- Slides: 20
Cellular Respiration Cellular respiration releases chemical energy from sugars and other carbonbased molecules to make ATP. It is an aerobic process. needs oxygen to take place.
Cellular Respiration Cell respiration takes place in the mitochondria. Foods are broken down into small molecules like glucose. Glucose is broken down during glycolysis.
Glycolysis Takes place BEFORE cell respiration. Splits the glucose molecule into two three-carbon molecules and makes two molecules of ATP. It takes place in the cytoplasm of the cell. It is an anaerobic process. ○ Does NOT require oxygen to take place.
Glycolysis 1. Two ATP molecules are used to energize a glucose molecule. – The glucose is then split into two three-carbon molecules. 2. Energized electrons from the three -carbon molecules are transferred to molecules of NAD+. – This makes NADH. (this is an enzyme that helps energy production) – A series of reactions convert the three-carbon molecules into pyruvate. (used in cellular respiration) – 4 ATP molecules are made.
Krebs Cycle The first part of cellular respiration. Sometimes called the citric-acid cycle. Produces molecules that carry energy to the second part of cellular respiration. (NADH and FADH 2) Takes place in the interior space (matrix) of the mitochondria.
Krebs Cycle 1. Pyruvate broken down. Pyruvate is split into a two- carbon molecule and carbon dioxide (given off as waste). The two-carbon molecule donates high energy electrons to NAD+, forming a molecule of NADH. ○ This will move to the electron transport chain. 2. Coenzyme A Bonds to the two-carbon molecule made by the breakdown of pyruvate.
Krebs Cycle 3. Citric acid formed. – The two-carbon molecule binds to a four-carbon molecule to form citric acid. – Coenzyme A returns to step 2. 4. Citric acid broken down. – The citric acid molecule is broken down by an enzyme, and a five-carbon molecule is formed. – A molecule of NADH is made and moves out of the Krebs cycle. – A molecule of carbon dioxide is given off as waste.
Krebs Cycle • 5. Five-carbon molecule broken down. – A four-carbon molecule, a molecule of NADH, and a molecule of ATP are formed. – NADH leaves the Krebs Cycle. – Carbon dioxide is given off as waste. • 6. Four-carbon molecule rearranged. – Enzymes rearrange the four- carbon molecule, releasing highenergy electrons. – NADH and FADH 2 (another enzyme/electron carrier) are made. – They leave the Krebs cycle and the four-carbon molecule remains.
Krebs Cycle Products The Krebs cycle will break down TWO pyruvate molecules at the same time. • Products: • – 6 carbon dioxide molecules. – 2 molecules of ATP – 8 molecules of NADH • Will go to the electron transport chain. – 2 molecules of FADH 2 • Will go to the electron transport chain.
Electron Transport Chain Second part of cellular respiration. Energy from the Krebs cycle (NADH and FADH 2) is transferred to a chain of proteins in the inner membrane of the mitochondrion. A large number of ATP molecules are made. Oxygen is used to make water molecules. Water and heat are given off as a waste
Electron Transport Chain 1. Electrons removed. Proteins inside the mitochondrion take high- energy electrons from NADH and FADH 2. ○ Two molecules of NADH and one of FADH 2 are used. 2. Hydrogen ions transported. Hydrogen ions are built up along the inner mitochondrial membrane using energy from the electrons.
Electron Transport Chain • 3. ATP produced. – The hydrogen pumps through a protein channel in the mitochondrial membrane with ATP synthase. – ATP synthase adds phosphate groups to ADP to make ATP molecules. • Each pair of electrons (hydrogen) that passes through results in an average of 3 ATP molecules made. • 4. Water formed. – Oxygen enters the cycle and picks up extraneous hydrogen, forming water. • This is given off as a waste.
Electron Transport Chain
Electron Transport Chain Products For EACH molecule of glucose the ETC can make: Up to 34 molecules of ATP
Cellular Respiration Products • Up to 38 ATP are made from the breakdown of ONE glucose molecule. – 2 ATP from glycolysis – 36 -34 ATP from cellular respiration (Krebs Cycle and Electron Transport Chain) Other products include carbon dioxide and water. • The equation for cellular respiration is: • – C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O
Fermentation is an anaerobic process that takes place when there is less oxygen in the body (i. e. during strenuous activity) • Fermentation does NOT make ATP, but it allows glycolysis to continue. • – Glycolysis needs NAD+ to pick up electrons when it splits glucose into pyruvate. – Fermentation removed electrons from NADH molecules and recycles NAD+ molecules for glycolysis.
Lactic Acid Fermentation in Animals 1. Pyruvate and NADH from glycolysis enter fermentation. Two NADH molecules are used to convert pyruvate into lactic acid. ○ As the NADH is used, it converts back to NAD+. 2. TWO molecules of NAD+ are recycled back to glycolysis. This allows your body to continue to break down sugar for energy!
Alcoholic Fermentation in Plants 1. Pyruvate and NADH from glycolysis enter alcoholic fermentation. The NADH molecules provide energy to break pyruvate into alcohol and carbon dioxide. ○ As the NADH are used, they are converted to NAD+. 2. The molecules of NAD+ are recycled back to glycolysis. The recycling of NAD+ allows glycolysis to continue.
Cellular Respiration and Photosynthesis Cellular Respiration and Photosynthesis are approximately the reverse of each other. Photosynthesis stores energy. Cellular Respiration releases it.