metabolismo general.ppt

8/10/2019 metabolismo general.ppt

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Carbohydrate metabolism

Most carbs absorbed by the body are

monosacharides

glucose

galactose

fructose

Glucose is catabolized to CO2and H2O

energy released is used to make ATP

When we study ATP production,

we are studying carbohydrate metabolism

C6H12O6+ 6 O2--> 6 CO2+ 6 H2O + energy


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Respiration is the cumulative function of

glycolysis, the citric acid cycle, and electron transport

Glycolysis

occurs in the cytoplasm

generates a netof two molecules of ATP

citric acid cycle

occurs in the matrix of mitochondria generates two more ATP

Electron transport chain

occurs on the inner membrane of the mitochondria

generates about thirty-four ATP About 38 ATP molecules produced from one molecule of glucose


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Glycolysis harvests

chemical energy by

catabolizing glucose to

pyruvate


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Steps 1-3

two ATP hydrolyzed some oxygen and hydrogen rearranged

Step 4

6 carbon chain split

into twosmaller molecules

3 C each


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Step 5

a second Pi added to each 3 C chain

a high energy electron (w/ a H+)

carried off

NAD+ is a shuttle for electrons

carried to other parts of cell and

used for energy Step 6 and 7

Pi removed from

three carbon chain

used to synthesize ATP

end up with two moleculesof pyruvic acid

Gl l i


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Glycolysis

the final product of glycolysis is two

molecules of pyruvic acid

A total of 4 ATP and 2 NADH+H+are

produced from one glc. But since 2 ATP used to start the process,

you are only ahead two ATP and two

NADH+H+.

What happens next depends on if oxygen

is present.

No oxygen, use an NADH+H+to convert

each pyruvic acid to lactic acid

(anaerobic respiration).

But, if oxygen present, go to Citric Acid

cycle (aerobic respiration)


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Beforethe carbon chains can enter

citric acid cycle

converted to acetyl-CoA

For eachpyruvic acid one C lost as CO2

oneNADH+H+produced

Total of

two CO2 and two NADH+H+

from this rxn.

If oxygen present Citric Acid cycle


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If oxygen present Citric Acid cycle Remainingcarbons (2 C chain)

enter Citric Acid cycle

The two carbon Acetyl CoA

enters the Citric Acid cycle

and combines with a four carbon

oxaloacetic acid

to form a six carbon citric acid.


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As other reactions proceed,

two more CO2molecules are

produced for eachacetyl CoA that

entered the Citric Acid cycle. Plusone ATP,

three more NADH+H+,

andone FADH2

after both acetyl CoA moleculesgo through,

totals for Citric Acid cycle =

2 ATP,

6 NADH+H+,

and 2 FADH2

Oxaloacetic acid (four carbons) is

eventually recycled.

If oxygen present Citric Acid cycle


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from glycolysis

2 ATP (net)

2 NADH+H

+

from Citric Acid cycle

2 ATP

2+6 NADH+H+

2 FADH2

plus produced 6 CO2(three per pyruvic acid)

but:the ten NADH+H+

and the two FADH2

are now sent to the

electron transport chain

4 ATPs so far

- not too impressive

TOTALS SO FAR:

El t T t Ch i


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Electron Transport Chain 10 NADH+H+ and 2 FADH2produced during glycolysis

and citric acid cycle

each one of these contains chemical energy need to transfer this energy to ATP

ATP is used by all parts of the cell

NAD+and FAD need to be recycled

chains of enzymes onthe inner

mitochondrial

membrane are

responsible for this.


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Electron Transport Chain

-NADH+H+ hands off high energy e-to enzyme complex 1

-Energy from the e-is used to drive the proton pump that moves

H+ out of the mito.

-This begins to create a... H+(proton) gradient

The H+from

the NAD+

just mixes in

here.


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-enzyme complex 1 passes high energy e-to coenzyme Q

-coenzyme Q shuttles e-to enzyme complex 2

- Energy from the e-is used to drive the proton pump that moves

H+out of the mito.What does this help create??

H+gradient(proton

motive force)


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-enzyme complex 2 passes high energy e-to cytochrome c

- cytochrome c shuttles e-to enzyme complex 3

- Energy from the e-is used to drive the proton pump that moves

H+out of the mito.What does this help create??

H+gradient(proton

motive force)


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-by now, those electrons are not so high energy anymore...

- the low energy electrons combine back with hydrogen and are

finally added to an oxygen atom

- two hydrogen and one oxygen form water


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We still have not done anything with the H+gradient we created:

- H+runs down its concentration gradient to provide energy for

the enzyme ATP synthase

- ATP synthase uses the energy from the H+gradient to...

Convert

ADP + P

into ATP(oxidative

phosphoryl

ation)


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-Each NADH carries two electrons which pump out enough H+

to make 3 ATP molecules(10 NADH yield 30 ATP).

- Each FADH

carries two electrons but...-So each FADHonly pumps out enough H

+to make

2 ATP molecules(2 FADH yield 4 ATP).

FADH hands

off e-

here.

El T Ch i


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C6H12O6+ 6O2 6 CO2+ 6H2O

Inhale oxygen, exhale french fries


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Cellular

respiration

generates 36-38 ATP

molecules for

each sugarmolecule it

oxidizes

yco ys s an t e c tr c ac cyc e cyc e


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yco ys s an t e c tr c ac cyc e cyc econnect to many other metabolic pathways

Glycolysis receives by

metabolic by-products of...

carbohydrates

proteins

fats

Acetyl-CoA rxn. receives

metabolic by-products from

glycolysis

proteins

fats

Citric acid cycle receivesmetabolic by-products from

proteins

F db k h i t l


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Feedback mechanisms control

cellular respiration

Glycolysis is stimulated by high concentrations ofADP

Glycolysis is inhibited by high concentrations of

ATP, and citrate (from the citric acid cycle). Many enzymes throughout the respiratory cycle

are subject to feedback inhibition

feedback inhibition is when the product of a reactioninhibits the enzyme catalyzing the reaction

metabolismo general.ppt

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