AP BIO Unit 3 Lesson 4

Current Focus in Class

• The focus of the current week is on the topic of respiration.

• Ensuring all students have the necessary resources to participate.

Recap of Previous Lessons

• Discussion on the Krebs cycle and its completion status in class.

• Importance of understanding glycolysis and the Krebs cycle as related processes.

  • Distinction in Locations:

  • Glycolysis occurs in the cytoplasm in eukaryotes.

  • The Krebs cycle occurs inside the mitochondrion (myocardium).

Locations Within the Mitochondria

• Mitochondria have two membranes:

  • Outer membrane

  • Inner membrane

• There are three distinct spaces within mitochondria:

  1. Cytoplasm: the space outside the mitochondria

  2. Intermembrane space: space between the two membranes

  3. Mitochondrial matrix: innermost space

• Pyruvate travels across both membranes to reach the mitochondrial matrix.

Energy Processing in Cellular Respiration

• Both glycolysis and Krebs cycle serve to process energy from glucose.

  • Glycolysis: Cutting glucose into pyruvate.

  • Krebs cycle: Completing the breakdown of pyruvate into carbon dioxide (CO₂).

• Primary goal: to harvest energy from glucose through cutting it up.

• Key concepts to remember:

  • ATP Production:

  • ATP generated through substrate-level phosphorylation.

  • Direct phosphorylation of ADP by cutting sugar substrate leads to ATP formation.

  • Electron Carriers Needed:

  • NAD⁺ (Nicotinamide adenine dinucleotide) picks up high-energy electrons and becomes NADH.

  • FAD (Flavine adenine dinucleotide) also functions similarly as an electron carrier.

• More energy is harvested in the Krebs cycle than in glycolysis.

Matter and Energy Flow in Respiration

• The original matter is in the sugar (C₆H₁₂O₆) and is converted largely into CO₂ that is exhaled.

• The energy initially stored in glucose bonds is transformed:

  • High-energy electrons carry most of this energy post-reaction.

  • Some energy is captured in the form of ATP, but some is also lost as heat during conversion processes.

Energy Dynamics in Respiration

• The body’s energy use adjusts based on ATP levels:

  • At resting states, ATP inhibition prevents unnecessary sugar breakdown.

  • As ATP is utilized, respiration processes are activated to replenish ATP stores.

Steps of Cellular Respiration

1. Glycolysis:

   • Occurs in the cytoplasm; glucose converted to pyruvate.

   • Inputs: 1 glucose; Outputs: 2 pyruvate (and some ATP, NADH).

   • Pyruvate next enters the mitochondria.

2. Krebs Cycle:

   • Takes place in the mitochondrial matrix; pyruvate completely oxidized to CO₂.

   • Inputs: 1 acetyl CoA; Outputs: energy carriers (NADH, FADH₂) and some ATP.

   • Most high-energy electrons generated here.

3. Electron Transport Chain:

   • Embedded in the inner mitochondrial membrane.

   • High-energy electrons are passed from NADH and FADH₂.

   • Electrons pump H⁺ into intermembrane space creating a proton gradient.

   • Oxygen is the final electron acceptor, forming water (H₂O).

4. Chemiosmosis:

   • Utilizes the proton gradient created by the electron transport chain.

   • H⁺ ions flow back through ATP synthase (turbine) generating ATP by combining ADP + P.

Summary Illustration Protocol

• For each step in the respiration pathway:

  • Identify inputs and outputs

  • Determine what is oxidized and what is reduced.

  • Trace where products go post-process.

• Students are reminded of the importance of groups working closely and checking progress collaboratively.

Final Remarks

• Critical understanding of these processes will also aid in grasping photosynthesis which shares similar principles.

• Regular practice with these concepts is advised since they frequently appear in assessments.