Chapter 2.8 Cell Respiration Flashcards
Cell respiration
the controlled release of energy from organic compounds to produce ATP.
Anaerobic cell respiration
gives a small yield of ATP from glucose
Aerobic cell respiration
requires oxygen and gives a large yield of ATP to glucose
Rapid oxidation
burning is the release of chemical energy. cells break down their organic nutrients by slow oxidation.
Goal of releasing energy
a controlled way to trap the released energy from a broken covalent bond in the form of ATP molecules.
Glycolysis
Glucose enters a cell through the plasma membrane and floats in the cytoplasm. An enzyme modifies the glucose, then a second even more. This is followed by an entire series of reactions that ultimately cleaves the 6-carbon glucose into two 3-carbon molecules. Each of these 3 carbon molecules is called pyruvate. Some but not all covalent bonds are broken, some of the energy that is released from the breaking of these bonds is used to form a small number of ATP molecules. 2 ATP molecules are needed to begin the process of glycolysis and a total of 4 ATP molecules are formed. This means there is a net gain of 2 ATP.
ATP production with anaerobic respiration
All of the pathways start with glycolysis, some organisms derive their ATP completely without the use of oxygen and are referred to as anaerobic.
Fermentation
the breakdown of organic molecules for ATP production in an anaerobic way, there are 2 pathways: alcoholic fermentation and lactic acid fermentation
Alcoholic fermentation
Yeast is a common single cell fungus that uses alcoholic fermentation for ATP generation when oxygen is not present. Yeast cells take in glucose from their environment and generate a net fain of two ATP by glycolysis. Yeast then converts both of the 3-carbon pyruvate molecules to molecules of ethanol. Ethanol is a 2-carbon molecule, so a carbon atom is lost in the conversion. The lost carbon atom is given off in a carbon dioxide molecule. Both the ethanol and carbon dioxide that are produced are waste products from the yeast and are simply released into the environment. Baker’s yeast is added to bread products for baking because the generation of carbon dioxide helps the dough to rise.
Lactic Acid Fermentation
Cells that are aerobic normally take 2 pyruvate molecules and metabolize them further in an aerobic series of reactions. But if a cell is not getting a sufficient amount of oxygen for the aerobic pathway, i.e is in a low-oxygen situation, excess pyruvate molecules are converted into lactic acid molecules. Lactic acid molecules are 3-carbon molecules so there is no production of carbon dioxide. Lactic acid fermentation allows glycolysis to continue with a small gain of ATP in addition to the ATP that is generated through the aerobic pathway.
Aerobic cell respiration glycolysis
cells that have mitochondria usually use an aerobic pathway for cell respiration. Begins with glycolysis, the two pyruvate molecules then enter a mitochondrion and are metabolized further. Each pyruvate first loses a carbon dioxide molecule and becomes a molecule known as acetyl-CoA. Each acetyl-CoA molecule enters into a series of reactions called the Krebs cycle. During this series of reactions, 2 more carbon dioxide molecules are produced from each original pyruvate molecule that entered it. Aerobic cell respiration breaks down a glucose molecule and the end-products are carbon dioxide and water plus a much higher number of ATP molecules than anaerobic respiration yields.
