Unit 1 biology notes with diagrams to label and past paper questions!

These are my notes i typed up for unit 1.

I have combined it into a biology revison booklet.

Pictures and diagrams to label are included.

There are some past paper question included at the end of the booklet from AQA's website.

Hope you enjoy feedback will be appreciated!!

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Causes of disease
A microorganism is a single-celled organism that can't be seen
without a microscope.
They include bacteria and viruses and can sometimes be
Some organisms cause disease and these are called pathogens.
Disease is a malfunction of the body or mind which affects good
A pathogen must gain entry to the host, colonise the tissues,
resist defences and cause damage to the host tissues.
Pathogens include bacteria, viruses and fungi.
Transmission - The transferring of pathogens from one individual
to another.…read more

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Enzymes and the digestive system
Many of the molecules in our food are polymers.
These are large complex molecules composed of chains of
Proteins and some carbohydrates are polymers. In carbohydrates
monomers are monosaccharides (contain carbon, hydrogen and
oxygen.) In proteins monomers are amino acids they contain
carbon, hydrogen, oxygen and nitrogen.
Polymers are insoluble in our food the cant be absorbed and
The polymers have to be hydrolysed into smaller, soluble
molecules this happens during digestion. Hydrolysis is catalysed
by digestive enzymes.…read more

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Physical Breakdown- Large food is broken down into smaller
pieces by teeth to give a large surface area.
Chemical Digestion - Breaks large insoluble molecules to smaller
soluble ones. It is carried out by enzymes.
Carbon atoms readily form bonds with other carbon atoms.
Organic molecules are made up of a chain of individual molecules.
Each individual molecule is called a monomer and longer chains of
repeating monomer units are called polymers.…read more

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The formation of a glycosidic bond by removal of water
Carbohydrates- disaccharides and
2cm3 of food tested to 2cm3 of Benedict's reagent.
Boil the test tube for 5 minutes.
No change in colour means no reducing sugar.
2cm3 of food 2cm3 of dilute hydrochloric acid and place in water
bath for 5 minutes.
Slowly add sodium hydrogen carbonate to neutralise the acid.
Test with PH paper to test solution is alkaline.
Re-test the resulting solution by heating with 2cm3 of B.R.…read more

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Carbohydrate Digestion
Enzymes are specific so it takes more than one to completely
breakdown a large molecule.
Starch Digestion
Firstly amylase is produced in the mouth and the pancreas. The
amylase hydrolyses the glycosidic bonds of the starch to produce
maltose. The maltose is then hydrolysed into a-glucose by
The process in humans
Food is taken into the mouth and chewed. This gives a large
surface area.
Saliva mixes with the food during chewing.
Amylase in saliva hydrolyses starch into maltose.…read more

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Lactose Intolerance
You are lactose intolerant if you don't make enough of the enzyme
Lactase hydrolyses Lactose into its monosaccharide's - glucose
and galactose
Undigested lactose is fermented by bacteria in the large intestine
and can go onto cause intestinal complaints such as...
- Stomach cramps
- Excessive flatulence due to large volume of gas
- Diarrhoea
Proteins are very large molecules.
Amino acids are the basic monomer units that combine to make a
polypeptide. Polypeptides can combine to form proteins.…read more

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Hydrogen bonds are formed between amino acids. This causes the
long polypeptide chain to be twisted into a 3-D shape known as
Tertiary Structure
The a-helices are twisted and folded even more to form the
tertiary structure. This is maintained by a number of bonds:
Disulfide bonds: Fairly strong and not easily broken down
Ionic bonds: Formed between any carboxyl and amino groups
that are not involved in forming peptide bonds. Weaker than
disulfide bonds and are easily broken by changes in PH.…read more

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Induced fit model
Newer model, as substrate binds the active site changes shape
slightly to complete the fit. This is more particular as the substrate
has to fit the enzymes the right way and it has to make the active
site change shape in the right way.
It is a better explanation because:
It explains how other molecules can affect enzyme activity.
It explains how the activation energy is lowered.…read more

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The pH of a solution is a measure of its hydrogen ion
A change in pH alters the charges on the amino acids that make up
the active site. This means the substrate can no longer become
attached to the active site and an enzyme-substrate complex
can't be formed.
A change in pH can break the bonds in the enzyme's tertiary
structure. The enzyme therefore changes shape so the substrate
may no longer fit. The enzyme has been denatured.…read more


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