B: Lipids Flashcards
Functions of Lipids
- energy storage
- thermal insulation
- structural components of cell membranes
- protection of organs
- storage and transport for hydrophobic vitamins
- hormones
- electrical insulation (protection of neurons - Myelin)
Energy of Fats vs Glucose
Fats
- Oxidation C57H100O6 // C = -1.54 —> CO2 C = 4
- Oxidation no. increases more –> gives more energy
- fats stored in cells and are hydrophobic –> do not affect the movement of H2O
Glucose
- Oxidation C6H12O6 // C = 0 —> CO2 C = 4
- oxidation number increases less than that of fat
- water soluble –> easily transported around the body
Triglycerides
- most abundant class of lipids
- most fats and oils in our diet contain triglycerides
- viscous because of H bonds
glycerol + fatty acids —> triglyceride + 3H2O
condensation reaction
Unsaturated Fats
- Saturated fats: No C=C bond
- Mono-saturated: 1 C=C bond
- Polyunsaturated: many C=C bonds
- difference of 2H atoms indicates the presence of C=C bonds
C2H3 C2H5
unsaturated saturated
- the arrangement of double bonds in fatty acids is almost always cis
Melting points of Lipids
Mr
- Larger the Mr, the higher the melting / boiling point
- more energy required for them to move faster and break free from their IMF
Length of Carbon bonded Chain
- Longer chain means greater degree of LDF –> will pack closer
- shorter chain has a smaller surface area of contact
Unsaturation
- number of C=C bonds in the carbon –> kinked chains can’t pack as closely
- the more unsaturation there is, the lower the melting point
Degree of Unsaturation - Iodine number
- Iodine molecules will add across a C=C
Iodine number: number of grams of iodine that will react with 100g of fat / oil
- completely saturated –> Iodine no. = 0
- High degree of unsaturation, high iodine number
Phospholipids
- main lipid found in cell membranes
- a membrane is made up of a bilayer of phospholipids surrounding each cell and phospholipids also surround inner structures in the cell (organelles)
Hydrolytic Rancidity
- The process whereby fats and oils in foods are hydrolysed to give fatty acids and glycerol
- process speeded up by
- enzymes
- high temps
- excess moisture
- high/low pHs
Oxidative Rancidity
- When presence of O2 breaks down the fats and oils in food
- Occurs in unsaturated fats / oils where C=C bonds react with O2 in a free radical reaction —> aldehydes and ketones
- Process speeded up by
- high con. of oxygen
- UV light
- high temps
- presence of metals
Hormones - Steroids
- chemical messengers
- all share the same steroidal backbone
- Uses - treatment for
- Asthma
- diabetes
- contraception
- skin conditions
- bone/ blood disorders
- muscle growth
Lipoproteins
Cholesterol is largely hydrophobic –> solubility in blood plasma is low –> normally transported throughout the body in Liporotein complexes
Low Density Lipoproteins
Bad cholesterol
- less soluble in blood plasma and are more likely to deposit as a solid (plaque) in artery walls –>
- blood clots –>
- oxygen and glucose can’t get to heart muscle cells
- can no longer respire –>
- cells don’t receive energy and die –> heart attack
High Density Lipoproteins
Good cholesterol
Lipoproteins Density and Solubility
- density - long chains and kinks increases, density decreases
- solubility - more lipids, more hydrophobic environment, solubility decreases
- density and solubility of lipoproteins decreases with increasing lipid content
Acid Hydrolysis of Fats
—–> glycerol + fatty acids
Alkaline Hydrolysis of Fats
—> glycerol + anion fatty acids
Phospholipids Hydrolysis of Fats
—-> Glycerol + Phosphoric acid + 2 Fatty acids +
