9.2 The Process of Cellular Respiration
What happens during the process of glycolysis?- What happens during the Krebs cycle?
- How does the electron transport chain use high-energy electrons from glycolysis and the Krebs cycle?
- How much ATP does cellular respiration generate?
glycolysis • NAD+ • Krebs cycle • matrix
Compare/Contrast Table As you read, make a compare/contrast table showing the location, starting reactants, and end products of glycolysis, the Krebs cycle, and the electron transport chain. Also include how many molecules of ATP are produced in each step of the process.
THINK ABOUT IT Food burns! It's true, of course, that many common foods (think of apples, bananas, and ground beef) have too much water in them to actually light with a match. However, foods with little water, including sugar and cooking oil, will indeed burn. In fact, flour, which contains both carbohydrates and protein, is so flammable that it has caused several explosions, including the one seen here at London's City Flour Mills in 1872 (which is why you're not supposed to store flour above a stove). So, plenty of energy is available in food, but how does a living cell extract that energy without setting a fire or blowing things up?
Glycolysis
What happens during the process of glycolysis?
The first set of reactions in cellular respiration is known as glycolysis, a word that literally means “sugar-breaking.” Glycolysis involves many chemical steps that transform glucose. The end result is 2 molecules of a 3-carbon molecule called pyruvic acid. During glycolysis, 1 molecule of glucose, a 6-carbon compound, is transformed into 2 molecules of pyruvic acid, a 3-carbon compound. As the bonds in glucose are broken and rearranged, energy is released. The process of glycolysis can be seen in Figure 9–4.
ATP Production Even though glycolysis is an energy-releasing process, the cell needs to put in a little energy to get things going. At the pathway's beginning, 2 ATP molecules are used up. Earlier in this chapter, photosynthesis and respiration were compared, respectively, to a deposit to and a withdrawal from a savings account. Similarly, the 2 ATP molecules used at the onset of glycolysis are like an investment that pays back interest. In order to earn interest from a bank, first you have to put money into an account. Although the cell puts 2 ATP molecules into its “account” to get glycolysis going, glycolysis produces 4 ATP molecules. This gives the cell a net gain of 2 ATP molecules for each molecule of glucose that enters glycolysis.
Table of Contents
- Formulas and Equations
- Applying Formulas and Equations
- Mean, Median, and Mode
- Estimation
- Using Measurements in Calculations
- Effects of Measurement Errors
- Accuracy
- Precision
- Comparing Accuracy and Precision
- Significant Figures
- Calculating With Significant Figures
- Scientific Notation
- Calculating With Scientific Notation
- Dimensional Analysis
- Applying Dimensional Analysis