Lab 6 Cellular Respiration
Electron Transport chain
-last step of aerobic respiration -takes place in the inner mitochondrial membrane -maintains an electrochemical gradient across the inner mitochondrial membrane that stimulates ATP synthesis -composed of 5 transmembrane proteins called complex I, II, III, and ATP synthase
After glycolysis, the pyruvate molecules can follow two different metabolic routes: aerobic and anaerobic respiration. What is the main difference between these?
Anaerobic respiration does not need oxygen to occur and aerobic respiration does
The first step of glycolysis consumes energy. Two high energy ATP molecules phosphorylation glucose. How do ATP molecules store energy?
high energy bonds between phosphate groups -the 3-phosphate ttail of the ATP molecule is responsible for energy storage high energy bonds between the phosphate groups break to allow the energy to be utilized
Why is the Krebs cycle so important if it only produces 2 ATTP molecules?
it produces reducing agents for the ETC -electron carriers are reducing agents this means that they donate e- -the Krebs cycle produces 8 NADH and 2 FADH2 molecules that are reducing agents and bring e- to the ETC
3 stages of cellular respiration
glycolysis, Krebs cycle, and electron transport chain
What technique is used to assess oxygen consumption?
respirometry -the respirometer measures the oxygen concentration in the air flow entering and exiting the chamber -can adjust available oxygen and exercise intensity
ETC process
1. 2 e- are supplied to Complex I from NADH produced during glycolysis and the Krebs cycle 2. these e- jump from redox center to redox center within complex I 3. the e- are eventually transferred to a lipid embedded in the membrane called coenzyme Q or ubiquinone 4. each time an e- jumps to a new redox center, it releases a little bit of energy 5. complex I uses the energy to pump 4 protons from the matrix to the intermembrane space 6. Coenzyme Q transports the e- flow from Complex I to Complex III 7. meanwhile, FADH2 produced during the krebs cycle brings 2 e- to complex II 8. coenzyme Q brings e- from complex I and complex II to complex III 9. Complex III transfers e- from coenzyme Q to cytochrome C 10. Complex III also pumps 4 protons through the membrane into the intermembrane space 11. Cytochrome C brings these e- to complex IV where oxygen is waiting to be the final e- acceptor 12. a rxn btwn the oxygen molecule, 4 e-, and 4 protons results in water being produced 13. 2 more protons are pumped into the intermembrane space. This contributes to the potential energy stored in the electrochemical gradient across the membrane 14. Since the protons flow down the gradient back to the mitochondrial matrix, they spin the rotor-like portion of ATP synthase 15. This causes a conformational change in ATP synthase that catalyzes the addition of a free phosphate group to an ADP molecule REVIEW: 1. NADH from glycolysis and the krebs cycle brings e- to complex I 2. Complex I uses the energy released from e- to pump protons through the inner mitochondrial membrane 3. Meanwhile, FADH2 from the Krebs cycle brings e- to complex II. e- from both complex I and II are transported to complex III 4. protons pumped through the membrane create an electrochemical gradient 5. in complex IV, oxygen is the final e- acceptor 6. ATP synthase uses the electrochemical gradient to synthesize ATP
What parameters could you use to measure the effect of exercise on cellular respiration in mice?
1. oxygen consumption 2. Blood lactic acid concentration 3. Blood glucose concentration oxygen consumption levels will tell us about the oxidative phosphorylation process
So in summary, glycolysis breaks down glucose into 2 pyruvate molecules. How many carbon atoms does one molecule of pyruvate contain?
3 C atoms
What is the net result of 1 glucose molecule going through the Krebs cycle?
8 NADH and 2 FADH2 molecules 2 ATP molecules CO2 molecules -glucose gets converted into 2 pyruvate molecules that each enter the Krebs cycle -so everything is doubled main products of krebs cycle are electron carriers electron carriers participate in redox rxns
Metabolism can be divided into catabolic and anabolic reactions. How are these connected?
Catabolic reactions generate energy that anabolic reactions use.
When free phosphate groups are transferred from ATP to other molecules, the molecules become phosphorylated.
Glucose gets phosphorylated by 2 ATP molecules to produce fructose 1,6-biphosphate
What will happen to oxygen consumption levels when the mouse starts running in the wheel?
Oxygen consumption will increase -oxygen and glucose consumption increases as energy requirement increases
What is oxygen used for in cellular respiration?
Oxygen is the last e- acceptor in the oxidation of electron carriers
Krebs cycle
Preparation step: pyruvate enters mitochondrion and undergoes preparation step that results in acetyl-CoA Occurs in the mitochondrial matrix 1. CO2 (1 C atom is released it combines with oxygen to form CO2 and is released when we breathe out) 2. NADH (NAD+ gets reduced by accepting e-, it then brings the e- to the ETC) 3. COA (Co-enzyme A is recycled during the krebs cycle preparation) 4. CO2 5. NADH 6. CO2 7. NADH 8. ATP (the only energy producing step) 9. FADH2 10. NADH
what 2 processes are coupled throughout the ETC that together make up oxidative phosphorylation?
The oxidation of electron carriers + the phosphorylation of ADP (final step, phosphorylation by ATP synthase to produce ATP)