Cellular Respiration Chapter 9

As you already know… Respiration is the process by which energy is produced from sugar Respiration takes place inside a cell’s Mitochondria There are two types of respiration: Aerobic respiration: Requires oxygen (Like aerobic activity) Anaerobic respiration: Does NOT require oxygen

Stuff you don’t know… A calorie is the amount of energy needed to raise 1 gram of water 1 degree Celsius The Calorie (Capital “C”) found on food labels, is really a Kilocalorie, or, 1,000 calories  When you eat food, you don’t actually burn glucose inside your body (as in “burning calories”) instead, you release small amounts of energy at a time from glucose or other food sources.

Overall Equation for Respiration Respiration is the exact opposite of photosynthesis Instead of using sun as energy, you create energy in the form of ATP C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + 36 ATP 1 sugar + 6 Oxygen  6 Carbon Dioxide + 6 Water + 36 ATP In order to create energy, a series of steps must take place Step 1: Glycolysis Step 2a (No oxygen): Fermentation Step 2b (Oxygen present): Kreb’s cycle

STEP 1: GLYCOLYSIS Glycolysis is the process by which one sugar (glucose) is broken in half and energy (ATP) is released. 1 st : 2 ATP molecules are used to break apart the glucose 2 nd : The process of breaking apart the glucose produces 4 ATP molecules + 2 pyruvic acids + 2 NADH Glycolysis produces a net gain of 2 ATP molecules NADH are electron transporters, unlike ATP, they very temporarily hold the energy The equation for Glycolysis is: 1 glucose + 2 ATP + 2NAD+  2 pyruvic acids + 4 ATP + 2 NADH

STEP 2a: Fermentation If there is NO OXYGEN in the cell, fermentation takes place (ANAEROBIC RESPIRATION) Fermentation recycles NADH back to NAD+ so that GLYCOLYSIS may continue Prokaryotic cells use Alcohol Fermentation 2 Pyruvic acids + 2NADH  Alcohol + 2CO2 + 2 NAD+ Eukaryotic cells (US and MULTICELL ORGANISMS) use Lactic Acid Fermentation 2 Pyruvic acids + 2NADH  2 Lactic Acids + 2 NAD+ Without fermentation, glycolysis may only happen for a few minutes! Otherwise, the NAD+ gets used up PROKARYOTESEUKARYOTES

STEP 2b: Kreb’s Cycle If there IS OXYGEN present (AEROBIC RESPIRATION), the 2 pyruvic acids from glycolysis are broken down into smaller pieces (using the oxygen) creating a large quantity of ATP 2 Pyruvic Acids + 6O 2  6H 2 O + 6CO ATP The cycle is named the Kreb’s cycle after Hans Kreb, the scientist who discovered it THE TOTAL ATP PRODUCED FROM RESPIRATION = 2 ATP (glycolysis) + 34 ATP (Kreb’s cycle) = 36 ATP

The Equations Total Respiration: 1 glucose + 6O 2  6CO 2 + 6H 2 O + 36 ATP Glycolysis: 1 glucose + 2 ATP + 2 NAD+  2 pyruvic acids + 4 ATP + 2 NADH Alcohol Fermentation: 2 Pyruvic acids + 2NADH  Alcohol + 2CO 2 + NAD+ Lactic Acid Fermentation: 2 Pyruvic acids + 2NADH  2 Lactic Acids + 2 NAD+ Kreb’s Cycle: 2 Pyruvic Acids + 6O 2  6H 2 O + 6CO ATP TOTAL ATP = 36 ATP