Cellular Respiration and Fermentation Chapter 9 Big Idea #1

Chemical Energy and Food Organisms get the energy they need from food! How do cells use this food? They don’t just burn food, they break it down gradually getting all the nutrients and energy out

Chemical Energy and Food Energy stored in food is expressed in units of calories The amount of energy needed to raise 1 gram of water by 1° Celsius 1 gram of glucose releases 3811 calories of heat energy when it is used

Chemical Energy and Food The Calorie (big C) that you see on food labels is actually a kilocalorie, or 1000 calories.

Chemical Energy and Food So only plants break down food right? WRONG! All living organisms break down energy sources This is called cellular respiration

Cellular Respiration If oxygen is available, energy is released from food Here is a summary: Oxygen + sugar  carbon dioxide + water + ENERGY

OR 6O2 + C6H12O6  6CO2 + 6H2O + ENERGY

Cellular Respiration There are 3 stages of cellular respiration Glycolysis Kreb’s cycle Electron transport chain

Cellular respiration These stages are called pathways Pathways that require oxygen are aerobic Kreb’s cycle Electron transport chain

Pathways that DO NOT require oxygen are anaerobic Cellular Respiration Pathways that DO NOT require oxygen are anaerobic glycolysis

What is the relationship between photosynthesis and cellular respiration? Photosynthesis “deposits” the energy and cellular respiration “withdraws” that energy.

Photosynthesis removes CO2 from the atmosphere and cellular respiration puts it back. Photosynthesis releases O2 into the atmosphere and cellular respiration uses that O2 to release energy from the food.

9.1 Quiz In what ways are cellular respiration and photosynthesis considered opposite processes? The Greek word glukus means “sweet,” and the Latin word lysis refers to a process of loosening or decomposing. Based on this information, write a definition for the word glycolysis.

Review There are 3 stages of cellular respiration Glycolysis produces only a small amount of energy. Most of glucose’s energy (90%) remains locked in the chemical bonds of pyruvic acid at the end of glycolysis.

Review 2. Kreb’s cycle - During the Krebs cycle, a little more energy is generated from pyruvic acid.

Review 3. Electron transport chain - produces the bulk of the energy in cellular respiration by using oxygen, a powerful electron acceptor.

Review Aerobic processes require oxygen to take place Kreb’s cycle Electron transport chain

Review Anaerobic processes DO NOT require oxygen to take place glycolysis

The Process of Cellular Respiration Glycolysis is the first step of CR Means “sugar breaking” Involves many steps transforming glucose The end result is 2 molecules of a 3-carbon molecule called pyruvic acid and 2 ATP

Fill in your chart: Glycolysis Materials used/consumed Materials produced/made (net total) 2 ATP 1 sugar/glucose (C6H12O6) 2 NADH   2 Pyruvic Acid http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html

In the presence of oxygen, pyruvic acid produced in glycolysis moves into Kreb’s cycle Named after Hans A. Krebs, British biochemist

During Kreb’s cycle, pyruvic acid is broken into carbon dioxide (CO2) in a series of energy extracting steps This happens in the mitochondrial matrix

2 ATP molecules are produced, along with many electrons and CO2 molecules

Fill in your chart: Kreb's Cycle Materials used/consumed Materials produced/made 2 pyruvic acids (2 cycles) 2 ATP   8 NADH 6 CO2 1 citric acid

Electron Transport Chain Electrons come from both glycolysis and Kreb’s cycle The electron transport chain uses the high energy electrons from glycolysis and Kreb’s cycle to convert ADP  ATP

Electron Transport Chain: Step 3 Hydrogen Ion Movement Channel Mitochondrion Intermembrane Space ATP synthase Inner Membrane Matrix ATP Production

Electron Transport Chain One “cycle” of the electron transport chain yields 32 molecules of ATP Electron Transport Chain Materials used/consumed Materials produced/made NADH H2O   32 ATP

The Totals How much energy does cellular respiration generate? Together, glycolysis, the Krebs cycle, and the electron transport chain release about 36 molecules of ATP per molecule of glucose. ATP

The Totals Total: 36 molecules of ATP per 1 molecule of glucose Glycolysis: 2 ATP Kreb’s cycle: 2 ATP Electron Transport Chain: 32 ATP Total: 36 molecules of ATP per 1 molecule of glucose

Fermentation What element does cellular respiration need to proceed? Oxygen! What happens when no oxygen is available for cellular respiration? Cells proceed into fermentation

Fermentation In the absence of oxygen, fermentation releases energy from food molcules by producing ATP There are 2 types of fermentation: Alcoholic fermentation Lactic acid fermentation

Pyruvic acid + NADH  Alcohol + CO2 + NAD+ Fermentation Alcoholic fermentation produces ethyl alcohol and carbon dioxide Yeasts and other microorganisms Alcoholic beverages and rising bread Pyruvic acid + NADH  Alcohol + CO2 + NAD+

Fermentation Lactic Acid Fermentation converts pyruvic acid from glycolysis into lactic acid Process used to make cheese, yogurt, sour cream, pickles, kimchi Muscle cells are lactic acid fermenters Pyruvic acid + NADH Lactic acid + NAD+