Lipids and Proteins spec Flashcards
(20 cards)
What are the 2 groups of lipids
Triglycerides anf phospholipids
What are lipids
varried group of substances that share the following characteristics:
contain carbon, hydrogen, and oxygen
insoluble in water
soluble in organic solvents
How are triglycerides formed
by condensation reactions of one molecule of glycerol and three molecules of fatty acid
what does a condensation reaction between glycerol and a fatty acid form
An ester bond (RCOOH)
the R-group of a fatty acid can be what?
saturated or unsaturated
Phospholipids what is substituted
one of the fatty acids of a triglyceride is substituted by a phosphate- containing group
what is the emulsion test
-take a completly dry and greese free test tube
-to the sample add ethanol
-shake throughly to disolve any lipid in the sample
-add water and shake gently
-a milky-white emulsion indicates the presence of a lipid
-as a control, repeat the procedure using water instead of the sample, the final solution should remain clear
Roles of lipids
-cell membranes
-source of energy
-waterproofing
-insulation
-protection
Triglycerides structure
they have three fatty acids combined with glycerol
each fatty acid forms an ester bond with glycerol in a condensation reaction
hydrolyis therfore produces glycerol and three fatty acids
Saturated triglyceride
there are no double bonds between carbon atoms
they tend to be solid as the chains can lie close together
Unsaturated triglyceride- mono-unsaturated
single double bond between carbon atoms
tend to be oils- liquid due to the ‘kinks’ in the chain
unsaturated triglyceride- polyunsaturated
if more than one double bond is present between carbon atoms
oils - liquid as the chains cant lie close together due to the ‘kinks’
The structure of triglycerides relates to their properties which are:
-high ratio of energy-storing carbon-hydrogen bonds to carbon atoms so good source of energy
-low mass to energy ratio- good storage molecules- small
-large non- polar molecules, insoluble so storage doesn’t effect osmosis or water potential
-high ratio og hydrogen-oxygen atoms, sso they release water when oxidised so provide an important source of water especially for organisms livining in dry desert conditions
Phospholipids
simillar to lipids except one fatty acid molecule is replaced bay a phosphate molecule
two parts to them a head and tail
phospholipid head
hydrophillic (attracted to water but not fats)
polar part of the phospholipid
Phospholipid tail
hydrophobic (oreintates itself away from water but mixes readily with fat)
non-polar part of the phospholipid
The structure of phospholipids related to their properties
- polar molecules , hydrophillic phosphate head and a hydrophpbic tail- this creates a bi-layer acting as a hydrophobic barrier between the inside and outside of a cell
- hydrophillic head help to hold at the surface of the cell-surface membrane
Proteins
very large molecules made up of amino acids
Structure of an amino acid
basic monomer unit which combine to make a polymer called a polypeptide
polypeptides are then combined to form proteins
has a central carbon atom to which an amino group, carboxyl group (-COOH), hydrogen atom and a R group is all attached
The formation of a peptide bond
condensation reaction between monomers of amino acids.
The water removal is made by combining an -OH from the carboxyl group of one amino acid and a -H from the amino group of another amino acid