today: kreb’s cycle today: kreb’s cycle –cell respiration homework due monday: electron...

• TodayToday: Kreb’s Cycle: Kreb’s Cycle– Cell Respiration Homework DueCell Respiration Homework Due

• MondayMonday: Electron Transport Chain, : Electron Transport Chain, • Pre-lab assignment due Thursday Pre-lab assignment due Thursday

(typed and shared)(typed and shared)• TuesdayTuesday: Workday: Workday• WednesdayWednesday: Family Reunion: Family Reunion• ThursdayThursday: Cellular Respiration Review, : Cellular Respiration Review,

• Read lab procedures for homework Read lab procedures for homework (emailed or on Google Drive)(emailed or on Google Drive)

• FridayFriday: Cellular Respiration Lab: Cellular Respiration Lab• Monday, 12/1Monday, 12/1: Cell Communication : Cell Communication

Independent Study (Test grade)Independent Study (Test grade)

• Graph data and calculate the reaction rate.• Explain why a change in reaction rate was

observed after so many minutes.• Draw and label another line on the graph to predict

the results if the concentration of the enzyme was doubled. Explain results.

• Identify TWO environmental factors that can change the rate of enzyme-mediated reactions.

Discuss how each of those two factors would affect the reaction rate of an enzyme.

2007-2008

Cellular Respiration

2007-2008

What’s thepoint?

The pointis to make

ATP!

ATP

Step 1: Glycolysis Glycolysis • Breaking down glucose

– “glyco – lysis” (splitting sugar)

– 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– anaerobic process

glucose pyruvate2x6C 3C

Evolutionary PerspectiveEvolutionary Perspective• Prokaryotes

– first cells had no organelles (NO MITOCHONDRIA)

• Anaerobic atmosphere– 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

OVERVIEWOVERVIEW10 reactions– convert

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

– produces: 4 ATP & 2 NADH

– consumes:2 ATP

– net: 2 ATP & 2 NADH

glucoseC-C-C-C-C-C

fructose-1,6bPP-C-C-C-C-C-C-P

DHAPP-C-C-C

G3PC-C-C-P

pyruvateC-C-C

DHAP = dihydroxyacetone phosphateG3P = glyceraldehyde-3-phosphate

ATP2

ADP2

ATP4

ADP4

NAD+22

2Pi

enzyme

enzyme

enzyme enzyme

enzyme

enzyme

enzyme

enzyme

2Pi

2H

Glycolysis summary endergonicinvest some ATP

exergonicharvest a little ATP & a little NADH

yield2 ATP2 NADH

like $$in the bank

4ATP

ENERGY INVESTMENT

ENERGY PAYOFF

G3PC-C-C-P

NET YIELD

IS THAT IT?!IS THAT IT?!• 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

Hard wayto makea living!

O2

O2

O2

O2

O2

glucose pyruvate6C 2x 3C

Fermentation (anaerobic)Fermentation (anaerobic)

• Bacteria, yeast

1C3C 2Cpyruvate ethanol + CO2

• Animals, some fungi

pyruvate lactic acid3C 3C

Makes beer, wine, bread

cheese, anaerobic exercise (no O2)

NADH NAD+

NADH NAD+

to glycolysis

to glycolysis

Alcohol Fermentation

1C3C 2Cpyruvate ethanol + CO2

NADH NAD+

Count thecarbons!

Dead end process at ~12% ethanol,

kills yeast can’t reverse the

reaction

bacteria yeast

Reversible process once O2 is available,

lactate is converted back to pyruvate by the liver

Lactic Acid Fermentationpyruvate lactic acid

3C 3CNADH NAD+

Count thecarbons!

O2

animals

Pyruvate is a branching point!!!

Pyruvate

O2O2

mitochondriaKreb’s cycle

aerobic respiration

fermentationanaerobicrespiration

2007-2008

What’s thepoint?

The pointis to make

ATP!

ATP

H+

H+H+

H+

H+ H+

H+H+H+

And how do we do that?• ATP synthase

– set up a H+ gradient– allow H+ to flow

through ATP synthase– powers bonding

of Pi to ADP

ADP + Pi ATP ATP

But… Have we done that yet?

ADP P+

2007-2008

NO!There’s still more

to my story!Any Questions?

Glycolysis Rap Song

2 ATP

CO2 out

O2 in

2 ATP

e- in 2 NADH

H2Oout

30+ ATP

CELLULAR RESPIRATIONCELLULAR RESPIRATIONStep 2Step 2

THE CITRIC ACID CYCLETHE CITRIC ACID CYCLE

OROR

THE KREB’S CYCLETHE KREB’S CYCLE

• The most important link to the electron transport chain (ETC makes a ton of ATP)

• Occurs in mitochondrial matrix• Some bacteria too (takes place in cytoplasm)• Sir Hans Adolf Krebs, 1937• BETWEEN GLYCOLYSIS AND CITRIC ACID CYCLE:

pyruvate acetyl-CoA

Coenzyme A

CO2NADH Kreb’s

Cycle

• Initiating step of Citric Acid Cycle: 4-C oxaloacetic acid + 2-C acetyl CoA 6-C citric acid

• During the cycle:– Citric acid rearranged; Stripped of 2-Cs– CO2 released– 4 e- released to electron carriers (NAD+ and FAD)– 1 molecule of oxaloacetic acid remains to begin the cycle

again– 2 ATP made

• Oxidation Reactions!!!– molecules that lose electrons…LEO goes GER– Loss of electrons at 4 specific places…to fuel ETC– Use NAD+ and FAD– Steps 4, 6, 10 (NAD+) & 8 (FAD)

• Page 183 – 184• #s 1 – 15• Typed in full sentences.