Role of Glucose in Cellular Respiration

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  • 0:00 What Is Cellular Respiration?
  • 0:55 Glucose In Cellular…
  • 1:35 Steps Of Cellular Respiration
  • 3:12 Importance Of Glucose
  • 5:03 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

This lesson is on the role of glucose in cellular respiration. In this lesson, we'll explain what cellular respiration is and what we need to start with to get the end products. We'll specifically look at the importance of glucose in this process.

What Is Cellular Respiration?

Sugar is everywhere in our world, from packaged foods in our diet, like tomato sauce, to homemade baked goods, like pies. In fact, sugar is even the main molecule in fruits and vegetables. The simplest form of sugar is called glucose. Glucose is getting a bad rap lately and many people are cutting sugar out from their diet entirely. However, glucose is the main molecule our bodies use for energy and we cannot survive without it. The process of using glucose to make energy is called cellular respiration.

The reactants, or what we start with, in cellular respiration are glucose and oxygen. We get oxygen from breathing in air. Our bodies do cellular respiration to make energy, which is stored as ATP, and carbon dioxide. Carbon dioxide is a waste product, meaning our bodies don't want it, so we get rid of it through exhaling.

Glucose in Cellular Respiration

To start the process of cellular respiration, we need to get glucose into our cells. The first step is to eat a carbohydrate-rich food, made of glucose. Let's say we eat a cookie. That cookie travels through our digestive system, where it is broken down and absorbed into the blood. The glucose then travels to our cells, where it is let inside. Once inside, the cells use various enzymes, or small proteins that speed up chemical reactions, to change glucose into different molecules. The goal of this process is to release the energy stored in the bonds of atoms that make up glucose. Let's examine each of the steps in cellular respiration next.

Steps of Cellular Respiration

There are three steps of cellular respiration: glycolysis, the citric acid cycle, and oxidative phosphorylation. The main role of glucose in each of these steps is to provide energy in its bonds.

Step 1: Glycolysis

In glycolysis, glucose enters the cell. Next, a series of enzymes convert it to a different form called pyruvate in the main compartment of the cell, the cytoplasm. Two pyruvate are formed from one glucose. During this process two ATP are formed, as are two more of another energy-rich molecule called NADH. NADH collects electrons from the bonds in glucose. It transports them to the last step, oxidative phosphorylation, where they will be used to make ATP. So, the end purpose of glycolysis is to get a little ATP and harvest electrons in the bonds of glucose.

Step 2: Citric Acid Cycle

In the citric acid cycle, the pyruvate is converted to another molecule called acetyl Co-A. Acetyl Co-A undergoes a similar sequence of conversions to harvest more electrons in the form of NADH and make two ATP. These steps occur in the powerhouse of the cell, the mitochondria.

Step 3: Oxidative Phosphorylation

In the last step, all of the electrons harvested in the form of NADH from glucose are transported to the membrane of the mitochondria. Here these electrons are used by proteins in the cell to ultimately convert the energy stored in them to ATP. In doing this, oxygen combines with the electrons and hydrogen ions to make water. Without oxygen, the glucose would be useless, and the chain of reactions in cellular respiration would get backed up and stop.

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