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Biology Revision ­ Biochemistry OCR

Biochemistry and metabolism
Page 88

Learning objectives
1. State the functions of biological molecules in organisms.
2. Define metabolism.

You are what you eat

The nutrients any organisms takes in build and maintain a healthy body because they
become part of our body and…

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Biology Revision ­ Biochemistry OCR

Water Takes part in many reactions, support in
plants, solvent/medium for most metabolic
reactions, transport.

Biological molecules

The chemical elements found in the biological molecules are carbon, hydrogen, oxygen and
nitrogen these elements make up over 99% of all organisms.

Some biological molecules also contain…

Page 3

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Biology Revision ­ Biochemistry OCR

Metabolism refers to the sum total of all the chemical reactions that take place in an
organism. These reactions include the breaking of larger molecules. These metabolic
reactions are known as catabolic reactions and example is digestion.

Anabolic reactions are when smaller molecules are built…

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Biology Revision ­ Biochemistry OCR

In some cases carbon forms two bonds with another atom, C = C (hydrocarbon chain)
C = O is a double bond found in many molecules, including organic acids.

Monomers and polymers

The term monomer refers to a single, small molecule, many of which can…

Page 5

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Biology Revision ­ Biochemistry OCR

Hydrogen bonds

Polymers often have specific functions that rely on their shape. Hydrogen bonds form when
a slightly negative charged part of a molecule comes close to a slightly positive charged
hydrogen atom in the same (or another) molecule.

Hydrogen bonds are not strong bonds…

Page 6

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Biology Revision ­ Biochemistry OCR

Carbohydrates contain the elements carbon, hydrogen and oxygen, they are found in the
form Cn(H2O)n. This means that for every carbon present in a carbohydrate, the equivalent
of a water molecule is also present.

Simple sugars

The simplest carbohydrates area called monosaccharides. These are the…

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Biology Revision ­ Biochemistry OCR

Joining monosaccharides and splitting disaccharides

Two monosaccharides molecules can be joined together in a condensation reaction forming
disaccharide molecule. A glycosidic bond is formed and a water molecule is released. The
reverse hydrolysis reaction uses a water molecule to break the glycosidic bond.

Condensation reaction…

Page 8

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Biology Revision ­ Biochemistry OCR

Animal and plant enzymes are unable to break down beta glucose due to the shape of the
molecule and the position of the hydroxide ion on carbon1 , this therefore means that the
enzymes shape fit the alpha glucose making it able to be respired.…

Page 9

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Biology Revision ­ Biochemistry OCR

The glycogen can form glycogen granules in animal cells (especially liver and muscle cells).

Features of the energystorage molecules starch and glycogen

The starch and glycogen are termed as energystorage molecules because they are made
by bonding many thousands of alpha glucose molecules together.


Page 10

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Biology Revision ­ Biochemistry OCR

Figure 1

These straight line chains can contain 10'000 beta glucose molecules. They are stronger
than the chains found in amylase. The beta glucose polymer chains are called cellulose


Cellulose fibres are arranged in a very specific way to form plant cell walls.…


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