Download Chapter 9. Cellular Respiration STAGE 1: Glycolysis

• Today: Kreb’s Cycle
– Cell Respiration Homework Due
• Monday: Electron Transport Chain,
• Pre-lab assignment due Thursday (typed and
shared)
• Tuesday: Workday
• Wednesday: Family Reunion
• Thursday: Cellular Respiration Review,
• Read lab procedures for homework (emailed or
on Google Drive)
• Friday: Cellular Respiration Lab
• Monday, 12/1: Cell Communication 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.
Cellular
Respiration
2007-2008
What’s the
point?
The point
is to make
ATP!
ATP
2007-2008
Step 1: Glycolysis
• Breaking down glucose
– “glyco – lysis” (splitting sugar)
glucose      pyruvate
2x 3C
6C
– 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
Evolutionary 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
OVERVIEW
glucose
C-C-C-C-C-C
10 reactions
enzyme
2 ATP
enzyme
2 ADP
– convert
fructose-1,6bP
glucose (6C) to
P-C-C-C-C-C-C-P
enzyme
enzyme
2 pyruvate (3C)
enzyme
DHAP
G3P
– produces:
4 ATP & 2 NADH P-C-C-C C-C-C-P
2H
– consumes:
2Pi enzyme
2 ATP
enzyme
– net:
2Pi
enzyme
2 ATP & 2 NADH
DHAP = dihydroxyacetone phosphate
G3P = glyceraldehyde-3-phosphate
pyruvate
C-C-C
2 NAD+
2
4 ADP
4 ATP
Glycolysis summary
endergonic
invest some ATP
ENERGY INVESTMENT
ENERGY PAYOFF
G3P
C-C-C-P
4ATP
exergonic
harvest a little
ATP & a little NADH
like $$
in the
bank
NET YIELD
yield
2 ATP
2 NADH
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
O2
O2
O2
O2
O2
glucose     pyruvate
2x 3C
6C
Hard way
to make
a living!
Fermentation (anaerobic)
• Bacteria, yeast
pyruvate  ethanol + CO2
3C
NADH
2C
1C
NAD+
to glycolysis
 Makes beer, wine, bread
• Animals, some fungi
pyruvate  lactic acid
3C
NADH
3C
NAD+to glycolysis
 cheese, anaerobic exercise (no O2)
Alcohol Fermentation
pyruvate  ethanol + CO2
3C
NADH
2C
NAD+
 Dead end process
 at ~12% ethanol,
kills yeast
 can’t reverse the
reaction
Count the
carbons!
1C
bacteria
yeast
Lactic Acid Fermentation
pyruvate  lactic acid

3C
NADH
3C
NAD+
 Reversible process
 once O2 is available,
lactate is converted
back to pyruvate by
the liver
Count the
carbons!
O2
animals
Pyruvate is a branching
point!!!
Pyruvate
O2
O2
fermentation
anaerobic
respiration
mitochondria
Kreb’s cycle
aerobic respiration
What’s the
point?
The point
is to make
ATP!
ATP
2007-2008
H+
H+
H+
H+
And how do we do Hthat?
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+
But… Have we done that yet?
NO!
There’s still more
to my story!
Any Questions?
Glycolysis Rap Song
2007-2008
O2 in
2 ATP
e- in 2
NADH
H2O
out
CO2
out
30+ ATP
2 ATP
CELLULAR RESPIRATION
Step 2
THE CITRIC ACID CYCLE
OR
THE 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:
Coenzyme A
pyruvate
CO2
NADH
acetylCoA
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.