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Fat for fuel .

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.


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?

 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

 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...

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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.
  • Ideal for a quick targeted revision sessions
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