BIOC13H3 Lecture Notes - Lecture 15: Cytosol, Glycerol, Mitochondrion

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BIOC13:(Lecture(17( ( Final(

March(15,(2018(

55"

Electron)Transport)Network!

Fate%of%NADH%

• NADH’s"oxidation"is"highly"exergonic"due"to"its"low"reduction"potential"

• Assuming"100%"efficiency,"1"NADH"can"produce"up"to"7"ATP"

o By"the"end"of"Krebs,"there"are"10"NADH"to"be"oxidized"per"glucose"

§ 70"ATP"

• At"more"realistic"50%"efficiency,"35"ATP"would"be"made"from"10"NADH"

molecules"

• Throughout"the"ETN,"electrons"are"passed"to"carriers"(with"oxygen"as"final"

acceptor)"to"physically"link"system"and"conserve"all"the"energy"

• Energy"is"released"in"small"pieces"to"improve"efficiency"

Inner%Mitochondrial%Membrane%

• The"inner"mitochondrial"membrane"is"completely"impermeable"to"NAD+"and"

NADH"

o No"transport"proteins"to"get"them"in"

• NADH"produced"in"Krebs"cycle"is"already"in"matrix"and"doesn’t"need"to"pass"

through"the"IMM"à"complex"already"there"to"oxidize"it"

• NADH"from"glycolysis"is"in"the"cytosol"and"needs"to"be"transported"to"the"ETN"

complexes"

Why$Keep$It$Impermeable$to$NADH?$

• Researchers"created"an"IMM"that"is"permeable"to"NADH"in"attempt"to"figure"

out"why"not"make"it"permeable"to"NADH/NAD+"

• Adding"a"transporter"caused"drastic"increase"in"presence"of"NADH/NAD+"in"the"

matrix"and"very"few"left"in"the"cytosol"for"glycolysis"

• It"is"therefore"concluded"that"the"IMM"is"impermeable"to"NADH"so"that"it"

doesn’t"steal"the"cytosol’s"pool"of"NADH"

%NADH%Shunt%

• There"are"2"shuttles"for"bringing"

electrons"from"NADH"in"the"

cytosol"to"the"ETN"

Glycerol-3-Phosphate$Shuttle$$

• NADH"is"oxidized"by"Gly3PDH"and"

electrons"are"passed"to"DHAP,"

creating"Gly3P"

• Gly3P"goes"to"the"mitochondria"

where"another"Gly3PDH"passes"

the"electrons"to"FAD,"creating"

FADH2"

o The"Gly3P"is"now"DHAP"

once"again"and"can"repeat"

the"process"

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BIOC13:(Lecture(17( ( Final(

March(15,(2018(

56"

• FADH2"passes"the"electrons"to"ubiquinone"(the"first"electron"carrier)"

• Free"energy"is"released"but"it"isn’t"conserved"à"shuttle"is"inefficient"

Malate-Aspartate$Shuttle$$

• This"shuttle"system"is"only"favourable"when"NADH/NAD+"is"greater"in"cytosol"

than"matrix"(this"rarely"occurs)"

• Malate(dehydrogenase"(MDH)"oxidizes"NADH"and"the"electrons"are"passed"to"

OAA,"forming"malate"

• The"malate"is"transported"across"

the"IMM"and"into"the"matrix,"

using"a"proton"from"the"gradient"

to"do"so"

• MDH"oxidizes"malate"back"into"

OAA"with"the"electron"being"

accepted"by"matrix"NAD"to"get"

NADH"in"the"matrix"

Getting"the"OAA"back"into"cytosol"is"

complicated"

• OAA"goes"through"

transamination(reaction"with"glutamate"to"create"aspartate"

o The"glutamate"is"thus"converted"to"α-ketoglutarate"

• Aspartate"is"then"transported"into"the"cytosol"by"an"H+/Aspartate"anti-porter"

(thus"using"proton"gradient"again)"

• Asparatate"then"reacts"with"α-ketoglutarate"(that"was"transported"from"matrix"

to"the"cytosol)"to"get"OAA"again"

o Glutamate"is"created"and"can"be"reused"

• This"OAA"can"be"used"again"

• Note:"Both"the"glutamate"and"OAA"are"thus"recycled,"conserving"energy"

Which$Shuttle$Being$Used?$

• The"type"of"shuttle"used"depends"on"

the"efficiency"of"metabolism"

• Researchers"had"participants"

complete"8"months"of"endurance"

training"and"measured"shuttle"

activity"before"and"after"the"training"

• Malate"shuttle"usage"increased"after"

the"8"months"endurance"while"the"

Gly3P"shuttle"usage"decreased"

• Since"it"is"more"efficient,"malate"

shuttle"increases"endurance"it"seems"

which"makes"sense"

• In"the"cold,"Gly3P"is"favourable"as"you"have"more"heat"to"stay"warm"

Mammalian%Mitochondria%

• The"ETN"is"mammals"is"relatively"simple"and"well"studied"

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Document Summary

Inner mitochondrial membrane: the inner mitochondrial membrane is completely impermeable to nad+ and. It is therefore concluded that the imm is impermeable to nadh so that it doesn"t steal the cytosol"s pool of nadh. Nadh shunt: there are 2 shuttles for bringing electrons from nadh in the cytosol to the etn. Glycerol-3-phosphate shuttle: nadh is oxidized by gly3pdh and electrons are passed to dhap, creating gly3p, gly3p goes to the mitochondria where another gly3pdh passes the electrons to fad, creating. Fadh2: the gly3p is now dhap once again and can repeat the process. Final: fadh2 passes the electrons to ubiquinone (the first electron carrier, free energy is released but it isn"t conserved shuttle is inefficient. Malate-aspartate shuttle: this shuttle system is only favourable when nadh/nad+ is greater in cytosol than matrix (this rarely occurs, malate dehydrogenase (mdh) oxidizes nadh and the electrons are passed to.

Related Questions

All True orFalse

6.___ During the process of human fermentation the pyruvatemolecule produced at the end of glycolysis is converted into athree carbon molecule called ethyl alcohol while NAD+ is reduced toNADH and a CO2 molecule is released to the atmosphere.

7.___ The proton pumps of the inner membrane of themitochondrion are examples of integral transmembrane,active-transport carrier proteins.

8.___ Photosynthetic pigment molecules of plants are able torelease electrons to an ETC that are utilized to power the eventsof chemiosmosis.

9.__ Photoautotrophs (plants) use inorganic CO2 molecules astheir carbon source for building organic molecules and they usepigment molecules as their proximate source of electrons for theprocess of chemiosmosis.

10.__ The overall process of the TCA/CAC is exergonic with theproduction of ATP molecules and NADH/FADH2 all having stored energyderived from the reactants.

11.__ If a chemical reaction is catalyzed by an enzyme then thereactants will be able to initiate a chemical reaction withslightly more activation energy and the reaction would beclassified as an endergonic process if the products have lessenergy than the reactants.

12.__ The chemical reactions of glycolysis, the Krebs Cycle (TCAcycle), and oxidative phosphorylation, are all processes that canonly be performed when O2 is present (aerobic conditions).

13.___ Photophosphorylation is a type of chemiosmotic processand it possesses a key component of electron transport a finalelectron acceptor and in this case an organic molecule (FEA).

14.___ The pigment molecules, that make up a component of thechloroplasts of a plant, absorb light best in the green wavelengthsand that is why the plants appear so green.

15.___ Features in common for oxidative phosphorylation andphotophosphorylation are an electron source from dinucleotideelectron carrier molecules and an inorganic final electronacceptor.

16.___ In the metabolic pathways we discussed one would expectto find a number of points where allosteric enzymes are associatedwith positive feedback and/or negative feedback systems, and insome systems the allosteric enzyme is affected by both types ofregulatory molecules.

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1. C6H12O6 + 6O2 Ã 6CO2 + 6H2O Glucose is being _____ to _____ and oxygen is being _____ to _____. a. oxidized; carbon dioxide; reduced; water b. oxidized; water; reduced; carbon dioxide Incorrect c. reduced; water; oxidized; carbon dioxide d. reduced; carbon dioxide; oxidized; water

2. Which of the following stages in the breakdown of the piece of toast you had for breakfast generates the most ATP? a. the citric acid cycle Incorrect b. glycolysis c. the digestion of starch to glucose d. oxidative phosphorylation

3. Which of the following is a catabolic pathway? a. gluconeogenesis b. production of starch Incorrect c. glycolysis d. production of glycogen

4. Per molecule, the oxidation of a fatty acid results in _____ energy storage than the oxidation of glucose. a. the same b. less Incorrect c. more d. None of the above; fatty acids cannot be oxidized.

5. Of the eight reactions in the citric acid cycle, how many are oxidation-reduction reactions? a. one b. two c. three d. four e. five

6. The process of glycolysis transfers the energy in sugar molecules into the stored energy of activated carriers such as ATP and NADH. Which statement is true about glycolysis? a. Only eukaryotic organisms do glycolysis. b. The ten reactions of glycolysis are identical in all eukaryotic cells, but are different in prokaryotic cells due to their diverse metabolic strategies. Incorrect c. The ten reactions of glycolysis are identical in almost all living organisms on the planet. d. There are many ways to oxidize glucose and transfer energy into activated carriers; the diversity of organisms on the planet is reflected in the diversity of their mechanisms of glycolysis.

7. Referring to the sentence completed in #13 above, the purpose of the latter reaction (in active muscle cells) is to _____. a. accumulate lactic acid in the cell, which provides additional energy for the production of ATP Incorrect b. slow down glycolysis until oxygen becomes available again c. accelerate the Krebs cycle, which will restore the oxygen supply d. regenerate NAD+ so that glycolysis can continue in the absence of oxygen

8. What are the products of the citric acid cycle? a. carbon dioxide, NADH, FADH2 and GTP b. carbon dioxide, NAD+, FAD and GTP c. NADH, FADH2, and acetyl CoA Incorrect d. carbon dioxide and water

9. Which statement is true about enzymes? a. Enzymes catalyze chemical reactions because they make inherently endergonic reactions exergonic. b. Each enzyme in a cell can catalyze many different chemical reactions involving chemically different substrates. Incorrect c. Enzymes can only catalyze reactions in one direction. d. After catalyzing a reaction, an enzyme is permanently altered and can no longer bind substrate. e. None of the above is true. 1

10. âG measures the change in free energy in a system as it converts reactant (Y) into product (X). When [X] = [Y], âG is equal to _____. a. RT b. ÎGÂ° + RT c. ÎGÂ° d. ln [X]/[Y]

11. The âGÂ° for the hydrolysis of ATP is -7.3 kcal/mol. What conditions in the cell would lead to a âG for ATP hydrolysis of -11 kcal/mol? a. An increase in the ATP/ADP ratio b. An increase in anabolic activity in the cell c. Transport of ATP out of the compartment where the reaction is occurring Incorrect d. A decrease in the ATP/ADP ratio

12. In the first reaction of glycolysis, a phosphate transferred from ATP to a glucose molecule to produce glucose-6-phosphate and ADP. Under conditions existing in the cell, the free energy change for this reaction is -8.0 kcal/mole. Which of the following statements is true? Recall that the âGÂ° for the hydrolysis of ATP is -7.3 kcal/mol. a. Glucose concentrations in the cell are always low, making this reaction more favorable than would be expected. b. This reaction is less favorable than would be expected, given the âGÂ° of ATP hydrolysis. c. Glucose-6-P concentrations in the cell are very low relative to glucose concentrations, making the reaction more favorable than would be expected. d. The âGÂ° for the addition of a phosphate to glucose must be -0.7 kcal/mole.

13. Protein E can bind to two different proteins, S and I. The binding reactions are described by the following equations and values: E + S --> ES Keq for ES = 10 E + I> EI Keq for EI = 2 Given the equilibrium constant values, which one of the following statements is true? a. When S is present in excess, no I molecules will bind to E. b. E binds I more tightly than S. c. The binding energy of the ES interaction is greater than that of the EI interaction. d. Changing an amino acid on the binding surface of I from a basic amino acid to an acidic one will probably make the free energy of association with E more negative.

A catabolic pathway would predictably result in the
A) reduction of a sugar.
B) synthesis of a macromolecule.
C) breakdown of a macromolecule.
D) breakdown of an atom.
2.
The drug Ritonavir is used to treat people with HIV/AIDS. It worksby binding to the active site of HIV-1 protease, an enzyme used bythe AIDS virus to create new proteins for production of newviruses.Once bound, the HIV-1 protease cannot produce proteins.Ritonavir can be classified as a(n)
A) competitive inhibitor.
B) allosteric inhibitor.
C) activator.
D) non-competitive inhibitor.
3.
During cellular respiration, __________ is the final electronacceptor that allows the regeneration of the cellâs supply of NAD+.In fermentation, ____________ is the final electron acceptor forNAD+ regeneration.
A) pyruvate / lactic acid
B) pyruvate / oxygen
C) ethanol / CO2
D) oxygen / pyruvate
4.
Which of the following clues would tell you if a cell isprokaryotic or eukaryotic?
A) whether or not the cell carries out cellular metabolism
B) the presence or absence of ribosomes
C) whether or not the cell is partitioned by internalmembranes
D) whether or not the cell contains DNA
5.
Phosphofructokinase (PFK) is an allosteric enzyme that regulatesglycolysis. When cellular concentrations of ATP and citrate become__________, this enzymeâs activity decreases. When cellularconcentrations of AMP become ________, the enzyme isactivated.
A) high / high
B) high / low
C) low / high
D) low / low
6.
______________ is an enzyme that can utilize the free energy in thehydrogen gradient (voltage) produced between the inner and outermembrane of the mitochondrion. The enzyme uses this energy toproduce ________.
A) ATP synthase/ ATP
B) PFK/ ATP
C) PFK/ glucose
D) ATP synthase/ ADP
7.
ATP is able to do cellular work because it
A) has a high energy phosphate bond that can be hydrolyzed torelease energy.
B) converts light energy into chemical bond energy.
C) contains the sugar ribose, which can provide additional energyfor a cell.
D) its hydrolysis is endergonic.
8.
A solution of starch at room temperature does not readily decomposeto form a solution of simple sugars because
A) the starch solution has less free energy than the sugarsolution.
B) the activation energy barrier for this reaction cannot besurmounted.
C) the hydrolysis of starch to sugar is endergonic.
D) starch hydrolysis is nonspontaneous.
9.
A person exposed to toxins would have more activity in their___________compared to an unexposed person.
A) lysosomes
B) Golgi bodies
C) rough endoplasmic reticulum
D) smooth endoplasmic reticulum
10.
Which of the following statements about fermentation is true?
A) The function of fermentation is to regenerate the fermentingcells' supply of NAD+.
B) Fermentation allows a fermenting cell to gain more energy perglucose molecule than a non-fermenting cell.
C) Fermentation produces either lactic acid or ethanol that thefermenting cell can use as an energy source.
D) Fermentation is a universal process that occurs in all cells andall organisms.
11.
A glucose molecule is completely broken down to carbon dioxide andwater in glycolysis and the citric acid (Krebs) cycle, but togetherthese two processes yield only a few molecules of ATP. Whathappened to most of the energy that the cell obtains from theoxidation of glucose?
A) It was lost as heat.
B) It is stored in the carbon dioxide and water molecules releasedby these processes.
C) It is stored in the ATP that was formed by glycolysis and thecitric acid cycle.
D) It is stored in NADH and FADH2
12.
The First Law of Thermodynamics states that
A) entropy tends to increase in a system.
B) entropy tends to decrease in a system.
C) energy cannot be created nor destroyed.
D) the quality of energy in the universe is decreasing.
13.
The endosymbiotic theory states that _______________ evolved as aresult of a symbiotic relationship between different types ofbacteria. _____________ is thought to be the selective factor thatmade this symbiosis advantageous.
A) mitochondria / A change in the Earthâs atmosphere from anaerobicto aerobic
B) endoplasmic reticulum / A decrease in the amount of foodavailable in the environment
C) chloroplasts / A change in the Earthâs atmosphere from aerobicto anaerobic
D) lysosomes / A decrease in the amount of food available in theenvironment
14.
A mutation in a fruit fly affects one of the proteins that pumphydrogen ions across the inner mitochondrial membrane; thismutation makes that particular protein function less efficiently.When comparing aerobic cellular respiration in this fly with awild-type fly, you would predict that the mutant fly would
A) produce less ATP than a wild-type fly.
B) show no difference in ATP production when compared to awild-type fly.
C) produce more ATP than a wild-type fly.
D) not be able to produce any ATP via aerobic cellularrespiration.
15.
Proteins that are destined to be exported from the cell have unique_________________ that are recognized by signal recognitionparticles and thus moved to the _________________ duringtranslation.
A) phosphofructokinases / nucleus
B) codons / rough endoplasmic reticulum
C) signal recognition sequences / rough endoplasmic reticulum
D) signal recognition sequences / free ribosomes
16.
During the Krebs cycle
A) NADH is oxidized.
B) ATP is produced.
C) pyruvate is produced.
D) Acetly CoA gains a carbon to form pyruvate.
17.
Why does the oxidation of organic compounds by molecular oxygen toproduce CO2 and water release free energy?
A) Electrons are being moved from atoms that have a lower affinityfor electrons (such as C) to atoms with a higher affinity forelectrons (such as O).
B) The electrons have a higher potential energy when associatedwith water and CO2 than they do in organic compounds.
C) The covalent bond in O2 is unstable and easily broken byelectrons from organic molecules.
D) The covalent bonds in organic molecules and molecular oxygenhave more kinetic energy than the covalent bonds in water andcarbon dioxide.
18.
In a chemical reaction, if ?G is negative, it means that thereaction is
A) exergonic, and work needs to be done for the reaction toproceed.
B) exergonic, and work can be done with energy released from thereaction.
C) endergonic, and work needs to be done in order for the reactionto proceed.
D) endergonic, and work can be done with energy released from thereaction.
19.
The energy for an endergonic reaction comes from a(n) ___________reaction.
A) ADP + P --> ATP
B) endergonic.
C) exergonic.
D) anabolic
20.
Glycolysis
A) involves catabolic reactions and ATP is produced.
B) involves anabolic reactions and ATP is produced.
C) involves catabolic reactions and creates energy.
D) involves anabolic reactions and creates energy.

BIOC13H3 Lecture Notes - Lecture 15: Cytosol, Glycerol, Mitochondrion

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