Lipids Flashcards
What are lipids and their general properties
-general term for fats and oils
-contain hydrogen, carbon and oxygen but proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates, so less oxygen
-insoluble in water but soluble in organic solvents eg alcohol and acetone
What are the three types of lipids
-triglycerides
-phospholipids
-cholesterol
Roles of lipids
-phospholipids contribute to flexibility of cell membranes and transfer of lipid-soluble substances across them
-when oxidised they provide energy
-insoluble in water so useful in waterproofing eg waxy cuticle
-fats are slow conductors of heat so help to retain body heat
-protection around delicate organs
-some hormones are lipid based
What are triglycerides
Made of three fatty acids(long chain hydrocarbons that contain a carboxylic group) combined with glycerol(an alcohol that contains three hydroxyl groups)
What are saturated fatty acids
The hydrocarbon chain has only single bonds meaning they can pack tightly so they are solids at room temperature
What are unsaturated fatty acids
The hydrocarbon chain consists of at least one double bond so liquid at room temperature due to bend at double bond meaning they cannot be packed so tightly
What type of bond is in a triglyceride and how does this form
Ester bond forms between fatty acid and glycerol, formed during a condensation reaction between hydroxyl group of glycerol and carboxyl group of fatty acid forming three water molecules for one triglyceride
Why are triglycerides not found in cell membranes
They do not have a hydrophilic region that could be in contact with fluid
Structure and properties of triglycerides
-excellent source of energy
-low mass to volume ratio so good storage molecule
-large and non-polar so are insoluble in water meaning their storage does not affect the water potential of cells
-high ratio of hydrogen to oxygen atoms so release water when oxidised which produces an important source of water for desert animals
Compare structure of triglyceride and phospholipid
-triglyceride molecules contain three fatty acids while phospholipids contain two
-phospholipids has polar phosphate head while triglyceride has non-polar glycerol head
-both consist of ester bonds and carbon, hydrogen and oxygen
Structure and properties of phospholipids
-polar molecules with hydrophilic phosphate head and hydrophobic fatty acid tails
-in aqueous environments form a bilayer and a hydrophobic barrier which is important in their role as part of cell surface membrane
How is cholesterol transported in bloodstream
-it is insoluble in water so is combined with proteins and lipoproteins which are transport cholesterol
What are the two major transport lipoproteins and which is good and bad
-low-density lipoproteins(LDLs) the bad one
-high-density lipoproteins(HDLs) the good one
How are LDLs formed and role
Formed when triglycerides from fats in diet combine with cholesterol and protein which transport cholesterol to body cells by circulating in bloodstream and binding to receptor sites on cell membranes before being taken up by cells
Why is an excess of LDLs a bad thing
-excess LDLs overload membrane receptors so accumulate in the bloodstream causing high blood cholesterol levels which can lead to the formation of an atheroma due to this cholesterol being deposited in artery walls leading to CVD
