1.1.3. Glucose

Prior Knowledge Quick Write: Explain why we need to eat. What does your body do with the food that you eat?

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Please read and mark the text for the paragraphs below. If you are unfamiliar with how to mark the text, please read the following instructions:

1. Before reading, please number the paragraphs. (Start with the number one and continue numbering sequentially throughout, placing the number near the start of the paragraph.)
2. Circle key terms and other essential words or numbers.
3. Put a box around any terms you do not know the meaning of or are unfamiliar with.
4. Underline information relevant to the reading purpose (concerns, claims, data, definitions, descriptions, evidence, examples, explanations, guiding language, hypotheses, “if then” statements, main ideas, methods, processes, etc.)

Glucose (C6H12O6) is a simple sugar (monosaccharide: mono = one; saccharide = sugar) that helps energize all the cells of your body. Our bodies get glucose (C6H12O6) from the food we eat. Complex carbohydrates, such as whole grains, are polysaccharides (poly = many; saccharide = sugar) that are digested slowly and release glucose into the blood over long periods of time. Refined sugar from pop and candy can cause sudden spikes in blood glucose levels due to a “sugar rush.” See Figure 1.1.3 and 1.1.4 below of the different chemical structure representations of glucose (C6H12O6). Start with the first carbon after the oxygen atom in the ring and count the carbons going clockwise around the ring.

Figure 1.1.3 Alpha-D-Glucose by Silvercat / Creative Commons Attribution-Share Alike 3.0 Unported

Figure 1.1.4 Glucose by Stephen Taylor / Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License.

After we eat, glucose (C6H12O6) is absorbed by the small intestine and is brought all over the body through our blood.

When there is a high level of glucose (C6H12O6) in the blood, your body works to reduce it (remember, your body is trying to maintain balance/homeostasis). In order to do this, the protein hormone insulin is secreted by clusters of cells in the pancreas called islets (beta pancreas cells secrete insulin.). Please see Figure 1.1.5 and circle the approximate location of the small intestine and pancreas.

Figure 1.1.5 Digestive System by Mariana Ruiz Villarreal / Public Domain

Insulin helps move glucose (C6H12O6) from the blood into the body’s cells (skin cells, nerve cells (neurons), muscle cells, etc.) by acting like a “key” that “unlocks” the cells.

Once the body’s cells are “unlocked” by the protein hormone insulin, glucose can enter the cell and can be used by the cell to make cellular energy (ATP). (This occurs in the mitochondria during cellular respiration. The mitochondria is an organelle in eukaryotic cells that acts as the “powerhouse” of the cell.) This causes blood glucose levels to drop.        

Please study the chemical equation for cellular respiration below. Cellular respiration is the process that converts glucose and oxygen into carbon dioxide, water, and ATP. Please circle the reactants in this equation. Please put a box around the products in this equation.

Once a cell has enough glucose (C6H12O6) for its energy (ATP) needs, any extra glucose (C6H12O6) in the blood is stored in the liver as a carbohydrate called glycogen. (Glycogen is a polysaccharide and is therefore a more complex sugar than glucose. Poly = many; saccharide = sugar).

If a person has not eaten for a long time and does not have much glucose (C6H12O6) in the blood (blood sugar has dropped), the protein hormone glucagon is released from alpha pancreas cells to reduce this change. The glucagon then travels to the liver. Please see the diagram above for the approximate location of the liver.

Once in the liver, glucagon breaks down glycogen into glucose (C6H12O6), which releases more glucose into the bloodstream. These glucose molecules (C6H12O6) are then taken into the body’s cells by insulin. (Remember: beta pancreas cells secrete the hormone insulin. Alpha pancreas cells secrete the hormone glucagon.)

Practice: Please write a brief description or draw a simple sketch that explains how each term below relates to the homeostasis of blood glucose regulation.

Please complete the sentences below by using the terms from the list above:

1. Remember, homeostasis is the process by which organisms keep their internal conditions relatively _____________________.
2. Maintaining stable blood glucose levels in the body is an example of a ________________ feedback mechanism in the body.
3. Negative feedback mechanisms ______________ changes in a system and tend to keep a system in equilibrium.
4. A typical blood glucose range in humans is between 70 and 110 mg/100mL. This range is controlled by the protein hormones __________________ and glucagon.
5. When the body senses that blood glucose levels have increased above the normal range, the protein hormone Insulin is released from beta _______________ cells.
6. Insulin works to “_______________” cells throughout the body, so they can use the blood glucose for energy (ATP).
7. This causes blood glucose levels to _____________ throughout the body.
8. Once blood glucose levels drop below the typical range, the protein hormone _________ is released from alpha pancreas cells.
9. This causes the liver to break down glycogen into _____________.
10. Glucose is then released back into the ____________.