OXIDATIVE PHOSPHORYLATION of ATP by The

OXIDATIVE PHOSPHORYLATION OF ATP by the

ELECTRON TRANSPORT CHAIN and CHEMIOSMOSIS

In the fourth and last stage of cellular respiration, the electron transport chain and chemiosmosis, the energy stored in the bonds of the reduced coenzymes NADH and FADH2 is used for oxidative phosphorylation of ATP. This process occurs across the inner mitochondrial membrane as shown:

ELECTRON TRANSPORT CHAIN (ETC)

The electron transport chain (ETC) is a series of 5 enzymes found embedded in the inner mitochondrial membrane. The first enzyme is NADH reductase which breaks NADH into NAD+, H+ and 2 energized electrons. The energy in the electrons is harvested through reduction-oxidation reactions at the enzymes. The FADH2 carries less energy and gives up its 2 energized electrons at the second enzyme called coenzyme Q or ubiquinone. The FADH2 breaks into FAD, H+ and 2 energized electrons.

Electronegative elements strongly attract electrons. Oxygen is highly electronegative. In order to keep electrons moving down the electron transport chain, oxygen is required to pick up the de-energized electrons at the end of the 5 coupled redox reactions of the ETC. If there is not enough O2 available then the electrons back up and the ETC stops moving and aerobic cellular respiration stops.

The energy in the electrons is used by the ETC redox enzymes to pump the H+ (protons) from the matrix into the intermembrane space. This makes a high concentration of H+ in the intermembrane space. This high [H+] provides two types of energy. There is chemical energy as a concentration gradient. Also there is a higher positive charge in the intermembrane space which is a form of electrical energy.

CHEMIOSMOSIS

At long last the energy from breaking up glucose is about to yield large amounts of ATP.

The electrical and chemical energy of the high [H+] in the intermembrane space is now used to phosphorylate ADP to ATP. This happens at the ATP synthase enzyme found on the inner mitochondrial membrane. This process is called chemiosmosis. Chemiosmosis refers to the protons (H+) providing a chemical energy push and an electrical push as they move from an area of high proton concentration in the intermembrane space to an area of low proton concentration in the matrix.

This entire process is called oxidative phosphorylation because the energy in the ATP bond came from the energy of the redox reactions in the electron transport chains.

For each oxidized NADH there is a pair of energized electrons entering the ETC that contain enough energy to pump 3 pairs of H+ into the inner membrane space. Each pair of protons (H+ ) carries enough energy to phosphorylate one ATP, so each NADH will phosphorylate 3 ATP.

For each FADH2 that is oxidized there is enough energy to pump 2 pairs of H+ into the inner membrane space. Each FADH2 has enough energy to phosphorylate 2 ATP at the ATP synthase.

OXIDATIVE PHOSPHORYLATION OF ATP by the

ELECTRON TRANSPORT CHAIN and CHEMIOSMOSIS

ELECTRON TRANSPORT CHAIN (ETC)

The electron transport chain (ETC) is a series of 5 enzymes found embedded in the inner mitochondrial membrane. The first enzyme is ______which breaks NADH into ______. The energy in the electrons is harvested through ______at the enzymes. The FADH2 carries less energy and gives up its 2 energized electrons at the second enzyme called ______or ______. The FADH2 breaks into ______.

Electronegative elements strongly attract electrons. Oxygen is ______. In order to keep electrons moving down the electron transport chain, oxygen is required to ______the ______reactions of the ETC. If there is not enough O2 available then the electrons back up and the ETC stops moving and ______.

The energy in the electrons is used by the ______from the ______. This makes a ______concentration of H+ in the intermembrane space. This high [H+] provides two types of energy. There is ______energy as a ______. Also there is a higher ______ in the intermembrane space which is a form ______ energy.

CHEMIOSMOSIS

At long last the energy from breaking up glucose is about to yield large amounts of ATP.

The electrical and chemical energy of the ______is now used to ______. This happens at the ______found on the inner mitochondrial membrane. This process is called ______. Chemiosmosis refers to the ______providing a chemical energy push and an electrical push as they move from an area of high proton concentration in the intermembrane space to an area of low proton concentration in the matrix.

This entire process is called ______phosphorylation because the energy in the ATP bond came from the energy of the ______reactions in the electron transport chains.

For each oxidized NADH there is a pair of energized electrons entering the ETC that contain enough energy to pump 3 pairs of H+ into the inner membrane space. Each pair of protons (H+) carries enough energy to phosphorylate one ATP, so each ______.

For each FADH2 that is oxidized there is enough energy to pump 2 pairs of H+ into the inner membrane space. Each FADH2 has enough energy to ______at the ATP synthase.

ETC and CHEMIOSMOSIS

Name: ______-

Read p 74 – 76 in the McGraw – Hill Ryerson text for Grade 12 biology.

1. Why are the reactions of the Krebs cycle important in taking energy from pyruvate?

2. Describe the relationship between the mitochondrial matrix, intermembrane space and cristae or inner mitochondrial membrane. Use your own well labelled sketch.

3.a) Write a chemical equation that shows what happens when NADH is oxidized at the ETC. Be sure to include the enzyme name above the arrow.

b) What is the fate of the oxidized NAD+?

c) What is the fate of the pair of energized electrons removed from NADH?

d) How is the energy “harvested” from the electrons used?

e) What is the fate of the H+ (proton) removed from NADH?

4. Compare the oxidation of FADH2 to the oxidation of NADH. Be sure to state 2 similarities and 2 differences.

5. Explain the importance of the folded cristae inside the mitochondria.

6. Explain the importance of the hydrogen ion concentration gradient across the inner mitochondrial membrane.

7. a) Label the following diagram. Study the text diagrams and diagrams from your handouts and transfer the knowledge to this diagram.

b) Starting with the reduced high energy NADH as #1, number each diagram item that receives the energy in the order that the energy is transferred.