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Unit 2 - Enzymes and the digestive
system
Enzymes and digestion - 2.1

The human digestive system is made up of a long muscular tube and it associated
glands. These glands secret enzymes in order to break down large molecules into
smaller ones, this allow them to absorbed.
The digestive…

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The large intestine - Absorbs water, most of which has come from the secretion in
the digestive glands. The food in the large intestine therefore becomes drier and
thicker in consistency in order to form faeces.
The rectum - The final section of the intestines. The faeces are stored here,…

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Carbohydrates - monosaccharides - 2.2
Some carbohydrate molecules are large whilst others are small.

Carbon atoms readily form bonds with other carbon atoms; this allows a sequence of
carbon atoms of various lengths to build up, which form a backbone along which
other atoms can attach to.

Carbon containing molecules…

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Carbohydrates - disaccharides and polysaccharides - 2.3

Disaccharides
Glucose + Glucose = Maltose
Glucose + Fructose = Sucrose
Glucose + Galactose = Lactose

When monosaccharides join a molecule of water is lost, therefore the reaction is
called a condensation reaction. The bond that is formed is called a glycosidic
bond.…

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4. Add another 2cm3 of the food sample to 2cm3 of dilute hydrochloric acid in a
test tube and place the test tube in gently boiling water bath for 5 minutes.
The dilute hydrochloric acids will hydrolyse any disaccharide present and break
it into its monosaccharides.
5. Slowly add hydrocarbonate…

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3. Saliva contains salivary amylase. This begins to hydrolyse any starch
in the food into maltose. It also contains mineral salts in order to
maintain a neutral pH. This is the optimal pH for amylase to work in.
4. Once the food is swallowed it enters the stomach with has…

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o They have to be fed special non-milk food rich in calcium and
vitamin D



Proteins - 2.5

Proteins are large molecules.
Each organism has numerous proteins that differ from species to species.
The shape of one type of protein differs from all over proteins.
Proteins are the most important…

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Protein structure cont.
Primary
Through condensation reactions many amino acid monomers can
join together in a process called polymerization
The new long chain is called a polypeptide
The sequence of the amino acids determines the primary structure
of any protein
Almost a limitless number of combinations
A proteins shape is…

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Enzymes are biological catalysts. They alter the rate of reactions without
going under permanent changes themselves. They do not make reactions
happen but speed them up.

Enzymes and lowering activation energy
For some reactions to take place naturally a number of conditions must be
satisfied:
1. There must be sufficient…

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For an enzyme to work it must come into physical contact with its substrate
and have an active site that fits the substrate.

Measuring enzyme-catalysed reactions
The two most frequently measured events are:
1. The formation of the products of the reactants
2. The disappearance of the substrate


Effect of…

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