CHAPTER 7: CELLULAR RESPIRATION  7-1: Glycolysis + Fermentation  7-2: Aerobic Respiration

Cellular Respiration  Most foods contain usable energy, stored in complex organic compounds such as: Proteins Proteins Carbohydrates Carbohydrates Fats Fats  All cells break down organic compounds into simpler molecules, a process that releases energy to power cellular activities

Harvesting Chemical Energy  Cellular Respiration Complex process in which cells make ATP by breaking down organic compounds Complex process in which cells make ATP by breaking down organic compounds Both autotrophs + heterotrophs undergo cell respirationBoth autotrophs + heterotrophs undergo cell respiration Some of the energy is used to make ATP; then energy used by cells to do workSome of the energy is used to make ATP; then energy used by cells to do work

Overview of Cellular Respiration  Biochemical pathway with Photosynthesis Products + Reactants Products + Reactants Redox reactions (‘OILRIG’: e - = energy) Redox reactions (‘OILRIG’: e - = energy)  Equation C 6 H 12 O O 2 6 CO H 2 O + NRG C 6 H 12 O O 2 6 CO H 2 O + NRG  Two Stages: Glycolysis Glycolysis Aerobic Respiration Aerobic Respiration

Glycolysis  Biochemical pathway in which one 6- C molecule of glucose is oxidized to produce two 3-C molecules of pyruvic acid Catalyzed by specific enzymes Catalyzed by specific enzymes Reactions occur within cytosol of cells Reactions occur within cytosol of cells Anaerobic process Anaerobic process

4 Major Steps of Glycolysis 1. Two phosphate groups are attached to one molecule of glucose, forming a new 6-C compound. ATP supplies the phosphate groups 2. The 6-C compound splits into 2 3-C compounds called G3P

Glycolysis (cont.) 3. The 2 G3P molecules are oxidized and each receives a phosphate group creating two new 3-C compounds. During the oxidation, NAD + picks up electrons lost by the oxidation of each G3P compound (redox) - NADH 4. All phosphate groups are removed which makes 2 new 3-C compounds called pyruvic acid. Each phosphate groups is added to ADP to make four molecules of ATP

Net Yield of NRG?  Glycolysis only produces 2 ATP molecules to be used by the cell from one molecule of glucose *Even though 4 ATP are produced at Step 4, 2 ATP were used in Step 1* *Even though 4 ATP are produced at Step 4, 2 ATP were used in Step 1*

Recap of Glycolysis

Video Recap…  Glycolysis Glycolysis

Fermentation  If oxygen is present after glycolysis, pyruvic acid enters Aerobic Respiration  In anaerobic conditions, some cells can convert pyruvic acid into other compounds through additional biochemical pathways  Glycolysis + additional pathways = Fermentation Takes place in the cytosol of cells Takes place in the cytosol of cells Does not produce any ATP Does not produce any ATP Helps regenerate NAD +, which is used throughout cellular respiration Helps regenerate NAD +, which is used throughout cellular respiration Differs in enzymes used and compounds made Differs in enzymes used and compounds made Two most common: Lactic Acid + Alcoholic Two most common: Lactic Acid + Alcoholic

Lactic Acid Fermentation  Pyruvic acid converted into lactic acid  L.A.F. involves the transfer of one H atom and one free proton (H + ) In the process, NAD + is regenerated and can be used again in glycolysis In the process, NAD + is regenerated and can be used again in glycolysis

Lactic Acid Fermentation

L.A.F. (cont.)  L.A.F. used by microorganisms in manufacturing dairy products such as yogurt and cheese

L.A.F. (cont.)  L.A.F. also occurs in your muscle during strenuous exercise During this type of exercise, muscle cells use up O 2 much more quickly than it can be delivered to them During this type of exercise, muscle cells use up O 2 much more quickly than it can be delivered to them As O 2 depletes, aerobic respiration is changed to L.A.F. As O 2 depletes, aerobic respiration is changed to L.A.F. The cytosol more acidic and muscles become fatigued or sore The cytosol more acidic and muscles become fatigued or sore Eventually lactic acid gets converted back to pyruvic acid by the liver Eventually lactic acid gets converted back to pyruvic acid by the liver

Alcoholic Fermentation  Pyruvic acid converted into ethyl alcohol + CO 2

Alc. Fermentation (cont.) 1. A CO 2 molecule is removed from pyruvic acid, leaving a 2-C compound 2. Two Hydrogen atoms are added to the 2- C compound to form ethyl alcohol (ethanol) H atoms transferred from NADH and H +, regenerating NAD + for use in glycolysis H atoms transferred from NADH and H +, regenerating NAD + for use in glycolysis

Alc. Fermentation (cont.)

AF by yeast cells to make beer + wine AF by yeast cells to make beer + wine These microorganisms eat the SUGAR in fruit or grains which cause fermentation to take place These microorganisms eat the SUGAR in fruit or grains which cause fermentation to take place AF also used in making bread. Rises due to loss of CO 2 AF also used in making bread. Rises due to loss of CO 2

Fermentation (anaerobic pathways)

Efficiency of Glycolysis  Glycolysis alone is only 2% efficient at extracting energy from glucose  So where is the rest of the energy? PYRUVIC ACID!!!!!!! PYRUVIC ACID!!!!!!!  Early Earth + Glycolysis? Some early unicellular organisms, such as bacteria, might have been able to survive on using glycolysis for energy production Some early unicellular organisms, such as bacteria, might have been able to survive on using glycolysis for energy production Most organisms need more energy (>2 ATP), so they needed to find a better energy-producing mechanism Most organisms need more energy (>2 ATP), so they needed to find a better energy-producing mechanism AEROBIC RESPIRATION!!!AEROBIC RESPIRATION!!!