1. Why do we need sugar? What is cellular respiration? sugar contains energy, cells need to access it sugar is broken down to make ATP 6O 2 + C 6 H 12 O 6  6CO 2 + 6H 2 O + energy (ATP) 1

1. Goal of cellular respiration make ATP (energy form cells can use) ATP is made when mitochondria break down sugars 2

2. Glycolysis 1 glucose (6C molecule)  2 pyruvates (3C molecules) happens in cytosol of all cells (facilitated diffusion of glucose into cytosol) need 2 ATP to start 3

Glycolysis – Step 1 2 ATP to start (2 ATP  2 ADP + 2 P) new 6C compound is formed when 2P are attached to glucose 4

Glycolysis – Step 2 new 6C compound splits into 2 G3P (3C each) 5

Glycolysis – Step 3 2 G3P gain 2P and lose 4e - (2 G3P + 2P – 4e -  2 new 3C compounds) 4 e - “picked up” by NAD + ( 2 NAD + + 4e - + 2H +  2 NADH “batteries”) 6

Glycolysis – Step 4 4P removed from 3C compounds  2 pyruvate molecules (3C each) 4 ADP + 4 P  4 ATP “batteries” NET YIELD of 2 ATP (2 ATP are needed to start glycolysis) MOST of the energy is still “trapped” in the 2 pyruvates 7

3. What happens next? Two pathways… ANAEROBIC respiration (cytosol) NO O 2 some unicellular organisms can “get by” with this leads to fermentation alcohol or lactic acid made AEROBIC respiration (mitochondria) O 2 present all energy in pyruvate is released larger organisms need this 8

4. Anaerobic pathway – alcoholic fermentation pyruvate (3C)  ethanol (2C) and CO 2 CO 2 removed, 2 hydrogen added  ethyl alcohol (2C) formed NAD + electron carrier regenerated (used in glycolysis) 2 ATP (from glycolysis) 9

4. Alcoholic fermentation – yeast yeast (unicellular eukaryote - fungus) enzymes in cytosol are needed for alcoholic fermentation ethyl alcohol accumulates to a point wine – CO 2 released (wine) or stays in (champagne) bread – CO 2 makes bread “fluffy”, alcohol evaporates when baked 10

5. Anaerobic pathway – lactic acid fermentation pyruvate (3C) converted to lactic acid (3C) NAD + electron acceptor regenerated (used in glycolysis) 2 ATP (from glycolysis) 11

5. Lactic acid fermentation – bacteria, fungi, muscles bacteria and fungi bacteria or fungi is added to milk sugar in milk converted is to lactic acid  cheese or yogurt is made muscles during strenuous exercise, O 2 is used up lactic acid accumulates  muscle aches and pains (acidic cytosol) lactic acid diffuses into the blood  liver  converted back to pyruvic acid when O 2 becomes available 12

6. Aerobic pathway Two parts Krebs cycle – make “batteries”, 2ATP electron transport chain (ETC) and chemiosmosis – use “batteries” to make LOTS of ATP OXYGEN needed! It’s the “clean up guy”. 13

7. Mitochondria Prokaryotes no mitochondria all respiration in cytosol Eukaryotes mitochondria pyruvate diffuses into mitochondrial matrix pyruvate (3C) + coenzyme A “bus”  acetyl CoA (2C) + CO 2 (released) NADH “battery” formed (NAD + + 2e - + H +  NADH) 14

8. The Krebs Cycle - Overview Krebs Cycle goal = make BATTERIES happens in mitochondrial matrix ATP (useable form of energy) made NADH, FADH 2 “batteries” used to make LOTS of ATP using the Electron Transport Chain (ETC) 15

Krebs Cycle Diagram 16

Step 1 acetyl CoA (2C) “delivered to” Krebs Cycle 2C + 4C = 6C citric acid made coenzyme A “bus” regenerated 17

Step 2 NADH “battery” made CO 2 released 5C compound made 18

Step 3 NADH “battery” made CO 2 released again 4C compound ATP made (ADP + P  ATP) new 4C compound made 19

Step 4 FADH 2 “battery” is made (FAD + 2H + + 2e - ) new 4C compound made 20

Step 5 4C compound releases H and regenerates 4C compound needed for Step 1 NADH “battery” made keeps Krebs cycle going 21

Krebs Cycle Totals 1 glucose causes TWO TURNS of the Krebs cycle (1 pyruvate processed at a time) 10 NADH “batteries” made glycolysis = 2 entering Krebs = 2 Krebs cycle = 6 2 FADH 2 “batteries” made 2 ATP made 6 CO 2 given off as waste 22

9. Electron Transport Chain - Overview Let’s make ATP! happens in cristae (lots of folds  lots of ATP) of mitochondria uses NADH and FADH 2 “batteries” 23

Electron Transport Chain Diagram 24

9. Electron Transport Chain – Details NADH and FADH 2 release H + and e - e - move down ETC (lose energy) energy used for H + pump H + PUMPED OUT of mitochondrial matrix to inner membrane space H + ions then DIFFUSE INTO mitochondrial matrix through ATP synthase ATP synthase spins = CHEMIOSMOSIS ADP + P  ATP 25

10. Why is oxygen needed? oxygen picks up leftover e - from ETC and leftover H + ions allows ATP to continue to be made prevents a “traffic jam of e - and H + H 2 O released (O 2 + 4e - + 4H +  2H 2 O) 26

11. Energy Yield glycolysis: _____ ATP total Krebs cycle: _____ ATP total each NADH: _____ ATP (x 10) each FADH 2 : _____ ATP (x 2) 2 ATP MAXIMUM of _____ ATP (depends on cell and conditions) 27

12. How efficient is cellular respiration? Your car? 20-25% efficient Your cells? 66% efficient remaining energy lost as HEAT 28