SC
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NEED TO KNOW
Key terms to help
you understand the
workings of cellsCELL
The ba sic unit of life —
ever y thing is made up of cells.
Human cells have genetic-
material containing a nucleus
and membrane-enclosed
organelles, all in a watery
substance called the cytosol
and surrounded by a
cell membrane.EUKARYOTIC
A t ype of cell that ha s a nucleus
and membrane-enclosed
organelles. Plant, animal and
fungal cells are eukaryotic,
as are some single-celled
organisms.ORGANELLE
A component of the cell that
has its own specialised
function, in much the same way
that an organ plays a specific
role in the body. They are often
separated from the cell by their
own membrane.PROKARYOTIC
A t ype of cell with no nucleus ,
mitochondria or other
membrane-enclosed
organelles. Most prokaryotes
are single-celled organisms,
such as bacteria.He renamed them ribosomes in 1955
and found that they produce proteins.
We now know that the membrane of
the ER joins the outer membrane of the
nucleus, providing a highway along
which DNA is translated into proteins.
Part of it, the ‘rough’ ER, has ribosomes
attached, and another, the ‘smooth’
ER, produces lipids.Waste disposal
Christian de Duve took these new
techniques further by discovering an
organelle without using a microscope- he didn’t even have one in his lab at
the time. In 1949, de Duve discovered
lysosomes – the waste disposal unit
of the cell – by accident when
researching insulin in rat liver cells.
He used cell fractionation and then
biochemical tests to determine that
the cell’s cytoplasm contains
numerous lysosomes – membranous
particles of enzymes playing a role in
cell communication and energy
metabolism, as well as breaking down
cellular components.
Researchers have discovered much
more about the cell since then. But it’s
fair to say that today’s cell biologists
are more preoccupied with how the
components work together than
finding new ones. They tease apart the
relationships between these cellular
subunits – how t hey talk to each ot her
to keep the delicate equilibrium of the
cell’s work ings in check; how t hey
behave in certain circumstances, and
how this knowledge can be exploited
to develop drugs and other treatments.
It is now possible to watch living
cells go about their business, using
t he moder n versions of va n
Leeuwenhoek’s saffron to watch
specific parts of the cell in action.
Today’s image of the cell is dynamic- a high-definition film to the 17th
century’s hand-drawn sketch.
by K A T H E R I N E N I G H T I N G A L E
(@kathnightingale) Katherine is a science writer
with a masters in molecular biology.THE COMPOSITION OF HUMAN CELLSA cross-section of a human cell taken with an electron microscope reveals the nucleus (large oval centre)
surrounded by cytoplasm. This is filled with the endoplasmic reticulum – seen as a red/orange network