Respiration Glycolysis | Aerobic Respiration | Anaerobic Respiration

Respiration Learning Objectives Explain the release of energy through glycolysis Describe the main steps of aerobic respiration Differentiate between the two main types of anaerobic respiration Compare and contrast the different forms of aerobic and anaerobic respiration After this lesson you will be able to explain the release of energy through glycolysis, describe the main steps of aerobic respiration, differentiate between the two main types of anaerobic respiration, and compare and contrast the different forms of aerobic and anaerobic respiration.  

Respiration Respiration takes place in three main stages: Glycolysis (anaerobic) Krebs cycle (aerobic) Electron Transport Chain (aerobic) ATP

Glycolysis occurs in the cytoplasm. Glycolysis occurs in the ________, but the Krebs cycle, and electron transport chain occurs in the ____________. cytoplasm mitochondria The Krebs cycle and the electron transport chain occur in the mitochondria. Glycolysis occurs in the cytoplasm.

2 molecules pyruvic acid G L Y C O S I Definition: Glycolysis is the process in which one molecule of glucose is broken down to produce two molecules of pyruvic acid. Glucose 2 molecules pyruvic acid

Glycolysis Glycolysis – breaks down glucose into two molecules of pyruvic acid Products: 2 pyruvate, 2 ATP, and 2 NADH Occurs in cytosol with or without oxygen The breakdown of glucose to generate ATP may occur by two different methods, depending on whether oxygen is available. Both types of respiration begin in the cell’s cytoplasm with the process of glycolysis. Glycolysis breaks down each molecule of glucose, a six-carbon sugar, into two molecules of pyruvic acid, a three-carbon molecule. The conversion of glucose to pyruvic acid occurs in several steps that include intermediate molecules of phosphorylated six-carbon sugar and three-carbon sugars. The transfer of phosphate groups from the three-carbon sugars to ADP produces ATP. Since a phosphate molecule is transferred from a substrate to ADP, this is known as substrate-level phosphorylation. Two molecules of ATP are needed to begin glycolysis, but four molecules of ATP are produced. This gives a net gain of two ATP molecules. Two molecules of the electron carrier NAD+ are also converted to NADH. Since oxygen is not required, glycolysis can occur in the presence or absence of oxygen.

There are 2 types of respiration: Aerobic Respiration: Requires oxygen Anaerobic Respiration: Does NOT require oxygen

Aerobic Respiration Aerobic respiration – the process of breaking down glucose to yield a maximum amount of ATP that takes place in the presence of oxygen Generates 36-38 ATP Citric acid cycle – a series of eight reactions that further breaks down the end product of glycolysis (acetyl CoA) to carbon dioxide Oxygen-dependent aerobic respiration occurs within the mitochondria of eukaryotic cells. When oxygen is present, the pyruvate produced in glycolysis enters the mitochondria and proceeds through another series of reactions. Aerobic respiration generates the maximum amount of energy possible from one glucose molecule. Combining the processes glycolysis and aerobic respiration, the maximum energy output for one glucose molecule is either 36 or 38 molecules of ATP, depending on the specific pathway used. Aerobic respiration occurs in several steps. The pyruvic acid generated in glycolysis is used in the citric acid cycle. Electron carriers charged from glycolysis and the citric acid cycle are used in an electron transport chain.

Aerobic Respiration Citric acid cycle Occurs in mitochondria Pyruvate from glycolysis is converted to acetyl CoA before entering cycle Cycle turns twice per glucose molecule One turn per acetyl CoA Each turn produces: 2 CO2 2 NADH 1 FADH2 1 ATP If oxygen is present, the two molecules of pyruvate produced in glycolysis enter the mitochondria, where they are converted to two molecules of acetyl coenzyme A (acetyl CoA). During this reaction, two molecules of carbon dioxide and two molecules of NADH are produced.   Acetyl CoA enters the citric acid cycle and interacts with oxaloacetate to form citrate, which then undergoes several subsequent conversions. Two turns of the citric acid cycle are required because there are two molecules of acetyl CoA. In each turn of the cycle, two molecules of carbon dioxide, two molecules of NADH and one molecule of FADH2 (another electron carrier) are produced. One molecule of ATP is also produced by substrate-level phosphorylation.

Aerobic Respiration Electron transport chain NADH and FADH2 donate electrons Phosphate group is added to ADP and makes ATP. Finally, the NADH and FADH2 produced by glycolysis, the conversion of pyruvate to acetyl CoA, and the citric acid cycle progress to the electron transport chain. Here a series of molecules receive the electrons from NADH and FADH2. The energy released as the electrons fall down the electron transport chain helps to pump hydrogen ions from the mitochondrial matrix into the intermembrane space. The hydrogen ions build up and flow back into the mitochondrial matrix through ATP-synthesizing enzymes. The use of energy such as that of a hydrogen ion gradient to perform work (like making ATP) is called chemiosmosis. This chemiosmosis provides the energy required to add a phosphate group to ADP, producing ATP in a process known as phosphorylation. The use of energy released from the electron transport chain to produce ATP is oxidative phosphorylation.

Aerobic Respiration Depending on the type of pathways used, one molecule of glucose generates 36 or 38 ATP molecules. The different stages of aerobic respiration are glycolysis, the citric acid cycle, and oxidative phosphorylation (chemiosmosis and the electron transport chain).

Fermentation will yield only a gain of _______ per molecule of ______. Fermentation occurs when: oxygen is not present. Since no oxygen is required, fermentation is an __________ process. anaerobic The anaerobic pathways are not very efficient in transferring energy from ________ to _____. glucose ATP Fermentation will yield only a gain of _______ per molecule of ______. 2 ATP glucose

There are two main types of fermentation: Alcoholic fermentation  Lactic acid fermentation

Alcoholic Fermentation _______ perform alcoholic fermentation. Yeasts convert _____________ into ______________ when they run out of _______. Yeasts pyruvic acid oxygen ethyl alcohol Yeasts are used to make breads and alcohol.

The Steps of Alcoholic Fermentation Glycolysis If no O2 available Glucose Pyruvic acid Ethyl alcohol CO2 2 ATP Yeasts are used in this way in both the ________ and the _______ industries. The alcohol makes alcoholic beverages. The ______________ that is given off causes bread dough to _____. Small bubbles are formed in the dough, making the bread rise. (The alcohol evaporates during the baking process.) alcohol baking carbon dioxide rise

The Steps of Lactic Acid Fermentation Glycolysis Glucose Pyruvic acid Lactic acid 2 ATP Pyruvic acid ____________ is converted to _________ by _______ cells when there is a shortage of ________. It is produced in muscle cells during strenuous exercise because the muscles are using up the _______ that is present and the body is not supplying the muscle tissue with enough additional oxygen. lactic acid muscle oxygen oxygen

This causes _____________ because it lowers the ___ of the muscle and reduces the muscle’s ability to ________. When oxygen _______ to the muscles, the __________ will be converted back to ____________. The pyruvic acid will then go into _______ respiration. severe cramps pH contract returns lactic acid pyruvic acid aerobic A wide variety of foods are produced by bacteria using lactic acid fermentation: cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut.

Anaerobic Respiration Lactic acid fermentation – the type of fermentation in which lactic acid is produced Alcoholic fermentation – a type of fermentation in which ethanol and carbon dioxide are produced Lactic acid fermentation Alcoholic fermentation Lactic acid fermentation converts pyruvate to lactic acid, while alcoholic fermentation converts pyruvate to alcohol (ethanol) and releases carbon dioxide. While NAD+ is regenerated in fermentation, the only resulting ATP are the two molecules from glycolysis.

Respiration Comparison Reaction Reactants Products Net Energy Gain Location Glycolysis Glucose Pyruvate 2 ATP Cytoplasm Aerobic respiration Pyruvate, oxygen Water, carbon dioxide 34 or 36 ATP Mitochondria Lactic acid fermentation Lactic acid   None Alcoholic fermentation Alcohol (ethanol), This table provides a summary of the different types of respiration.

Respiration Learning Objectives Explain the release of energy through glycolysis Describe the main steps of aerobic respiration Differentiate between the two main types of anaerobic respiration Compare and contrast the different forms of aerobic and anaerobic respiration You should now be able to explain the release of energy through glycolysis, describe the main steps of aerobic respiration, differentiate between the two main types of anaerobic respiration, and compare and contrast the different forms of aerobic and anaerobic respiration.