Exam 1: Oxidative Phosphorylation

Question 1

Oxygen is involved in the generation of more than 90% of all the ATP we need.

Oxygen is delivered to _________ by transport in the blood attached to ________ molecules in the RBCs.

Answer 1

mitochondria

hemoglobin

Question 2

How does O2 get to the mitochondria in the cells?

• ________ from capillaries
• ________ (primarily in type I and myocardial cells)

Answer 2

Diffusion

Myoglobin

Question 3

Oxidative phosphorylation takes place in cell ___________.

-It encompasses the tricarboxylic acid (TCA) cycle and the electron transport chain (ETC).

Answer 3

mitochondria

Question 4

The ______ of mitochondria in a cell parallels its capacity for oxidative phosphorylation.

Mitochondria contain carrier molecules that remove electrons from hydrogen (_______) and eventually pass them to oxygen (_______).

Answer 4

density

oxidation
reduction

Question 5

It is convenient to think of aerobic ATP production as a three-stage process:

1. Generation of the 2-carbon molecule, _____-____.
2. Oxidation of acetyl-CoA in the ______ _____.
3. ATP formation in the _______ _______ _____.

Answer 5

acetyl-CoA
Krebs cycle
electron transport chain

Question 6

Acetyl-CoA

Entry into the Krebs cycle requires the preparation of a two-carbon molecule, _____-____.
Acetyl-CoA can be formed from the breakdown of either CHO, PRO, or Fats.

Answer 6

acetyl-CoA

Question 7

Where does acetyl-CoA come from?

3 sources:
\_\_\_\_\_\_\_\_\_ oxidation (breakdown)
\_\_\_\_ oxidation (breakdown)
\_\_\_\_\_\_. oxidation (breakdown)

Answer 7

Carbohydrate
Fat
Protein

Question 8

• The primary function of the Krebs cycle is to complete the ________ (hydrogen removal) of CHO, fats or proteins.
• To do this, it uses ___ and ___ as hydrogen (energy) carriers.
• The importance of hydrogen removal is that hydrogens (by virtue of the electrons that they possess) contain the potential energy in food molecules.
• This energy can be used in the ETC to combine ADP + Pi to reform ATP (electrochemical gradient).
• _______ does not participate in the reactions of the Krebs cycle but is the _____ electron acceptor at the end of the ETC
• Water is formed (H2 + O → H2O)

Answer 8

oxidation
NAD and FAD
Oxygen
final

Question 9

Acetyl-CoA combines with _________ (4-carbon molecule) to form _____ (six carbons).

What follows is a series of reactions to regenerate oxaloacetate and two molecules of CO2, and the pathway begins all over again.

Answer 9

oxaloacetate

citrate

Question 10

• The primary function of the Krebs cycle is to remove ________ and the energy associated with those hydrogens from various substrates involved in the cycle.
• During each turn of the Krebs cycle, __ molecules of NADH and __ molecule of FADH2 are formed.

Answer 10

hydrogens

3
1

Question 11

Krebs Cycle Summary

• Completes the ________ of carbohydrates, proteins, and fats.
• Produces ___ and supplies _______ to be passed through the ETC to provide the energy for the aerobic production of ATP.
• Enzymes catalyzing Krebs cycle reactions are located inside the __________.

Answer 11

oxidation

CO2
electrons

mitochondria

Question 12

NADH and FADH2

• Nicatinamide adenine dinucleotide (NAD+)
• ______ pairs of electrons (energy) from hydrogen
• While the substrate oxidizes and gives up hydrogens (electrons), NAD+ gains hydrogen and two electrons and reduces to NADH.
• The other hydrogen appears as H+ in the cell fluid.
• Flavin adenine dinucleotide (FAD)
• Serves as the other important electron ______ in oxidizing food fragments.
• FAD catalyzes dehydrogenation and accepts electron pairs.
• FAD becomes FADH2 by accepting both hydrogens.

-NADH and FADH2 provide energy-rich molecules because they carry electrons with a high energy-transfer potential.

Answer 12

Accepts

acceptor

Question 13

Oxidative phosphorylation synthesizes ATP by transferring electrons from ____ and _____ to oxygen.

Answer 13

NADH

FADH2

Question 14

-The electron transport chain (ETC) uses the potential energy available in reduced hydrogen carriers such as NADH and FADH2 to ____________ ADP to ATP.

-The reduced hydrogen carriers do not directly react with oxygen.
-Electrons are removed from the hydrogen atoms and are passed down a series of electron carriers known as __________.
During this passage of electrons down the ________ chain, enough energy is released to rephosphorylate ADP to form ATP.

Answer 14

rephosphorylate

cytochromes
cytochrome

Question 15

• FADH2 enters the cytochrome pathway at a point just below the entry level for NADH.
• The level of FADH2 entry bypasses one of the sites of ATP formation and thus each molecule of FADH2 that enters the ETC has enough energy to form only __ ATP.
• NADH entry into the ETC results in the formation of __ ATP.

Answer 15

2

3

Question 16

At the end of the ETC, ______ accepts the electrons that are passed along , and combines with hydrogen to form water.

If O2 is not available to accept those electrons, ________ ___________ is not possible.

Answer 16

oxygen

oxidative phosphorylation

Question 17

• The mechanism to explain the aerobic formation of ATP is known as the __________ _________.
• As electrons are transferred along the cytochrome chain, the energy released is used to “pump” hydrogens (protons) released from NADH and FADH2 from the inside of the mitochondria across the inner mitochondrial membrane.
• The accumulation of H+ is a source of potential energy which can be captured and used to recombine Pi with ADP to form ATP.

Answer 17

chemiosmotic hypothesis

Question 18

• The increase in H+ within the space between the inner and outer mitochondrial membranes results in a H+ _______.
• This gradient creates a strong drive for H+ to diffuse back across the inner mitochondrial membrane.
• Since most of the inner mitochondrial membrane is not permeable to H+, the H+ can only cross the membrane through specialized H+ channels.

Answer 18

gradient

Question 19

The reaction that recombines ADP with Pi to form ATP is catalyzed by the enzyme ___ _________.

Answer 19

ATP synthetase

Question 20

Where does O2 enter this picture?

After the H+ pass through these channels they combine with oxygen to form _____.

Oxygen is essential to oxidative phosphorylation because in order for ATP to continue to be formed as H+’s enter the inner mitochondria, these H+’s must be removed by combining with ______ to form _____.

Therefore, oxygen is essential in aerobic production of ATP because it serves as the _____ electron acceptor of hydrogens.

Answer 20

water

oxygen
water

final

Question 21

Oxidative Phosphorylation Summary

• Oxidative phosphorylation (or aerobic ATP production) occurs in the mitochondria as a result of a complex interaction between the _____ _____ and the _______ ________ _____.
• The primary role of the Krebs cycle is to complete the oxidation of substrates and form ____ and _____ to enter the electron transport chain.
• The end result of the electron transport chain is the formation of ___ and _____.
• Water is formed by ______-accepting electrons; hence the reason we breathe oxygen is to use it as the final acceptor of electrons in aerobic metabolism.

Answer 21

Krebs cycle
electron transport chain

NADH and FADH2

ATP and water.

oxygen

Question 22

NAD and FAD are carrier molecules…
When they pick up H+ electrons, they become NADH and FADH2 –> they become ________.

When NADH and FADH2 drop off H+ to oxygen, NADH and FADH2 become ________.

Answer 22

reduced

oxidized

Question 23

What is Acetyl-CoA’s job?

Answer 23

To enter the Krebs Cycle

Question 24

The Krebs cycle produced __ NADH and __ FADH2

Answer 24

3 NADH

1 FADH2

Question 25

__________ __________ is very slow, but provides a lot of ATP.

Answer 25

Oxidative Phosphorylation