Feel the Burn Do you like to run, bike, or swim? These all are good ways to exercise. When you exercise, your body uses oxygen to get energy from glucose, a six-carbon sugar. 1. How does your body feel at the start of exercise, such as a long, slow run? How do you feel 1 minute into the run; 10 minutes into the run? 2. What do you think is happening in your cells to cause the changes in how you feel? 3. Think about running as fast as you can for 100 meters. Could you keep up this pace for a much longer distance? Explain your answer.

Chapter 9-1 Chemical Pathways

Chemical Energy & Food Food – source of:  Raw materials calorie  amount of energy needed to raise 1g of water by 1C “Calorie” 1 kcal, or 1000 calories Cells breakdown food slowly & gradually Cells can’t use food energy directly  convert to ATP If all at once, too explosive and most energy lost as heat Slowly releases energy of food to make ATP

Cellular Respiration The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen 6O2 + C6H12O6  6CO2 + 6H2O + Energy Three main steps: Glycolysis, Krebs cycle, Electron Transport Chain oxygen glucose carbon dioxide water

Electron Transport Chain Section 9-2 Flowchart Cellular Respiration Glucose (C6H1206) + Oxygen (02) Glycolysis Krebs Cycle Electron Transport Chain Carbon Dioxide (CO2) + Water (H2O)

Fermentation (without oxygen) Chemical Pathways Section 9-1 Glucose Krebs cycle Electron transport Glycolysis Alcohol or lactic acid Fermentation (without oxygen)

Electron Transport Chain Cellular Respiration: 3 Stages 1. Glycolysis ( in cytoplasm) 2. Krebs Cycle ( in mitochondria) 3. Electron Transport Chain ( in mitochondria) Glucose Glycolysis Cytoplasm Pyruvic acid Electrons carried in NADH Krebs Cycle Electrons carried in NADH and FADH2 Electron Transport Chain Mitochondrion

Net vs. Gross Gross  amount of product made Ex: Made $20.00 babysitting Net  amount of product made minus amount of product used Ex: Made $15.00 babysitting $5.00 for gas to get to babysitting job $20.00 babysitting made $20.00 - $5.00 = $15.00 net

Glycolysis Process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound. 6 carbon molecule (glucose) to two 3-carbon molecules (pyruvic acid) Takes place in the cytoplasm Does not require oxygen

Glycolysis 2 ATP molecules must be added to get the reaction started Can be considered activation energy 4 ATP molecules are produced (4 – 2 = net gain of 2 ATP) 2 NADH molecules are also created NADH Electron carrier =  NAD+ (nicotinamide adenine dinucleotide) NAD+ + H+ + 2 high energy electrons  NADH Takes electrons to other parts of respiration Glycolysis nets  2 ATP, 2 NADH, and 2 pyruvic acids

To the electron transport chain Glycolysis Glucose 2 Pyruvic acid To the electron transport chain

Glycolysis: Advantages vs. Disadvantages  Occurs quickly Can produce 1000s of ATP in a few milliseconds  Does not require oxygen Can occur w/o oxygen Disadvantages  Net gain of only 2 ATP  NAD+ become filled with electrons quickly Can’t make more ATP

Anaerobic Respiration = Fermentation an = “without” aerobic = “air”  Occurs after glycolysis only if no oxygen is available NADH from glycolysis used, turned back into NAD+ Goes back to glycolysis Keeps glycolysis going Generate as many ATP as possible Important because it recycles the NAD+ molecules so that the cell can continue to make energy

Alcoholic Fermentation  In the absence of oxygen, pyruvic acid is broken down to produce alcohol and carbon dioxide Carried out by yeasts and a few other microorganisms pyruvic acid + NADH → alcohol + CO2 + NAD+  Used to make alcoholic beverages and to cause bread dough to rise

Lactic Acid Fermentation  In many cells, the pyruvic acid that accumulates due to glycolysis is converted to lactic acid. pyruvic acid + NADH → lactic acid + NAD+  Occurs in muscles during heavy exercise Lactic acid buildup in muscles causes painful, burning sensation = why muscles feel sore  Prokaryotes also produce lactic acid Used to make cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut, and kimchi.

Lactic Acid Fermentation Glucose Pyruvic acid

Respiration Videos Aerobic Respiration Glycolysis

Review Questions 1. What is cellular respiration? What is the equation for it? 2. What are the 3 stages of cellular respiration in order? 3. What is glycolysis and where does it take place in a cell? What are the products of glycolysis? 4. What are the advantages and disadvantages of glycolysis? 5. What is anaerobic respiration and what is its purpose? 6. Compare and contrast alcoholic fermentation with lactic acid fermentation.