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Summary AQA A Level Biology - Cornell Style Notes - Unit 1 - Biological Molecules £4.96
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Summary AQA A Level Biology - Cornell Style Notes - Unit 1 - Biological Molecules

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Clear and concise Cornell styled notes for Unit 1 Biology A Level - Biological Molecules. The notes include diagrams and colours to make revision more visually appealing. The whole course is covered by my notes and is written in a detailed way that is still easily understandable, and each page incl...

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  • June 15, 2024
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  • 2023/2024
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Monosaccharides and Disaccharides Eve Holland

Key Points: Notes:
Monosaccharides, also called simple sugars, are the simplest forms
Mono = 1
of sugar. They cannot be hydrolysed to give a simpler sugar. The
prefix mono means one.
3 types of monosaccharides that
need to be learnt: There are 3 main monosaccharides you have to learn for A-Level
Glucose, Galactose, Fructose biology, these are: Glucose, fructose and galactose

There are 2 isomers of glucose, For A-Level biology you must be able to draw the structure of the 2
alpha and beta glucose in which isomers of glucose: alpha and beta glucose.
the hydroxyl group and the
hydrogen flip which are connected
to carbon 1.
Glucose - C6H12O6
Di = 2
A rule for labelling which carbon is which, is counting clockwise
3 types of disaccharides that need from the oxygen
to be learnt:
Glucose + glucose > maltose A disaccharide is the sugar formed when two monosaccharides are
Glucose + fructose > sucrose joined.
Glucose + galactose > lactose
There are 3 types of disaccharides you must learn:
The formation of a disaccharide is Glucose + glucose > maltose
uses a condensation reaction and Glucose + fructose > sucrose
the monosaccharides join with a Glucose + galactose > lactose
1.4 glycosidic bond
The reaction in which monosaccharides become disaccharides is
called a condensation reaction, however this reaction is reversible
so can happen backwards using a hydrolysis reaction (using H2O to
break bonds)

When the condensation reaction occurs a water molecule is
released and then the 1 oxygen left joins to carbon 1 and 4.

The bond that connects the monosaccharides to form a
disaccharide is called a 1,4 glycosidic bond


Summary:
Monosaccharides are the simplest sugars. Examples of them are glucose, fructose and galactose.

A disaccharide is formed when 2 monosaccharides join using a 1,4 glycosidic bond, within a condensation
reaction in which a water molecule is released. This reaction is reversible and in the opposite direction, this
reaction is called a hydrolysis reaction

There are 3 types of disaccharides you must learn:
Glucose + glucose > maltose Glucose + fructose > sucrose Glucose + galactose > lactose

, Starch AND GLYCOGEN Eve Holland

Key Points: Notes:
Starch is a polysaccharide used for Starch and Glycogen are examples of polysaccharides -
the storage of glucose, for energy, polysaccharides are polymers formed by many
in plants. monosaccharides joined by glycosidic bonds in a condensation
reaction (removal of a water molecule) to form chains
Starch has a spiral structure for
compact storage and many Starch:
branches so it is easier to hydrolyse - Spiral in shape so it is compact for storage
when the plant needs energy - large and insoluble, so no osmotic effect
- large long molecules so it does not leave the cell
Starch is large and insoluble so it - made up on many glucose molecules
does not leave the cell and no - 1’4 and 1,6 glycosidic bonds
osmotic effect - the spiral chain is branched so it is easier to hydrolyse glucose
as starch is a store of glucose for energy; easier energy release.
The main spiral in joined with 1,4 - only alpha glucose molecules
glycosidic bonds (amylose); the - All glucose molecules are the same way up
branches are joined using 1,6 - 20-30% amylose and 70-80% amylopectin (amylose is a
glycosidic bonds (amylopectin). straight chain polymer whereas amylopectin is a branched
chain polymer)
Made up of ONLY alpha glucose - used in PLANT storage
which are all the same way up


Glycogen:
Glycogen is a polysaccharide used - Made from alpha glucose molecules
for the storage of glucose, for - made with 1,4 and 1,6 glycosidic bonds
energy in animals and fungi - HIGHLY branched so it is more easily hydrolysed for higher
rates of respiration (more terminal glucose molecules)
HIGHLY BRANCHED for more easy - Storage of glucose for energy in animals and fungi.
hydrolysis due to higher respiration
rates

Made up of ONLY alpha glucose
which are all the same way up


Summary:
Starch is a polysaccharide used as a storage of glucose thus energy in plants
It has a spiral structure which is also branched - compact and more ends to hydrolyse for energy
It consists of only alpha glucose which are bonded with 1,4 and 1,6 glycosidic bonds

Glycogen is quite similar although it used for glucose, thus energy, storage in animals and fungi.
It is MORE HIGHLY BRANCHED due to high rates of respiration in these organisms

, Cellulose Eve Holland

Key Points: Notes:
Cellulose is a polysaccharide - polysaccharides are polymers
Cellulose is a polysaccharide used formed by many monosaccharides joined by glycosidic bonds
for structural support in cell walls. in a condensation (removal of a water molecule) reaction to
form chains
Cellulose is made from the
condensation reactions between Cellulose:
BETA glucose which is joined with - made from beta glucose
ONLY 1,4 glycosidic bonds as there - only 1,4 glycosidic bonds - no branching so no 1,6 bonds
is no branching - alternate molecules flip so the hydroxyl groups of the beta
glucose match up to ensure the polysaccharide forms a
In cellulose, alternate molecules of straight line
beta glucose flip so that the - forms long straight chains
hydroxyl groups match up, thus a - hydrogen bonds link chains that lie side by side to form
straight strands and not diagonal (micro) fibrils
strands are formed - Cellulose fibres are strong (bonds hard to break) thus making
cell walls strong, this means it can resist turgor pressure /
Cellulose forms long strands in osmotic pressure / pulling forces
which neighbouring strands form - resists digestion/ action of microorganisms / enzymes
hydrogen bonds to crosslink the - unlike starch, cellulose is very strong and prevents cells from
strands. These are called bursting when they take in excess water.
microfibrils - Cellulose fibres are freely permeable which allows water and
solutes to leave or reach the cell surface membrane
Cellulose is very strong - resists
turgor pressure and actions of
microorganisms and enzymes




Summary:
Cellulose function is the structural integrity of cell walls, it is very strong.

It is made of beta glucose and is bonded with 1,4 glycosidic bonds only in condensation reactions

Unlike starch and glycogen, cellulose is not branched and instead forms crosslinks between the straight strands to
form (micro) fibrils

In cellulose every second beta glucose molecule flips so the hydroxyl groups are next to each other

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