Energy Generation In Mitochondria And Chloroplasts Pt. 1

Front 1

What is cell respiration?

Back 1

A set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products.

Front 2

By what mechanisms do cells obtain most of their energy?

Back 2

By membrane-based mechanisms

Front 3

By what process is ATP produced for the majority of cells?

Back 3

Oxidative phosphorylation

Front 4

How does oxidative phosphorylation differ from the way ATP is produced during glycolysis?

Back 4

It requires a membrane and depends on an electron transport process that drives the transport of protons (H+) across the inner mitochondrial membrane to create a gradient. (Occurs in chloroplasts in plants).

Front 5

What source do mitochondria use to create the proton gradient? How about chloroplasts?

Back 5

Food and light (photosynthesis) respectively.

Front 6

What is stage 1 for making ATP?

Back 6

1. High energy electrons derived from oxidation of energy sources such as food and light are transferred along an electron-transport chain embedded in the membrane (aka, a proton pump).

2. These transfers release energy used to pump protons (H+) across the membrane.

3. This creates an electrochemical proton gradient across the mitochondrial inner membrane.

Front 7

Where are the H+ protons for stage 1 of the process derived?

Back 7

From water, which is ubiquitous in the aqueous environment of cells.

Front 8

What is stage 2 for the process of oxidative phosphorylation (process to make ATP)?

Back 8

The proton gradient created in stage 1 allows protons to flow back down their electrochemical gradient through the enzyme ATP synthase, which catalyzes the reaction to synthesize ATP from ADP and an inorganic phosphate.

Front 9

Explain how cells harness energy in a similar way to batteries.

Back 9

1. Batteries use energy from electron transfer to perform work.

2. If a battery's terminals are connected, all the energy is converted into heat.

3. If the battery is connected to something, like a pump, the energy released can instead be harnessed to do work such as pump water.

4. Cells, like batteries, harness the energy of electron transfer in a similar way. For example, using electron transfer to pump H+ across the membrane.

Front 10

What is chemiosmotic coupling?

Back 10

It is the process that links the electron transport chain to the chemical bond-forming reactions that synthesize ATP.

Front 11

What is some of the evidence that mitochondria and chloroplasts evolved from bacteria that was engulfed by ancestral cells more than a billion years ago?

Back 11

1. Both reproduce in a manner similar to most prokaryotes. It is a fission process that is similar to bacterial division.

2. They harbor bacterial-like biosynthetic machinery for making RNA and proteins

3. They retain their own genomes and have ribosomes.

4. They contain protein complexes involved in ATP production.

Front 12

What are the inner compartments of mitochondria and chloroplasts called (where you can find their DNA and special set of ribosomes)?

Back 12

1. Mitochondrial matrix

2. Chloroplast stroma

Front 13

Where will you find the complexes involved in ATP production in mitochondria and chloroplasts?

Back 13

1. The inner membrane

2. The thylakoid membrane

(Respectively)

Front 14

How many molecules of ATP are created by oxidative phosphorylation compared to glycolysis?

Back 14

About 30 per glucose molecule vs the 2 per molecule from glycolysis.

Front 15

What can mitochondria do in order to suit a cell's needs?

Back 15

Change their shape, locations, and number.

Front 16

In what cases would a mitochondrion remain in a fixed location?

Back 16

In areas where they supply ATP directly to a site of unusually high energy consumption.

Ex: close to the contractile apparatus of cardiac muscles to provide energy for contraction.

Ex: wrapped tightly around the motile flagellum of a sperm tail

Front 17

In cells that don't have an unusually high energy consumption, how can mitochondria be found?

Back 17

Fused to form elongated, dynamic tubular networks that can extend throughout the cytoplasm. Such networks are continually breaking apart by fission and reforming again.

Front 18

What are the four separate compartments a mitochondrion is organized into?

Back 18

1. The matrix

2. The inner membrane

3. The outer membrane

4. The intermembrane space.

This design supports the efficient production if ATP.

Front 19

What is the mitochondrial matrix?

Back 19

It is the space in the organelle that contains a highly concentrated mixture of hundreds of enzymes, including those for oxidation of pyruvate and fatty acids for the citric acid cycle.

In the liver, ~67% of total mitochondrial protein is in the matrix.

Front 20

Describe the mitochondrial inner membrane.

Back 20

It is folded into many structures called cristae. It contains the proteins that carry out oxidative phosphorylation, including the electron-transport chain and the ATP synthase that makes ATP.

Also contains transport proteins that move selected molecules into and out of the matrix.

21% of total mitochondrial protein in liver cell.

Front 21

Describe the mitochondrial outer membrane.

Back 21

Contains porins (large, channel-forming proteins). Because of this, it is permeable to all molecules of 5000 daltons or less.

6% of total mitochondrial protein in liver cells.

Front 22

Describe the mitochondrial intermembrane space.

Back 22

Contains several enzymes that use the ATP passing out of the matrix to phosphorylate other nucleotides. Also contains proteins that are released during apoptosis.

6% of total mitochondrial protein in liver cells.

Front 23

From where are the high energy electrons required for the generation of ATP derived?

Back 23

Carbohydrates, fats, and other foodstuffs during glycolysis of the citric acid cycle. Occurs in the mitochondrial matrix.

Front 24

How is the crucial metabolic intermediate, acetyl CoA, produced in the mitochondria?

Back 24

1. Pyruvate produced during glycolysis and fatty acids derived from the breakdown of fats enter the mitochondrion from the cytosol via porins.

2. Once inside the mitochondrial matrix, both are converted into acetyl CoA and then oxidized into CO2 via the citric acid cycle, leaving NADH and FADH2

Front 25

What are NADH and FADH2?

Back 25

Carriers that, when activated, hold the high-energy electrons produced by the citric acid cycle.

Front 26

What happens to the high-energy electrons held by carriers like NADH and FADH2?

Back 26

They are donated to an electron transport chain. A hydride ion (a hydrogen atom with two electrons) is removed and converted into a proton and two electrons, leaving NAD+ and FAD.

Front 27

What happens to the high energy electrons after NADH and FADH2 donate them?

Back 27

They are quickly passed along the electron transport chain to molecular oxygen (O2). As this happens, protons are pumped across the inner mitochondrial membrane.

Front 28

What is oxidative phosphorylation?

Back 28

The chemiosmotic mechanism for ATP synthesis. It involves the consumption of oxygen and the addition of a phosphate group from ADP to ATP.

This is essentially the name for the process by which high-energy electrons from NADH and FADH2 are converted to the phosphate bond of ATP.

Front 29

Summarize the production of ATP starting with pyruvate and fatty acids.

Back 29

1. Pyruvate and fatty acids enter the mitochondrial matrix where they are converted to acetyl CoA.

2. Acetyl CoA is metabolized by the citric acid cycle, which produces NADH and FADH2.

3. Oxidative phosphorylation occurs, harnessing the high-energy electrons of NADH and FADH2 and passing them along the electron transport chain in the inner membrane to ultimately be handed off to O2 (oxygen).

4. This generates a proton gradient across the inner membrane

5. The proton gradient is used to drive production of ATP by ATP synthase.

Front 30

How many electrons from NADH are required to convert O2 to H2O?

Back 30

Four

Front 31

How many molecules of NADH and FADH2 are made during each of the following: glycolysis, pyruvate dehydrogenase, and citric acid cycle?

Back 31

1. 2 NADH

2. 2 NADH

3. 6 NADH + 2 FADH2

Front 32

What are the three respiratory enzyme complexes in the inner mitochondrial membrane that high-energy electrons are transferred through? Describe the process.

Back 32

NADH dehydrogenase complex, cytochrome C reductase complex, and cytochrome C oxidase complex.

Protons derived from water are pumped across the membrane from the matrix into the intermembrane space by each complex during the transfer of electrons from NADH to oxygen.

Front 33

What are ubiquinone and cytochrome C?

Back 33

Mobile carriers that ferry electrons from one respiratory enzyme complex to the next.

Front 34

What is proton-motive force, and how is it generated?

Back 34

It is the combination of the membrane potential and the pH gradient, which pulls H+ back into the mitochondrial matrix.

1. pH gradient: The intermembrane space is slightly more acidic than the matrix because of the concentration of protons is higher there (due to electron transport chain pumping protons from the inner membrane to the intermembrane space.

2. Membrane potential: created by a voltage gradient and ion concentration gradient.

Front 35

Describe how ATP synthase uses energy stored in the electrochemical proton gradient to produce ATP.

Back 35

1. ATP synthase is composed of a stationary head called the F1 ATPase and a rotating portion called F0, both of which are formed from multiple subunits.

2. Driven by the electrochemical proton gradient, The F0 part (which consists of the transmembrane H+ carrier and a central stalk) spins rapidly within the stationary head of the F1 ATPase.

3. This spinning causes the synthase to generate ATP from ADP and a phosphate.

Front 36

What is the peripheral stalk?

Back 36

An elongated protein arm that secures the ATP synthase to the mitochondrial inner membrane.

Front 37

Why is the head of ATP synthase called F1 ATPase?

Back 37

Because is can carry out the reverse reaction --- the hydrolysis of ATP to ADP and a phosphate. To do this, it must be detached from the F0 portion of the complex.

Front 38

Describe how ATP synthase works as a reversible coupling device?

Back 38

To create ATP, it harnesses the electrochemical H+ gradient. To reverse, it pumps protons against this gradient by hydrolyzing ATP.

If the electrochemical proton gradient falls below a certain level, delta G (net free energy change) for H+ into the matrix won't be high enough to drive ATP. Because of this, ATP will be hydrolyzed to rebuild the proton gradient.

Front 39

How does the electrochemical proton gradient across the inner mitochondrial membrane move pyruvate and inorganic phosphate into the matrix?

Back 39

Both pyruvate and inorganic phosphate are negatively charged, so typically their movement across the inner membrane is opposed by the negative membrane potential. However, the H+ concentration gradient (aka the pH gradient) is harnessed to drive their transport inward regardless of the opposed negative charge.

Front 40

How is ADP pumped into the matrix while ATP is also pumped out?

Back 40

By an antiport process that uses the voltage gradient across the membrane to drive the exchange.

Front 41

What do porins in the outer mitochondrial membrane allow?

Back 41

They allow the outer membrane to be freely permeable to all compounds pumped in and out of the inner membrane (pyruvate, inorganic ions, ADP, ATP, etc.).

Front 42

True or false: the slow conversion of ADP to ATP in mitochondria maintains a low ATP/ADP ratio in cells.

Back 42

False. The conversion is rapid, and it maintains a high ATP/ADP ratio in cells.

Front 43

True or false: ADP molecules (produced by hydrolysis of ATP in the cytosol) are rapidly drawn back into mitochondria for recharging. The bulk of ATP is also exported from the mitochondria into the cytosol where it is most needed.

Back 43

True.

Front 44

True or false: electrons that enter further down the respiratory chain (for example to the ubiquinone mobile carrier rather than the NADH dehydrogenase complex) promote more pumping of protons and therefore produce more molecules of ATP.

Back 44

False. By entering later, they promote less pumping and therefore produce fewer molecules of ATP.

Front 45

Approximately how much energy that could be released by burning sugars or fats is stored in ATP phosphate bonds during cell respiration?

Back 45

About 50%. Cell respiration is amazingly efficient.