Biomedical Engineering Reference
In-Depth Information
inside and bared to the muscle tissue at the open end of the needle. The needle forms
the other conductor.
Indwelling electrodes are influenced by waves that actually pass by their con-
ducting surface and by waves that pass within a few millimeters of the bare conductor.
The same is true for surface electrodes.
A.6
ATP
Adenosine triphosphate is an important molecule for life of the living cells. It
provides energy for various cellular activities such as muscular contraction, move-
ment of chromosomes during cell division, movement of cytoplasm within cells,
transporting substances across cell membranes, and putting together larger molecules
from smaller ones during synthetic reactions.
Structurally, ATP consists of three phosphate groups attached to an adenosine
unit composed of adenine and five-carbon sugar ribose. ATP is the energy reserve
of the living systems. When a reaction requires energy, ATP can transfer just the
right amount because it contains two high-energy phosphate bonds. When the ter-
minal phosphate group (PO
), symbolized by
P
in the following formula, is hydro-
lyzed by addition of a water molecule, the reaction releases energy. This energy is
used by the cell to power its activities. The resulting molecule after removal of the
terminal phosphate groups is adenosine diphosphate (ADP). This reaction maybe
represented as follows:
4
3-
ATP
→+
ADP
P
E y
+
(A.1)
The energy supplied by the catabolism of ATP into ADP is constantly being
used by the cell. Since the supply of ATP at any given time is limited, a mechanism
exists to replenish it. A phosphate group is added to ADP to manufacture more ATP.
The reaction maybe represented as follows:
ADP
P
E y ATP
++
→
(A.2)
The energy required to attach phosphate groups to ADP to make ATP is provided
by breakdown of glucose in cellular respiration process, which has two phases:
Anaerobic: In the absence of oxygen, glucose is partially broken down by
the glycolysis process into pyruvic acid. Each glucose molecule that is
converted into a pyruvic acid molecule yields two molecules of ATP.
Aerobic: In the presence of oxygen, glucose is completely broken down into
carbon dioxide and water. These reactions generate heat and 36-38 ATP
molecules from each glucose molecule.
