1.5-LIPIDS Flashcards
Lipids is a varied group of substances but what characteristics do they share? (4)
contain carbon, hydrogen and oxygen
proportion of oxygen to carbon and hydrogen smaller than in carbohydrates
insoluble in water
soluble in organic solvents i.e. alcohols and acetone
What are the main groups of lipids?
triglycerides (fats and oils)
phospholipids
Where is one of the roles of lipids?
in the cell membrane (cell-surface membranes and membranes around organelles)
What does phospholipids contribute to?
the flexibility of membranes and the transfer of lipid-soluble substances across them
What is a role of lipids? (1)
source of energy
when oxidised, lipids provide more than twice the energy as the mass of carbohydrates and release valuable water
What is a role of lipids? (2)
waterproofing
lipids are insoluble in water and so useful as waterproofing. both plants ans insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sebaceous glands in skin
What is a role of lipids? (3)
insulation
fats are slow conductors of heat and when stored beneath the body surface help to retain body heat. also act as electrical insulators in myelin sheath around nerve cells
What is a role of lipids? (4)
protection
fat is often stored around delicate organs i.e. kidneys
What is the state of fats and oils at room temperature (10-20℃)?
fats are solid
oils are liquid
Why are triglycerides so called?
as they have three (tri) fatty acids combined with glycerol (glyceride)
What does each fatty acid form?
forms an ester bond with glycerol in a condensation reaction
What does the hydrolysis of a triglyceride produce?
produces glycerol and three fatty acids
What is the same in all triglycerides?
the glycerol molecule
Where does the difference in the properties of different fats and oils come from?
variation in the fatty acids
How many fatty acids are there?
over 70 different fatty acids
What do all the fatty acis have?
a carboxyl (-COOH) group with a hydrocarbon chain attached
What is the fatty acid known as if this chain had no carbon-carbon double bond?
describes as saturated, because all the carbon atoms are linked to the max no. of hydrogen atoms
What is it called when there is a single double bond?
mono-unsaturated
What is it called if more than one double bond is present?
polyunsaturated
What does it mean for triglycerides to have a high ratio of energy-storing carbon-hydrogen bonds to carbon atoms?
an excellent source of energy
What does it mean for triglycerides to have low mass to energy ratio?
makes them good storage molecules because much energy can be stored in a small volume
How is triglycerides being good storage molecules especially beneficial in animals?
as it reduces the mass they have to carry as they move around
What property do triglycerides have by being large, non-polar molecules?
insoluble in water
What does triglycerides being insoluble in water mean?
their storage does not affect osmosis in cells or the water potential of them