Chapter 9 Notes

Cellular Respiration

Core Standard: Describe features that are common to all cells and contrast those with distinctive features that allow cells to carry out specific functions.


Cellular Respiration: The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.




6O2 + C6H12O6 6CO2 + 6H2O + 36 ATP (energy)


There are 3 major steps in Cellular Respiration:


1.        Glycolysis

2.        The Krebs Cycle

3.        The Electron Transport Chain




  one molecule of glucose is broken in half, producing two molecules of pyruvic acid and energy (ATP and NADH)


  2 ATP molecules are required to start glycolysis.

  Glycolysis makes 4 ATP molecules.

  The net ATP molecules made in glycolysis is 2.


Krebs Cycle:


  Occurs in the mitochondria of the cell.

  Mitochondria = energy producer

  Pyruvic acid is broken down into carbon dioxide in a series of reactions that requires the ATP and NADH energy made during glycolysis.



Electron Transport Chain:


  Uses high energy electrons from the Krebs cycle to convert ADP into ATP.


If there is no or low oxygen present in the environment the procedure is altered and cellular respiration does not occur!  Fermentation occurs instead.


When no oxygen is available there are 2 steps:


1.        Glycolysis

2.        Fermentation




  Same as before.  Glucose is broken down into pyruvic acid and ATP and NADH.


No or low oxygen available




1.        Lactic Acid Fermentation:


  Pyruvic acid + NADH Lactic Acid + NAD+

  Usually occurs in the muscles when exercising.

  Build up of lactic acid causes pain and fatigue.


2.        Alcoholic Fermentation:


  Pyruvic acid + NADH Alcohol + CO2 + NAD+

  Yeast uses alcoholic fermentation to form ethyl alcohol and carbon dioxide as waste

  This is what causes dough to rise and your soda to have bubbles.



 How efficient is cellular respiration in making energy?


  The 36 ATP molecules made represents 36% of the energy of glucose.


How efficient is fermentation in making energy?


  Only 2 ATP molecules made because of low oxygen.


What types of cells would you expect to find more mitochondria?



What is the function of the heart?

Pumps blood, made out of muscle

What is the function of the liver?

Makes the enzyme bile (protein), stores glycogen

What is the function of the pituitary gland?

Makes and secretes hormones (proteins)


NOTE: Those cells that use more energy (ATP) will have more mitochondria.


Comparing photosynthesis and cellular respiration: