2.6 ATP Synthesis & Electron Carriers + 2.7 Glycolysis + 2.9 ETS

DIAGRAMS ABOUT THE STEPS OF CELLULAR RESPIRATION NOT IN FLASHCARDS, LOOK AT SLIDES

What is the source of energy for all organisms?

The sun

What is the only type of energy that organisms can use?

Chemical

What are electron carriers?

Molecules that are easily reduced and oxidized in coupled reactions

What is NAD?

• A biological electron carrier

• Derived from vitamin B_1-12

• Carries H+ and e- to electron transport system where they are used to produce ATP

• Easily reduced to NADH and oxidized to NAD⁺ releasing energy

• NADH → NAD⁺ + H⁺ + 2e^-

What is FAD?

• A biological electron carrier

• Derived from Vitamin B₂

• Carries H+ and e- to electron transport system where they are used to produce ATP

• Easily reduced to FADH₂ and oxidized to FAD releasing energy

• FADH₂ → FAD + 2H⁺ + 2e^-

What is coenzyme A?

• A molecule that contains a sulfhydryl group derived from vitamin B₂

• Brings the acetyl group from transition reaction into the Krebs Cycle

• Allows acetyl group to bind to the first enzymes of the Krebs Cycle

What are porphyrins?

• Globular proteins

• 4° structure

• Contains cofactors (metallic ions)

  • Metallic ions are within a tetrapyrrole ring (4N within C rings)

What is substrate-level phosphorylation?

• A type of ATP synthesis

• The substrate molecule donates its P to ADP to make ATP

• Coupled reactions:

  • Substrate~P → Substrate + P + energy

  • ADP + P → ATP

• The limitation is that only one ATP is produced at a time

What is oxidative phosphorylation & chemiosmosis?

• The generation of ATP due to H+ ions moving across a proton channel down their concentration gradient

• The concentration difference over the membrane results in both a chemical and electrical difference across the membrane known as electrochemical gradient

• The flow of protons back into the matrix of the mitochondria via a proton channel provides enough energy for ADP to combine with P forming ATP, catalyzed by the enzyme ATP synthase

• Oxygen combines with H and is reduced to water

• Occurs on the surface of the inner mitochondrial membrane (on the cristae)

• Uses proton pumps and proton channels

How does oxidative phosphorylation & chemiosmosis use proton pumps?

• Actively transports H⁺ into the intermembrane space out of the matrix

• Builds a protein gradient across the membrane

  • High concentration of H⁺ in the intermembrane space

  • Low concentration of H⁺ in the matrix

• Proteins are positively charged, therefore repel

How does oxidative phosphorylation & chemiosmosis use proton channels?

• H⁺ escapes through the channel

  • H⁺ diffuses through passively from high to low concentration

• H⁺ flows through of the activates ATP synthase to help bond ADP + P → ATP

What is cellular respiration?

• A series of reactions carrying out the controlled oxidation of glucose

• C₆H₁₂O₆ + 6O₂ →→→→ 6CO₂ + 6H₂O + 36 ATP

  • Each arrow represents the four stages of the reaction

What happens by the end of cellular respiration?

• C₆H₁₂O₆ has been completely oxidized

• O₂ has been reduced to H₂O

• Net gain of 36 molecules of ATP

What are the four stages of cellular respiration?

1. Glycolysis

   • In the cytoplasm

   • Anaerobic

2. Transition reaction

   • In the matrix

3. Krebs cycle

   • In the matrix

4. Electron transport chains

   • In the cristae of mitochondria

What is the purpose of glycolysis?

• To break down glucose into pyruvate

  • 1 glucose is broken down into 2 pyruvate

• Has a net gain of 2 ATP

What is the transition reaction?

• A reaction that involves a series of oxidative decarboxylations

• Breaks down pyruvate into acetyl coA

  • 2 pyruvate make 2 acetyl coA

• It links glycolysis to Krebs

• Involves a protein embedded in the inner membrane

What are the 3 coupled reactions in the transition reaction?

1. CO2 removed from pyruvate (decarboxylation)

2. Pyruvate is oxidized, while NAD+ is reduced

3. Acetyl group is transferred from CoA → Acetyl CoA

The reactions are catalyzed by pyruvate dehydrogenase complex

What is the purpose of krebs cycle?

• To oxidize acetyl CoA to produce energy

• High-energy electron carriers such as NADH and FADH2 are generated

• Carbon dioxide is released as a byproduct

What is the purpose of ETC?

• To create a concentration gradient across the inner mitochondrial membrane, which drives the production of ATP through oxidative phosphorylation

• As one protein is reduced, the previous one is oxidized as e-’s move down the chain releasing energy to pump H+ into the intermembrane space

• At the end, O2 is the final electron acceptor and joins with H+ to make H2O

What is the purpose of ATP synthase?

• To make ATP

  • As electrons are passed along the ETC, they release energy that is used to pump protons (H+) out of the mitochondrial matrix, creating a concentration gradient

  • This gradient is then used by ATP synthase to synthesize ATP as protons flow back into the matrix

What happens when O₂ is not present when doing glycolysis in HUMANS?

• Lactic acid fermentation

  • NADH is recycled into NAD+

  • Produces lactic acid

What happens when O₂ is not present when doing glycolysis in YEAST?

• Alcohol fermentation

  • NADH is recycled into NAD+

  • Produces CO₂ and Ethanol

Why is lactic acid and alcohol fermentation important?

So that it can restart or continue to do glycolysis and produce ATP until oxygen levels are back to normal