Chapter 9 Chemical Pathways Cellular Respiration Ms. Lew Biology Chapter 9 Chemical Pathways

Vocabulary Aerobic Anaerobic calorie Cellular respiration Fermentation Glycolysis

Basic Need for Energy Energy in Food: What is the difference between a: calorie(lower case c) and Calorie (upper case C)? A calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree C. A Calorie is a kilocalorie, or 1000 calories For example, 1 gram of glucose releases 3811 calories, on a food label 3.8 Calories

Basic Need for Energy Energy in Food: Organisms cannot use glucose directly, it must be broken down into smaller units. This process in living things begins with glycolysis. If oxygen is present, glycolysis is followed by the Krebs Cycle and electron transport chain – This is called Cellular Respiration

An Overview: Cellular Respiration The equation for cellular respiration is exactly the opposite of photosynthesis. Equation: 6O2 + C6H12O6  6CO2 + 6H2O and energy

Breaking Down Energy Slowly: Glucose needs to be broken down in small steps so that energy is not wasted.

Glycolysis Definition: The process of breaking glucose in half to form 2 molecules of pyruvate (a 3 carbon chain). Uses 2 ATP to start reaction Produces 4 ATP and 2 NADH

Glycolysis Does not require oxygen Very Fast – thousands of ATP produced in milliseconds Stops when it runs out of NAD+ (electron carrier) If oxygen is available: Cellular respiration starts If oxygen is NOT available, to make more NAD+, your body goes through fermentation. This way ATP can be made even without Oxygen.

Why use ATP in Glycolysis if you want ATP? You have to use a little energy to make even more energy. Like a bank, you put money in to earn interest. NAD+ and NADH are like NADP+ and NADPH . They can hold electrons. Animation

Fermentation Fermentation is releasing energy in the absence of oxygen. It is an ANAEROBIC process. Ultimately it allows NADH to be converted to NAD+, allowing glycolysis to continue. There are two main types of fermentation Alcoholic Fermentation Lactic Acid Fermentation

Alcoholic Fermentation Alcoholic fermentation is found in Yeasts, and a few other microorganisms. The equation is: Pyruvic acid + NADH  alcohol + CO2 + NAD+ Note: Carbon Dioxide is also produced, so when yeast conducts fermentation, there is the release of carbon dioxide as well as alcohol.

Alcoholic Fermentation Alcoholic fermentation diagram

Lactic Acid Fermentation Pyruvic acid from glycolysis can be converted to lactic acid. This conversion regenerates NAD+ for glycolysis to continue The equation is: Pyruvic acid + NADH  lactic acid + NAD+ Lactic acid fermentation is used by muscles when they run out of oxygen, ultimately causing soreness. Lactic acid is also created by unicellular organisms in the production of cheese, pickles, kimchi and other foods.

Lactic Acid Fermentation Lactic Acid fermentation diagram

Krebs Cycle In the Krebs Cycle, pyruvic acid is broken down into carbon dioxide.

Krebs Cycle Where does it occur: Mitochondria It requires oxygen – it is AEROBIC It is also known as the Citric Acid Cycle

Krebs Cycle So far, from 1 glucose Glycolysis produced: 2 NADH and 2 ATP Krebs Cycle produced: 8 NADH and 2 FADH2 and 2 ATP Animation

Krebs Cycle What happens to the Krebs cycle products? Carbon Dioxide is released to the atmosphere ATP is used for cellular activities NADH and FADH2 are used in the electron transport chain to produce large amounts of ATP

Electron Transport Chain Uses the high energy electrons from the Krebs cycle to convert ADP into ATP

Electron Transport Chain Where does it occur: Inner membrane of the Mitochondria It requires oxygen – it is AEROBIC

Electron transport chain

Cellular Respiration totals So far, from 1 glucose Glycolysis: 2 ATP + Krebs Cycle: 2 ATP + Electron Transport: 32 ATP Totals: 36 ATP from 1 glucose This is 38% efficiency The rest of the energy is released as heat

Energy use by humans Cells contains small amounts of ready ATP About 5 seconds worth After that, your body uses lactic acid formation This lasts for about 90 seconds You breathe hard to get rid of the lactic acid buildup For exercise longer than 90 seconds, cellular respiration is used This is a slow method to generate ATP Glycogen (a form of carbohydrate) is used for the first 15-20 minutes of cellular respiration After that other molecules, such as fats, are broken down