2 What is Cellular Respiration? The process of converting food energy into ATP energyC6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 36 ATP
3 Why are both Photosynthesis and Cell Respiration important to Ecosystems? Light is the ultimate source of energy for all ecosystemsChemicals cycle and Energy flowsPhotosynthesis and cellular respiration are complimentary reactions
4 Why do plants need both chloroplasts and mitochondria? Chloroplasts use energy from the sun to make glucoseMitochondria convert glucose to ATP—the energy currency of the cell
5 What is ATP? Adenosine Triphosphate Energy currency of the cell 5-Carbon sugar (Ribose)Nitrogenous base (Adenine)3 Phosphate groupsEnergy currency of the cellThe chemical bonds that link the phosphate groups together are high energy bondsWhen a phosphate group is removed to form ADP and P, small packets of energy are released
6 How is ATP used?As ATP is broken down, it gives off usable energy to power chemical work and gives off some nonusable energy as heat.Synthesizing molecules for growth and reproductionTransport work – active transport, endocytosis, and exocytosisMechanical work – muscle contraction, cilia and flagella movement, organelle movement
7 Why use ATP energy and not energy from glucose? Breaking down glucose yields too much energy for cellular reactions and most of the energy would be wasted as heat.1 Glucose = 686 kcal1 ATP = 7.3 kcal1 Glucose → 36 ATPHow efficient are cells at converting glucose into ATP?38% of the energy from glucose yields ATP, therefore 62% wasted as heat.
8 Cellular Respiration is a Redox Reaction (Oxidation)C6H12O6 + 6 O2 → 6 CO2 + 6 H2OOxidation is the loss of electrons or H+Reduction is the gain of electrons or H+Glucose is oxidized when electrons and H+ are passed to coenzymes NAD+ and FAD before reducing or passing them to oxygen.Glucose is oxidized by a series of smaller steps so that smaller packets of energy are released to make ATP, rather than one large explosion of energy.(Reduction)
9 Cell Respiration can be divided into 4 Parts: 1) Glycolysis2) Oxidation of Pyruvate / Transition Reaction3) The Krebs Cycle4) The Electron Transport Chain andChemiosmotic Phosphorylation
10 Where do the 4 parts of Cellular Respiration take place? Glycolysis:CytosolOxidation of Pyruvate:MatrixThe Krebs Cycled:Electron Transport Chain and Cheimiosmotic Phosphorylation:Cristae
12 Anaerobic Respiration (no oxygen required, cytoplasm) Glycolysis(substrate level)Glucose 4 ATP (Net 2 ATP)2 ATP 2 NADH2 PyruvateAerobic Respiration (oxygen required, mitochondria)2. OxidationofPyruvate2 Pyruvate 2 CO22 NADH2 Acetyl CoAKrebs Cycle(substrate level)2 Acetyl CoA 4 CO22 ATP6 NADH2 FADH2ElectronTransportChain(chemiosmotic)10 NADH 32 ATP2 FADH2 6 H2O6 O2Total: 36 ATP produced
13 ATP is made in two ways:1) Substrate Level Phosphorylation (glycolysis & Krebs cycle)2) Chemiosmotic Phosphorylation (electron transport chain)Substrate-Level Phosphorylation:Energy and phosphate are transferred to ADP using an enzyme, to form ATP. Phosphate comes from one of the intermediate molecules produced from the breakdown of glucose.
14 Glycolysis Glucose 2 Pyruvate 2 ATP 4 ATP (Net 2 ATP) 2 NADH Glucose (C6) is split to make2 Pyruvates (C3)1st: ATP energy used to phosphorylate glucose (stored energy)2nd: phosphorylated glucose broken down into two C3 sugar phosphates3rd: the sugar phosphates are oxidized to yield electrons and H+ ions which are donated to 2 NAD+ → 2 NADH (stored electron and hydrogen for the Electron Transport Chain)4th: The energy from oxidation is used to make 4 ATP molecules (net 2 ATP)This is substrate level phosphorylation because an enzyme transfers phosphate to ADP making ATPGlycolysis produces very little ATP energy, most energy is still stored in Pyruvate molecules.
15 Oxidation of Pyruvate /Transition Reaction 2 Pyruvate 2 CO22 NADH2 Acetyl CoAWhen Oxygen is present, 2 Pyruvates go to the matrix where they are converted into 2 Acetyl CoA (C2).Multienzyme complex:1st: each Pyruvate releases CO2 to form Acetate.2nd: Acetate is oxidized and gives electrons and H+ ions to 2 NAD+ → 2 NADH.3rd Acetate is combined with Coenzyme A to produce 2 Acetyl CoA molecules.2 NADH’s carry electrons and hydrogens to the Electron Transport Chain.
16 The Krebs Cycle / Citric Acid Cycle 2 Acetyl CoA 4 CO22 ATP6 NADH2 FADH28 Enzymatic Steps in Matrix of Mitochondria: Break down and Oxidize each Acetyl CoA (2-C’s) to release 2 CO2 and yield electrons and H+ ions to NAD+ + 1 FAD → 3 NADH + FADH2. This yields energy to produce ATP by substrate level phosphorylation.The first step of the Krebs cycle combines Oxaloacetate (4 C’s) with Acetyl CoA to form Citric Acid, then the remaining 7 steps ultimately recycle oxalacetate.Two Turns of the Krebs Cycle are required to break down both Acetyl Coenzyme A molecules.The Krebs cycle produces some chemical energy in the form of ATP but most of the chemical energy is in the form of NADH and FADH2 which then go on to the Electron Transport Chain.
17 The Electron Transport Chain 10 NADH 32 ATP2 FADH2 H2OOxygenNADH and FADH2 produced earlier, go to the Electron Transport Chain.NADH and FADH2 release electrons to carriers/proteins embedded in the membrane of the cristae. As the electrons are transferred, H+ ions are pumped from the matrix to the intermembrane space up the concentration gradient. Electrons are passed along a series of 9 carriers until they are ultimately donated to an Oxygen molecule.½ O2 + 2 electrons + 2 H+ (from NADH and FADH2) → H2O.
18 Chemiosmotic Phosphorylation Hydrogen ions travel down their concentration gradient through a channel protein coupled with an enzyme called ATP Synthase.As H+ ions move into the matrix, energy is released and used to combine ADP + P → ATP.Hydrogens are recycled and pumped back across the cristae using the Electron Transport Chain.ATP diffuses out of the mitochondria through channel proteins to be used by the cell.
19 ATP Synthase Multisubunit complex with 4 parts: Rotor – spins as H+ ions flowStator – holds the rotor and knob complex together in the cristaeInternal Rod – extends between rotor and knob, spins when rotor spins which then turns the knobKnob – contains 3 catalytic sites that when turned change shape and activate the enzyme used to make ATP
20 Review ATP Production: 1) Glycolysis → 2 ATP2) Oxidation of Pyruvate → No ATP3) The Krebs Cycle → 2 ATP4) The Electron Transport Chain and Chemiosmotic Phosphorylation:Each NADH produces 2-3 ATP so NADH → 28 ATPEach FADH2 produces 2 ATP so FADH2 → 4 ATPTotal = 36 ATP1 Glucose = 686 kcal1 ATP = 7.3 kcal1 Glucose → 36 ATPHow efficient are cells at converting glucose into ATP?38% of the energy from glucose yields ATP, therefore 62% wasted as heat (used to maintain body temperature or is dissipated)Ex. Most efficient Cars: only 25% of the energy from gasoline is used to move the car, 75% heat.
21 All Types of Molecules can be used to form ATP by Cell Respiration: Proteins, Carbohydrates, and Lipids must first be broken down into their monomers and absorbed in the small intestine.Monomers may be further broken down into intermediate molecules before entering different parts of Cell respiration to ultimately form ATP.
22 Anaerobic Respiration: Fermentation If there is NO oxygen, then cells can make ATP by FermentationWithout oxygen, Oxidation of Pyruvate and the Electron Transport Chain do not operate.Glucose → Pyruvate → LactateNAD+ Glycolysis 2 NADH Reduction Rxn or2 ATP Alcohol + CO2Fermentation yields a net gain of 2 ATP by substrate level phosphorylation for every 1 Glucose. (Inefficient)Two Forms of Fermentation:Lactic Acid Fermentation (animals)Alcohol Fermentation (yeast)