Revision notes for all of unit 1 a level biology (AQA) - Biological Molecules, including: Carbohydrates, proteins, enzymes, lipids, biochemical tests, DNA and RNA, DNA replication, and ATP and inorganic molecules. I’ve made and added to these notes over the two years of college and have finished ...
Unit 1 – Biological Molecules
Carbohydrates
monomers - small, single units that act as the building blocks to
create larger molecules
polymers - made up of many monomers, usually in the thousands,
chemically bonded together
condensation reaction - forms monomers together by removing a
water molecule
hydrolysis - the use of a water molecule to break a bond between
monomers
monosaccharides - glucose, galactose, fructose - they are sugars
that are soluble in water. they are either used to provide energy or
create larger molecules - they contain carbon, hydrogen and
oxygen
glucose C6H12O6
has two isomers (same formula but atoms are arranged differently)
these are the two types of glucose isomers: alpha glucose and beta
glucose:
dissarcharides - made of two monosaccharides bonded together
with a glycosidic bond
this shows the condensation reaction between two monosaccharides
to create a disaccharide:
,a water molecule is being removed from the hydroxyl group of
carbon 1 and carbon 4 on the two monosaccharides.
disaccharides can be broken back down into monosaccharides by a
hydrolysis reaction by adding a water molecule:
polysaccharides
polymers made of many monosaccharides via condensation
reactions
the three key polysaccharides are:
starch
cellulose
glycogen
Starch
starch is found in plants, not animal cells, and is a store of
carbohydrates
it is made from extra glucose from photosynthesis reactions for
storage
structure of starch
, starch is made of alpha glucose joined by condensation
reactions to form 1-4 and 1-6 glycosidic bonds.
it is made up of amylose and amylopectin
amylose - glucose joined by only 1-4 glycosidic bonds to give a
spiral shaped polymer
amylopectin - glucose joined by 1-4 and 1-6 glycosidic bonds
which create branches
properties of starch
insoluble (due to the fact its large) - this means it can be
stored within cells and not dissolve; not changing the water
potential of the cell so won’t cause osmosis
as amylose is spiral shaped, it can be readily compacted
as amylopectin is branched, it provides a larger surface area
for enzymes to attach to - this means it can be readily
hydrolysed back to glucose when it is needed for respiration.
glycogen
main store of carbohydrates in animal cells, mainly in liver and
muscle cells due to these having the biggest need for access
to glucose to respire and release energy.
it is made of the excess glucose that has been eaten and
absorbed into the bloodstream
glucose is used in respiration but if more is eaten that the cells
need it is converted to glycogen for storage
structure of glycogen
made of alpha glucose and is quite similar to amylopectin in
starch held together by condensation reactions forming 1-4
and 1-6 glycosidic bonds.
however glycogen contains more 1-6 glycosidic bonds so is
more branched in structure
properties of glycogen
insoluble so it can be stored in cells and not dissolve, therefore
does not change the water potential of the cell causing
osmosis to occur
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