Division Ave. High School Ms. Foglia AP Biology

Division Ave. High School

AP Biology

Ms. Foglia

Cellular Respiration Harvesting Chemical Energy

ATP

AP Biology

2006-2007

Harvesting stored energy

Energy is stored in organic molecules

carbohydrates, fats, proteins

Heterotrophs eat these organic molecules food

digest organic molecules to get...

raw materials for synthesis fuels for energy

controlled release of energy "burning" fuels in a series of

step-by-step enzyme-controlled reactions

AP Biology

Harvesting stored energy Glucose is the model

catabolism of glucose to produce ATP

glucose + oxygen energy + water + carbon

dioxide

C6H12O6 + 6O2 ATP + 6H2O + 6CO2 + heat

respiration

COMBUSTION = making a lot of heat energy by burning fuels in one step

fuel (carbAoPhBydioralotegsy)

O2 CO2 + H2O + heat

RESPIRATION = making ATP (& some heat) by burning fuels in many small steps

ATP enzymes

ATP

glucose

O2

CO2 + H2O + ATP (+ heat)

How do we harvest energy from fuels?

Digest large molecules into smaller ones

break bonds & move electrons from one molecule to another

as electrons move they "carry energy" with them that energy is stored in another bond,

released as heat or harvested to make ATP

loses e-

gains e-

+

AP Biology

e-

oxidized

reduced

++ ?

e-

oxidation reduction

redox

How do we move electrons in biology? Moving electrons in living systems

electrons cannot move alone in cells

electrons move as part of H atom e

p

move H = move electrons

loses e-

gains e-

+

H

oxidized

reduced

++ ?

H

oxidation reduction

oxidation

C6H12O6 + 6O2

AP Biology

H e-

6CO2 + 6H2O + ATP

reduction

Coupling oxidation & reduction

REDOX reactions in respiration

release energy as breakdown organic molecules

break C-C bonds strip off electrons from C-H bonds by removing H atoms

C6H12O6 CO2 = the fuel has been oxidized electrons attracted to more electronegative atoms

in biology, the most electronegative atom? O2 H2O = oxygen has been reduced

O2

couple REDOX reactions &

use the released energy to synthesize ATP

oxidation

C6H12O6 + 6O2 6CO2 + 6H2O + ATP

AP Biology

reduction

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Division Ave. High School

AP Biology

Ms. Foglia

Oxidation & reduction

Oxidation

Reduction

adding O

removing O

removing H

adding H

loss of electrons gain of electrons

releases energy

stores energy

exergonic

endergonic

oxidation

C6H12O6 + 6O2 6CO2 + 6H2O + ATP

reduction

AP Biology

Moving electrons in respiration

Electron carriers move electrons by

shuttling H atoms around

NAD+ NADH (reduced) FAD+2 FADH2 (reduced)

reducing power!

NAD+ nicotinamide

HO

NADH H H O

Vitamin B3

C NH2

C NH2

niacin

O?

N+

+H

reduction

O?

N

O? P ?O

oxidation O? P ?O

O

phosphates

O? O? P ?O

adenine

O

O? O? P ?O

O

AP Biology

ribose sugar carries electrons as a reduced molecule

O

Overview of cellular respiration 4 metabolic stages

Anaerobic respiration

1. Glycolysis respiration without O2 in cytosol

Aerobic respiration

respiration using O2 in mitochondria 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain

APCBi6oHlog1y2O6 + 6O2 ATP + 6H2O + 6CO2 (+ heat)

What's the point?

ATP

The point is to make

ATP!

AP Biology

2006-2007

H+

And how do we do that?

H+ H+

H+

H+

H+ H+ H+

ATP synthase enzyme

H+ flows through it

conformational changes

bond Pi to ADP to make ATP

set up a H+ gradient

allow the H+ to flow ADP + P

down concentration

gradient through ATP

synthase

ATP

H+

ADP + Pi ATP

APBBuiotlo...gyHow is the proton (H+) gradient formed?

Cellular Respiration Stage 1: Glycolysis

AP Biology

2006-2007

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Division Ave. High School

AP Biology

Ms. Foglia

Glycolysis

Breaking down glucose

"glyco ? lysis" (splitting sugar)

glucose pyruvate

6C

2x 3C

In the cytosol? Why does that make evolutionary sense?

ancient pathway which harvests energy

where energy transfer first evolved

transfer energy from organic molecules to ATP

still is starting point for ALL cellular respiration

but it's inefficient

generate only 2 ATP for every 1 glucose

occurs in cytosol

AP Biology

That's not enough ATP for me!

Evolutionary perspective

Prokaryotes

first cells had no organelles

Anaerobic atmosphere

Enzymes of glycolysis are "well-conserved"

life on Earth first evolved without free oxygen (O2) in atmosphere

energy had to be captured from organic molecules

in absence of O2

Prokaryotes that evolved glycolysis are ancestors

of all modern life

ALL cells still utilize glycolysis

AP Biology

Overview

10 reactions

convert glucose (6C) to

glucose

C-C-C-C-C-C

enzyme

2 ATP

enzyme

2 ADP

fructose-1,6bP

P-C-C-C-C-C-C-P

2 pyruvate (3C) enzyme

enzyme

produces:

DHAP enzyme G3P

4 ATP & 2 NADH P-C-C-C C-C-C-P

consumes:

2H 2Pi enzyme

2 ATP

enzyme

2 NAD+ 2

net yield: 2 ATP & 2 NADH

DHAP = dihydroxyacetone phosphate G3APP B=ioglolygcyeraldehyde-3-phosphate

2Pi

enzyme

pyruvate C-C-C

4 ADP 4 ATP

Glycolysis summary

ENERGY INVESTMENT

endergonic invest some ATP

ENERGY PAYOFF

NET YIELD AP Biology

G3P C-C-C-P

-2 ATP 4 ATP

exergonic harvest a little ATP & a little NADH

like $$ in the

bank

net yield 2 ATP 2 NADH

1st half of glycolysis (5 reactions)

Glucose "priming"

get glucose ready to split

Glucose

ATP

1 hexokinase

ADP

Glucose 6-phosphate

CH2OH O

CH2 O P O

phosphorylate glucose

2

phosphoglucose isomerase

CH2 O P O CH2OH

molecular rearrangement

Fructose 6-phosphate

ATP

3 phosphofructokinase

split destabilized

ADP Fructose 1,6-bisphosphate

P O CH2 O CH2 O P

glucose

4,5 aldolase

P O CH2

isomerase

H

CO CH2OH NAD+

Dihydroxyacetone phosphate

Pi 6 Pi

Glyceraldehyde 3 -phosphate (G3P)

NAD+

CO CHOH

CH2 O P

AP Biology

NADH

glyceraldehyde 3-phosphate

NADH P O

O

dehydrogenase

1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate

CHOH

(BPG)

(BPG)

CH2 O P

2nd half of glycolysis (5 reactions)

DHAP

G3P

Energy Harvest

P-C-C-C C-C-C-P

NADH production

G3P donates H oxidizes the sugar reduces NAD+ NAD+ NADH

ATP production

G3P pyruvate PEP sugar donates P

NAD+ NADH

Pi 6 Pi

NAD+ NADH

ADP ATP

7 phosphoglycerate

kinase

ADP ATP

3-Phosphoglycerate (3PG)

3-Phosphoglycerate (3PG)

8

phosphoglyceromutase

2-Phosphoglycerate (2PG)

2-Phosphoglycerate (2PG)

"substrate level phosphorylation"

9

H2O

enolase

H2O

ADP ATP

Phosphoenolpyruvate Phosphoenolpyruvate

(PEP)

(PEP)

AP Biology

ADP ATP

10 pyruvate kinase

Pyruvate

Pyruvate

ADP ATP

OC CHOH CH2 O P

OCO HC O P CH2OH OCO COP CH2 OCO CO CH3

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Division Ave. High School

AP Biology

Ms. Foglia

Substrate-level Phosphorylation

In the last steps of glycolysis, where did

the P come from to make ATP?

the sugar substrate (PEP) 9

H2O

enolase

H2O

P is transferred from PEP to ADP kinase enzyme

ADP ATP ATP

Phosphoenolpyruvate Phosphoenolpyruvate

(PEP)

(PEP)

ADP ATP

10 pyruvate kinase

Pyruvate

Pyruvate

ADP ATP

OCO COP CH2 OCO CO CH3

AP Biology

Energy accounting of glycolysis

2 ATP 2 ADP

glucose pyruvate

6C

2x 3C

4 ADP 4 ATP

2 NAD+ 2

Net gain = 2 ATP + 2 NADH

some energy investment (-2 ATP) small energy return (4 ATP + 2 NADH)

AP 1Bio6loCgysugar two 3C sugars

Is that all there is?

Not a lot of energy...

for 1 billon years+ this is how life on Earth survived

no O2 = slow growth, slow reproduction only harvest 3.5% of energy stored in glucose

more carbons to strip off = more energy to harvest

O2 O2

O2

glucose pyruvate

6C

2x 3C

O2

AP Biology

O2

But can't stop there! DHAP

G3P

raw materials products

NAD+

Pi

Pi

NAD+

NNAADD+H

Pi 6

NADH 1,3-BPG

Pi 1,3-BPG

NAD+H NADH

ADP

7

ADP

Glycolysis

ATP

ATP

3-Phosphoglycerate 3-Phosphoglycerate

glucose

+

2ADP

+

2Pi

+

2

NAD+

2

(3PG)

pyruvate

+

2A8 TP

+

(3PG)

2NADH

Going to run out of NAD+

without regenerating NAD+,

2-Phosphoglycerate (2PG)

9 H2O

2-Phosphoglycerate (2PG)

H2O

energy production would stop! Phosphoenolpyruvate Phosphoenolpyruvate

(PEP)

(PEP)

another molecule must accept HADP

10

ADP

from NADH

ATP

ATP

AP Biologsyo NAD+ is freed up for another round Pyruvate

Pyruvate

How is NADH recycled to NAD+?

Another molecule

with oxygen aerobic respiration

must accept H

from NADH

pyruvate

H2O

NAD+

without oxygen anaerobic respiration

"fermentation"

CO2

O2

recycle NADH

which path you use depends on wAhP oBioyloogyu are...

NADH acetyl-CoA

Krebs cycle

NADH

acetaldehyde

NAD+

NADH

lactate NAD+

lactic acid fermentation

ethanol

alcohol fermentation

Fermentation (anaerobic) Bacteria, yeast

pyruvate ethanol + CO2

3C

2C 1C

NADH NAD+

beer, wine, bread back to glycolysis

Animals, some fungi

pyruvate lactic acid 3C NADH NAD+ 3C

back to glycolysis

AP Biology cheese, anaerobic exercise (no O2)

4

Division Ave. High School

AP Biology

Ms. Foglia

Alcohol Fermentation

pyruvate ethanol + CO2

3C NADH NAD+ 2C

1C

back to glycolysis

Dead end process

at ~12% ethanol,

kills yeast

can't reverse the

reaction

Count the carbons!

bacteria yeast

recycle NADH

AP Biology

Lactic Acid Fermentation

pyruvate lactic acid O2

3C

NADH

NAD 3C

+

back to glycolysis

Reversible process

once O2 is available, lactate is converted

back to pyruvate by

the liver

animals some fungi

recycle NADH

AP Biology

Count the carbons!

Pyruvate is a branching point

Pyruvate

O2

O2

fermentation anaerobic respiration mitochondria

Krebs cycle

aerobic respiration

AP Biology

H+

And how do we do that?

H+ H+

H+

H+

H+ H+ H+

ATP synthase

set up a H+ gradient

allow H+ to flow through ATP synthase

powers bonding of Pi to ADP

ADP + P

ADP + Pi ATP

ATP

H+

BAPuBti...ologHy ave we done that yet?

Cellular Respiration Stage 2 & 3: Oxidation of Pyruvate Krebs Cycle

AP Biology

2006-2007

Glycolysis Overview

10 reactions

convert glucose (6C) to 2 pyruvate (3C)

glucose C-C-C-C-C-C

2 ATP

2 ADP

fructose-1,6bP P-C-C-C-C-C-C-P

produces:

DHAP

G3P

4 ATP & 2 NADH P-C-C-C C-C-C-P

consumes:

2H 2Pi

2 ATP

2 NAD+ 2

net: 2 ATP & 2 NADH

AP Biology

2Pi

pyruvate C-C-C

4 ADP 4 ATP

5

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