Glucose - How We Use It

I had to think about how I would explain to someone how glucose is used in our bodies. It's actually not as complex as one would think, and I will make an attempt to explain it in terms that someone who hasn't studied Biochemistry might understand.

We ingest glucose. It is the basic unit of potential energy that our bodies use. It can be in the form of a plate of pasta, a peanut butter and jelly sandwich, or a bowl of pork fried rice. For that matter, most of the foods we consume contain glucose in some quantity. When we eat that food product that contains glucose, a number of things happen. First, there is an enzyme in our saliva - salivary amylase - which initiates the breakdown of glucose for further processing.

Once the glucose is broken down, it is absorbed into the bloodstream, causing the blood glucose level to rise and triggering the secretion of insulin from the pancreas. Cells that need glucose have specific receptors attached to them - insulin receptors - which encourages the glucose to enter and be used.

Inside the cells, ATP - adenosine triphosphate - is used within the cell to store and release energy. There are two ways which this is accomplished: either anaerobic metabolism (without oxygen), or aerobic metabolism (with oxygen). Anaerobic metabolism is inefficient and produces small amounts of energy as compared to aerobic metabolism, which produces considerably larger amounts of energy. It is oxygen used by aerobic metabolism that makes the difference in energy produced. This is accomplished through a cycle of processes known as the Citric Acid Cycle, where through a series of  chemical reactions involving products, chemicals known as substrates, and enzymes which transform a given substrate in the cycle to another substrate. Ultimately, the cycle makes its way back to converting back to Citrate, which is an intermediate that precedes Citric Acid. This is done in the mitochondria, or the part of the cell that is involved in generating energy.

Because of the amount of energy that is generated in this cycle, it continues until the energy source - glucose - is completely used up.