Everything Life Sciences Grade 10

FACT

WATCH:View a
video
demonstration of
the experiment to
test for proteins:
See video:
SHORTCODEat
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Figure 2.18: Biuret test: this is the expected colour change if protein is present

Observations:

Record your observations, noting any key differences between the positive control, negative

control and experimental samples

Enzymes

Enzymes are protein molecules that help chemical reactions in living organisms to take place.

The term enzyme has a specific meaning:an enzyme is a biological catalyst that speeds up

the rate of a chemical reaction without being used up in the chemical reaction itself. Let

us analyse this definition in greater detail.

Biological: Enzymes are protein molecules which are made of long chains of amino acids.

These fold into unique three-dimensional structures with a region known as anactive site

where reactions take place.

Catalyst: Enzymes speed up chemical reactions without being used up in the reaction them-

selves. All chemical reactions require a certain minimum amount of energy to take place.

This energy is known as thefree energy of activation. Enzymes lower the energy of activa-

tion thus speeding up chemical reactions (Figure 2.19).

42 2.4. Organic compounds