study exercise biology 13-15

8/10/2019 Study Exercise Biology 13-15

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Study exercise Biology 13 15

1. How are the two products of glycolysis connected to the reactionsof the TCA cycle?

2 products of glycolysis Pyruvate & NADH, can be metabolized in 2 different ways depending on

cell type in which they are formed & the presence or absence of oxygen ! prese!ce of "2 in mitochondria# aerobic organisms extract large amounts of energy from

the pyruvate& NADH made during glycolysis !"# more A$%s

P$%$A'(o 'sed as a generator of ')A cycle

(n the mitochondrion, several enzymes catalyze the conversion of ")carbon

pyruvate to 2)carbon acetyl *oA, yielding a molecule of NADH and one *+2

$he acetyl *oA enters the citric acid or $*A cycle

o Process1* is transported into mitochondrial matrix across the inner mitochondrial

membrane2* decarboxylated -! forms a 2 * fragment -*H"*++). acetyl group / *+23* Acetyl group is transferred to coenzyme A to ma0e acetyl *oAwhich carries

the 2 * fragment to 1rebs cycle

+* +verall reaction %yruvate / H3-*oA / NAD/ -! Acetyl *oA / *+2 /

NADH / H/. catalyzed by a giant multienzyme complex pyruvate

dehydrogenase

o

$*A cycle is important


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- accepts metabolites from or contributes them to other pathways entry point for

catabolic mechanism regardless of nature of starting material All of cell4s

energy)providing macromolecules polysaccharides, fats, proteins brea0 down to

$*A cycle metabolites

Acetyl *oA ) brea0down product of fatty acids degraded 2 *4s at a time

in matrix fatty acids are also synthesized that way with acetyl *oA as

donor & other catabolic pathways

%roteins brea0 down to amino acids, which are catabolized & enter $*A

cycle at various sites. enter matrix via special transport systems in inner

mitochondrial membrane

o reduced coe!,y-es i! A'P for-atio! .NADH & /ADH20- are the primary product of pathway electrons they carry came from oxidized

1rebs substrates & used to ma0e A$%

-

lycolytic NADH 5nters mitochondrion via malate)aspartate shuttle reduci!g NAD

NADH 'ra!sfers electro!s to /AD /ADH2via glycerol phosphate shuttle

- 'ur!i!g NADH & /ADH2 A'P .)e-ios-osis4 Step 1

$he electrons from NADH are transferred to the electron carrier

proteins & the protons are transferred across the membrane

As electrons move from cytochrome to cytochrome, down the

electron transport chain, more protons are carried across the

membrane including the electrons from 6ADH2 *ytochrome c transfers electron to cytochrome c oxidase

complex %rotons are also transferred to the outside of he

membrane by the cytochrome c oxidase complex

$he cytochrome oxidase complex then transferred electron from

cytochrome c to oxygen, the terminal electron acceptor that

formed water as the product

$he protons generate a proton motive force across the membrane

of the mitochondrion 3ince membranes are impermeable to ions,

the protons that reenter the matrix pass through special proton

channel proteins called A$% synthase

Step 2

$he energy derived from the movement of these protons is used

to synthesize A$% from AD% and %oxidative phosphorylation


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! ase!ce of

"2 fermentation

is carried

out in

cytoplasm

2.Why is

the TCA cycleconsidered

to be the central pathwayin the energy metabolism of a cell?

o accepts metabolites from or contributes them to other pathways entry point for catabolic

mechanism regardless of nature of starting materials

o All of cell4s energy)providing macromolecules polysaccharides, fats, proteins brea0 down to

$*A cycle metabolites

Acetyl *oA ) brea0down product of fatty acids degraded 2 *4s at a time in matrix

fatty acids are also synthesized that way with acetyl *oA as donor & other catabolic

pathways


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%roteins brea0 down to amino acids, which are catabolized & enter $*A cycle at

various sites. enter matrix via special transport systems in inner mitochondrial

membrane


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3. escribe the steps by which the transport of electrons down therespiratory chain leads to the formation of a proton gradient !see"igure #.1$%

$he energy released as electrons from NADH is pass down through the complexes of the

respiratory chain ( 7 NADH dehydrogenase, ((( 7 cytochrome c reductase, and (8 7 cytochrome

c oxidase to pump protons H/ against their concentration gradient from the matrix of the

mitochondrion into the intermembrane space active tra!sport

As their concentration increases there which is the same as saying that the pH decreases, a

strong diffusion gradient is set up protons is passed through the A$% synthasecomplex

resulting the synthesis of A$%ce-ios-osisand is an example of facilitated diffusio!*

"9 A$% are made from the products of : molecule of glucose

$he process is a step6ise -ove-e!t of electro!s fro- ig e!ergy to lo6 e!ergy tat -a7es

te proto! gradie!t

$he proto! gradie!t po6ers A'P productio!N+$ the flow of electrons
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/A.html#active_transporthttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ATPsynthase.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/Diffusion.html#facilitatedhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ATPsynthase.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/Diffusion.html#facilitatedhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/A.html#active_transport


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$his electron transport cai! o!ly occurs 6e! oxyge! is availale *

P%")(SSo 3tep :

$he electrons from NADH are transferred to the electron carrier proteins & the

protons are transferred across the membrane As electrons move from cytochrome to cytochrome, down the electron transport

chain, more protons are carried across the membrane including the electrons from

6ADH2

*ytochrome c transfers electron to cytochrome c oxidase complex %rotons are

also transferred to the outside of he membrane by the cytochrome c oxidase

complex

$he cytochrome oxidase complex then transferred electron from cytochrome c to

oxygen, the terminal electron acceptor that formed water as the product

$he protons generate a proton motive force across the membrane of themitochondrion $he number of hydrogen atoms also called proton gradient will

build up and flow bac0 to the matrix simultaneously powering the production of

A$% and dince membranes are impermeable to ions, the protons that reenter the

matrix pass through special proton channel proteins called A$% synthase

o 3tep 2

$he energy derived from the movement of these protons is used to synthesize

A$% from AD% and % oxidative phosphorylation


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&. What is the effect of initrophenol on AT' formation by

mitochondria? Why is this case?

2,9)Dinitrophenol 2,9)DN%, or simply DN%, *;H9N2+


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#. escribe the basic structure of the AT' synthase

$he structure of A$% synthase consists of two rotary motors, labeled 6: and 6o, that are connected by a

flexible shaft

'nder normal operation, the 6o motor uses the energy stored in a transmembrane ion gradient todrive the 6: motor in reverse so that A$% is synthesized from AD% and phosphate

(n bacteria, anerobic conditions wipe out the ion gradient whereupon the 6: part becomes a

motor, using the energy of A$% hydrolysis to turn the 6o part in reverse so that it functions as an

ion pump

a* Sperical /1 ead .89: ; dia-eter< very si-ilar i! -itoco!dria & acteria# te structure

is igly co!served0 = 3>:#::: dalto!s

=oth bacterial & mitochondrial A$% synthasescontain < different polypeptides >, ?, @, ,B

with the following stoichiometry >"?"@B

> & ? subunits arranged alternately in 6: head li0e orange segments

5ach 6: contains " catalytic sites for A$% synthesis one on each ? subunit

$he subunit runs from outer tip of 6: head through central stal0 & contacts the 6#

basepiece

(n the mitochondrial enzyme, all < 6: polypeptides are encoded by nuclear DNA, made in

the cytosol & imported into mitochondrion posttranslationally


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* 'e /: ase is e-edded i! i!!er -itoco!drial -e-ra!e< co!tai!s ca!!el tat co!ducts

proto!s fro- i!ter-e-ra!e space ac7 to -atrix prese!ce of ca!!el so6! y

experi-e!t

=rea0 inner mitochondrial membrane into fragments forming membrane vesicles

submitochondrial particles0

(ntact submitochondrial particles containing A$% synthase embedded in vesicle membrane

can oxidize substrates, generate a proton gradient & synthesize A$%

(f 6: spheres are removed from particles by urea treatment, vesicle membrane can no longer

maintain a proton gradient despite continuing substrate oxidation & electron transport

%rotons translocated across membraneduring electron transport simply cross bac0 through

beheaded A$% synthase & energy is dissipated

(. escribethe structureand functionof

pero)isomes and glyo)ysome.

P(%?"S"@(

organelles found in nearly all eu0aryoticcells

single membrane microbodies found in photosynthetic cells of plants and liver and 0idney cells of

vertebrates

first discovered by C hodin in :E


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o surrou!ded y a lipid ilayer -e-ra!ewhich e!closes te crystalloid coreo the bilayer is enclosed with a plasma membrane which regulates what enters and exits the

peroxisome

o $here are at least "2 0nown peroxisomal proteins, called peroxins, which carry out

peroxisomal function inside the organelle

/u!ctio!o to rea7 do6! lo!g a!d ra!ced fatty acid cai!s# D=a-i!o acids# a!d polya-i!es

usi!g its e!,y-estransported to mitochondria where the maGority of catabolism

happen in both eu0aryotic and pro0aryotic cells. however in pro0aryotes only happen in

peroxisome wihout the mitochondriao site of cataolis- of fats a!d fat=solule vita-i!s, such as vitamin A and vitamin 1, as

well as the productio! of ile acidso for-atio! a!d degradatio! of ydroge! peroxide .H2"20are able to brea0 it down

into water H2+, is harmless to the cell and oxygen +2, can be used in the next

digestive

o help in sy!tesi,i!g plas-aloge!s a!d eterpospolipidsthat are necessary for

proper brain and lung function

o aid certai! e!,y-es 6it e!ergy -etaolis-in many eu0aryotic cells as well with

colesterol sy!tesisin animalso i!volved i! detoxificatio! of poiso! i! te cell# ger-i!ati!g seedsin the glyoxylate

cycle, potosy!tesisin leaves, and oxidatio! of a-i!esin various yeasts

"?$S"@(

also single membrane microbodies has similar structure as peroxisome but found only in plant


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cells

contains many enzymes li0e isocratic lyase, malate synthetase, glycolate oxidases, etc for

glyoxylate cycle ie, metabolism of glycolic acid

specializedperoxisomesfound inplantsparticularly in thefatstorage tissues of germinating

seeds and also in filamentous fungi

/u!ctio!so participate i! potorespiratio! a!d !itroge! -etaolis-in root noduleso contain enzymesthat i!itiate te rea7do6! offatty acidsand possess the enzymes to

produce i!ter-ediate products fro- te fats for te sy!tesis of sugarsy

gluco!eoge!esisseedling uses these sugars synthesized from fats until it is mature

enough to produce them byphotosynthesisand to generate new cell walls during growth

$. *)plain the basics of AT' formation according to the binding

change mechanism + 'aul ,oyer and -itchel'e asics of A'P for-atio! accordi!g to te i!di!g ca!ge -eca!is- Paul Boyer# )A

.19C90

1* (!ergy released y proto! -ove-e!t ca!ges active site i!di!g activity for sustrate &

producto 5nergy released by proton movement does not directly phosphorylate AD% to A$%, but it

principally changes the active site binding affinity for the A$% product

o (n an aueous environment where reactants & products are dissolved in medium, energy

is needed to drive the formation of the covalent bond lin0ing AD% with inorganic

phosphate to form A$%

o =ut when AD% & %i bind to A$% synthase catalytic site, they condense to form a tightly

bound A$% molecule without the input of additional energy

o *onsiderable energy F" 0calImole under standard conditions is needed to form A$%

when reaction occurs in water solution when AD%, %( & A$% are soluble

2* (ac active site goes successively troug 3 disti!ct co!for-atio!s tat ave differe!t

sustrate & product affi!ities te /1 co-plex as 3 catalytic sites# o!e o! eac of te 3

=suu!itso %roperties of the " ? catalytic sites in a static enzyme one not engaged in enzymatic

turnover, the different sites exhibited different chemical properties

o =oyer proposed that at any one time, each of the " sites is present in different

conformations that have differing affinities for nucleotides one in J, one in $, one in +

Joose J conformation ) AD% & %i are loosely bound

$ight $ conformation ) AD% / %( substrates or A$% product are tightly bound

+pen + conformation 7 it has a very low affinity for nucleotides allowing

release of tightly bound A$%. thus, it is considered empty
http://en.wikipedia.org/wiki/Peroxisomeshttp://en.wikipedia.org/wiki/Peroxisomeshttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/Fathttp://en.wikipedia.org/wiki/Fathttp://en.wikipedia.org/wiki/Germinationhttp://en.wikipedia.org/wiki/Germinationhttp://en.wikipedia.org/wiki/Enzymeshttp://en.wikipedia.org/wiki/Fatty_acidhttp://en.wikipedia.org/wiki/Fatty_acidhttp://en.wikipedia.org/wiki/Sugarshttp://en.wikipedia.org/wiki/Sugarshttp://en.wikipedia.org/wiki/Gluconeogenesishttp://en.wikipedia.org/wiki/Photosynthesishttp://en.wikipedia.org/wiki/Peroxisomeshttp://en.wikipedia.org/wiki/Plantshttp://en.wikipedia.org/wiki/Fathttp://en.wikipedia.org/wiki/Germinationhttp://en.wikipedia.org/wiki/Enzymeshttp://en.wikipedia.org/wiki/Fatty_acidhttp://en.wikipedia.org/wiki/Sugarshttp://en.wikipedia.org/wiki/Gluconeogenesishttp://en.wikipedia.org/wiki/Photosynthesis


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3* A'P is produced y rotatio!al catalysis = o!e part of A'P sy!tase rotates relative to

a!oter parto =oyer proposedthat the > & ? subunits, which form a hexagonal ring of subunits within

the 6: head, rotate relative to the central stal0 rotational catalysis

o otation is driven by proton movement through membrane into matrix via the channel

in6# base

o $hus, electrical energy stored in proton gradient is transduced into the mechanical energy

of a rotating stal0, which is transduced into chemical energy stored in A$%

study exercise biology 13-15

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