What we will coverAdenosine triphosphate ATP is the immediate source of energy for most cellular processesATP breaks down to ADP and releases energyATP is generated in the aerobic breakdown of carbohydrateIn anaerobic respiration ethanol and lactate are produced and NAD (a coenzyme) is regenerated and can be used to make ATP
ATP to ADP +Pi Releases Energy
There are three phases to Aerobic Respiration ... they are:
1. Glycolysis (same as the glycolysis of anaerobic respiration)
2. Krebs cycle (AKA - Citric Acid cycle)
3. Oxidative Phosphorylation and The Electron Transport Chain
The Separate Biochemical StepsGLYCOLYSISLINK REACTIONTRICARBOXYLIC ACID OR KREBS CYCLEELECTRON TRANSPORT SYSTEM OR OXIDATIVE PHOSPHORYLATION
Phase One: Glycolysis(takes place in the cytoplasm) 4 ATP Yield = 2 ATP Net Gain 2 NAD+ + 2 e- 2 NADH
The First Stage of Respiration for ALL living organisms, anaerobes or aerobes, is called Glycolysis and takes place in the Cytosol.
Glycolysisglyco means glucose/sugar, and lysis means to split. Therefore, glycolysis means to split glucose
This process was likely used to supply energy for the ancient forms of bacteria.
GlycolysisFunction - to split glucose and produce NADH, ATP and Pyruvate (pyruvic acid).
Location - Cytosol
Reactants for Glycolysis Glucose2 ATP. As activation energy4 ADP and 4PEnzymes2 NAD+ (Nicotinamide Adenine Dinucleotide, an energy carrier)
GlycolysisGlucose (6 carbons)Pyruvic Acid (3 Carbons)Pyruvic Acid (3 Carbons)2 ATPs supply the activation energy4 ATPs are produced4 ATP Yield = 2 ATP Net Gain2 NAD+ + 2 e- 2 NADH
Products of Glycolysis 2 Pyruvic Acids (a 3C acid)4 ATP2 NADH
Net Result2 Pyruvic Acid2 ATP per glucose (4 2 = 2)2 NADHIn summary, glycolysis takes one glucose and turns it into 2 pyruvates (molecules of pyruvic acid), 2 NADH and a net of 2 ATP.
Cellular RespirationRecap phase 1 - GlycolysisPhase 2 Krebs Cycle
GlycolysisFunction - Split down the glucose molecules so they are small enough to enter the MitochondriaProducts:2 Pyruvic Acids (a 3 Carbon acid)4 ATP2 NADHATP is the immediate source of energy for most cellular processesNADH carries electrons to the Electron Transport Chain
Glycolysis1 molecule of glucose62 molecules of triose phosphate332 molecules of pyruvate33What is the net production of ATP?phosphorylation(What you need to know)
The story so far
NADH and FADHNAD = Nicotinamide Adenine DinucleotideFAD = Flavin Adenine Dinucleotide NADH and FADH are Coenzymes which carry energy in the form of electronsNADH = reduced NADFADH = FADH2 = reduced FAD
Oxidation and ReductionOxidation describes the loss of electrons / hydrogen or gain of oxygen (NAD/ FAD)Reduction describes the gain of electrons / hydrogen or a loss of oxygen. (NADH/ FADH)
In order for Aerobic Respiration to continue the Pyruvic acid is first converted to Acetic Acid by losing a carbon atom and 2 oxygens as CO2. The Acetic acid then must enter the matrix region of the mitochondria. The CO2 produced is the CO2 animals exhale when they breathe. The Link Reaction
Phase Two: The Krebs Cycle(AKA the Citric Acid Cycle)Sir Hans Adolf Krebs Once the Acetic Acid enters the Matrix it combines with Coenzyme A to form a new molecule called Acetyl-CoA. The Acetyl-CoA then enters the Krebs Cycle.CoA breaks off to gather more acetic acid. The Acetic acid is broken down.Produces most of the cell's energy in the form of NADH and FADH2 not ATP
Does NOT require O2
The Link reactionCitric Acid ProductionMitochondrion
Link ReactionNADReduced NADcoenzyme ACarbondioxideacetyl coenzyme A2
The Krebs cycle
The Krebs CycleCitric Acid ProductionMitochondrion
Krebs Cycleacetyl coAcitrateoxaloacetateATPReduced co enzymes 3NADH1 FADH2 Carbon dioxide642
SummaryAs a result of one turn of the Krebs cycle the cell makes:1 FADH2 3 NADH1 ATPHowever, each glucose produces two pyruvic acid molecules. So the total outcome is: 2 FADH26 NADH2 ATPThe key function of the Krebs cycle is to provide electrons for the Electron Transport Chain, the production of ATP is a bonus.
The story so far
Phase Three:Oxidative PhosphorylationFunction: Extract energy (in the form of electrons) from NADH and FADH2 in order to add a phosphate group to ADP to make ATP.
Location: Mitochondria cristae.
Oxidative PhosphorylationRequiresNADH or FADH2ADP and PO2
Electron Transport Chain Uses NADHDuring the electron transport chain, H+ is moved against a gradient. The energy needed to do this is supplied by electrons carried by NADH
What happens along the inner membrane of the mitochondria?The loss of electrons from NADH result in the addition of energy to protein pumps in the membrane resulting in a H+ being moved from the inside to the outside of the inner membraneThis happens many times creating an imbalance (gradient) of H+.Oxygen pulls electrons to keep them moving.
What happens along the inner membrane of the mitochondria?ATP is made as H+ ions are allowed back into the matrix of the mitochondria by a different protein (ATP synthase). The energy released by the rush of H+ is used by this enzyme to make ATP (kind of like a rush of water in a stream being used to turn a water wheel).Ultimately, aerobic respiration produces ~36 ATP molecules from each individual glucose molecule.
The Electron Transport Chain
Cytochrome cCytochrome c: is one of the proteins of the electron transport chain;exists in all living organisms;is often used by geneticists to determine relatedness.
Chemiosmotic HypothesisBiologists still dont know exactly how ATP is made. The best theory we have is called the Chemiosmotic Hypothesis.
The Chemiosmotic Hypothesis proposes that the Electron Transport Chain energy is used to move H+ (protons) across the cristae membrane, and that ATP is generated as the H+ diffuse back into the matrix through ATP Synthase.
Electron Transport ChainNADReduced NADCarrier 2ReducedCarrier 2Carrier 3ReducedCarrier 3Carrier 4ReducedCarrier 4WaterOxygen
ATP Sum10 NADH x 3 = 30 ATPs 2 FADH2 x 2 = 4 ATPs 2 ATPs (Gly) = 2 ATPs 2 ATPs (Krebs) = 2 ATPs
Max = 38 ATPs per glucose
However...Some energy (2 ATPs) is used to shuttle the NADH from Glycolysis into the mitochondria..So, some biologists teach there is an actual ATP yield of 36 ATPs per glucose.
The Final story