Presentation on theme: "Cellular Respiration: Harvesting Chemical Energy"— Presentation transcript:
1 Cellular Respiration: Harvesting Chemical Energy Chapter 9 notesCellular Respiration: Harvesting Chemical Energy
2 Concept 9.1Metabolic pathways that release energy are called catabolic pathways- fermentation and cellular respirationFermentation: partial degradation of sugars that occurs w/out the help of O2Cellular respiration: O2 is consumed as a reactant along w/ the sugar- more efficient
4 Concept 9.1ATP is the central molecule responsible for energy used by the cellThe cell uses enzymes to transfer phosphate groups from ATP to other compounds (making them phosphorylated)ATP ADP + phosphate
5 Concept 9.1Redox reactions release energy when electrons move closer to electronegative atoms- the relocation of electrons releases the energy stored in food molecules, and this energy is used to synthesize ATP
6 Concept 9.1There is a transfer of one or more e- from one reactant to another; the electron transfers are called oxidation-reduction reactions or redox rxns.- the loss of e- from one substance is called oxidation- the addition of e- to another substance is called reduction
8 Concept 9.1Electrons “fall” from organic molecules to oxygen during cellular respirationC6H12O6 + 6O2 6CO2 + 6H2O + Energy- by oxidizing glucose, cellular respiration takes energy out of storage and makes it available for ATP synthesis- carbohydrates and fats are reservoirs of electrons associated w/ hydrogen
9 Concept 9.1The “fall” of electrons during respiration is stepwise, via NAD+ and an electron transport chainGlucose is broken down over a series of steps that are each catalyzed by a specific enzymeHydrogen atoms are stripped from the glucose and usually passed to NAD+.- NAD+ is reduced in the rxn.
10 Concept 9.1 NAD+ is transformed to NADH - NADH will later be tapped to make ATP as the electrons continue their fall from NADH to oxygenRespiration uses an electron transport chain to break the fall of electrons to oxygen into several energy-releasing steps instead of one explosive rxn.
12 Concept 9.1Electrons removed from food are shuttled by NADH to the “top” end of the chain. At the “bottom”, oxygen captures the electrons along with H+ ions to form waterFood NADH ETC oxygen
13 Concept 9.1 Respiration consists of three stages: - glycolysis, the Krebs cycle, electron transport chain (ETC)Glycolysis breaks down 1 glucose into 2 molecules of pyruvate- occurs in the cytosolKrebs cycle breaks down pyruvate into CO2- occurs in the mitochondrial matrix
14 Concept 9.1ETC accepts electrons from the breakdown products of the first 2 stages- the energy released at each step of the chain is used to make ATP (oxidative phosphorylation); through redox rxns.oxidative phosphorylation accounts for 90% of generated ATP
20 Concept 9.2 Glycolysis means “splitting of sugar” - the 10 steps of glycolysis are broken down into two phases: energy investment and energy payoff- glucose (6C) 2 pyruvate (3C)Energy investment phase: the cell spends 2 ATP to phosphorylate the fuel molecules
21 Concept 9.2Energy payoff phase: 4 ATP are produced by substrate-level phosphorylation; 2 NAD+ are reduced to 2 NADH by the oxidation of foodNet energy yield: 2 ATP and 2 NADH
23 Concept 9.3If O2 is present, energy stored in NADH can be converted to ATPUpon entering the mitochondrion, each pyruvate is first converted to a molecule of acetyl CoA (2C)- another NAD+ is reduced to NADH
25 Concept 9.3Acetyl CoA will enter the Krebs cycle for further oxidationKrebs cycle- 8 steps, each catalyzed by a specific enzyme- Acetyl CoA (2C) enters, 2 CO2 (1C) leave, 3 NAD+ 3 NADH, 1 FAD 1 FADH2, 1 ADP 1 ATP
27 Concept 9.4 Cristae: inner membrane folding of the mitochondria - increases surface area for more ETC’sElectrons removed from food during gycolysis/Krebs are transferred by NADH to the first molecule of the ETC
29 Concept 9.4Most of the electron carriers in the ETC are proteins called cytochromes (cyt).The process goes downhill with oxygen being the final e- acceptor- for every 2 NADH, 1 O2 molecule is reduced into 2 molecules of water
30 Concept 9.4FADH2 adds its e- at a lower energy level than NADH on the ETC.-NADH = 3 ATP- FADH2 = 2 ATPETC makes no ATP directly. It moves e- from food to oxygen breaking the energy drop to manageable amounts.
31 Concept 9.4 Inside the inner membrane are enzymes called ATP synthase. - makes ATP from ADP and a phosphateATP synthase uses energy from the ion gradient to synthesize ATP.- proton gradient
33 Concept 9.4The ETC is an energy converter that uses the exergonic flow of e- to pump H+ ions across the membrane- from the matrix to the inner membrane space.ATP synthases are the only place that are freely permeable to H+
34 Concept 9.4H+ gradient across a membrane couples the redox rxns. of the ETC to ATP synthesis- chemiosmosis: connection between the chemical rxn. Makes ATP and transport across a membrane
35 Concept 9.4H+ ions are pumped by members of the ETC. The resulting gradient is called a proton-motive force: the gradient has the capacity to do work
43 Concept 9.5 Lactic acid fermentation: pyruvate lactic acid - human cells make ATP by (LAF) when oxygen is scarce- lactate is carried away by blood to the liver; lactate is converted back to pyruvate by liver cells
45 Concept 9.5w/out oxygen, the energy still stored in pyruvate is unavailable to cellsFacultative anaerobes: yeasts and bacteria that can make enough ATP to survive using either fermentation or respiration
46 Concept 9.5Ancient prokaryotes probably used anaerobic fermentation before oxygen was present in the atmosphereAlso, glycolysis does not require mitochondria to occur
47 Concept 9.6Fats, proteins, and complex carbs can all be used to make ATPFats can be broken into monomers- glycerol can be converted and can enter glycolysis- fatty acids can be converted into acetyl CoA
49 Concept 9.6 Proteins must be broken down to amino acids - various amino acids can be converted as intermediates of glycolysis and the Krebs cycle
50 Concept 9.6Carbohydrates can be hydrolyzed to form glucose monomers to enter into glycolysisMetabolism works on supply and demand!!!!
51 Concept 9.6Carbs and fats can be converted to fats through intermediates of glycolysis and the Krebs cycleWe will store fat even if we have a fat free diet
52 Concept 9.6 Cellular respiration is controlled by feedback mechanisms Feedback inhibition: end products inhibit the enzymes that catalyze the early steps of the processPhosphofructokinase (enzyme for step 3 of glycolysis) is the pacemaker