The Amazing
hemoglobin Molecule
A Miracle of Design
BREATHING – What could be more
natural? Most of us rarely give it a thought. Breathing, however, could not
keep us alive if it were not for the human Hemoglobin molecule, a
complex molecular masterpiece is signed by our Creator.
The Hemoglobin that is inside each of
our 30 trillion red blood cells transports the Oxygen from the lung to the
tissue throughout the body. Without Hemoglobin, we would die almost instantly.
In The Oxygen-rich environment After the First oxygen molecule binds,
Hemoglobin transports the oxygen
of the Lungs, an oxygen
molecule a slight change in the shape
of Hemoglobin
molecules
away from the Lungs and then
will bind to the Hemoglobin allows three more oxygen molecules release them
where they are needed in the body
to bind rapidly
How do Hemoglobin molecules
manage to pick up tiny oxygen molecules at the right time, hold them safely
until the right time, and release them at the right time? Several amazing feats
of molecular engineering are required.
Tiny Molecular “Taxis”
You might think of each Hemoglobin
molecule in a cell as a tiny four-door taxi, with room for exactly four
“passengers.” This molecular taxi does not require a driver, since it is riding
inside a red blood cell, which could be described as a traveling container full
of these hemoglobin molecules.
The journey for a Hemoglobin molecule
begins when red blood cells arrive at the alveoli of the lungs—the “airport.”
As we inhale air into our lungs, the huge crowds of tiny recently arrived
oxygen molecules start looking for a ride in a taxi. These molecules quickly
diffuse into red blood cells, the “containers.” At this point, the doors of the Hemoglobin
taxis within each cell are closed. However, it does not take long before a
determined oxygen molecule in the bustling crowd squeezes in and takes a seat
in a Hemoglobin taxi.
Now something very interesting
happens. Inside the red cell, the Hemoglobin
molecule begins to change its shape. All four “doors” of the Hemoglobin
taxi begin to open automatically as the first
passengers get in, which allows the remaining passengers to hop aboard more
easily. This process, called cooperatively, is so efficient that in the time it
takes to draw a single breath, 95 percent of the “seats” in all the taxis
in a red blood cell are taken. Together the more than one quarter of a billion Hemoglobin
molecules in a single red blood cell can carry about a billion oxygen
molecules! Soon the red blood cell containing all these taxis is off to deliver
its precious supply of oxygen to body tissues that
need it. But, you might wonder, ‘What keeps oxygen atoms inside the cell from
getting out prematurely?’
The answer is that inside each
hemoglobin molecule, oxygen molecules attach to waiting atoms of iron. You have
probably seen what happens when oxygen and iron get together in the presence of
water. The result is usually iron oxide, rust. When iron rusts, the oxygen is
locked up permanently in a crystal. So how does the Hemoglobin molecule
manage to combine and uncombined iron and oxygen in the watery environment of
the red blood cell without producing rust?
Taking a Closer Look
To answer that question, let us
take a closer look at the Hemoglobin
molecule. It is made up of some 10,000 atoms of hydrogen, carbon, nitrogen, sulfur, and oxygen that are carefully
assembled around just 4 atoms of iron. Why do four iron atoms need so much
support?
First, the four iron atoms are
electrically charged and must be carefully controlled. Charged atoms, which are
called ions, can do a lot of damage inside cells if they get loose. So each of
the four iron ions is secured in the middle of a protective rigid plate.*
Next, the four plates are carefully fitted into the
hemoglobin molecule in such a way that oxygen molecules can get to the iron
ions but water molecules cannot get to them. Without water, rust crystals are
unable to form.
By itself the iron in the
hemoglobin molecule cannot bind and unbind oxygen. Yet, without the four
charged iron atoms, the rest of the hemoglobin molecule would be useless. Only
when these iron ions are perfectly fitted into the hemoglobin molecule can the
transport of oxygen through the bloodstream occur.
Releasing the Oxygen
As a red blood cell leaves the
arteries and moves into the tiny capillaries deep in the body tissues, the
environment around the red blood cell changes. Now the environment is warmer
than in the lungs, and there is less oxygen and more acidity from the carbon
dioxide surrounding the cell. These signals tell the Hemoglobin
molecules, or taxis, inside the cell that it is time to release their precious
passengers, oxygen.
When the oxygen molecules get out
of the Hemoglobin
molecule, it changes its shape once more. The change is just enough to “close
the doors” and leave the oxygen outside, where it is most needed. Having the
doors shut also prevents the hemoglobin from transporting any stray oxygen on
the way back to the lungs. Instead, it readily picks up carbon dioxide for the
return trip.
Soon the deoxygenated red blood cells are back in the lungs, where the
hemoglobin molecules will release the carbon dioxide and be recharged with
life-sustaining oxygen—a process that is repeated many thousands of times
during a red blood cell’s life span of about 120 days.
Clearly, Hemoglobin is
no ordinary molecule. It is, as stated at the beginning of this article, “a
giant molecule of vast complexity.” Surely, we are awed and thankful to our
Creator for the brilliant and meticulous micro engineering that makes life
possible!
TAKE GOOD CARE OF YOUR HEMOGLOBIN!
“Iron
poor blood,” an expression common in some places, is really Hemoglobin-poor
blood. Without the four essential iron atoms in a Hemoglobin molecule,
the other 10,000 atoms in the molecule are useless. So, it is important to get
enough iron by eating a healthful diet. Some good sources of iron are listed in
the accompanying chart.
Besides
consuming foods rich in iron, we should heed the following advice: 1. Get
regular and appropriate exercise. 2.
Do not smoke. 3. Avoid secondhand
smoke. Why are cigarette and other forms of tobacco smoke so dangerous?
It is because such smoke is loaded with carbon monoxide,
the same poison emitted as exhaust by automobiles. Carbon monoxide is the cause
of accidental deaths and is also a means by which some people commit suicide.
Carbon monoxide binds to iron atoms in Hemoglobin over
200 times more readily than oxygen does. So cigarette smoke quickly affects a
person adversely by crowding out his intake of oxygen.
