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3.1.2 Biological molecules and digestion
Carbohydrates
These are used as an energy source in aall living organisms. They are also structural
molecules, used in call membranes and cell walls e.g. cellulose and chitin. Carbohydrates
contain three elements ­ carbon, hydrogen and oxygen.

Monosaccharides
These are monomer of which larger carbohydrates…

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Some disarccharides (maltose and lactose) are reducing sugars. Sucrose is a non-reducing
sugar. It would firstly need to be hydrolised to split it into -glucose and fructose before
testing it with Benedict's reagent.

Polysaccharides
These are polymers formed when many monosaccharides join by condensation reactions.
They are insoluble in water…

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condensation reaction ­ removing one molecule of water. When 2 amino acids join they
form a dipeptide.

A dipeptide had a free amino acid group at one end and a free carboxyl group at the other ­
these can join with more amino acids to form a longer chain called…

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Disulphide bridge formation




Tertiary protein structure describes the overall 3D shape of a polypeptide chain. The shape is
stabilised by hydrogen bonds (-C=O --- H-N-), ionic bonds and disulphide bridges which form
between R groups (e.g. a disulphide bridge can form between two cystine amino acids.)
Quaternary protein structure describes…

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Enzymes are globular proteins that act as biological catalysts ­ they are not used up in the
reactions, and usually increase the rate. Enzymes control almost every chemical reaction
inside organisms (metabolism). There are 2 types of metabolic reaction:

1. Anabolic reactions ­ larger molecules are built from smaller ones…

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Q10

The change in the rate of reaction for each 10°C rise in temperature is called the
temperature coefficient or Q10.



pH

Each enzyme has an optimum pH at which it catalyses its
reaction fastest ­ the active site of the enzyme and the
complimentary substrate collide and bind most…

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enzyme-substrate complex formation. To reduce the effect of competitive inhibitors
the substrate concentration can be increased.



Non-competitive inhibitors

These bind with the enzyme away from the active site (their shape is not
complementary to the active site). Once it has bound the enzyme undergoes a shape
change (conformational change), which…

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The pancreas is a large gland found below the stomach. It produces pancreatic juice, which
contains the following enzymes:

Proteases that hydrolyses proteins into amino acids
Amylase that hydrolyses starch into maltose
Lipase which hydrolyses lipids into fatty acids and glycerol.

The duodenum is the first part of the small…

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absorbed into the bloodstream and assimilated into the body.

Carbohydrate digestion
Chemical digestion is carried out by enzymes. All digestive enzymes function by hydrolysis ­
the splitting up of molecules by adding water to the chemical bonds that hold them
together.

The enzymes amylase is produced by the salivary glands…

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