AP Biology review - oxidative phosphorylation

Question 1

What is oxidative phosphorylation?

Answer 1

• a process that couples the oxidation of NADH and FADH by the electron transport chain with the synthesis of ATP by phosphorylation of ADP

Question 2

What is the electron transport chain?

Answer 2

• The electron transport chain is a series of electron carriers and proteins that are embedded in the inner membrane of the mitochondrion
• electrons donated by NADH and FADH are transported through the chain, providing the energy needed for oxidative phosphorylation
• it is not until the end of this part of the overall process of aerobic respiration that oxygen acts as an electron acceptor and is converted to water

Question 3

Info about NAD+ and FAD+

Answer 3

• When NAD+ accepts electrons, it accepts two electrons and one hydrogen ion
• FAD accepts two electrons and two hydrogen ions
• When NADH and FADH2 pass these electrons onto the electron acceptors in the ETC, they pass only one at a time and the hydrogen ions do not accompany the electrons, but instead say in the matrix

Question 4

Arrange the components of the ETC in order of increasing electronegativity, from weakest to strongest

Answer 4

1. NADH dehydrogenase
2. Ubiquinone
3. Cytochrome b-c1 complex
4. Cytochrome c
5. cytochrome oxidase complex

Question 5

Important information of the electron transport chain

Answer 5

• NADH passes its electrons on to the first protein complex, NADH dehydrogenase, and FADH2 transfers its electrons to ubiquinone, the second component of the chain
• the electrons are passed down this chain of proteins. As they move down, they lose potential energy. This energy is used to pump H+ ions from the matrix into the fluid filled intermembrane space
• the enzyme cytochrome oxidase catalyzes the reaction between the electrons, protons (H+ ions), and oxygen to form water

Question 6

Energy statement for Electron transport chain

Answer 6

For every H+ ion pumped out of the matrix, 1 ATP is made:
the result is that 2 ATP are formed per FADH2 and 3 ATP are formed per NADH
FADH2= 2 ATP, NADH= 3 ATP

Question 7

What is chemiosmosis?

Answer 7

Chemiosmosis is a process that uses energy in a hydrogen ion gradient across the inner mitochondrial membrane to drive phosphorylation of ADP to ATP

Question 8

the process of chemiosmosis?

Answer 8

• As protons (H+ ions) accumulate in the intermembrane space, there are two gradients that are established: chemical and electrical
• Increased number of protons establishes a concentration gradient (chemical gradient)
• Increased intensity of positive charge establishes an electrical gradient
• The increased electrochemical gradient across the inner mitochondrial membrane creates a “battery” effect where the potential for H+ ions to move back into the matrix is high - the free energy stored in the electrochemical gradient is referred to as a proton motive force (PMF)
• The intermembrane space becomes a H+ reservoir since the inner mitochondrial membrane is impermeable to H+ ions
• Since the protons (H+ ions) cannot diffuse through he lipid bilayer of the inner membrane, they are forced to move through the ATP synthase complex
• The PMF drives the hydrogen ions to move back into the matrix, via ATP synthase
• When protons are moving down their gradient through an ATP synthase complex, the energy is used to phosphorylate ADP to form ATP - chemiosmosis

Question 9

What is the purpose of cellular respiration?

Answer 9

to create ATP

Question 10

Summary of cellular respiration

Answer 10

• the overall purpose of these ‘domino’ reactions is to take the potential energy stored in the bonds of glucose and release it, so it can charge the “chemiosmotic batter” in the mitochondrion, which will power ATPase to phosphorylate ADP into ATP