Cellular Respiration Overview AP BIO

Cellular Respiration Organic Compounds Oxygen Water Energy + CO2 + + Aerobic Cellular Respiration occurs in the presence of oxygen in the cytosol and the mitochondria The process can be summarized as: C6H12O6 + 6O2  6CO2 + 6H2O + Energy (ATP and Heat) Organic Compounds Oxygen Water Energy + CO2 + +

Redox Reaction Redox Reactions – Reactions involving the transfer of electrons Oxidation – When a substance loses electrons in a redox reaction The substance accepting the electron is known as the oxidizing agent Reduction – When a substance gains electrons in a redox reaction The substance donating the electron is known as the reducing agent

Example: Sodium Chloride Becomes Oxidized (loses electron) Oxidizing Agent + Na Cl - Na Cl + + Reducing Agent Becomes Reduced (gains electron)

Production of ATP C6H12O6 6O2 6CO2 6H2O + + + Energy Becomes Oxidized Oxidizing Agent C6H12O6 6O2 6CO2 6H2O + + + Energy Reducing Agent Becomes Reduced

Overview of the Process With oxygen present, there are 3 main steps in cellular respiration: Glycolysis The Citric Acid Cycle (Krebs Cycle) Oxidative Phosphorylation: ETC and chemiosmosis

Citric Acid Cycle ATP ATP ATP Glycolysis Oxidative Phosphorylation: NADH NADH and FADH2 Oxidative Phosphorylation: ETC And Chemiosmosis Citric Acid Cycle Glycolysis Glucose Pyruvate ATP ATP ATP

Types of Phosphorylation Phosphorylation is how ATPs are formed Oxidative Phosphorylation – Phosphates added to ADP via the redox reactions in the ETC Substrate Level Phosphorylation – An enzyme transfers a phosphate from a substrate, to ADP (glycolysis and citric acid cycle)

Glycolysis Glyco=Sugar; Lysis= Split In Gylcolysis, Glucose is split into two 3-carbon pyruvate (pyruvic acid) molecules In order to begin, glycolysis requires the input of energy (ATP) Glycolysis occurs in the cytosol Lets look at Glycolysis in a very simple form:

Glycolysis (Simplified) 2 ATP are added in the presences of glucose 2 NADH are produced 4 ATP are produced (Net gain of 2) 2 Pyruvate molecules are formed

4 ADP 2 ADP 2ATP Glucose 4ATP 2 NADH Pyruvic Acid 2 NAD+ C C C C C C C

Citric Acid Cycle Also referred to as the Krebs Cycle Takes place in the matrix When oxygen is present, the Citric Acid Cycle follows Glycolysis This cycle takes pyruvate from glycolysis to make ATP, NADH, and FADH2

Citric Acid Cycle Simplified Pyruvate turns into acetyl CoA via coenzyme A (CoA) (this is the link between glycolysis and the Citric Acid Cycle) Acetyl CoA enters the Citric Acid Cycle and is then transformed into citrate There are 7 intermediate molecules, until Oxaloacetate is reformed to begin the cycle again

Citric Acid Cycle - Products 3 NADH, 1 FADH2, 1ATP, and CO2 are produced in the Citric Acid Cycle Each NADH will generate about 3 ATP FADH2 will generate about 2 ATP The CO2 released from this cycle is the same CO2 that you exhale while breathing

Oxidative Phosphorylation This is the process of extracting ATP form the energy in NADH and FADH2 Occurs in the cristae of the mitochondria The electrons are passed through an ETC to release ATP The final electron acceptor is oxygen Oxygen bonds with 2 electrons (carried by Hydrogen) to produce water

e- ADP ATP ADP ATP ADP ATP Energy Level ADP ATP H O

Totals +2 ATP + 2 ATP + 32 ATP = 36 ATP ETC Glycolysis Krebs Cycle

Anaerobic Environments When no oxygen is present, the cell will have to do one of two things: Die due to the fact that there is no Oxygen to accept electrons at the end of oxidative, so no more NAD+ are made or They can undergo Fermentation: Lactic Acid Alcoholic

Fermentation Takes place in the mitochondrial inner membrane Does not require oxygen to occur Does not directly produce ATP

Lactic Acid Fermentation Pyruvate comes from glycolysis and is turned into lactate (lactic acid) NADH gives an electron to become NAD+

Alcoholic Fermentation Pyruvate comes from glycolysis, and is changed into acetaldehyde, and a CO2 is given off in the process Acetaldehyde is turned into ethanol with the help of an electron from NADH The products are CO2, Ethanol, and NAD+

Why fermentation? Why do cells switch to fermentation? Why can’t cells use glycolysis and the Krebs cycle in an anaerobic environment? Right now with your table compare and contrast aerobic and anaerobic respiration