acquiring energy chapter 6. energy for life all energy comes from the sun – producers convert...
TRANSCRIPT
ACQUIRING ENERGYChapter 6
Energy for Life• All energy comes from the sun
– Producers convert light into chemical energy (glucose bonds)
– Consumers eat/break bonds to release energy
• Energy coupling reactions recycle components– Cellular respiration (break):
• 6O2 + C6H12O6 6CO2 + 6H2O + ATP– Photosynthesis (make):
• ATP + 6CO2 + 6H2O C6H12O6 + 6O2
• Which reaction term applies to each?
Redox Reactions• Coupled reactions that move electrons between
molecules– Review: electrons form bonds and energy is released
when they break (endergonic or exergonic?)
• LEO goes GER– Lose an electron = oxidation
• Glucose oxidized to CO2
– Gain an electron = reduction• O2 reduced to H20
• NAD+ reduced to NADH
– What do all these reactions have in common?
Electron Carriers• NADH and NADPH hold e-’s = high energy bonds
– Carry 2 e-’s and a H+ – Precursor = NAD + and NADP +
• Molecules oxidized e-’s released & captured– Dehydrogenase
Cellular Respiration• Aerobic respiration
– Requires O2
– High energy (ATP) yield– Glycolysis
• Common to all paths• Energy from sugar (glucose)
– Citric acid cycle (Kreb’s cycle)• Requires O2
– Oxidative phosphorylation (ETS and Chemiosmosis)
• Requires O2
• Anaerobic respiration– Doesn’t require O2
– Organisms w/o mitochondria– Low energy yield
Step 1: Glycolysis• Aerobic and anaerobic• In the cytoplasm• Starts with:
– Glucose (6C’s)– 2 ATP
• Ends with:– 2 pyruvate (3C’s)
• Important products of this process:– Net 2 ATP
• 4 ATP substrate-level phosphorylation
– 2 NADH
Intermediate Step: ‘Grooming’
• Starts with:– 2 Pyruvate (3C’s)
• High energy product
• Ends with:– 2 Acetyl-CoA (2C’s)
• Important products of this process:– 2 CO2
• Decarboxylation
– 2 NADH
Step 2: Citric Acid Cycle
6 C’s4 C’s
4 C’s
• In the mitochondrial matrix• Starts with:
– 2 Acetyl CoA• Ends with:
– 4 CO2
• Important products of this process:– 2 ATP substrate level
phosphorylation– 6 NADH – 2 FADH2
Step 3: Electron Transport System (ETS)
• In the inner mitochondrial membrane• Starts with:
– 10 NADH (previous steps)– 2 FADH2 (citric acid cycle)– O2
• Ends with:– H2O
• Important products of this process:– H + gradient
Electrons and the Importance of Oxygen• Review
– Electron energy determined by arrangement• e-’s further from the nucleus = more PE• e-’s dropping levels release E
– Oxygen is highly electronegative• Integral protein complexes use a little less energy to ‘hold’ the
electrons• Extra energy transports a H+ across out of the matrix into the
intermembrane space• O2 is the last molecule to accept e-’s to become water
Electrons from reactions in glycolysis and Kreb’s cycle
Step 4: ATP Generation (Chemiosmosis)
• In the inner mitochondrial membrane• Starts with:
– H + gradient
• Ends with:– 32 – 34 ATP• ATP synthase facilitates
A Review of Cellular Respiration
Substrate level phosphorylation
Fermentation
• If no O2 available• Starts with:
– Glucose • Ends with:
– Lactate or– CO2 and ethanol
• Important products of this process:– 2 pyruvate– 2 ATP– 2 NADH/NAD+
• Makes yogurt, bread, alcoholic beverages