Glucose and Everything You Need to Know About It
With the chemical formula C6H12O6, glucose is one of the most common molecules
essential in organic chemistry. It is also known as D-glucose, dextrose, grape sugar, and various
other names that signifies its important in everyday life. Andreas Sigismund Marggraf, a German
chemist from Berlin and pioneer of analytical chemistry, was the first to extract glucose out of
beets by using a method involving alcohol. The experiment was taken a step further by his
student, Franz Achard, who purified the chemical down to its molecular form. The discovery of
glucose had led te way to much advancement in the field of organic chemistry because of the
importance of glucose in many organisms. Seemingly a simple molecule, it ironically has much
significance not only to humans, but also in other animals, plants, and everyday life.
Glucose can be found in the form of a white powder, therefore it is always color in as a
liquid form. It is very soluble in water, acetic acid, and several over solvents. It can also be
crystallized from these solvents and form three major structures: alpha-glucopyranose, betaglucopyranose, and beta-glucopyranose hydrate. Glucose is essential in many life processes, not
just only in the human body but in other living creatures, including plants. It is also present in
various chemical mechanisms, such as glycolysis, gluconeogenesis, and diabetes.
In plants, glucose is stored as starch, which is a repeating unit of sugar. Starch is the
major component in the cell walls of photosynthetic cells, providing its structure. Plants use
glucose as an energy source, although it is used primary during periods of darkness.
Photosynthetic organisms still require energy when it cannot perform photosynthesis. They
acquire it through aerobic respiration using oxygen and glucose and breaking it down to water
and carbon dioxide.
A key biological process that requires glucose is glycolysis. Glycolysis is the breakdown
of glucose into pyruvate with a net production of 2 ATP and the reduction of 2 NAD+ to NADH.
The entire process is energetically downhill and mediated by 10 enzymes. Variable
concentrations of AMP and ADP control glycolysis by phosphorylation and dephosphorylation
of phosphofructokinase.
Another key process that requires glucose is gluconeogenesis. The main site of
gluconeogenesis is the liver in animals. Under certain conditions, it occurs in the small intestine
and the kidney to a more limited extent. This process forms glucose from fats and proteins,
substances other than carbohydrates. Gluconeogenesis is described by the following reaction: 2
pyruvate + 2 NADH + 4 ATP + 2 GTP à Glucose + 2 NAD+ + 4 ADP + 2 GDP + 6 Pi. The
mechanism for which it happens is spontaneous and is illustrated in the diagram below.
During fasting or starvation of carbohydrate, glucose can still be obtained. The source of
oxaloacetate or pyruvate for gluconeogenesis is obtained from amino acid catabolism. Protein
obtained from muscle may have to be broken down to supply the body with amino acids. They
are transferred to the liver and deaminated to convert to gluconeogenesis inputs. Fat cells also
contribute to gluconeogenesis inputs. They provide triacylglycerol, which is hydrolyzed to
glycerol. When the blood glucose level is low, the hormone glucagon triggers liver cells to
activates the effects of cyclic AMP cascade. Protein Kinase A or cAMP-Dependent Protein
Kinase stimulates gluconeogenesis by phosphorylating regulatory proteins and enzymes in the
liver. To prevent gluconeogenesis and the production of glucose when there is already a high
concentration of glucose, fructose-1,6-bisphosphatase is inhibited by AMP. When there is a high
concentration of AMP and a low concentration of ATP, glucose will not be synthesized because
the cell would have to expend energy.
Another disease that glucose largely impacts is diabetes. Diabetes affects nearly 25.8
million children and adults in the United States. If left untreated, it can result in blindness,
multiple cardiovascular diseases, high blood pressure, and in serious cases, amputation of limbs.
People with this deadly disease must perform regular checks on their glucose level in their blood.
The most inexpensive and widely used way of monitoring glucose level is to poke their fingers
to draw the blood needed for the test.
Officially known as diabetes mellitus, this is a disease that is caused by a decreased
response to insulin in its target tissues or a deficiency of insulin. Diabetes mellitus is one of the
best-known endocrine disorders, which is marked by elevated levels of blood glucose. There
are two types of diabetes, type 1 diabetes mellitus and type 2 diabetes mellitus. Type 1 diabetes
mellitus is insulin-dependent. This is an autoimmune disorder that occurs when the immune
system destroys the beta cells in the pancreas. Type 2 diabetes mellitus is more common. This
type is non-insulin-dependent. This occurs when there is a deficiency in insulin or there is a
reduced response to the target cells because the insulin receptors have been changed or modified,
which will not recognize insulin at its receptors.
As an energy storage, glucose is stored in the body in the form of glycogen and broken
down when the body needs it. When glucose levels are low in the blood, the pancreas responds
by producing the hormone, glucagon from alpha cells. Glucagon acts as a ligand and binds to the
glucagon receptors on liver cells. Cyclic adenosine monophosphate acts as a messenger to
promote glycogen degradation into glucose, which brings the blood glucose level back to
homeostasis. When glucose levels are high in the blood, the pancreas responds by producing the
hormone, insulin produced by beta cells of the pancreas. Insulin acts as a ligand and binds to the
insulin receptors located on both muscle and liver cells. As glucose molecules enter both liver
and muscle cells via glucose transporter proteins, glucose is taken up as glycogen. Glycogen
degradation is also promoted when the hormone, epinephrine, binds to alpha-adrenergic
receptors on liver cells, which leads to increased cytosolic calcium ions. These events also bring
the body back to homeostasis.
Works Cited
Google Blog. Introducing Our Smart Contact Lens Project. 2014.
http://googleblog.blogspot.com/2014/01/introducing-our-smart-contact-lens.html
Joyce J. Diwan. Gluconeogenesis; Regulation of Glycolysis and Gluconeogenesis. Molecular
Biochemistry I. 2007.
https://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/part2/gluconeo.htm#intro
Michael McDarby. Online Introduction to the Biology of Animals and Plants. The Basic Needs
for Photosynthesis. 2014. http://faculty.fmcc.suny.edu/mcdarby/Animals&PlantsBook/Plants/01Photosynthesis.htm
TechCrunch. Google Unveils Smart Contact Lens That Lets Diabetics Measure Their Glucose
Levels. 2014. http://techcrunch.com/2014/01/16/google-shows-off-smart-contact-lens-that-letsdiabetics-measure-their-glucose-levels/
Voet, Donald, Judith G. Voet, and Charlotte W. Pratt. Fundamentals of Biochemistry: Life at the
Molecular Level. Hoboken, NJ: Wiley, 2013. Print.