forming lipoproteins. High levels of Low Density Lipopoteins (LDLs) are associated with the development of blockages in arteries (atheromas). LDLs are produced by the body and high levels can be linked with consumption of large amounts of saturated fats. High Density Lipoproteins (HDLs) help carry cholesterol to the Liver to be broken down so can protect against atheroma formation. HDLs are also made by the body and are associated with the consumption of unsaturated fats.
Exploring the molecules
Use the animation explore the fatty acid, glycerol and triglyceridemolecules.
Use the buttons at the top to show or hide the functional groups, the different formula types and the polar and non-polar parts of the molecules.
Fatty acids
All fatty acid molecules contain a non-polar hydrocarbon chain . In some cases the chain contains double bonds between neighbouring carbon atoms . The C=C double bond is an alkene functional group and is an unsaturated hydrocarbon. If all the bonds are single the chain is "saturated"
All fatty acid molecules contain the -CO2H or "- COOH "functional group.
This is the carboxylic acid functional group
Glycerol
Glycerol molecules have three OH functional groups
Glycerol molecules contain three - OH or hydroxyl functional groups . The OH group is indicated by the suffix "OL" as in ethanol or, as in this case glycerol
Condensation reaction
Carboxylic acid groups will react with hydroxyl groups to produce ester functional groups. A water molecule is also produced and the reaction is therefore an example of a condensation reaction
Polar and non polar.....
Water is a polar molecule; hydrogen atoms (white) carry a partial positive charge, oxygen atoms, a partial negative charge.
Methane is a very symmetrical molecule with an even distribution of electrons. It is therefore non - polar.
- Polar molecules have areas of positive and negative charge. This happens when electrons are unevenly distributed around the molecule.
- Uneven electron distribution can the the result of differing electronegativity of the atoms involved. It can also be the result of an asymmetric arrangement of electrons.
- Water molecules are polar. The oxygen atom is negatively charged and the hydrogen atoms are positively charged. Other polar molecules are attracted to water molecules and dissolve in them. For example, glucose, dissolves in water.
- In non polar molecules the charges are evenly distributed in the molecule. They do not interact with polar water molecules and so are insoluble in them.
- Most parts of a triglyceride molecule are non polar.
- Phospholipids have a polar 'head' which attracts water (hydrophilic) the fatty acid tails of the phospholipid molecule do not attract water ( i.e. are hydrophobic) and sit on the inside of the membrane.
Explaining Lipids clearly...
Jayne's youtube channel is where she is sharing her "no frills" explanations of the major biological ideas, concepts and knowledge to be found in the current A level courses.
These are simple, no frills explanations produced live by Jayne with her pen, her whiteboard and her calm, clear, methodical commentary.
- Each video lasts somewhere between 5 and 10 minutes.
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