Cellular Respiration (8.2)
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See Topic 2.8 for Core basics
REview:
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The Mitochondria
The mitochondria is a double membrane bound organelle (1 of 3). The inner membrane folds inward toward the matrix forming cristae.
STRUCTURE/ FUNCTION RELATIONSHIPS
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Electron Tomography:
A TECHNIQUE RECENTLY DEVELOPED HAS ENABLED SCIENTISTS TO THE SEE 3D IMAGES OF THE INTERIOR OF THE MITOCHONDRI
“The new take home message about the mitochondrial inner membrane is that the cristae are no simple infoldings but are invaginations, defining micro-compartments in the organelle…. Likely restrict diffusion of proteins and metabolites between the compartments. The membranes are not only very flexible but also dynamic, undergoing fusion and fission in response to changes in metabolism and physiological stimuli…. The working hypothesis is that the observed changes in the membrane shape (topology) are not random and passive but rather a specific mechanism by which mitochondrial function is regulated but changes in internal diffusion pathways…”
-Dr. Carmen Mannella (Former director of Molecular Medicine, Wadsworth Center, Albany NY: Resource for Vizualization of Biological Complexity) SOURCE: Biology, 2014 edition, Oxford, pg 388 |
Chemical Reaction Terminology
Oxidation and Reduction
Oxidation and reduction occur throughout cellular respiration.
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In Cellular Respiration, the gaining and loss of electrons is often seen through the gaining and loss of H+ ions in
NAD + 2 electrons => NAD+ NAD+ +2H+ ions =>NADH + H+ ion Note that the addition and removal of H+ ions is often synonymous with the addtion and removal of elections. When a hydrogen is removed, it often looses an electron too. As a H atom has one proton and one electron, a H+ ion has a proton but no electrons. For this reason a H+ ion is often referenced as a proton interchangeably. |
Phosphorylation
Phosphorylation is the addition of a phosphate molecule
(PO4 3-).
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Carboxylation and Decarboxylation
Stage 1: Glycolysis
Notes about the steps:
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The Link Step
When oxygen is present, pyruvate is moved into the matrix of the mitochondria. There the following processes occur first:
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Note that the link step is often connected to the Krebs cycle although it is technically not apart of glycolosis nor the Krebs cycle. However, acetyl-CoA is necessary to be able to begin the Krebs cycle (stage 2)
Krebs Cycle/ Citric Acid Cycle
What is required to make it happen?
Processes of Krebs Cycle:
Oxidation of acetyl groups releases energy
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Electron Transport Chain
Complex I and III use NADH as electron providers.
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Oxidative Phosphorylation= Addition of phosphorous to ADP to make ATP
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The Role of Oxygen
With all the free electrons roaming around, something needs to be able to receive these electrons
- Oxygen binds the free electrons at the end of Complex IV
- Oxygen binds the electrons, splitting apart to combine with H+ ions to form water.
- O2 + 4H+ --> 2 H2O
- Without oxygen present there is nothing to bind the electrons from the transport chain.
- Hence, when oxygen is depleted or not present pyruvate does not enter the mitochondria.
- This also means there is a lot less ATP produced. (See section 2.8 for more information)
- It is the primary reason WHY you breathe oxygen!