1. Wednesday, 30 May 2018
3.5 Energy transfer in and between organisms Respiration – Oxidative Phosphorylation
• explain the process of electron transfer associated with oxidative phosphorylation • explain chemiosmosis and the role of ATP synthase in producing ATP • apply knowledge to explain trends in data.

2. Oxidative Phosphorylation
Is the process where the energy carried by electrons, from reduced coenzymes (reduced NAD and FAD by oxidising them) is to make ATP
It uses the Electron transport chain (chain of proteins where excited electrons travel) and chemiosmosis (electrons flowing down the electron transport chain and creating a proton gradient across a membrane to drive ATP synthesis)

3. Respiration
The process of aerobic respiration can be split into 4 stages:
Glycolysis (splitting of the 6-carbon glucose molecule into two 3-carbon pyruvate molecules)
Link reaction (the 3-carbon pyruvate molecules enter a series of reactions which lead to acetylcoenzyme A – a 2-carbon molecule)
Krebs Cycle (acetylcoenzyme A into a cycle of oxidation-reduction reactions that yield some ATP and a large quantity of reduced NAD and FAD
Oxidative phosphorylation (electrons from NAD and FAD are released from the Krebs cycle to synthesis ATP with water produced as a by-product

5. Complete the Table ATP Carbon Dioxide Reduced NAD Reduced FAD
How many of each one is produced during the following stages of Aerobic Respiration?
GLYCOLYSIS
LINK REACTION
KREBS CYCLE
2x ATP, zero carbon dioxide, 2x reduced NAD, zero reduced FAD
zero ATP, 2x carbon dioxide, 2x reduced NAD, zero reduced FAD
2x ATP, 4x carbon dioxide, 6x reduced NAD, 2x reduced FAD
Glycolysis = 2x ATP, zero carbon dioxide, 2x reduced NAD, zero reduced FAD
Link Reaction = zero ATP, 2x carbon dioxide, 2x reduced NAD, zero reduced FAD
Krebs cycle = 2x ATP, 4x carbon dioxide, 6x reduced NAD, 2x reduced FAD

6. So where does the rest of the energy come from?
Where does the remaining 28 ATP come from?
The Electron Transport Chain!
The ETC makes ATP from the reduced NAD and Reduced FAD made in the earlier stages.
Each reduced FAD will generate 1.5ATP
Each reduced NAD will generate 2.5ATP

7. Where they come from and how many?
Reduced FAD
2 (from Krebs)
1.5 X 2 = 3 ATP (ETC)
Reduced NAD
2 (from Glycolysis)
2 (from 2x link reaction)
6 (from 2x Krebs)
2.5 X 10 = 25 ATP (ETC)
3 ATP + 25 ATP = 28 ATP
Add this to the 4 ATP made directly in glycolysis and krebs and you have 32 ATP altogether!

8. What Happens Where? Glycolysis = Cytoplasm of the cell.
Link reaction = Matrix of the mitochondria.
Krebs cycle = Also in the matrix.
Electron transport chain Utilises proteins found in the membrane of the cristae.
Discuss adaptations of mitochondria and metabolically active cells e.g. Muscle cells

10. Oxidative Phosphorylation

11. Oxidative phosphorylation is the terminal process of cellular respiration.
During oxidative phosphorylation electrons are transferred from NADH or FADH2, to molecular oxygen via a series of protein complexes located in the inner mitochondrial membrane.
Protons are pumped from the mitochondrial matrix into the intermembrane space as a result of this flow of electrons

12. Electron Transport Chain
The ETC is a series of hydrogen and electron carriers (proteins) located on the membranes of the cristae
2H atoms are ionised into 2H+ and 2e-
Electrons (e-)are passed from one carrier to the next – losing energy as they go

13. Electron Transport Chain
The energy released in this stepwise process is used to produce ATP
Oxygen is the final electron acceptor and is reduced to water
The formation of ATP, via the electron transport chain in a mitochondrion is called oxidative phosphorylation

15. The Fate of the hydrogens –The Electron transport chain.
ETC and Chemiosmosis Summary
The Fate of the hydrogens –The Electron transport chain.
Chemiosmosis Theory
STUDENT HANDOUT
This method of ATP production is termed
Oxidative Phosphorylation

16. Electron Transport Chain
THE MOVIE!

17. Electron Transport Chain

19. Why is the theoretical maximum yield of ATP per glucose molecule rarely achieved?
Some protons leak across the mitochondrial membrane, reducing the number of protons to flow through the ion channels and generate ATP
Some ATP produced is used to actively transport pyruvate into the mitochondria
Some ATP is used for the shuttle to bring hydrogen from reduced NAD made during glycolysis, in the cytoplasm, into the mitochondria

21. The energy released from hydrolysis of ATP

22. Coenzyme A

23. Nicotinamide adenine dinucleotide (NAD)

24. FAD

25. http://highered. mheducation
Respiration Song

26. Respiratory substrate
A respiratory substrate is an organic substance that can be used for respiration

27. Respiratory substrate Mean energy value/kJg-1
Difference in relative energy values of carbohydrate, lipid and protein
The more hydrogen there are in a molecule of respiratory substrate, the more ATP can be generated when that substrate is respired
Respiratory substrate
Mean energy value/kJg-1
Carbohydrate
15.8
Lipid
39.4
Protein
17.0

28. Difference in relative energy values of carbohydrate, lipid and protein
Carbohydrates
Animals store glucose as glycogen and plants store it as starch
Both can be hydrolysed to glucose for respiration
Fructose and galactose are changed to glucose for respiration

29. Difference in relative energy values of carbohydrate, lipid and protein
During starvation or prolonged exercise, protein from muscle can be hydrolysed to amino acids which can be respired
Some can be converted to pyruvate, or to acetate, which can be respired via the Krebs Cycle
Some can enter Krebs Cycle directly

30. Difference in relative energy values of carbohydrate, lipid and protein
Lipids
Glycerol can be converted to glucose, and then respired
Fatty acids are long-chain hydrocarbons. There are therefore many hydrogen atoms as a source of protons for oxidative phosphorylation
The fatty acids are broken down to 2 carbon acetyl groups and enter the Krebs cycle

31. Questions!
Explain why palmitic acid, a large molecule, can pass into the matrix of the mitochondria
Why can fats and proteins only be respired aerobically?
Explain why children whose diet does not contain enough fat or carbohydrate can suffer from muscle wastage

32. Answers!
It is a fat so dissolves in the lipid bilayer of the mitochondrial membranes
Fats and proteins are respired via the Krebs Cycle
They will use muscle protein as a source of amino acids for respiration

33. IN DETAIL - Oxidative Phosphorylation produces lots of ATP
Hydrogen atoms are released from NADH + H+ and FADH2 (as they are oxidised to NAD+ and FAD). The H atoms split to produce protons (H+) and electrons (e-) for the chain.
The electrons move along the electron chain (made up of three electron carriers) losing energy at each level. This energy is used to pump the protons (H+) into the space between the inner and outer mitochondrial membranes (the intermembrane space)

34. Oxidative Phosphorylation produces lots of ATP
The concentration of protons is higher in the intermembrane space than in the mitochondrial matrix, so an electrochemical gradient exists.
The protons then move back through the inner membrane down the electrochemical gradient, through specific channels on the stalked particles of the cristae- this drives the enzyme ATP synthase. By spinning like a motor, this enzyme supplies electrical potential energy to make ATP from ADP and inorganic phosphate
The protons and electrons recombine to form hydrogen, and this combines with molecular oxygen (from the blood) at the end of the transport chain to form water. Oxygen is said to be the final electron acceptor