cellular respiration (glycolysis, citric acid cycle, phosphorylation, fermentation pathways, food energy)

[[Introduction to Carbohydrate Breakdown Pathways[[

Aerobic Respiration - Cellular respiration that ==requires oxygen==

• Glucose and oxygen are converted to Carbon dioxide + water, yielding ATP
  • Consists of four metabolic pathways: glycolysis, acetyl-CoA formation, citric acid cycle, electron transfer phosphorylation
  • All involve electron transfer chains (ETCs) and share products/substrates

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Fermentation - Glucose-breakdown pathways that ==make ATP w/o oxygen or ETC’s==

• Many organisms use this as an ==alternative to cellular respiration== due to a ==lack of available oxygen==

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]]Glycolysis - Sugar Breakdown Begins]]

Glycolysis - series of reactions that @@converts ATP to pyruvate@@, takes place in cytosol

• Pyruvate - Organic compound w/ @@3 carbon backbone@@

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Breaks one carbon-carbon bond of a glucose molecule, @@uses 2 ATP and produces 4@@

• 2 net atps

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Investment (Energy-Requiring)

1. Phosphate group is transferred from @@ATP to glucose@@, forming a @@glucose-6-phosphate@@
2. phosphate group is transferred from 2nd ATP to an intermediate, forming a @@6-carbon molecule w/ 2 phosphate groups@@
3. 6-carbon molecule splits in half, forms @@2 G3P molecules@@

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Energy-Harvesting

1. Redox reaction transfers e- and h+ from @@PGAL to NAD+ (coenzyme),@@ reduces to @@NADH@@, and also attaches a phosphate group to 3-carbon intermediate
2. Transfers a phosphate group to ADP, @@makes ATP@@
3. Remaining phosphate group @@transfers from 1 carbon to another@@
4. Goes to another ADP, so @@another ATP forms@@, finally @@producing pyruvate@@

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{{Acetyl-CoA Formation and the Citric Acid Cycle{{

• Acetyl-CoA and the citric acid cycle break both carbon-carbon bonds
  • Energy released from breaking is carried by NADH and phosphate bonds of ATP

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Acetyl-CoA Formation

• Pyruvate is transported across 2 mitochondrial membranes, goes into inner compartment (filled with gel-like substance called matrix)
• Redox reaction splits a carbon from pyruvate which diffuses out of cell, produces NADH
• Carries 2 carbons into citric acid cycle

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Citric Acid Cycle

• Harvests energy from Acetyl-CoA
  • Substrate of first reaction is product of last reaction
• 2 carbon atoms form citrate w/ oxaloacetate
• Redox reactions occur: NADH forms
  • NAD+ → NADH and FADH → FADH2
• Carbon is removed from intermediate, releasing e- and h+, forming NADH (NADP+ as well)
• Product: oxaloacetate
• 2 rounds of the citric acid cycle will harvest the energy

}}Aerobic Respiration’s Big Energy Payoff}}

Electron Transfer Phosphorylation is similar to the light-dependant reactions of photosynthesis.

• Excess energy transports H+ from matrix to intermembrane space
• Occurs w/ NADH and FADH2 delivering e- and h+ to ETCs in membrane
• Energy loss fuels H+ active transport H+ flow back to matrix through ATP synthase
  • drives ADP → ATP
• Oxygen accepts e- and h+, forming water (reverse photolysis)

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