S
Today we are
looking at how
Carbon and
Nitrogen cycle
through our
ecosystem.
But why do we
need carbon and
nitrogen anyway?
Carbon is the smallest element
that can readily form four
covalent chemical bonds
simultaneously.
Carbon atoms are the
structural backbones of
most biomolecules.
Molecules that contain
carbon are generally
called organic molecules.
S
Nitrogen atoms are similar in size to
carbon atoms and can form three
covalent bonds simultaneously.
Nitrogen is important to living
systems as it is an essential
component of DNA and
amino acids, the building blocks
of proteins.
Get a copy
of the
Stemscopes
textbook and
turn to the
Carbon and
Nitrogen
Cycles on
page 183.
Research the Carbon
and Nitrogen Cycles
and draw a diagram
of each in your
biology notebook
Photosynthesis and cellular respiration cycle
carbon, moving it through the ecosystem.
Carbohydrates are
produced during
photosynthesis; carbon
from the atmosphere is
incorporated with
inorganic matter to
create organic
compounds.
Carbon is released by
cellular respiration
back into the
atmosphere as carbon
dioxide. The carbon
cycle links the
atmosphere and
biosphere.
The carbon cycle can be disrupted
in various ways. Removing
fallen leaves and other
material from an area
and
burying them in a
landfill prevents the
carbon compounds from
being broken down as compost
and recycled, resulting in lower
carbon dioxide levels.
Burning fossil fuels
increases the amount of
carbon dioxide in the
atmosphere.
Nitrogen exists in
different forms,
and only a small
portion of it is
available for
plants to absorb
(in the form of
ammonium or nitratecontaining compounds.)
The nitrogen cycle is important
because nitrogen is a key
component of DNA as well as
amino acids, which make
up the proteins
Nitrogen enters
the ecosystem
through the
decomposition of
organic material,
or through
nitrogen fixation
via symbiotic
relationships
between bacteria
and plants.
Bacteria form a
mutualistic
relationship with
legumes (plants) and
convert nitrogen to
ammonia or nitrates
they can use.
Nitrogen fixation is
the process by which
bacteria combine
atmospheric nitrogen (N2) with
hydrogen to produce ammonia
(NH3+), which they then further
convert into ammonium (NH4+) or
nitrate (NO3-) for use in organic
synthesis.
Some nitrogen-fixing bacteria
are free-living and others
form symbiotic relationships
with plants. One such
mutualistic symbiotic
relationship involves bacteria
that live in nodules within the
root tissues of certain plants
and fix nitrogen from the
atmosphere, while the plants obtain
fixed nitrogen from the bacteria
and provide carbohydrates in return.
Over millions of years, the remains of ancient
organisms gradually turn into fossil fuels. What is
a by product given of when humans burn fossil
fuels?
Nitrogen (N) is a necessary component of amino
acids and nucleic acids. How do animals obtain
useable nitrogen in the nitrogen cycle?
From the food they eat.