Lipids Flashcards
What characteristics do lipids share
They contain carbon, hydrogen and oxygen.
• The proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates.
• They are insoluble in water.
• They are soluble in organic solvents such as alcohols and acetone.
The main groups of lipids are triglycerides (fats and oils) and phospholipids
Roles of lipids and phospholipids general
Lipids are used in the cell membrane and phospholipids contribute flexibility to membrane and transfer lipid soluble substances across them
Roles of lipids all 4
Source of energy : when oxidised they provide more than twice amount of energy per mass than carbs and release valuable water
Water proofing lipids are insoluble in water and therefore waterproof
Insulation fats are slow conductors of heat and when stored beneath body surface helps it retain body head
Protection fat is often stored around delicate organs
Triglycerides
3 fatty acids bonded to 1 glycerol molecules and each fatty acid forms an ester bond with glycerol in a condensation reaction
What are saturated, monounsaturated, polyunsaturated triglycerides
Saturated is no double C bonds, monounsaturated is 1 double C bond,polyunsaturated is more than 1 double C bond
The structure of triglycerides and how it relates to their properties
They have a high ratio of energy storing carbon and hydrogen bonds and is therefore an excellent energy source
They have a low mass to energy ratio making them good storage molecules because more energy can be stored in a small volume
Are insoluble and therefore doesn’t effect water potential
High ratio of hydrogen to oxygen atoms ,forming water when oxidised, therefore an important source of water
Phospholipids
One fatty acid molecule is replaced by a phosphate molecule
Where the fatty acid molecule is hydrophilic and the phosphate molecule is hydrophobic
Phospholipids and structure and how r related to the function
Phospholipids are polar molecules having a hydrophilic phosphate head and a hydropbobic tail of two fatty acids.
in an aqueous environment, phospholipid molecules form a bilayer within cell-surface membranes. As a result, a hydrophobic barrier is formed between the inside and outside of a cell.
• The hydrophilic phosphate heads of phospholipid molecules help to hold at the surface of the cell-surface membrane.
• The phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell-surlace membrane.
These glycolipids are important in cell recognition.
Test for lipids
Take a completely dry and grease-free test rule.
2 To 2cm’ of the sample being tested, add 5cm’ of ethanol.
3 Shake the tube thoroughly to dissolve any Epid in the semple.
4 Add Scm’ of water and shake gently.
5 A milky-white emulsion indicates the presence of a lipid.
6 As a control, repeat the procedures using water instcad of the sample; the final solution should remain
