Unformatted text preview: AP Biology: Cellular AP Biology: Cellular Respiration & Fermentation
Chapter 9 Energy Flows Sun to heat Chemicals Cycle How can cells “unlock” the energy How can cells “unlock” the energy stored in glucose? All breakdown of glucose starts with a universal process: GLYCOLYSIS
No O2 required
2 phases (10 steps) Energy investment (use 2 ATP) Energy payoff 4 ATP made by substratelevel phosphorylation 2 NADH made GLYCOLYSIS
GLYCOLYSIS Glycolysis animation Energy
Investment Phase EnergyPayoff Phase
EnergyPayoff Phase End of energy payoff phase
End of energy payoff phase Cellular Respiration & Cellular Respiration & Fermentation are Catabolic Processes – Both start with glycolysis Purpose: to regenerate ATP from ADP + P
Energy rich molec > simpler molec + stored energy+ heat
Fermentation: anaerobic Cellular respiration: Aerobic Complex org cpd + O2 > CO2 + H2O + ATP + heat What is used in cellular respiration?
What is used in cellular respiration? Carbs, fats, proteins can be used
Start by considering the oxidation of glucose Exergonic ΔG = 686 kcal/mol
oxidation C6H12O6 + 6O2 > 6CO2 + 6H2O
Reduction How do electrons “fall” from glucose How do electrons “fall” from glucose to oxygen? Glucose to NAD+ using dehydrogenase H – C – OH + NAD+ > C=O + NADH + H+ NAD+ to an ETC
ETC to oxygen HW Challenge problem
HW Challenge problem Based on the basic chemistry of food, explain how the energy content of food compares in the major classes of organic molecules. Carbs, Lipids, Proteins. Steps of Cellular Respiration
Steps of Cellular Respiration
STEP LOCATION 1. Glycolysis Cytoplasm
2. Krebs Cycle
3. ETC MAIN EVENTS Glucose (6C) split to pyruvate (3C)
On the way into Pyruvate (3C) to CO2 mitochondria
and acetyl CoA (2C)
Matrix of Acetyl CoA (2C) to mitochondria
Inner Electrons collected membrane of from past steps used to mitochondria
make ATP via Highlight on the Highlight on the start of glycolysis
Occurs shortly after glucose enters cell; charge traps glucose inside
Important in regulating pace of respiration – inhibited by high ATP levels or citrate levels (citrate is made later in Krebs cycle) Transition phase
Junction between glycolysis & Kreb’s Online tutorial on pyruvate dehydrogenase complex Kreb’s Cycle
Kreb’s Cycle Animation for transition phase & Kreb’s
Occurs in the matrix of the mitochondria
No O2 needed
Big picture: Acetyl CoA binds to oxaloacetate to form citrate For each Acetyl CoA that enters, the cycle forms 2CO2 , 3NADH , 1FADH2 , and 1 ATP (substrate level phosphorylation) Oxaloacetate is regenerated (hence: Kreb’s cycle) Animation #2
Step 6: FAD reduced to FADH2 Steps 3 & 4:
RELEASE CO 2 Step 5: ATP made by substrate level phosphorylatio
n (GTP acts as a P shuttle) Steps 3, 4, 8: Reduce NAD+ to NADH Where is our energy stored so Where is our energy stored so far?
ATP (sublevel NADH
phosphor.) FADH Glycolysis 2 2 0 Transition 0 1x2 = 2 0 Krebs 1x2=2 3x2=6 1x2=2 What will happen to all those e What will happen to all those e carried by NADH & FADH2?
They carry most of the energy originally in glucose Electron transport chain on the inner membrane harnesses energy Pumps H+ into intermembrane space Proton motive force Terminal electron acceptor is oxygen Oxidative phosphorylation using ATP synthase Second animation of ETC / ATP Synthase Summary
Most of the energy in this process moves from
Glucose > NADH > ETC > H+ gradient > ATP How much ATP have we built AFTER the ETC + oxidative phosphorylation? Each NADH = about 3 ATP Each FADH = about 2 ATP
2 Total possible ATP = 4 (by SLP) + 10 NADH*3 + 2 FADH2*2 = 38 ATP Process has efficiency around 40% Click to view
animation. animation What does a cell do if no oxygen or What does a cell do if no oxygen or no mitochondria are present? Can’t stop glycolysis – need ATP
Can’t continue forever – Why?
What can be done? Fermentation
Fermentation Occurs in cytosol when NO Oxygen is present (anaerobic).
Remember: glycolysis is part of fermentation.
1. Alcohol Fermentation 2. Lactic Acid Fermentation WHY BOTHER MAKING THESE??? Alcohol Fermentation
Alcohol Fermentation Reduces acetaldehyde to regenerate NAD+
Generates 2 Ethanol+2CO2
Used in bacteria, yeast
Useful for beer, wine, bread Lactic Acid Fermentation
Lactic Acid Fermentation Pyruvate is reduced directly to regenerate NAD+
Generates 2 Lactate
Used by bacteria, muscle cells
Helps make yogurt, cheese, sauerkraut, sore muscles! What else can be used by the body What else can be used by the body for fuel? Proteins Hydrolysis, deamination
Compounds can enter as pyruvate, acetyl CoA, others Fats These can also be removed as needed Hydrolysis
Fatty acids beta oxidation forms 2C fragments (used to make acetyl CoA) Evolutionary Implications
Evolutionary Implications Glycolysis Anaerobic, Cytosolic, Present in nearly every cell Chloroplasts & Mitochondria Endosymbiotic hypothesis: Eukaryotes arose from a symbiotic relationship between various prokaryotes.
Heterotrophic bacteria became mitochondria. Cyanobacteria became chloroplasts. Host cell was a large eukaryotic cell. Evolution of the eukaryotic cell ...
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