BIOL 2020 Lecture 2: Biological Macromolecules
Biological Macromolecules
o Life would not be possible without these four macromolecules
o They are huge long chains of molecules, however lipids are typically smaller
o They can form polymers - long chains of repeating structures called monomers
o Building block of all macromolecules
o Why aren't we made of silicon instead of carbon?
o Because the structure to be unstable
o Electrons, being negatively charged
o When the electrons are closer to the positively charged nucleus
o Oligosaccharides - up to ten (ish) monosaccharides
o They tend to have variability so they're not just the same monosaccharide
repeated over and over again
o Monosaccharides are connected to each other to make larger molecules by glycosidic
bonds
o It's basic building block is (CH2O)n
o Has an alpha bond
o We either have an alpha or beta bond and alpha goes under the ring while beta
goes from under and then over the surface of the ring
o Typically of repeated monosaccharides or disaccharides
o We are able to digest starch and glycogen but not cellulose because cellulose has
a beta bond and we cannot digest it
o We store glycogen
o Also known as triglycerides - they have three fatty acids and a linker molecule called
glycerol
o Triacylglycerol is also another name for a fat
o Measured in mJ/kg
o Monomer of fat and also a component of lipids is the fatty acid
o The long chains are water insoluble
o COH - a carboxyl group is water soluble and fat insoluble, the acid portion
o The molecule with the kinks that represent double bonds is liquid at room temperature
o Carbons can make double bonds with each other, making it unsaturated with
hydrogen
o These are polyunsaturated fats
o Two fats with double bonds, however the first one has a kink in it
o The trans fatty acid also has a double bond, however it is on the opposite side of the
cis-fatty acid so it doesn't have a kink in it
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o It has a similar affect in its physical properties as saturated fats, but physiologically in
our body, trans fatty acids are unhealthy
o They are unhealthy for us, they are made by bubbling up hydrogen and the fat
becomes solid
o There's a lot less of the "good" cholesterol in trans fat - so higher chance of
cardio problems
o Not all unsaturated fats are good
o Fats (triglcerides)
o 3 fatty acids attached to a glycerol moiety via ester bonds
o Fatty acids are amphipathic, but fats are not
o Amphipathic means they have both a hydrophilic area and a hydrophobic
area
o Properties of fats are determined by their fatty acids
o Carbon in the middle is called an alpha carbon
o The R group is the only thing that changes within these amino acids, they all have an
amino group, an alpha carbon and a carboxyl group
o R groups determine the chirality of amino acids
o Amino acids always have the L stereoisomer in proteins
o The D stereoisomer is possible but only as free floating amino acids
o Polar charged - the charged side of the chain is the carboxyl group
o The structural pH is between 7.2 and
o Hydrophilic side chain is important in chemical reactions by forming ionic bonds
o These are polar uncharged molecules that also participate in chemical reactions but
they make hydrogen bonds rather than ionic bonds
o They are also hydrophilic so they can associate with water
o Non polar charged amino acids are hydrophobic
o Their side chains are hydrocarbons which are made out of entirely carbon and
hydrogen
o They are important in the folding process of proteins
o Glycine is only hydrogen, doesn’t have an R group at all
o Cysteine has sulphur in it, if you have two cysteine's they can be bonded together with
a disulphide link
o Proline has a cyclic conformation between an alpha carbon
o Alpha carbon is the only carbon that is not a part of a bond between the amino
acid
o It produces kinks in the protein
o Peptide bonds are how proteins are made, where amino acids come together by
covalent bonds that are produced by a condensation reaction
o Alpha carbons are never apart of a peptide bond
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