respiration

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respiration

• A REVISION OF THE PRE-SUMMER WORK

2
What respiration actually is

• "Respiration is the chemical process of releasing
  energy from organic compounds."

3
It is important that you understand the correct
terms for some of the processes

• Gas exchange - The movement of oxygen into an
  organism and carbon dioxide out of an organism.
• Breathing - The ventilation movements that are
  needed in some larger animals so that efficient
  gas exchange can take place. It involves ribs,
  intercostal muscles, the diaphragm and lungs.
• Respiration - The process by which complex
  organic molecules are broken down to release
  energy.
• Aerobic respiration - Requires oxygen to fully
  oxidise the organic molecule. This releases lots
  of energy.
• Anaerobic respiration -The breakdown of the
  molecule without oxygen. This releases much less
  energy.

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ATP

• ATP (adenosine triphosphate) is the universal
  currency of energy. It is a small molecule with 3
  phosphate groups (P) attached to an adenosine
  molecule i.e. Adenosine-P-P-P
• During respiration, high energy C-C, C-H and C-OH
  bonds are broken. Lower energy bonds are formed
  and the difference is released and used to attach
  a P to Adenosine-P-P (ADP adenosine diphosphate),
  making ATP. When energy is required at a later
  time by a cell, it can use the ATP and break a P
  off the end. This releases the energy needed
  (30.6kJ for every ATP, ADP P). The more ATPs
  used, the more energy is released.
• For aerobic respiration to occur, the cell needs
  to possess mitochondria.

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An outline of the stages of respiration

• Glycolysis (splitting of sugar)  What
  formation of pyruvic acid from glucose.  Where
  cytoplasm of a cell.   
• Krebs cycle  What removal of hydrogen from
  pyruvic acid.  Where matrix of the
  mitochondria.   
• Electron transport chain / oxidative
  phosphorylation  What using hydrogen to
  produce ATP.  Where inner mitochondrial
  membrane.

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Electron / hydrogen carriers

• Many of the reactions in the stages of
  respiration involve oxidation by the removal of
  electrons or hydrogen atoms (H). These are
  transferred to electron/hydrogen carriers.
  Ultimately they are passed to oxygen to form
  water right at the very last stage of
  respiration.
• Two important electron/hydrogen carriers are NAD
  (nicotinamide adenine dinucleotide), and FAD
  (flavin adenine dinucleotide).

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Oxidation / reduction

• Oxidation is the addition of oxygen, the removal
  of hydrogen or the loss of electrons.
• Reduction is the addition of hydrogen, the
  removal of oxygen or the gain of electrons.
• A quick way to remember this is "OILRIG"
• Oxidation Is Loss, Reduction Is Gain.

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Glycolysis
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Glycolysis

• 1.Glucose is phosphorylated twice to make a 6C
  sugar phosphate. 2 ATPs are used to supply the P
  groups. This makes the glucose more reactive and
  so
• 2.The 6C sugar phosphate breaks down to form 2,
  3-carbon sugar phosphates, called triose
  phosphates (TP).
• 3.Hydrogen is removed from each of the 2 TP
  molecules. The hydrogens are passed to 2 NADs
  (the NADs are reduced). 2 ATPs are made directly
  from the conversion of each TP to pyruvic acid
  (written shorthand as PA or called pyruvate) as
  the phosphate groups are removed.

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Glycolysis

• Into glycolysis
• 1 glucose (6C)
• 2 NAD
• 2ATP

• Out of glycolysis
• 2 pyruvic acid (3C)
• 2 reduced NAD (2NADH H)
• 4 ATP

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Glycolysis

• Net Gain 2 ATP and 2 NADH H
• This stage occurs in the cytoplasm. The next
  stage occurs in the mitochondria. From here, the
  reaction will only proceed if oxygen is available.

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The link reaction
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The link reaction

• 1.The PA molecules enter the mitochondrion.
• 2.CO2 and hydrogen are removed from each PA to
  create 2 2-C molecules. The hydrogen is
  transferred to NAD
• 3.The 2-C molecule is then combined with coenzyme
  A (CoA) to form the 2C compound, acetylCoA. (CoA
  is a vitamin derivative which acts as a
  transporter of the 'acetate' psrt left from the
  PA molecule)

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The link reaction

• Into link
• 2 PA and 2 CoA
• 2NAD

• Out of the link
• 2 Acetyl CoA
• 2CO2
• 2 reduced NAD (2NADH H)

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Krebs Cycle

• This is also known as the citric acid cycle or
  the tricarboxylic acid cycle.
• For each glucose molecule, there were 2 pyruvic
  acid molecules formed, (and therefore 2 acetylCoA
  molecules formed) so the whole cycle takes place
  twice for every glucose molecule respired.

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Krebs Cycle

• 1.Each acetylCoA (2C) combines with an
  oxaloacetic acid (4C) to make a 6C compound
  (citric acid).
• 2.In a series of steps, for each 6C compound, 2
  CO2 molecules are released, 3 NAD molecules are
  reduced, 2 FAD molecules are reduced,1 ATP
  molecule is made directly.
• 3.The 4C compound is regenerated (by the removal
  of the 2 Cs in 2 CO2 molecules) so that the
  cycle can begin again with more molecules of
  acetylCoA.

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Krebs Cycle

• Into Krebs
• 2 acetylCoA
• 6 NAD
• 2 FAD
• 2 ADP P

• Out of Krebs
• 2 oxaloacetate
• 4 CO2
• 6 reduced NAD (6 NADH H)
• 2 reduced FAD (2 FADH H)2 ATP