Lipids Flashcards
What are lipids soluble and insoluble in
Insoluble in water, soluble in solvents
Roles of lipids
Insulation (fats are slow conductors and are insulators in myelin sheath)
Waterproofing as insoluble in water e.g. waxy cuticle of leaves
Protection (fat is stored around delicate organs)
Store of energy for producing ATP in respiration
Production of phospholipids for formation of CSM
What bond is between the fatty acids and glycerol
Ester bond between hydroxyl groups 0( on the glycerol and carboxyl if groups C00H on fatty acids
What does saturated mean
No double bonds only C-C so from linear hydrocarbon chains. Pack close together and stick more strongly, higher melting point, solid at room temp
What are triglycerides/ how are they formed
One group of lipid, they have 3 fatty acids and glycerol held with ester bond (condensation reaction)
The r group of a fatty acid may be saturated or unsaturated, what dies this mean
Saturated: no carbon-carbon double bonds unsaturated: one or more double bonds
How does the structure of triglycerides relate to their properties
-High ratio of carbon hydrogen bonds to carbon atoms so good source of energy
-good storage molecules as they have a low mass to energy ratio (good 4 animals as less mass to carry
- large and non polar so are insoluble so their storage does affect water potential of cells
- high ratio of hydrogen to oxygen and provide water when oxides (good for animals in deserts)
How does a phospholipid differ from a triglyceride
Both are insoluble and both have ester bonds, both have glycerol and fatty acids. A phospholipid has one glycerol bonded to 2 fatty acids and a phosphate group/head. where a triglyceride has one glycerol + 3 fatty acids. phosphate is hydrophilic so a phospholipid has a hydrophilic head and a hydrophobic tail but triglycerides are only hydrophobic. Phospholipids form micelles in water, tri don’t
How does the properties of phospholipids relate to their structures
-polar molecules which means in an aqueous environment, they form a bi layer within cell membranes which acts as a hydrophobic barrier
- hydrophilic heads help to hold the surface of cell membranes
- structure allows them to form glycolipids by joining with carbs (important in cell recognition
Describe the emulsion test for lipids
To 2 cm3 of sample add 5cm3 ethanol, shake tube, add 5cm water and shake: a milky white emulsion indicates lipid (due to lipid being finely dispersed and light passes through
Properties of a triglyceride
Non polar, hydrophobic, insoluble in water but soluble on solvents
Unsaturated fatty acid definition
One or more double bonds present c=c and not all carbon saturated/ bonded to hydrogen- causes hydrocarbon chain to bend . Don’t pack close together and stick less strongly lower melting point and liquid at room temp
Roles of the phospholipid bilayer
CSM: boundary between cells cytoplasm and external environment. Controls movement of substances in and out. Non polar can diffuse directly through but polar require transport channels. Organelle membranes: control entry and exit of substances
