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Cellular Respiration A series of chemical reactions needed to break down carbohydrates and other molecules in order to release the energy they contain.

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Presentation on theme: "Cellular Respiration A series of chemical reactions needed to break down carbohydrates and other molecules in order to release the energy they contain."— Presentation transcript:

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2 Cellular Respiration A series of chemical reactions needed to break down carbohydrates and other molecules in order to release the energy they contain. C 6 H 12 O 6 + 6O > 6CO 2 + 6H 2 O + ATP

3 Energy in Living Organisms Energy harvested from the breakdown of sugar is stored in energy carrier molecules: adenosine triphosphate (ATP) nicotinamide adenine dinucleotide (NADH) flavin adenine dinucleotide (FADH 2 ).

4 Energy Carrier Molecule: ATP ATP consists of adenine (red), ribose (purple) and three phosphate groups (blue).

5 Energy Carrier Molecule: ATP The bonds between the phosphate groups are high energy bonds. When energy is needed, the bond between the 2 nd and 3 rd phosphate groups is broken. About 30 kJ/mol of ATP is released. The remaining molecule is now called adenosine diphosphate (ADP). ATP ADP + P + energy

6 Energy Carrier Molecules: NADH & FADH2 NADH carries an amount of energy equivalent to 3 ATP. FADH 2 carries an amount of energy equivalent to 2 ATP.

7 Types of Cellular Respiration Aerobic respiration: the process that requires sufficient O 2 produces 36 ATP Anaerobic respiration: The process that occurs when there is insufficient O 2 supply Produces ONLY 2 ATP C 6 H 12 O 6 + 6O > 6CO 2 + 6H 2 O + ATP Sufficient: Aerobic Insufficient: Anaerobic

8 Aerobic Cellular Respiration 3 Main Phases: 1.Glycolysis 2.Krebs Cycle 3.Electron Transport Chain

9 Phase 1: Glycolysis A series of 10 steps that breaks down glucose (6- carbon molecule) into two pyruvate molecules (3-carbon molecules) This process does not use oxygen.

10 Phase 1: Glycolysis Energy Yield 2 ATP are used 4 ATP are made (net of 2 ATP) 2 NADH are made The 2 ATP can be used directly, however, the 2 NADH need to go into the 3 rd phase (ETC) to be converted into ATP. The process occurs in the cytoplasm.

11 Phase 2: Krebs Cycle A process by which 2 pyruvate molecules are sent through a cycle to release CO 2. During the cycle, a 6- carbon molecule of citrate is produced, thus this cycle is also known as the citric acid cycle.

12 Phase 2: Krebs Cycle Energy Yield / pyruvate 1 ATP 4 NADH 1 FADH 2 Since glycolysis produces 2 pyruvate molecules, the energy yield should be doubled. ADP ATP

13 Phase 2: Krebs Cycle This phase occurs in the matrix of a mitochondria. The 2 ATP can be used directly. The 8 NADH and 2 FADH 2 go into the 3 rd phase (ETC) to be converted into ATP. CO 2 is a waste product that is blown off when breathing.

14 Phase 3: The Electron Transport Chain (ETC) Process by which NADH and FADH 2 are converted into ATP. H 2 O molecules are also formed during this phase. This phase occurs on the cristae of the mitochondria.

15 Phase 3: ETC Details 1.NADH and FADH 2 that are formed during glycolysis and Krebs cycle each have a pair of electrons. 2.These electrons are brought to the cristae of the mitochondria and transferred to proteins called cytochromes. 3.The electrons are passed down through a series of cytochromes known as the ETC. 4.As the electron pairs move through each cytochrome, 2 hydrogen ions (H + ) are pumped out of the matrix into the intermembrane space. 5.This causes the intermembrane space to have a high concentration of H + and so H + want to diffuse back into the matrix. 6.They do this through a protein known as ATP synthase. Energy from H + is provided to join ADP+ P > ATP. 7.At the end of the ETC, the electrons join with oxygen and 2 H + to produce H 2 O.

16 Phase 3: ETC The electrons from NADH start at the beginning of the chain and pump 3 pairs of H + across. The electrons from FADH 2 start farther down the chain and only pump 2 pairs of H + across. Since each pair of electrons passes through ATP synthase to make 1 ATP, each NADH can produce 3 ATP and FADH 2 can produce 2 ATP.

17 Energy Yield Overview 2 ATP (glycolysis) 2 ATP (Krebs cycle) 2 NADH (glycolysis) ----> 4 ATP in ETC** 8 NADH (Krebs cycle) --> 24 ATP in ETC 2 FADH 2 (Krebs cycle) --> 4 ATP in ETC 36 ATP from 1 glucose molecule **Krebs cycle and ETC both occur in the mitochondria therefore NADH made in Krebs cycle is converted into 3 ATP each. Glycolysis occurs in the cytoplasm and therefore the 2 NADH produced there must enter the mitochondria to get to the ETC. This costs energy. Therefore, each NADH from glycolysis is only worth 2 ATP each.

18 Question How many ATP could a prokaryotic cell get from 1 glucose molecule? Explain. Answer: A prokaryotic cell could get 38 ATP from 1 glucose molecule because prokaryotes do not have mitochondrial membranes. Therefore, glycolysis, Krebs cycle, and ETC all happen in the cytoplasm. ALL NADH are worth 3 ATP. Since the NADH produced in glycolysis does not have to enter the mitochondria, there in NO energy cost!

19 Review: Cellular Respiration C 6 H 12 O 6 + 6O > 6CO 2 + 6H 2 O + ATP Glycolysis ETC Krebs Cycle ETC All Phases: 2 from glycolysis 2 from Krebs cycle 32 from ETC

20 Anaerobic Cellular Respiration Glucose is converted into 2 pyruvate molecules in glycolysis which will then go to the Krebs cycle IF O 2 if available. Sometimes, the amount of O 2 available is insufficient and the 2 pyruvate molecules undergo a process called fermentation.

21 Anaerobic Cellular Respiration During fermentation in eukaryotic cells, pyruvate will either be converted into: 1.Ethanol through Alcoholic Fermentation 2.Lactic Acid through Lactic Acid Fermentation

22 Alcoholic Fermentation Ethanol: produced when yeast cells ferment A source of ethyl alcohol (beer and wine) Glucose > 2 pyruvate > ethanol + CO 2 glycolysis fermentation 2 ATP

23 Lactic Acid Fermentation Lactic Acid Produced by cells of multicellular organisms during O 2 deficient times (exercise) Lactic acid causes the “burn” felt in muscle cells Blood circulation moves excess lactic acid Glucose > 2 pyruvate > lactic acid glycolysis fermentation 2 ATP

24 Anaerobic Respiration Consider that aerobic respiration can produce 36 ATP/ glucose molecule. Therefore, how efficient is anaerobic respiration at getting energy from glucose? 2 ATP / 36 ATP * 100% = 5.6% efficient


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