lipids Flashcards
what are the two groups of lipid
triglycerides and phospholipids
how are triglycerides formed
by the condensation of one molecule of glycerol and three molecules of fatty acid
what bond is formed between a glycerol and a fatty acid
ester bond
what is one of the fatty acids in a phospholipid substituted by
a phosphate-containing group
biochemical test for lipids
(crush the sample if it is a solid)
dissolve the sample in ethanol
add it to cold water
result - if lipid is present, an emulsion is formed. if lipid is not present, no emulsion is formed
what are triglycerides
long-term energy store in animals and plant seeds
- compared to carbs, fat stores more energy per gram
BUT more difficult to access as it takes more O2 to respire it and release its energy
why are phospholipids considered to be both polar and non-polar
the phosphate group has a charge, the fatty acid/hydrocarbon tails do not
functions of lipids
source of metabolic water
phospholipids - cell membrane
less dense - efficient storage of energy in seeds
waxy cuticle (waterproofing) on leaves to reduce water-loss
thermal insulation - sub-cutaneous fat (adipose tissue)
electrical insulation (neurones are surrounded by insulating myelin sheath)
bouyancy eg squaline that fills a shark’s liver
oils to protect and condition hair and skin produced by sebaceous glands
what elements are present in lipids
carbon, hydrogen and oxygen
triglyceride - energy storage
high ratio of carbon-hydrogen bonds to carbon-carbon bonds
triglyceride - metabolic water source
high ratio of hydrogen to oxygen atoms
triglycerides - insoluble
doesnt affect water potential due to triglycerides being hydrophobic
phospholipid charge?
it is a polar molecule
hydrophilic head
hydrophobic fatty acid tails
form a bilayer
saturated
only single bonds between the carbons within the hydrocarbon chain
ester bond
the covalent bond formed by a condensation reaction between the -OH group of a carboxylic acid and the -OH group of an alcohol
glycerol role
bonds to fatty acids/a phosphate group to form lipids/phospholipids
COOH
carboxylic acid group
two differences between a triglyceride and a phospholipid
triglycerides have 3 fatty acids and phospholipids have 2
phospholipids have a phosphate group in place of one fatty acid
two properties of triglycerides that make them excellent storage compounds
insoluble
contains many bonds which release energy when broken
state two advantages to a mammal of having fat in its tissues
insulation
buoyancy
protection of organs
define the term hydrophobic as it relates to phospholipids
parts of the phospholipid repel water
two parts of a phospholipid
phosphate group/head
fatty acid chain/ hydrocarbon chain
what is a saturated fatty acid saturated with
hydrogen
identify and explain the structural feature of saturated fats that causes them to be solid at room temperature
straight hydrocarbon chains in the fatty acids
so molecules pack closely together so they are less able to flow around eachother
