How cells use food and oxygento make energy in the form of ATP and do work.
Types of Cellular Respiration• Aerobic Cellular Respiration- Cells make ATP using Oxygen in mitochondria• Anaerobic Cellular Respiration- Cells make ATP without using Oxygen in the cytoplasm of the cell. Also referred to as fermentation.
Big PictureBoth are catabolic reactions that produceenergy in the form of ATP.
Aerobic cellular respiration is thechemical (metabolic) reaction that usesO2 and produces CO2 so it is the reason why we need to breathe.
Equation for Aerobic Cellular RespirationGlucose + O2 CO2 + H2O + ATP
3 main chemical reactions in aerobic cellular respirationGlycolysisKrebs CycleElectron Transport System
1. Glycolysis• Catabolic reaction that breaks glucose into 2 molecules of pyruvic acid or pyruvate.• Occurs in the cytoplasm of the cell• Does not use O2 (it is part of cellular respiration but it is also the first step in the fermentation process as well)
2. Krebs Cycle• Complex sequence of reactions that occur in the mitochondrial matrix.• Reactions complete the breakdown of the original glucose molecule by acting on pyruvic acid
We call it a cyclebecause it iscontinuously runningand it is alwaysrecycling the startingmolecule.
Major Impact of the Krebs Cycle•Completes the break down of glucose•Makes a lot of electron carriers (NADH,FADH2)•Produces the majority of CO2 that must beeliminated from the system
Matrix Cristae Sometimes called the matrix reactions because of where they occur in the mitochondria
How?Pyruvic acid enters the mitochondria fromthe cell cytoplasm and then is converted intoanother molecule called Acetyl Co-A.
How much energy is made during the Krebs Cycle ? 1. 2- ATP 2. 8 NADH 3. 2 FADH2 4. 6 CO2 (We get rid of it by exhaling)
3. Electron Transport System The electron transport system is a series of molecules embedded in the cristae of the mitochondria that accept and transfer electrons. (Oxidation-Reduction)
The ETS uses the shuttling of electronsdonated by NADH and FADH2 to make a lotof ATP.
Oxidation- molecule loses an electronReduction- molecule gains an electron
The ETS proteins take the electronsfrom NADH and FADH2 and movethem down to oxygen.NADH NAD+FADH2 FADH
At each transfer (oxidation-reduction)some energy is lost.This creates energy that is used to take Pi(inorganic PO4) and add it to ADP tomake ATP in a process called oxidativephosphorylation.
Phosphorylation Adding phosphate to another molecule Oxidative PhosphorylationAdding phosphate to another molecule in theelectron transport system in the presence ofOxygen
Substrate level phosphorylation Any other phosphorylation in the cell
Chemiosmosis Oxidative phosphorylation of ADP to make ATP occurs through Chemiosmosis.As electrons are being transferred through the etsthe energy is used to pump Hydrogen ions acrossone side of the membrane.This builds up a higher concentration on one sidethan the other. Like a Hydrogen ion dam.
Because substances havea tendency to movefrom a higherconcentration to a lowerconcentration, thehydrogen ion dam canbe usedto do work.
The only way for theHydrogen ions tomove down theirconcentrationgradient is backthrough themembrane throughthe enzyme ATPSynthase.
The Hydrogen ionturns on theenzyme allowing itto phosphorylateADP and make anATP molecule
The electron transport system uses all of the electron carriers to produce about 34 molecules of ATP.This system uses oxygen as its final electron acceptor.
Anaerobic Cellular Respiration (Fermentation)There are lots of different kinds of fermenationsThey are usually named after their end-product6. Ethanol and CO2- alcohol8. Lactic acid- yogurt- also occurs in muscles
Glycolysis always occurs first with glucosebeing converted into 2 molecules of pyruvate. Ethanol Fermentation Pyruvate Ethanol + CO2
Lactic Acid Fermentation Pyruvate Lactic AcidThis can occur by adding microbes to milk tomake cheese or yogurt but also occurs in themuscles when O2 is not being delivered fastenough to run aerobic cellular respiration.
Glycolysis and fermentation onlyproduces 2 ATP per glucose moleculeso it is a very inefficient way to make ATPfor cells.Once we add the mitochondria in and useO2 to make ATP we can get as many as36-38 ATP’s being formed per glucosemolecule