Why does the camel have a hump?

Biological Molecules: Lipids  Links to G.C.S.E  Bonding  Balanced diet and food tests  Hormones  Respiration

 State that lipids (fats & oils) are a range of biological molecules including triglycerides

Key definition: lipids  Lipids are a diverse group of chemicals that dissolve in organic solvents, such as alcohol, but not in water.  They include fatty acids, triglycerides and cholesterol.

Functions of lipids  An energy source for respiration  Energy storage  Constituent of biological membranes  Insulation- e.g. whale blubber  Protection e.g. waxy cuticle in plants  Make up steroid hormones e.g. testosterone, oestrogen, progesterone

Molecular structure of glycerol

Fatty acid molecule showing acid group

Fatty acids  All fatty acids have an acid group at one end (the same as on an amino acid)  The rest is a hydrocarbon chain, anything from 2-20 carbons long  The most common fatty acids Have 18 carbons in the hydrocarbon chain  The terms unsaturated and polyunsaturated is often used when discussing healthy foods.  Saturated fats are a feature of a poor diet.  A saturated fatty acid is one where all bonds possible are made with hydrogen.

Saturated and unsaturated fatty acids

Formation of triglyceride molecule

Compare the structure of triglycerides and phospholipids. Compare the structure of triglycerides and phospholipids. Explain how the structure of triglyceride and phospholipid and cholesterol molecules relates to their functions in living organisms. Explain how the structure of triglyceride and phospholipid and cholesterol molecules relates to their functions in living organisms.

Formation of a phospholipid molecule

How does the structure of these molecules aid their function? PHOSPHOLIPIDS  Phospholipids are almost identical to triglycerides with one important difference, the addition of a phosphate molecule.  The phosphate head is HYDROPHILIC while the rest is hydrophobic.  This gives the phospholipid molecule the capacity to form cell membranes  The molecules may vary in how saturated the fatty acids are which alters the fluidity of the membrane and is useful at varying temperatures.

TRIGLYCERIDES  Respiration of these molecules requires the hydrolysis of the ester bonds that hold the fatty acids and glycerol together  Then both can be respired to carbon dioxide and water which releases energy for the generation of ATP.  Lipids contain about twice the energy as the same amount of carbohydrate.  Their insolubility means they can be stored in a compact way without affecting the water potential of the cell contents  The respiration of these molecules gives out more water than carbohydrate.  This is metabolic water vital to many organisms.

Cholesterol structure

 CHOLESTEROL  A small molecule made from 4 carbon based rings which is found in al biological membranes.  Its small, narrow structure and hydrophobic nature allow it to sit between the phospholipid hydrocarbon tails.  Here it regulates the fluidity of the membrane.  Testosterone, oestrogen and vit D are made from cholesterol

 The lipid nature of these hormones means they can pass through the lipid bilayer  Cholesterol is vital to living organisms and can be made in the liver  High cholesterol is a problem in humans because it can cause gall stones and/ or atherosclerosis  There is also a genetic condition called hypercholesterolaemia which is caused because the cells don’t respond to the signal to stop production

Lipids & respiration

  Respiring lipids requires the hydrolysis of the ester bonds holding the fatty acids & glycerol together.   Both the glycerol & fatty acids can be broken down to give carbon dioxide & water.   This releases energy to generate ATP molecules.   The insolubility of lipids means they make good compact storage molecules that do not affevt the water potential of the cell.   It also gives out more water than carbohydrate.   This ‘metabolic water’ is vital to some organisms

 State that lipids (fats & oils) are a range of biological molecules including triglycerides  Compare the structure of triglycerides and phospholipids.  Explain how the structure of triglyceride and phospholipid and cholesterol molecules relates to their functions in living organisms.