Chapter 6 How Cells Harvest Chemical Energy. Cellular Respiration Is the main way that chemical energy is harvested from food and converted to ATP

Transcription

1 Chapter 6 How Cells Harvest Chemical Energy Standard 1.g. Cellular Respiration Is the main way that chemical energy is harvested from food and converted to ATP Is an aerobic process Yields The Relationship between Cellular Respiration and Breathing Cellular respiration and breathing are closely related. Cellular respiration requires a cell to Breathing exchanges these gases between the blood and outside air. Cellular respiration banks energy in ATP molecules Cellular respiration breaks down glucose molecules and stores the released energy in ATP The process uses O 2 and releases CO 2 and H 2 O During cellular respiration Organic compounds such as glucose are The chemical energy which is released is stored

2 The efficiency of cellular respiration a typical cell stores around 40% of the chemical energy released in ATP, the rest is released as heat ATP is produced in 2 ways 1. The movement of electrons along an electron transport chain creates a proton gradient across the inner membrane. The protons diffuse back across the membrane through ATP synthase releasing energy that is used to make ATP by 2. ATP can also be made by transferring phosphate groups from organic molecules to ADP. This process is called The Metabolic Pathway of Cellular Respiration Cellular respiration is an example of a metabolic pathway, All of the reactions involved in cellular respiration can be grouped into three main stages: Glycolysis Electron transport

3 Glycolysis harvests chemical energy The purpose of glycolysis is to split/breakdown glucose into two 3 carbon compounds (pyruvic acid) During the 9 chemical steps in glycolysis: 2 molecules of ATP are used 4 molecules of ATP are produced by 2 molecules of NAD + gain electrons to form the electron carrier NADH The net gain of ATP during glycolysis is Glycolysis Review 1. What is the general equation for cellular respiration? 2. What is the purpose of glycolysis? 3. Where does glycolysis occur? 4. What is needed for glycolysis? 5. What process produces ATP during glycolysis? 6. How is NADH produced during glycolysis? 7. How many ATP are produced during glycolysis? 8. What is the net gain of ATP during glycolysis? 9. Why is the number produced and the net gain different?

4 Fermentation Under anaerobic conditions, many kinds of cells can use glycolysis alone to produce small amounts of ATP After functioning anaerobically for about 15 seconds, muscle cells will begin to generate ATP by the process of fermentation. Fermentation relies on But a cell must have a way of In alcoholic fermentation, pyruvic acid is converted to CO 2 and ethanol In lactic acid fermentation, pyruvic acid is converted to lactic acid Accumulation of lactic acid in muscles causes fatigue and soreness. The lactic acid is transported to the liver where it is converted to pyruvic acid. Fermentation Review 1. How many ATP are produced during the fermentation step(s)? 2. What is the purpose of fermentation?

5 3. What is produced during alcoholic fermentation? 4. What is produced during lactic acid fermentation? Structure of the Mitochondria Pyruvic acid is chemically groomed for the Krebs cycle In the matrix each pyruvic acid molecule is broken down to form CO 2 and a two-carbon acetyl group, which enters the Krebs cycle For each glucose molecule The Krebs Cycle The Krebs cycle is a series of reactions in which enzymes strip away electrons and H + from each acetyl group

6 The purpose of the Krebs cycle is to Occurs in the Each step is catalyzed by enzymes in the matrix of the mitochondria Acetyl CoA is completely broken apart Since 2 molecules of acetyl CoA enter the Krebs cycle for each glucose molecule, the Krebs cycle produces Krebs Cycle Review 1. Where does the Krebs cycle occur? (Be specific) 2. What is the purpose of the Krebs cycle? 3. What is produced during the conversion step for each glucose? 4. How many ATP are produced during the Krebs cycle for 1 glucose molecule?

7 5. What process produces the ATP? 6. How many NADH and FADH 2 are produced during the Krebs cycle for each glucose molecule? 7. How many CO 2 are produced during the Krebs cycle for each glucose molecule? Chemiosmosis in the Mitochondrion Electron Transport Chain Consists of ordered groups of molecules embedded in the inner membrane of the mitochondria Electrons are transferred from NADH and FADH 2 along the electron transport chain until the reach The O 2 gains the electrons and joins with the 2 H + in the surrounding fluid to produce Chemiosmosis produces ATP The movement of electrons along the electron transport chain creates a proton gradient across The H + ions diffuse back through the inner membrane through ATP synthase, which captures the energy to make ATP Chemiosmosis produces around

8 Summary of Cellular Respiration A maximum of 38 ATP are produced during cellular respiration ETC and Chemiosmosis Review 1. What is the role of NADH and FADH2? 2. Where does the electron transport chain and chemiosmosis occur? 3. How many ATP are made during this stage? 4. What process produces the ATP? 5. A maximum of 38 ATP are produced during cellular respiration where are they produced, how many are made, and what process produces them The Versatility of Cellular Respiration Cellular respiration can burn other kinds of molecules besides glucose: