Cellular Respiration Harvesting Chemical Energy Respiration is the

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 Reactants C 6 H 12 O 6 + 6 O 2 Products 6 CO 2 + 6 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.

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

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 4 P Enzymes 2 NAD+ (Nicotinamide Adenine Dinucleotide, an energy carrier)

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

Products of Glycolysis • 2 Pyruvic Acids (a 3 C 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 (Ethyl Alcohol or Ethanol) 2 C 2 H 5 OH + 2 CO 2 As a result of Alcoholic Fermentation, Glucose is converted into 2 molecules of Ethyl Alcohol and 2 Molecules of Carbon Dioxide.

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

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 Barley Grapes Juniper Cones Agave Leaves Rice Potatoes Gin Saki Tequila Vodka Beer Wine 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 Glycolysis 4 ATP’s are produced Pyruvic Acid (3 C) Lactic Acid (3 C) Glucose (6 carbons) 2 ATP’s supply the activation energy 2 NAD+ + 2 e- 2 NADH 2 NAD + + 2 e- 4 ATP Yield = 2 ATP Net Gain

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

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) Once the Acetic Acid enters the Matrix it combines with Coenzyme A to form a new molecule called Acetyl-Co. A. The Acetyl-Co. A then enters the Krebs Cycle. Sir Hans Adolf Krebs Produces most of the cell's energy in the form of NADH and FADH 2… not ATP Does NOT require O 2 Co. A breaks off to gather more acetic acid. The Acetic acid is broken down. + 3 H 3 NADH

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˜ http: //vcell. ndsu. nodak. edu/animations/etc/movie. htm

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 (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.