Cellular Metabolism Biol 105 Lecture 6 Read Chapter 3 (pages 63 69)
Metabolism Consists of all of the chemical reactions that take place in a cell
Metabolism Animation Breaking Down Glucose For Energy http://wps.aw.com/bc_goodenough_boh_4/177/45509/11650544.cw/index.html
Cellular Metabolism Aerobic cellular respiration requires oxygen, produces carbon dioxide Anaerobic Fermentation does not require oxygen
Summary of Cellular Respiration Blood vessel Electrons transferred by NADH Electrons transferred by NADH Cytoplasm Carrier protein Glucose Plasma membrane Electrons transferred by NADH and FADH 2 Glycolysis glucose pyruvate Transition Reaction Citric Acid Cycle Electron Transport Chain Oxygen Mitochondrion Extracellular fluid +2 ATP +2 ATP +32 ATP 36 ATP Figure 3.27
Aerobic Cellular respiration In aerobic cellular respiration cells take in sugar (glucose) and breaks it down to into carbon dioxide and water, this requires oxygen. This process produces energy in the form of ATP C 6 H 12 O 6 + 6O 2 6CO 2 +6H 2 O + Energy
Aerobic Cellular respiration There are four steps of aerobic cellular respiration: 1. Glycolysis 2. Transition Reaction 3. Citric Acid Cycle (Krebs Cycle) 4. Electron Transport Chain
NADH and FADH 2 are important carriers of electrons
Cellular Respiration - Glycolysis Phase 1: Glycolysis Occurs in the cytoplasm Splits one glucose into two pyruvate molecules Generates a net gain of 2 ATP and 2 NADH molecules Does not require oxygen
Cellular Respiration - Glycolysis Starts with glucose Ends with 2 ATP, 2 NADH, 2 pyruvate
Glycolysis Glycolysis (in cytoplasm) Cytoplasm During the first steps, two molecules of ATP are consumed in preparing glucose for splitting. Glucose Energyinvestment phase 2 ADP 2 ATP During the remaining steps, four molecules of ATP are produced. 4 ADP The two molecules of pyruvate then diffuse from the cytoplasm into the inner compartment of the mitochondrion, where they pass through a few preparatory steps (the transition reaction) before entering the citric acid cycle. 2 Pyruvate 4 ATP 2 NAD + 2 NADH Energyyielding phase Two molecules of nicotine adenine dinucleotide (NADH), a carrier of high-energy electrons, also are produced. Figure 3.23
In Cytosol
Cellular Respiration Transition Reaction Phase 2: Transition reaction Occurs within the mitochondria Coenzyme A combines with pyruvate and CO 2 is removed from each pyruvate Forms 2 acetyl CoA molecules Produces 2 NADH
Transition Reaction Start with: 2 pyruvate (3 carbon molecules) 2 Coenzyme A End with: 2 CO 2 2 NADH 2 Acetyl CoA (2 carbon molecule)
Transition Reaction Transition Reaction (in mitochondrion) Pyruvate (from glycolysis) A molecule of NADH is formed when NAD + gains two electrons and one proton. NAD + One carbon (in the form of CO 2 ) is removed from pyruvate. CO 2 NADH (electron passes to electron transport chain) Acetyl CoA CoA Coenzyme A The two-carbon molecule, called an acetyl group, binds to coenzyme A (CoA), forming acetyl CoA, which enters the citric acid cycle. Citric Acid Cycle Figure 3.24
Cellular Respiration Citric acid cycle Phase 3: Citric acid cycle Occurs in the mitochondria Acetyl CoA enters the citric acid cycle Releases 2 ATP, 2 FADH 2 and 6 NADH, 4 CO 2 molecules Requires oxygen
Citric Acid Cycle Also called the Krebs Cycle Start with 2 Acetyl CoA End with: 4 CO 2 2 ATP 6 NADH and 2 FADH 2
Citric Acid Cycle Citric Acid Cycle (in mitochondrion) The citric acid cycle also yields several molecules of FADH 2 and NADH, carriers of high-energy electrons that enter the electron transport chain. NADH Oxaloacetate Acetyl CoA Acetyl CoA, the two-carbon compound formed during the transition reaction, enters the citric acid cycle. CoA CoA Citrate NAD + Malate FADH 2 FAD Citric Acid Cycle ATP ADP + Pi NAD + CO 2 leaves cycle NADH Succinate NADH NAD + -Ketoglutarate CO 2 leaves cycle The citric acid cycle yields One ATP from each acetyl CoA that enters the cycle, for a net gain of two ATP. Figure 3.25
Cellular Respiration Phase 4: Electron transport chain Electrons of FADH 2 and NADH are transferred from one protein to another, until they reach oxygen Releases energy that results in 32 ATP Requires oxygen
The Big Pay Off Electron Transport Chain NADH and FADH 2 are important carriers of electrons They donate electrons to the electron transport chain At the end of the chain oxygen accepts the electrons.
The Big Pay Off Electron Transport Chain Electron Transport Chain produces ATP using the ATP synthase protein molecule The Electron Transport Chain produces 32 ATP
Electron Transport Chain Potential energy Electron Transport Chain (inner membrane of mitochondrion) High The molecules of NADH and FADH 2 produced by earlier phases of cellular respiration pass their electrons to a series of protein molecules embedded in the inner membrane of the mitochondrion. NAD + NADH 2e As the electrons are transferred from one protein to the next, energy is released and used to make ATP. FADH 2 FAD 2e 2e Membrane proteins 2e Eventually, the electrons are passed to oxygen, which combines with two hydrogens to form water. 2e H 2 O Low Energy released is used for synthesis of ATP 2 H + + 1 2 O 2 Figure 3.26
How is ATP made using the ETC 1. In the mitochondria, the NADH and FADH donate electrons to the electron transport chain (ETC) 2. Oxygen is the final electron acceptor from the ETC 3. The ETC uses the energy from the electrons to transport H + against the concentration gradient, transporting them from the lumen of the mitochondria to the intermembrane space.
How is ATP made using the ETC 4. The ATPsynthase transports the H + back to the lumen of the mitochondria. 5. The H + falling through the ATPsynthase provides the energy for the ATPsynthase to catalyze the reaction of ADP + P ATP
Summary of Cellular Respiration Table 3.5
Summary of Cellular Respiration One molecule of glucose is broken down and 36 ATP are generated. Oxygen is used by the electron transport chain it accepts electrons from the ETC Carbon dioxide is produced by the Transition Reaction and the Citric acid cycle
Summary of Cellular Respiration Glycolysis: Starts the process by taking in glucose. Produces 2 ATP The Transition Reaction produces CO 2 and NADH The Citric acid cycle: Produces 2 ATP but also produces lots of NADH and FADH 2. Produces CO 2.
Summary of Cellular Respiration Electron transport chain Takes electrons from NADH and FADH 2 and uses them to produce ATP using the ATP synthase molecule. Requires oxygen. Oxygen is the final electron acceptor on the electron transport chain One glucose can produce a total of 36 ATP
Complex Carbohydrates must first be broken down into glucose before entering glycolysis Fats and proteins enter the process at different steps
Oxygen Cellular respiration requires oxygen this is aerobic cellular respiration Sometimes organisms, including humans, need to produce energy without using oxygen When you need energy quick, or if there is not enough O 2 then the cell will use only glycolysis
Anaerobic Fermentation Breakdown of glucose without oxygen Takes place entirely in the cytoplasm It is very inefficient - results in only two ATP
Anaerobic Fermentation Anaerobic Fermentation: Anaerobic pathway to produce ATP from glycolysis without the Krebs and ETC
Fermentation in Animals When cells need energy quick they will use this pathway for a short time 2 pyruvic acid + 2 NADH 2 lactate and 2 NAD + End result = lactate and 2 ATP produced (from glycolysis) and NAD + is regenerated
What is the starting molecule of glycolysis? 1. Acetyl CoA 2. Protein 3. Glucose 4. Pyruvate (pyruvic acid)
Which stage produces CO 2 1. Glycolysis 2. Electron Transport Chain 3. Transition 4. Citric acid Cycle 5. Both 3 and 4
Which stage uses O 2 1. Glycolysis 2. Krebs Cycle 3. Electron Transport Chain
Which stage produces the most NADHs 1. Glycolysis 2. Krebs Cycle 3. Electron Transport Chain
Which stage produces the most ATP 1. Glycolysis 2. Krebs Cycle 3. Electron Transport Chain
Important Concepts Read Ch 4 What is Cellular respiration and Anaerobic Fermentation and what are the differences between them. What are the four steps of aerobic cellular respiration, what happens in each step, what are the starting molecules, what comes out of each step, where in the cell does each step occur, how many ATP and NADH/FADH 2 are produced in each step.
Important Concepts Describe in detail how is ATP made using the electron transport chain What is the role of ATPsynthase, H +, O 2, NADH and FADH 2 and the electron transport chain in ATP production? Know the overall picture of cellular respiration (summary slides)
Important Concepts What is the role of oxygen in cellular respiration, what steps produce carbon dioxide What is anaerobic fermentation, what steps are involved in fermentation, what end products are produced in humans, is oxygen required? when is it used.
Definitions Aerobic cellular respiration, anaerobic fermentation, ATP synthase, metabolism