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Cellular Respiration Notes

Cellular Respiration

  • Unlike photosynthesis, cellular respiration has three main parts, plus a linking reaction.

Overview

  • Glycolysis (today's topic)
  • Krebs Cycle (tomorrow's topic)
  • Electron Transport Chain (tomorrow's topic)
  • Anaerobic Respiration (Wednesday's topic, separate from cellular respiration)
  • Lab on Thursday
  • Review on Friday
  • Unit Test on June 2nd (Monday)
  • Final Exam Review (fun things planned)

Unit Test Rewrites

  • Option to redo one unit test or major assignment.
  • Google Form sign-up will be available before the last day of classes.
  • The higher mark will be taken, regardless of whether it's the original or rewrite grade.
  • Rewrite available after this test.

Cellular Respiration vs. Respiration

  • Cellular respiration is different from respiration (breathing).
  • Respiration (breathing) - Unit D
  • Cellular respiration is the metabolism of cells and how they make energy.

Where Does Cellular Respiration Take Place?

  • In the mitochondria of cells.
  • Occurs in both animals and plants (anything with mitochondria).

Equation for Cellular Respiration

  • C6H{12}O6 (glucose) + 6O2 (oxygen) → 6CO2 (carbon dioxide) + 6H2O (water) + ATP (energy)
  • ATP stands for adenosine triphosphate.

Importance of Cellular Respiration

  • Eukaryotes rely on cellular respiration for energy.

Mitochondria Structure

  • Outer membrane: general membrane of the mitochondria
  • Intermembrane space: space between the outer and inner membranes
  • Cristae: folds in the inner membrane
  • Matrix: inside the inner membrane
  • Most of cellular respiration takes place in the cristae and matrix.

Glycolysis

  • Glycolysis occurs in the cytoplasm.
  • Krebs cycle and electron transport chain occur in the mitochondria.

Glycolysis - Starting Reaction

  • Makes NADH (electron carrier, similar to NADPH – transports electrons from one process to another).
  • Produces four ATP molecules (net gain is two). Produces two pyruvate molecules (intermediate molecules) that help things go from one thing to the other
  • First main step of aerobic cellular respiration (requires oxygen).
  • Anaerobic cellular respiration: doesn't require oxygen.
  • Glycolysis: occurs in both aerobic and anaerobic respiration.
  • Krebs cycle and electron transport chain: only in aerobic respiration (require oxygen).

Reduction and Oxidation

  • Reduction: electrons are added to the reactants.
  • Oxidation: electrons are generally taken away.
  • Mnemonic: LEO the lion says GER (Loss of Electrons is Oxidation, Gain of Electrons is Reduction) or OIL RIG (Oxidation Is Loss, Reduction Is Gain).

Glycolysis Summary

  • Anaerobic reaction (doesn't require oxygen).
  • Glucose (input) requires two ATP.
  • Products: four ATP (net gain of two), two NADH, and two pyruvate molecules.

Glycolysis Steps

  • Main purpose: split glucose and obtain two molecules of pyruvate.
  • Occurs inside the cytoplasm.

Step 1

  • Glucose molecule requires two ATP to break apart.
  • Glucose → two G3P molecules (glyceraldehyde-3-phosphate) [two G3P molecules make up a glucose]

Step 2

  • Each G3P molecule reacts with NAD+ (found in the cytoplasm).

  • G3P + NAD+ → NADH + two ATP + pyruvate (three-carbon molecule).

  • Products (from two G3P molecules):

    • Two NADH molecules
    • Four ATP molecules (net gain of two, because two were used to initially break up the glucose)
    • Two pyruvate molecules

Fate of NADH

  • Goes to the Krebs cycle.
  • G3P is being reduced (gaining electrons) to make pyruvate

Glycolysis Overall Equation

  • Glucose + 2ATP → 2 Pyruvate + 2NADH + 4ATP (net 2ATP)

Linking Reaction: Pyruvate to Acetyl Coenzyme A

  • Pyruvate is an intermediate; it's transformed into acetyl coenzyme A before entering the Krebs cycle.
  • Linking reaction connects glycolysis to the Krebs cycle.
  • Each pyruvate reacts with NAD+ again creating 3 things:
    • CO_2 (which we breathe out)
    • NADH (NAD+ yields NADH)
    • Acetate (acid), also an intermediate

Last Step of Linking Reaction

  • Acetate reacts with coenzyme A (CoA, an enzyme like Rubisco in the Calvin cycle).
  • Acetate + CoA → Acetyl CoA (can now be used in the Krebs cycle).
  • Enzyme joins the reactant and becomes part of the product (weak bond).