Presentation on theme: "Cellular Respiration Honors Biology. What is Cellular Respiration? The process of converting food energy into ATP energy C 6 H 12 O 6 + 6 O 2 → 6 CO 2."— Presentation transcript:
What is Cellular Respiration? The process of converting food energy into ATP energy C 6 H 12 O 6 + 6 O 2 → 6 CO 2 + 6 H 2 O + 36 ATP
Why are both Photosynthesis and Cell Respiration important to Ecosystems? Light is the ultimate source of energy for all ecosystems Chemicals cycle and Energy flows Photosynthesis and cellular respiration are complimentary reactions
Why do plants need both chloroplasts and mitochondria? Chloroplasts use energy from the sun to make glucose Mitochondria convert glucose to ATP—the energy currency of the cell
What is ATP? Adenosine Triphosphate –5-Carbon sugar (Ribose) – Nitrogenous base (Adenine) –3 Phosphate groups Energy currency of the cell The chemical bonds that link the phosphate groups together are high energy bonds When a phosphate group is removed to form ADP and P, small packets of energy are released
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 reproduction Transport work – active transport, endocytosis, and exocytosis Mechanical work – muscle contraction, cilia and flagella movement, organelle movement
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 kcal 1 ATP = 7.3 kcal 1 Glucose → 36 ATP How efficient are cells at converting glucose into ATP? –38% of the energy from glucose yields ATP, therefore 62% wasted as heat.
Cellular Respiration is a Redox Reaction C 6 H 12 O 6 + 6 O 2 → 6 CO 2 + 6 H 2 O Oxidation 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. (Oxidation) (Reduction)
Cell Respiration can be divided into 4 Parts: 1) Glycolysis 2) Oxidation of Pyruvate / Transition Reaction 3) The Krebs Cycle 4) The Electron Transport Chain and Chemiosmotic Phosphorylation Chemiosmotic Phosphorylation
Where do the 4 parts of Cellular Respiration take place? Glycolysis: –Cytosol Oxidation of Pyruvate: –Matrix The Krebs Cycled: –Matrix Electron Transport Chain and Cheimiosmotic Phosphorylation: –Cristae
Anaerobic Respiration (no oxygen required, cytoplasm) 1.Glycolysis (substrate level) Glucose 4 ATP (Net 2 ATP) 2 ATP2 NADH 2 Pyruvate Aerobic Respiration (oxygen required, mitochondria) 2. Oxidation of Pyruvate 2 Pyruvate 2 CO 2 2 NADH 2 Acetyl CoA 3.Krebs Cycle (substrate level) 2 Acetyl CoA 4 CO 2 2 ATP 6 NADH 2 FADH 2 4.Electron Transport Chain (chemiosmotic) 10 NADH 32 ATP 2 FADH 2 6 H 2 O 6 O 2 Total: 36 ATP produced
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.
Glycolysis Glucose (C 6 ) is split to make 2 Pyruvates (C 3 ) –1 st : ATP energy used to phosphorylate glucose (stored energy) –2 nd : phosphorylated glucose broken down into two C 3 sugar phosphates –3 rd : 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) –4 th : 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 ATP Glycolysis produces very little ATP energy, most energy is still stored in Pyruvate molecules. Glucose 2 Pyruvate 2 ATP4 ATP (Net 2 ATP) 2 NADH
Oxidation of Pyruvate /Transition Reaction When Oxygen is present, 2 Pyruvates go to the matrix where they are converted into 2 Acetyl CoA (C 2 ). Multienzyme complex: – –1 st: each Pyruvate releases CO 2 to form Acetate. – –2 nd: Acetate is oxidized and gives electrons and H + ions to 2 NAD + → 2 NADH. – –3 rd Acetate is combined with Coenzyme A to produce 2 Acetyl CoA molecules. 2 NADH’s carry electrons and hydrogens to the Electron Transport Chain. 2 Pyruvate 2 CO 2 2 NADH 2 Acetyl CoA
The Krebs Cycle / Citric Acid Cycle 8 Enzymatic Steps in Matrix of Mitochondria: Break down and Oxidize each Acetyl CoA (2-C’s) to release 2 CO 2 and yield electrons and H + ions to 3 NAD + + 1 FAD → 3 NADH + FADH 2. 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 FADH 2 which then go on to the Electron Transport Chain. 2 Acetyl CoA 4 CO 2 2 ATP 6 NADH 2 FADH 2
The Electron Transport Chain NADH and FADH 2 produced earlier, go to the Electron Transport Chain. NADH and FADH 2 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 O 2 + 2 electrons + 2 H + (from NADH and FADH 2 ) → H 2 O. 10 NADH 32 ATP 2 FADH 2 H 2 O Oxygen http://vcell.ndsu.nodak.edu/animations/etc/movie.htm
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. http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm
ATP Synthase Multisubunit complex with 4 parts: –Rotor – spins as H + ions flow –Stator – holds the rotor and knob complex together in the cristae –Internal Rod – extends between rotor and knob, spins when rotor spins which then turns the knob –Knob – contains 3 catalytic sites that when turned change shape and activate the enzyme used to make ATP
Review ATP Production: 1) Glycolysis → 2 ATP 2) Oxidation of Pyruvate → No ATP 3) The Krebs Cycle → 2 ATP 4) The Electron Transport Chain and Chemiosmotic Phosphorylation: –Each NADH produces 2-3 ATP so 10 NADH → 28 ATP –Each FADH 2 produces 2 ATP so 2 FADH 2 → 4 ATP Total = 36 ATP Total = 36 ATP 1 Glucose = 686 kcal 1 ATP = 7.3 kcal 1 Glucose → 36 ATP How 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.
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.
Anaerobic Respiration: Fermentation If there is NO oxygen, then cells can make ATP by Fermentation Without oxygen, Oxidation of Pyruvate and the Electron Transport Chain do not operate. Glucose → Pyruvate → Lactate NAD + Glycolysis 2 NADH Reduction Rxn or 2 ATP Alcohol + CO 2 Fermentation 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)