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Home > Chemistry > Options > The Biochemistry of Movement > The Biochemistry of Movement: 9. ATP is continually regenerated

9.7 The Biochemistry of Movement: 9. ATP is continually regenerated

Syllabus reference (October 2002 version)
9. ATP used in muscle contraction is continually regenerated	Students learn to: identify NADH and FADH2 as compounds essential for respiration describe the NADH/FADH2 oxidation as part of an oxidation–reduction process leading to ATP production construct an equation to summarise the reduction/oxidation process in ATP regeneration define oxidative phosphorylation as the process that couples the oxidation of NADH and FADH2 to the production of ATP	Students: process information from a simplified flow chart of biochemical pathways to analyse the steps in oxidative phosphorylation

Extract from Chemistry Stage 6 Syllabus (Amended October 2002) © Board of Studies, NSW.
[Edit:27 Jun 08]

identify NADH and FADH₂ as compounds essential for respiration

describe the NADH/FADH₂ oxidation as part of an oxidation–reduction process leading to ATP production

• The energy released from glucose in respiration is mostly trapped in the high energy carriers NADH and FADH₂.
  
  
• The reduced compounds NADH and FADH₂ are capable of releasing energy as ATP when oxidised.

process information from a simplified flow chart of biochemical pathways to analyse the steps in oxidative phosphorylation

• Process and analyse information given about oxidative phosphorylation in the Biochemical Pathways Flowchart.

  Note the different arrangement of information compared with that for glycolysis and oxidative decarboxylation in the flowchart. Hydrogens at the top react with oxygen from the left to form water at the right. Energy released by this oxidation causes phosphorylation of ADP to ATP.

• The first step in oxidative phosphorylation requires H atoms to be released from the reduced carriers, the electrons passing to cytochromes and H⁺ ions released. The carriers are oxidised and the cytochromes are reduced as they receive the electrons. The cytochromes are iron-rich proteins arranged in a chain capable of transferring electrons.
  
  
• The last step in oxidative phosphorylation occurs when the electrons at the end of the cytochrome chain are passed to oxygen, reducing it.
  
  
• H⁺ ions, O₂ and electrons react to form water.

  2H⁺ + O₂ + 2e^- → H₂O

• As the electrons from NADH are passed along the full length of the cytochrome chain, three ADP are converted to three ATP. FADH₂ interacts further along the cytochrome chain so only two ATP are formed from the oxidation of each FADH₂.

  

• Construct a similar diagram for FADH₂.

  Answer

The two diagrams should be similar. However, you may like to note that the NADH oxidation releases 3 ATP whereas the FADH₂ oxidation releases only 2 ATP.

construct an equation to summarise the reduction/oxidation process in ATP regeneration

• Construct completed balanced equations by placing appropriate whole numbers above the underlines __:

  NADH + H⁺ + __ADP + __P_i + 1/2 O₂ → NAD⁺ + __ATP + H₂O

  FADH₂ + __ADP + __P_i + 1/2 O₂ → FAD + __ATP + H₂O .

Answer.

define oxidative phosphorylation as the process that couples the oxidation of NADH and FADH₂ to the production of ATP

• Define the process of oxidative phosphorylation, recognising the oxidation of NADH + H⁺ and FADH₂ to NAD⁺ and FAD. At the same time the energy in these energy carriers is transferred via cytochromes to ADP to form ATP. The formation of the energy phosphate bonds of ATP is the phosphorylation step.
  
  
• Now calculate the total amount of ATP produced from respiration by completing this table:
  
  

  Processes	No. molecules produced
  	NADH	FADH2	ATP
  Step 1. Glycolysis of one glucose	?		?
  Step 2. Two pyruvic acid → acetyl CoA	?
  Step 3. Two turns of the TCA cycle	?	?	?
  Total	?	?	?
  Step 4. Oxidative phosphorylation
  No. of ATP produced from each NADH	?		?
  No. of ATP produced from each FADH2		?	?
  Total ATP from one glucose after completion of the four steps			?

  
  
  
• Note that only 4 of the 38 ATP are produced directly.
  34 of the 38 ATP from one glucose molecule require oxidative phosphorylation of NADH and FADH₂.

  Answer

• You could do a role play in which suitable objects can be passed along representing H atoms. These split into electrons and H⁺ ions. The electrons are passed along the cytochrome chain and are finally accepted by oxygen. The oxygen and electrons join with hydrogen ions to form water. Those representing ADP can move across the chain at certain points and as they pass across the chain, they transform to ATP.