Your body uses processes to keep blood glucose levels within the normal range. Learn how your body decreases blood glucose levels through glycogenesis and how it boosts glucose levels through glycogenolysis and gluconeogenesis in this lesson.
There's nothing like Thanksgiving dinner to fill your belly. That one day of the year, people all over America are gobbling down tons of carbohydrates as they treat their taste buds to stuffing, potatoes, and, of course, a big piece of pumpkin pie for dessert. All of those carbohydrates enter your digestive tract where they are broken down into simple sugars, known as glucose. These glucose molecules are small enough to move out of your digestive system and into your bloodstream.
As you can imagine, eating a big Thanksgiving meal dumps a lot of glucose into your blood. What your body does with this excess of glucose and what your body does when all of this blood glucose is used up is what we will discuss in this lesson.
Your bloodstream is closely monitored and regulated by your hormones, so it never has too much or too little of any compound. When we consider blood glucose, or blood sugar levels, your body likes to keep the amount between 70 to 100 mg/dL, which is considered normal for a fasting sample.
If your blood glucose level rises, your body springs into action to sweep out the excess sugar. It does this by promoting a process called glycogenesis, which is the creation and storage of glycogen. This term is easy to remember if you recall the suffix 'genesis' means creation; so, glycogenesis is literally the creation of glycogen, which is the name we give to the stored form of glucose. You have glycogen storage in your liver and in your muscles, so you might want to think of these structures like a pantry, where you store bags of sugar to use later.
After gorging yourself on all the delicious foods at your Thanksgiving meal, you'll probably not feel like eating again for many hours. This gives your blood glucose level time to return to normal, but if you continue your fast, your blood sugar level could actually drop too low. This is because your body cells are constantly taking glucose from the blood to use as energy.
But before blood glucose levels get too low, your body springs into action again; however, this time it wants to add glucose to your blood, not sweep it away. One way to do this is through glycogenolysis. Now, if we look closely at this term, we see the word 'glycogen' and the word 'lysis.' Lysis means to break down, so it's easy to see that glycogenolysis is simply the breakdown of glycogen into glucose. Now that the glucose molecules are free, they can move back into your bloodstream and maintain the normal blood glucose level.
Glycogenolysis is a quick and easy way to move glucose into the blood when your body has an urgent need, but there's another way to get more glucose into your blood that's effective but requires energy. This process is called gluconeogenesis. Do you see the word 'neo?' That means new. So, if we dissect this term, we see that it means 'glucose-new-creation,' or in other words, the creation of new glucose from molecules that are not carbohydrates, such as proteins and lipids. This process will often take place after a night's sleep, which is a period of time your body is not taking in food or when you have used up available glycogen stores.
Now, gluconeogenesis and glycogenolysis are both ways your body can increase the glucose level in your blood, but if you recall, I mentioned that gluconeogenesis requires energy. This process occurs in your liver, and during the gluconeogenesis pathway, your liver cells use six high-energy molecules, like ATP and GTP, for each glucose molecule produced. The fact that your body is willing to use energy to maintain a normal blood glucose level shows how much it wants to maintain a stable internal environment, or homeostasis.
Let's review. Carbohydrates in the foods you eat are broken down into glucose, which are simple sugars that easily pass into your bloodstream. After a carbohydrate-rich meal, your blood glucose level rises. Excess sugar is cleared out of the bloodstream and into your muscles and liver via glycogenesis, which is the creation and storage of glycogen.
If you do not eat for a period, your blood sugar level could actually drop too low, triggering glycogenolysis, which is the breakdown of glycogen into glucose. If glycogen stores are used up and fasting continues, your body can also increase blood glucose levels through a more energy-intensive process called gluconeogenesis, which is the creation of new glucose molecules that are not carbohydrates, such as proteins and lipids.
The lesson's main intent is to prepare you to:
- Determine the importance of glucose to the body
- Highlight the processes of glycogenesis, glycogenolysis and gluconeogenesis, including the ways in which they occur and their purposes