|How do you know that the cells in your body are
This is a great question, for many reasons. In
essence, you are asking the question of "What is
life?" and then "How do we detect that life?"If we
keep our scope fairly narrow here, we can look at
some very basic principles of what it means for a
cell to be "alive." Think about this for a minute.
You can even ask yourself what it means for your
entire body to be "living."
Let's start with
a few basics.
How about "breathing?" Do cells
breathe? Not in the way you might think about your
lungs working, but they do "exchange gas" (like
Hmmm... do they "eat" (or "consume
energy")? They sure do! Your cells have metabolic
enzymes that break down proteins, fats and sugars
into energy packets that can be used to build and
regulate the cells.
Another key aspect of
being "alive" is being able to reproduce. Do cells
do that? Yep, most (but not all) of them do,
especially the ones that make up your skin, your
hair and the lining of your gut. They undergo cell
division (a process called
Finally, cells that are alive and
healthy are able to maintain their structural
integrity - they do not have rips in their outer
membranes and their nuclei and other intracellular
organelles are also membrane bound.
do we detect these things in cells? It turns out
that there are lots of ways to do so. If a cell is
not alive, it breaks down structurally and we can
detect this pretty easily under a microscope.
There are many biochemical ways to detect gas
exchange and metabolic processes. And finally, we
can detect cell division microscopically as well.
Some types of human cells can be kept alive in a
culture dish, at least for a while, if provided
with the right nutrients and conditions (as well
as proper temperature). Looking at cells in
culture (in vitro) helps us understand how they
work.Keep asking good questions!
Um, well, because if your cells weren't alive,
then YOU wouldn't be either! Cells have to be
living in order to perform functions; dead muscle
cells don't contract, dead nerve cells don't carry
information, dead red blood cells don't carry
oxygen (and you know this if you're faint, short
of breath, etc,) etc. Cells involved in digestion
may be less obvious, but generally speaking, if
your cells aren't living, then they don't
function, and pretty soon the rest of you won't be
It makes you think about what it means to be
alive, doesn't it? Some things that living things
do are to take in energy, give off wastes, trade
gasses (like oxygen and carbon dioxide) with the
environment, and reproduce.
to see these things going on because each cell is
so small. , but our bodies are made of trillions
of cells doing these things. Our blood has to
carry oxygen to each cell and carry off carbon
dioxide so that our cells can turn food into a
type of energy they can use.
piece of evidence is that some of our cells are
always reproducing. Think of all the cells you
lose every day. They get scraped off your skin
and the inside of your digestive system. They die
defending you from disease, but they are replaced
when your cells divide by reproducing. Not all of
our cells reproduce, but most do. If we were made
of non-living parts, like a car, our tiny parts
couldn't replace themselves and we'd be getting
smaller every time we lost one.
separates living things from non-living things?
Is fire alive? Thanks for asking,
There are a number of ways in which we can tell
which cells in our body are alive. The first of
which is that they undergo metabolism, which
involves the intake of raw materials into the cell
and then chemically converting these materials
using enzymes to release energy or to produce
other useful substances that allow the cell to
function. The products of these metabolic
pathways are crucial to maintain a regulated
internal environment in the cell (aka
homeostasis). Cells that are unable to maintain
homeostasis will ultimately die. These products
are also used in two other important fashions: for
cell growth, and cell reproduction. Live cells
are able grown by increasing in size, and
sometimes if they achieve sufficient size will
reproduce by dividing, producing two new cells.
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