Cellular Respiration and Fermentation Chapter 9 Big Idea

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 6 O 2 + C 6 H 12 O 6 6 CO 2 + 6 H 2 O + ENERGY

Cellular Respiration • There are 3 stages of cellular respiration 1. Glycolysis 2. Kreb’s cycle 3. Electron transport chain

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

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 CO 2 from the atmosphere and cellular respiration puts it back. • Photosynthesis releases O 2 into the atmosphere and cellular respiration uses that O 2 to release energy from the food.

9. 1 Quiz 1. In what ways are cellular respiration and photosynthesis considered opposite processes? 2. 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 1. 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 produced/made (net total) 2 ATP 1 sugar/glucose (C 6 H 12 O 6) 2 NADH 2 Pyruvic Acid http: //www. science. smith. edu/departments/ Biology/Bio 231/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 (CO 2) in a series of energy extracting steps – This happens in the mitochondrial matrix

• 2 ATP molecules are produced, along with many electrons and CO 2 molecules

Fill in your chart: Kreb's Cycle Materials used/consumed produced/made 2 pyruvic acids (2 cycles) 2 ATP 8 NADH 6 CO 2 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 Electron Transport 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 H 2 O 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 – 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

Fermentation • Alcoholic fermentation produces ethyl alcohol and carbon dioxide – Yeasts and other microorganisms – Alcoholic beverages and rising bread Pyruvic acid + NADH Alcohol + CO 2 + 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+