ENERGY FOR CELLS

RespirationChapter 91Energy and Living Things

2ENERGY FOR CELLSWhere do cells get their energy?How do cells get energy?3TWO TYPES OF CHEMICAL REACTIONSEndergonic energy is absorbed. Energy of the products is greater than the energy of the reactants. Uphill4Exergonic Energy is released. Energy of the products is less than the energy of the reactants. Downhill

5Endergonic Reaction

X-axis=timeY-axis=energy

Still requires activation energyRP6Exergonic Reaction

X-axis=timeY-axis=energy

Still requires activation energyRP7ENERGY FOR CELLSAll living things get energy from the sun either directly or indirectly.8Plants use the suns energy directly to make foodSunlight energy must be changed to energy trapped within the bonds of food

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10Animals use the suns energy indirectly through the food made by plants

Both plants and animals systematically break the bonds in food to make energy11ATPAdenosine TriPhosphateIt is the major energy currency of the cellIt is made of a nitrogen base (adenine), a sugar (ribose), and three phosphate groups

12When the third phosphate group of ATP is removed by hydrolysis, a large amount of energy is released.Hydrolysis = when a molecule is broken down by adding water

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14ATP + H2O ADP + PiADP is Adenosine DiPhosphate. Pi is inorganic phosphate 15Your body can use the energy released from breaking the 3rd phosphate bond of ATP to do work.The amount of energy given off from ATP is the perfect amount for cells.Your body can also make ATP from ADP. 16CELLULAR RESPIRATIONCellular respiration is the process by which the chemical energy of "food" molecules is partially transferred to ATP. Breaking down food for energy.17Lipids, proteins, fats, and carbohydrates can be broken down for energy.Our focus is on glucose.

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19Two types of respiration:Aerobic uses oxygenOccurs in the mitochondriaAnaerobic uses no oxygen (also called fermentation)Occurs in the cytoplasm20AEROBIC RESPIRATONThe energy in the chemical bonds of glucose is partially transferred to ADP to make ATP.60% of the energy from glucose is lost as heat.21Glucose is broken down.Oxygen is needed to completely break down glucose.Carbon dioxide is released.

Oxygen + Glucose CO2 + water + energy22GlycolysisThe first set of reactions in cellular respiration is GlycolysisGlycolysis is the process in which 1 molecule of glucose (C6) is broken in half, producing two molecules of pyruvic acid (C3)Glycolysis occurs in the cytoplasm23Glucose2 ADP4ATP4 ADP2ATP2 NAD+2NADH2 Pyruvic Acid24ATP ProductionGlycolysis is an energy-releasing process, but the cell needs to invest a little energy to get things started2 ATPs are needed to get glycolysis started, but at the end 4 ATPs are producedSince we already invested 2 ATP, we have a net gain of 2 ATP25NADH ProductionOne of the reactions in glycolysis removes high energy electrons from each 3 carbon molecule and passes them to an electron carrier, NAD+NAD+ hold on to the electrons until it can pass them to other molecules within the mitochondria26

27The Krebs CycleAfter glycolysis, about 90% of the chemical energy of glucose is still trapped in the high-energy electrons of pyruvic acidDuring the Krebs cycle, pyruvic acid is broken down and carbon dioxide is releasedThe Krebs cycle occurs in the mitochondria28The Krebs cycle begins when pyruvic acid enters the mitochondrion and is changed to another moleculePyruvic acid joins with a compound called Coenzyme-A to make acetyl-CoACO2 is given offAcetyl-CoA joins with a 4 carbon molecule to make citric acid (6C)

29Pyruvic AcidCO2NAD+NADHCo-ACo-ACo-ACitrate30Citric acid enters the Krebs cycle and is eventually broken down into a 4 carbon moleculeThe products of the Krebs cycle include CO2, ATP, NADH, and FADH2 (a different electron carrier)The Krebs cycle is where the energy pay-off is the largest

31Citric Acid5 Carbon Compound4 Carbon CompoundCO2NAD+NADHCO2NAD+NADHADPATPFADFADH2NAD+NADH32What Happens to all of these Products???NADH and FADH2 go to the Electron Transport Chain to make ATPsThe CO2 released is the carbon dioxide you breathe out when you exhaleThe ATPs can be used for cellular activity33

34Electron TransportThe Electron Transport Chain (ETC) is a series of proteins in the inner mitochondrial membrane that pass along the high energy electrons of NADH and FADH2These high-energy electrons are used by the ETC to convert ADP to ATP35

36How ATPs are MadeNADH and FADH2 bring their high energy electrons to specific proteins within the inner mitochondrial membraneThese special proteins are arranged in a line and make up the Electron Transport Chain

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38The electrons then jump from one protein to the next and lose a bit of energy in each jump NADH electrons have more energy than FADH2 electrons, thus they are dropped off higher in the ETCEvery time the electrons make a jump they carry with them a proton (H+) and drop them off in the space between membranes39Whats the Point?At the end of every ETC there is a special enzyme called ATP synthaseThe H+ diffuse through the ATP synthase creating enough energy to add a phosphate to ADP to make ATP40What about our electrons?At the end of the ETC the electrons need a place to goOxygen is the final electron acceptor which accepts two electrons and 2 H+ per oxygen atomThe point? No oxygen, no Krebs cycle41This oxygen is the oxygen that we breathe in every time we take a breath42WHOA!This means that for each molecule of glucose you can make a maximum of 38 ATPs43ANAEROBIC RESPIRATION (FERMENTATION)In many cells, if oxygen is not present, glucose is broken down in a process called fermentation.

44Less ATP is made in anaerobic respiration than in aerobic respiration.In animals, lactic acid is made.In yeast, alcohol (ethanol) and carbon dioxide are made.45Lactic Acid FermentationIn animals, if enough oxygen is not present, respiration stops at GlycolysisPyruvic acid is converted to Lactic acid so that NAD+ can be regenerated

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GlucosePyruvic acidLactic acid47ALCOHOLIC FERMENTATIONIn yeast, if oxygen is not present, respiration also stops at GlycolysisPyruvic acid is converted to an Alcohol (ethanol) so that NAD+ can be regenerated

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GlucosePyruvic acidEthanol

49Aerobic vs. Anaerobic RespirationAerobic respiration gives us 38 ATPs (maximum) from each molecule of glucoseAnaerobic respiration gives us 2 ATPs from each molecule of glucose50Figure 9.6 An overview of cellular respiration (Layer 3)