Metabolism III

Question 1

Where does the ETC take place?

Answer 1

Along the inner mitochondrial membrane

Question 2

What is REDOX potential?

Answer 2

Different ability to accept electrons

Question 3

What is another name for complex I?

Answer 3

NADH dehydrogenase

Question 4

What is another name for complex II?

Answer 4

Succinate dehydrogenase

Question 5

What is another name for coenzyme Q?

Answer 5

Ubiquinone

Question 6

What is another name for complex III?

Answer 6

Cytochrome C reductase

Question 7

What is another name for complex IV?

Answer 7

Cytochrome C oxidase

Question 8

What are the steps of electron transport through the ETC?

Answer 8

1) electrons from NADH–>NAD+ travel through complex I which contains FMN prosthetic groups and FeS cofactors which reduce the oxidized form of Q
2) electrons from FADH–>FAD travel through complex II which contains FeS cofactors which reduce an oxidized form of Q
3) electrons are transferred one at a time through complex III which contains heme prosthetic groups and Fe*S cofactors Q is oxidized and Cyt C is reduced
4) Cyt C is reduced by accepting a single electron at a time and bringing it to complex IV
5) electrons are transferred one at a time through complex IV which contains heme prosthetic groups, this reduces O2 which bonds with H+ from the matrix to form H2O (oxygen is the final electron acceptor)

Question 9

What happens to ubiquinone (Q) in the ETC?

Answer 9

It is reduced by complexes I and II and from there it travels through the membrane where it is oxidized by complex III

Question 10

What happens to H+ ions in the ETC?

Answer 10

They are pumped through the protein complexes from the mitochondrial matrix to the intermembrane space, creating a proton gradient

Question 11

How many H+ are pumped to the intermembrane space per cycle of the ETC?

Answer 11

4H+ at complex I, 0H+ at complex II, 4H+ at complex III, and 2H+ at complex IV

Question 12

What are the results of partial reduction in the ETC?

Answer 12

Potentially hazardous products, if one electron is transferred to O2 it forms a superoxide ion, if two are transferred peroxide is formed

Question 13

What are some pathological conditions that would yield free-radical injury?

Answer 13

atherogenesis, bronchitis, emphysema, Parkinson disease, Duchenne muscle dystrophy, cervical cancer, alcoholic liver disease, diabetes, acute renal failure, Down syndrome, retrolental fibroplasia, cerebrovascular disorders, ischemia, and reperfusion injury

Question 14

Define the chemiosmosis theory

Answer 14

• ADP+Pi–>ATP is highly unfavourable so phosphorylation will not happen directly from the reaction between ADP and a high-energy P carrier, energy is needed
• This energy can be provided by proton flow down an electrochemical gradient
• Energy released from the ETCis used to transfer protons against the electrochemical gradient
• ETC sets up a proton motive force which provides the energy to drive ATP synthesis

Question 15

What is ATP synthase and how does it function?

Answer 15

ATP synthase: an enzyme that synthesizes ATP

It functions by protons moving down a channel inside it which drives the production of ATP from ADP+Pi

Question 16

What re the two components of ATP synthase?

Answer 16

The ATPase (F1 unit) and the proton-transporting base (F0 unit) which are connected by a shaft that is held in place by a stator

Question 17

What happens if the direction of the spinning rotator changes in ATP synthase?

Answer 17

The conformation of the F1 unit changes and ATP–>ADP+Pi instead of ADP+Pi–>ATP which dissipates the proton gradient

Question 18

What is the definition of chemiosmosis?

Answer 18

Process fo ATP production that is dependant on a proton motive force generated by a proton electrochemical gradient

Question 19

What are the net products of ETC?

Answer 19

For each NADH: 10 H+
For each FADH: 6 H+
Ideally 28 ATP
H2O

Question 20

What are the net products of cellular respiration?

Answer 20

Glycolysis: 2NADH, 2ATP, 2H2O (H2O are used during P.O.)
Pyruvate Oxidation: 2NADH, 2CO2
Citric Acid Cycle: 6HADH, 2FADH2, 4CO2, 2ATP
ETC: H2O, 28ATP
Total: 32ATP, 6CO2, H2O

Question 21

What is the malate-aspartate shuttle?

Answer 21

• Occurs in the liver, kidney, and heart
• NADH from the cytosol enters the inter membrane space through porins
• the net effect is NADH (inter membrane) becomes NADH (matrix) with the help of malate–>oxaloacetate–>aspartate cycle and glutamate–>α-ketoglutarate cycle, this allows NADH produced in the citric acid cycle to travel into the matrix for use in the ETC

Question 22

What are porins?

Answer 22

Openings in the outer membrane

Question 23

What is the G3P shuttle?

Answer 23

Allows NADH synthesized in glycolysis (in the cytosol) to travel into the inter membrane space and contribute to ATP synthesis
- aided by cytosolic G3P dehydrogenase and mitochondrial G3P dehydrogenase (enzymes) to send the NADH to complex III

Question 24

What is the key element of aerobic respiration?

Answer 24

O2 is the final electron acceptor

Question 25

Which is more effective, aerobic or anaerobic respiration? Why? What does this mean for the growth of organisms with this type of respiration?

Answer 25

Aerobic
O2 is the most effective electron acceptor because it’s highly electronegative and has a large potential electron energy from NADH so it allows a large proton motive force to generate
Organisms with aerobic respiration grow faster and reproduce faster

Question 26

What is fermentation?

Answer 26

Metabolic pathways that regenerate NAD+ from NADH without oxygen as the final acceptor

Question 27

What happens when there is no electron acceptor in a pathway?

Answer 27

The electrons have nowhere to go and the ETC will stop, NADH will build up without being regenerated to NAD+ so there will be no NAD+ to accept electrons, glycolysis/P.O./C.A.C. all stop too, this is a life threatening event

Question 28

_____ can produce ATP via _____-level phosphorylation in the absence of O2 with NAD+ generated by _______.

Answer 28

Glycolysis/substrate/fermentation

Question 29

What is lactic acid fermentation and when/where does it occur?

Answer 29

Glucose–>2pyruvate+2ATP+2NADH+2H–>2lactate+2NAD+

Occurs in muscle cells when the can’t get enough O2

Question 30

What does lactate dehydrogenase do?

Answer 30

Converts lactate back to pyruvate when O2 is restored after lactic acid fermentation

Question 31

What is alcohol fermentation and what does it do?

Answer 31

Glucose–>2pyruvate+2ATP+2NADH–>2acetylaldehyde-2CO2–>2ethanol+2NAD+
Occurs in yeast, used in production of yogurt and by prokaryotes in human intestines

Question 32

What are biofuels?

Answer 32

Renewable fuel produced form a mixture of organic compounds produced by living organisms
ex. ethanol produced from corn or sugarcane

Question 33

What is the controversy surrounding biofuels?

Answer 33

• growing corn for fuel required more fuel expenditure
• requires more water
• requires more land
• required more fertilizer use
• less cropland is available for food
• increases cost of corn for those in developing nations
• may not actually reduce greenhouse gas emissions

Question 34

How is corn made into ethanol?

Answer 34

The kernels are removed and fermented so the starch breaks down into glucose and eventually ethanol when enzymes and yeast are added, this is distilled to remove water, leaving pure ethanol which can be mixed with petroleum or used on its own as fuel

Question 35

How can fats/phospholipids catabolically and anabolic ally contribute to the path of metabolism?

Answer 35

Catabolically: they split into glycerol and fatty acids, glycerol can enter into glycolysis and fatty acids can become acetyl-CoA
Anabolically: acetyl-CoA can become fatty acids which can be used to build phospholipids and fats

Question 36

How can proteins catholically and anibolically contribute to metabolism?

Answer 36

Catabolically: they break down into amino acids which lose their amine groups and can join the C.A.C. or become pyruvate or acetyl-CoA
Anabolically: C.A.C. substrates can act as substrates for amino acid synthesis