3.7 CELLULAR RESPIRATION. How are these two images related?

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1 3.7 CELLULAR RESPIRATION How are these two images related?

2 CELLULAR RESPIRATION Cellular respiration is the process whereby the body converts the energy that we get from food (glucose) into an energy form that the body can use ATP! FOOD = GLUCOSE ATP!!!!!!

3 CELLULAR RESPIRATION The overall chemical equation for cellular respiration is as follows: C 6 H 12 O 6(aq) + 6O 2(g) 6CO 2(g) + 6H 2 O (l) + 36 ATP glucose oxygen Carbon dioxide water ENERGY! In other words, the combustion of one molecule of glucose yields 36 molecules of ATP along with carbon dioxide and water as by-products. Since the activation energy needed for the combustion of glucose is quite high, each step in cellular respiration is catalyzed by specific enzymes that lower the activation energies and allow the reactions to occur at a pace fast enough to maintain cell needs.

4 CELLULAR RESPIRATION The 3 overall goals of this process are: 1. to break the bonds between the six carbon atoms of glucose, resulting in 6 carbon dioxide molecules. 2. to move hydrogen atom electrons from glucose to oxygen, forming 6 water molecules. 3. to trap as much of the free energy released in the process as possible in the form of ATP. C 6 H 12 O 6(aq) + 6O 2(g) 6CO 2(g) + 6H 2 O (l) + 36 ATP

5 CELLULAR RESPIRATION Overall, there are 4 stages to cellular respiration: 1. GLYCOLYSIS a 10 step process occurring in the cytoplasm 2. PYRUVATE OXIDATION a one-step process in the mitochondrial matrix 3. THE KREBS CYCLE an 8 step cyclical process occurring in the mitochondrial matrix 4. ELECTRON TRANSPORT CHAIN a multistep process occurring in the mitochondrial membrane

6 STEP ONE: GLYCOLYSIS Glycolysis involves 10 enzyme-catalyzed reactions (each step has its own specialized enzyme!) Each reaction of glycolysis occurs in the cell's cytoplasm 2NADH 2ATP C 6 H 12 O 6 (aq) Two 3-C molecules of pyruvate

7 STEP ONE: GLYCOLYSIS In glycolysis, a total of 2 ATP molecules are USED in step one and three 2 ATP are produced in the 7 th step, when BPG phosphorylates ADP to ATP 2 ATP are produced in the 10 th step when PEP phosphorylates ADP to ATP (-2ATP) + 4ATP = 2ATP (net yield)

8 CELLULAR RESPIRATION There are 2 major types of cellular respiration» 1. AEROBIC CELLULAR RESPIRATION» 2. ANAEROBIC CELLULAR RESPIRATION The big difference is oxygen!!!!!

9 CELLULAR RESPIRATION There are 2 major types of cellular respiration» AEROBIC CELLULAR RESPIRATION» Uses oxygen and produces MORE energy!» ANAEROBIC CELLULAR RESPIRATION» Does NOT use oxygen, produces LESS energy but much faster!

10 STEP TWO: PYRUVATE OXIDATION TIME TO MOVE INTO THE MITOCHONDRIA!!!!» the 2 molecules of pyruvate from glycolysis are transported through the two mitochondrial membranes into the matrix» In the matrix, a multi-enzyme complex catalyzes 3 MAJOR CHANGES!!!!

11 STEP TWO: PYRUVATE OXIDATION 1. A low-energy carboxyl group is removed as CO 2.

12 STEP TWO: PYRUVATE OXIDATION 2. NAD+ is reduced by two H atoms

13 STEP TWO: PYRUVATE OXIDATION 3. A sulfur-containing compound called coenzyme A (CoA) is attached to the remaining acetic acid portion forming a molecule called acetyl-coa

14 STEP TWO: PYRUVATE OXIDATION The following is the overall equation for pyruvate oxidation: 2 pyruvate + 2NAD + + 2CoA 2acetyl-CoA + 2NADH + 2H + +2CO 2 Acetyl-CoA moves on the third step! = Krebs Cycle! NADH skips step three and moves on to stage four! = electron transport chain!

15 WARNING!!!!!! Acetyl-CoA is a CENTRAL MOLECULE IN ENERGY METABOLISM!!!!! ALL molecules that are catabolized for energy are converted into acetyl-coa including proteins, lipids and carbohydrates! acetyl-coa is MULTIFUNCTIONAL it can be used to produce fat or ATP if the body needs energy, acetyl-coa will enter the KREBS CYCLE and transfer its free energy into ATP if the body does not need energy, acetyl-coa is channelled into an anabolic pathway that synthesizes lipids.

16 STEP THREE: KREBS CYCLE The Krebs Cycle is an 8-step process!!!!» each step is catalyzed by its own enzyme It is a cyclic process! the product of step 8 (oxaloacetate) is the reactant in step 1!!!!! The Krebs Cycle is a cyclic series of reactions that transfers energy from organic molecules to ATP, NADH, and FADH 2 and removes carbon atoms as CO 2.

17 STEP THREE: KREBS CYCLE By the end of the Krebs cycle, the original glucose molecule is entirely consumed!» the 6 carbon atoms leave as low energy CO 2 molecules The Krebs Cycle produces: - 2 molecules of CO 2-3 NADH - 1 ATP - 1 FADH 2 X 2 Because there are 2 acetyl-coa molecules that go through

18 The Krebs Cycle produces: - 4 molecules of CO 2-6 NADH - 2 ATP - 2 FADH 2 Energy is harvested in steps 3,4,5,6 & 8 : The reduced coenzymes now go on to stage 4 ELECTRON TRANSPORT CHAIN -In steps 3, 4 and 8 NAD+ is reduced to NADH - In step 5 ATP is formed by phosphorylation - In step 6 FAD is reduced to FADH 2

19 STEP FOUR: ELECTRON TRANSPORT CHAIN each NADH molecule results in 3 ATP molecules each FADH 2 molecule results in 2 ATP molecules

20 20

How Cells Release Chemical Energy. Chapter 7

How Cells Release Chemical Energy Chapter 7 7.1 Overview of Carbohydrate Breakdown Pathways All organisms (including photoautotrophs) convert chemical energy of organic compounds to chemical energy of