Essay
The Importance of Shapes Fitting Together in Cells and Organisms
- Module
- Unit 2 - Cells
- Institution
- AQA
The Importance of Shapes Fitting Together in Cells and Organisms full essay. Word count 1005, mark = 14/25
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The Importance of Shapes Fitting Together in Cells and OrganismsIn cells and organisms, there are many different molecules that require shapes fitting together in
order for them to properly carry out their function. Some examples of this are enzymes,
digestion, antigens and antibodies, DNA replication, and regulation of transcription. It is
necessary for all of these to occur properly in order for organisms to survive.
Shapes fitting together is incredibly important for enzymes. These work using the induced fit
model, in which the substrate binds to the active site of an enzyme, which changes shape
slightly as this occurs. This requires the active site of the enzyme and the substrate molecule to
be complementary in shape to each other. Furthermore, enzymes are specific to the reaction
that they catalyse. This means that only certain substrates have a complementary shape to an
enzyme, and will only bind to that specific enzyme. However, this can be prevented by
inhibitors. Non-competitive inhibitors bind to the allosteric site of an enzyme, and change its
shape. This means that the substrate cannot bind to the active site, and no enzyme-substrate
complex can be formed. This can be detrimental towards organisms, as it prevents reactions
and processes taking place. Enzymes are used in many essential processes in organisms that
would die without them - for example, respiration. If the enzymes involved in respiration could
no longer bind to substrates as the shape had completely changed, the organism would be
unable to respire and so would die. They are also important in plants, as they are used in
photosynthesis. If this process could not occur, the plant would die as it would no longer be able
to produce glucose. Therefore, shapes fitting together is very important in enzyme activity, as if
they did not fit, certain processes would not take place, and organisms would die.
Shapes fitting together is also very important in digestion. Enzymes catalyse the
breakdown of food in places such as the stomach and intestines. An example of this
is maltase, an enzyme which catalyses the breakdown of starch, to ⍺-glucose, which
can then be converted to glycogen and stored, used to maintain energy levels, or
used in respiration. Without this breakdown of maltose by maltase, important
processes such as respiration could not occur. As digestion uses enzymes, shapes
fitting together are important. This can also be shown in the enzyme lactase. This
enzyme hydrolyses the single glycosidic bond in lactose molecules to form glucose
and galactose. However, a mutation of the lactase enzyme can cause the active site
to change shape. This means it cannot function as it is supposed to, and leads to
the person being lactose intolerant. This means they cannot digest lactose, and feel
ill when they eat foods containing lactose. This shows that shapes fitting together is
important in organisms, because if they don’t they can result in issues such as
digestive problems.
Another example of the importance of shapes fitting together is antigens and antibodies. An
antigen is a non-self molecule that triggers an immune response, and is usually in the form of a
pathogen. An antibody is a protein produced by lymphocytes in response to the presence of an
antigen. They have binding sites specific to a certain antigen, and bind to them when they are
found in the body. They are produced by B lymphocytes in humoral immunity, and are
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