Topic 1 Biomolecules - Lipids Flashcards
What are lipids?
lipids are compounds that are insoluble in water, but soluble in an organic solvent (e.g. ether, benzene, acetone, chloroform) - most are hydrophobic
What is a fat?
A lipid that is solid at room temperature
What is an oil?
A lipid that is a liquid at room temperature
What are major physiological roles of lipids?
Fuel molecules
Highly concentrated energy store and provide insulation
essential components of cell membrane (e.g. phospholipids, glycolipids and cholesterol)
Signal molecules and messengers in signal-transduction pathways
Used as a fuel store
What does it mean if a compound is amphipathic?
Compounds which exhibit both hydrophilic (water-loving) (polar) and hydrophobic (water-hating) (non-polar) properties
What are examples of types of lipids?
fatty acids
triacylglycerols
phospholipids - glycerophospholipids, sphingolipids
Glycosphingolipids
Cholesterol - steroid hormones, bile acids
What does a fatty acid consist of?
a hydrocarbon chain with a terminal carboxylic acid group
Give examples of lipids are membrane lipids (polar)
phospholipids, glycolipids
Give examples of storage lipids (neutral)
Triacylglycerols
Are fatty acids weak or strong acids?
they are weak acids due to carboxylic group, and they have a pKa of around 4.5
Describe saturated fatty acids
No double bonds between carbons e.g. animal fats, solid at room temperature
they have higher melting points than unsaturated fatty acids.
Fatty acids in biological systems usually contain an even number of carbon atoms. fatty acids vary in chain length. describe these different chain lengths?
Short= 2-8 (or less than 6) carbons (volatile and smelly)
Medium= 10-14 (or 6-12 ) carbons
Long = 16-18 (or more than 12) carbons
How do chain lengths and degree of saturation affect fatty acid properties?
short chain length and unsaturation enhance the fluidity of fatty acids and their derivatives
What fatty acid chain lengths are considered amphiphillic?
medium and long
In most naturally occurring fatty acids, what is the orientation/conformation around the double bonds?
cis conformation
Describe unsaturated fatty acids
contain one or more double bonds e.g. vegetable oils, liquid at room temperature
have lower melting points than saturated fatty acids
describe triglycerides structure?
Triglycerides are uncharged (neutral) esters where glycerol is bonded to three fatty acids
Why is the cis conformation of double bonds in fatty acids important?
important for structure because each cis double bond inserts a bend/kink into the hydrocarbon tail.
What are triglycerides?
Triglycerides are a class of lipids commonly referred to as FATS, and are an important part of our diet.
What are triglycerides function?
they are highly concentrated stores of metabolic energy because the are reduced and anhydrous (i.e containing no water)
What are lipid droplets?
large globules formed by the coalescence (joining or merging) of triacylglycerols
They may occupy most of the adipocyte volume and are surrounded by a phospholipid monolayer and proteins required for lipid metabolism
What is adipose tissue ?
adipose tissue is a major site of triglyceride accumulation and specialised for triglyceride synthesis, storage and mobilisation into fuel.
Describe phospholipids structure?
one or more fatty acids
a platform to which the fatty acids are attached
a phosphate
an alcohol or choline attached to the phosphate
What are phospholipids function?
major component of cell membrane
