Lecture notes

Biology A level AQA - Unit 1 - Biological Molecules

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Module
Unit 1 - Biological molecules

Institution
AQA

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 ...

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Uploaded on July 2, 2024
Number of pages 17
Written in 2023/2024
Type Lecture notes
Professor(s) Sophie
Contains Biological molecules (unit 1)

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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