Cellular Respiration: Harvesting Chemical Energy

Respiration is the process of extracting stored energy from glucose and storing it in the high energy bonds of ATP.

Cellular Respiration Equation C 6 H 12 O O 2 6 CO H 2 O and energy As a result of respiration, energy is released from the chemical bonds and used for “phosphorylation” of ATP. Phosphorylation is the process of adding a phosphate group to a molecule…. By adding a phosphate ADP it becomes ATP. The respiration reactions are controlled by ENZYMES. Reactants Products

Cellular Respiration There are two types of Respiration: Anaerobic Respiration and Aerobic Respiration Some organisms use the Anaerobic Respiration pathway, and some organisms use the Aerobic Respiration pathway.

Anaerobes Anaerobes are organisms that use the Anaerobic Respiration pathway Most anaerobes are bacteria (not all). Anaerobes do NOT require oxygen.

Aerobes Aerobes are organisms that use the Aerobic Respiration pathway. Aerobes require oxygen.

Anaerobic Respiration Anaerobic Respiration does NOT NOT require oxygen! The 2 most common forms of Anaerobic Respiration are: 1. Alcoholic Fermentation, and 2. Lactic Acid Fermentation

ALL The First Stage of Respiration for ALL living organisms, anaerobes or aerobes, is called Glycolysis and takes place in the Cytosol.

Glycolysis glyco 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.

Glycolysis Function - to split glucose and produce NADH, ATP and Pyruvate (pyruvic acid). Location - Cytosol Occurs in 9 steps- 6 of the steps use magnesium (Mg) as a cofactor.

Reactants for Glycolysis Glucose 2 ATP…. As activation energy 4 ADP and 4P Enzymes 2 NAD + (Nicotinamide Adenine Dinucleotide, an energy carrier )

Glycolysis Glucose (6 carbons) Pyruvic Acid (3 Carbons) 2 ATP’s supply the activation energy 4 ATP’s are produced 4 ATP Yield = 2 ATP Net Gain 2 NAD e- 2 NADH

Products of Glycolysis 2 Pyruvic Acids (a 3C acid) 4 ATP 2 NADH

Net Result 2 Pyruvic Acid 2 ATP per glucose (4 – 2 = 2) 2 NADH In summary, glycolysis takes one glucose and turns it into 2 pyruvates (molecules of pyruvic acid), 2 NADH and a net of 2 ATP.

Alcoholic Fermentation is carried out by yeast, a kind of fungus.

Alcoholic Fermentation Uses only Glycolysis. Does NOT require O 2 Produces ATP when O 2 is not available.

Alcoholic Fermentation C 6 H 12 O 6 2 C 2 H 5 OH + 2 CO 2 (Ethyl Alcohol or Ethanol) As a result of Alcoholic Fermentation, Glucose is converted into 2 molecules of Ethyl Alcohol and 2 Molecules of Carbon Dioxide.

Alcoholic Fermentation Glucose (6 carbons) Pyruvic Acid (3C) 2 ATP’s supply the activation energy 4 ATP’s are produced 4 ATP Yield = 2 ATP Net Gain 2 NAD e- 2 NADH 2 NAD e- CO 2 Ethyl Alcohol (2C) (C 2 H 5 OH) Glycolysis Released into the environment

Question Why is the alcohol content of wine always around 12-14%? Because Alcohol is toxic and kills the yeast at high concentrations. Oh Yeah…..The Holes in Swiss Cheese are bubbles of CO 2 from fermentation.

Matching Sugar Cane Gin Barley Saki Grapes Tequila Juniper Cones Vodka Agave Leaves Beer Rice Wine Potatoes Rum

Importance of Fermentation Alcohol Industry - almost every society has a fermented beverage. Baking Industry - many breads use yeast to provide bubbles to raise the dough.

Lactic Acid Fermentation Uses only Glycolysis. Does NOT require O 2 Produces ATP when O 2 is not available.

Lactic Acid Fermentation Carried out by human muscle cells under oxygen debt. Lactic Acid is a toxin and causes fatigue, soreness and stiffness in muscles.

Lactic Acid Fermentation Glucose (6 carbons) Pyruvic Acid (3C) 2 ATP’s supply the activation energy 4 ATP’s are produced 4 ATP Yield = 2 ATP Net Gain 2 NAD e- 2 NADH 2 NAD e- Lactic Acid (3C) Glycolysis

Fermentation - Summary Releases 2 ATP from the breakdown of a glucose molecule Provides ATP to a cell even when O 2 is absent.

Aerobic Respiration requires oxygen!

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

Phase One: Glycolysis (takes place in the cytoplasm) Glucose (6 carbons) Pyruvic Acid (3C) 2 ATP’s supply the activation energy 4 ATP’s are produced 4 ATP Yield = 2 ATP Net Gain 2 NAD e- 2 NADH Glycolysis

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 CO 2. The Acetic acid then must enter the matrix region of the mitochondria. The CO 2 produced is the CO 2 animals exhale when they breathe.

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. 3 NADH + 3H Produces most of the cell's energy in the form of NADH and FADH 2 … not ATP Does NOT require O 2

Summary As a result of one turn of the Krebs cycle the cell makes: 1 FADH 2 3 NADH 1 ATP However, each glucose produces two pyruvic acid molecules…. So the total outcome is: 2 FADH 2 6 NADH 2 ATP

Phase Three: Oxidative Phosphorylation Function: Extract energy from NADH and FADH 2 in order to add a phosphate group to ADP to make ATP. Location: Mitochondria cristae.

Oxidative Phosphorylation Requires NADH or FADH 2 ADP and P O 2

Oxidative Phosphorylation Requires the Electron Transport Chain. The Electron Transport Chain is a collection of proteins, embedded in the inner membrane. It is used to transport the electrons from NADH and FADH 2. ˜ A link to an Internet Animation of the Electron Transport Chain ˜

The Electron Transport Chain

Cytochrome c Cytochrome 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 Hypothesis Biologists still don’t 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.

ATP Synthase Uses the flow of H + to make ATP. Works like an ion pump in reverse, or like a waterwheel under the flow of H + “water”.

Comparing Aerobic and Anaerobic Respiration Aerobic Respiration- –requires a mitochondrion and oxygen –is a three phase process Anaerobic – –does not require oxygen –consists of one phase only-Glycolysis

Strict vs. Facultative Respiration Strict - can only carry out Respiration only one way… aerobic or anaerobic. Ex - you Facultative - can switch respiration types depending on O 2 availability. Ex – yeast Aerobes – organisms that require oxygen Anaerobes - organisms that DO NOT require oxygen Obligate Anaerobes – oxygen is LETHAL to these organisms Facultative – organisms that can live with or without oxygen

ATP Sum 10 NADH x 3 = 30 ATPs 2 FADH 2 x 2 = 4 ATPs 2 ATPs (Gly) = 2 ATPs 2 ATPs (Krebs) = 2 ATPs Max = 38 ATPs per glucose

However... Some energy (2 ATP’s) is used to shuttle the NADH from Glycolysis into the mitochondria…..So, some biologists teach there is an actual ATP yield of 36 ATP’s per glucose.