Chapter 9

 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.  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?  What do you think is happening in your cells to cause the changes in how you feel?  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.

 Food serves as a source of energy.  calorie: the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. ◦ 1 gram of glucose releases 3811 calories of energy.  Calorie = 1000 calories or a kilocalorie ◦ These are the Calories reported on food labels  In our bodies the energy from food is gradually released through cellular respiration.  Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria.

 What are some similarities in the structure of the mitochondria compared to the chloroplast?

 The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.  The overall chemical reaction is:  6O 2 + C 6 H 12 O 6 6CO 2 + 6H 2 O  The three main stages of respiration are: ◦ Glycolysis (cytoplasm) ◦ Krebs Cycle (Mitochondria) ◦ Electron Transport Chain (Mitochondria)

Glucose Glycolysis Krebs cycle Electron transport Fermentation (without oxygen) Alcohol or lactic acid

Needs Oxygen

Glucose Glycolysis Cytoplasm Pyruvic acid Electrons carried in NADH Krebs Cycle Electrons carried in NADH and FADH 2 Electron Transport Chain Mitochondrion Go to Section:

 Glycolysis: “breaking sugar”  The first step of cellular respiration.  Releases a small amount of energy.  One glucose (6-carbon) molecule is broken into two pyruvate (3-carbon) molecules.  Two NADH are produced  Two ATP are used to start glycolysis.  Four ATP are produced by glycolysis.  A net gain of two ATP molecules from glycolysis.

 NAD + is an electron carrier in respiration  NAD + accepts two high energy electrons and a hydrogen ion to form NADH.  Glycolysis can produce ATP very rapidly until all of the NAD + is changed to NADH.

Glucose To the electron transport chain 2 Pyruvic acid

The Kreb’s Cycle  90% of the energy in a glucose molecule still remains at the end of glycolysis.  To extract this energy, the two pyruvates enter the Kreb’s Cycle

 After glycolysis, the two pyruvates enters the mitochondrion.  In the Mitochondrion, pyruvate is broken down into carbon dioxide in a series of energy-extracting reactions.  Remember that 2 pyruvates are produced from each glucose molecule so the energy produced from each cycle is doubled.

Kreb’s Cycle Prep Step  First, the pyruvate molecules produced by glycolysis are transformed into acetyl-CoA (two carbon molecules), releasing a CO 2.  The two carbons from Acetyl CoA then enter the Krebs cycle.

The Kreb’s Cycle  Location: Mitochondria (matrix)  Products: CO 2, ATP, NADH, FADH 2

Carbon Dioxide Product Released when you breath Go to Section: Electron Carriers Produced Sent to make lots of ATP in ETC ATP Generated Used for cellular activities

Electron Transport Chain  Uses the high energy electrons from the Krebs cycle and glycolysis to convert ADP to ATP.  Location: Mitochondria (Inter- membrane Space)

 Electrons from NADH ◦ Electrons pass through 3 pumps, pumping 3 hydrogen ions across the membrane  Electrons from FADH 2 ◦ Electrons pass through 2 pumps, pumping 2 hydrogen ions across the membrane  Hydrogen ions are pumped into the inter-membrane space

 Hydrogen ions in the inter- membrane space become concentrated and begin flowing back into the matrix through ATP Synthase  ATP Synthase harnesses the energy from the flow of H+ and adds a Phosphate group to ADP creating ATP  Oxygen picks up the electron at the end, forming water

Figure 9–7 Electron Transport Chain Figure 9–7 Electron Transport Chain Section 9-2 Electron Transport Hydrogen Ion Movement ATP Production ATP synthase Channel Inner Membrane Matrix Intermembrane Space Go to Section: Video

Totals  ATP ◦ 2 ATP from Glycolysis ◦ 2 ATP from Krebs Cycle  NADH = 3 ATP ◦ 2 NADH from Glycolysis=6 ATP ◦ 8 NADH from Kreb’s Cycle=24 ATP  FADH 2 = 2ATP ◦ 2 FADH 2 from Kreb’s Cycle=4ATP  Total ATP = 38 ATP ◦ 2 ATP to move NADH from cytosol to mitochondria  Total ATP production from one glucose molecule is 36 ATP.

 Certain organisms as well as certain cells in our bodies can produce energy without oxygen ◦ mainly our muscle cells.  Anaerobic respiration is the process that releases energy from food molecules in the absence of oxygen.  Through fermentation, anaerobic organisms and cells can exist w/o oxygen by using the small amount of energy supplied by glycolysis.

 Each time we go through glycolysis, NADH is formed from NAD +  In aerobic respiration, this NADH then goes to the ETC and ends up as NAD + again.  Without oxygen, the ETC cannot function, therefore, we get a build up of NADH, and a lack of NAD +  Under these conditions, glycolysis would stop.  Therefore, we need a process to replenish the NAD + in the cell - this is fermentation

 Lactic Acid Fermentation ◦ Occurs in animal cells, and some types of bacteria and fungi  Alcoholic Fermentation ◦ Occurs in many types of bacteria and fungi, and some plants

 Lactic acid is a waste product ◦ In animals, Lactic Acid is sent to the liver to be converted back to pyruvate which will enter the Kreb’s cycle as soon as oxygen is available. ◦ In unicellular organisms, lactic acid is released into the environment.  Lactic acid fermentation done by some types of bacteria and molds is used to make cheese and yogurt

 Ethanol is a waste Product ◦ Ethanol is released into the environment.  This Ethanol is used in alcoholic beverages  Ethanol fermentation is also used to make bread rise