Transcript Chapter 9. Cellular Respiration STAGE 1: Glycolysis

Unit 3 Topic 3
Cellular respiration
C6H12O6 + 6O2 --> 6CO2 +6H2O
The Big Picture
Cellular respiration
Cellular Respiration
Stage 1:
Glycolysis
Glycolysis
 Breaking down glucose

“glyco – lysis” (splitting sugar)
glucose      pyruvate
2x 3C
6C
Occurs in the cytoplasm
 A little ATP energy is harvested,
 but it’s inefficient

 generate only 2 ATP for every 1 glucose
That’s not enough
ATP for me!
Overview
10 reactions
convert
glucose (6C) to
2 pyruvate (3C)
 produces:
4 ATP & 2 NADH
 consumes:
2 ATP
 net yield:
2 ATP & 2 NADH

Substrate-level
phosphorylation
Substrate-level
phosphorylation
Products of glycolysis move on to stage 2
Cellular Respiration
Stage 2:
Pyruvate "grooming"
& the Krebs Cycle
Cellular respiration
Mitochondria — Structure
 Double membrane energy harvesting organelle



smooth outer membrane
highly folded inner membrane
intermembrane space
 fluid-filled space between membranes

matrix
 inner fluid-filled space


DNA, ribosomes
enzymes
 free in matrix & membrane-bound
outer
intermembrane
membrane
inner
space
membrane
cristae
matrix
What cells would have
a lot of mitochondria?
mitochondrial
DNA
This happens
twice for each
glucose
molecule
Electron Carriers = Hydrogen Carriers
H+
 Krebs cycle
produces large
quantities of
electron carriers
NADH
 FADH2
 go to Electron
Transport Chain!

H+
H+
H+
+
H+ H H+
H+
ADP
+ Pi
ATP
H+
Cellular Respiration
Stage 3:
Electron Transport Chain
Cellular respiration
ATP payoff!
 Electron Transport Chain

series of proteins built into
inner mitochondrial membrane
transport of electrons down ETC pumps H+
across the membrane to create H+ gradient
 just like in the light reactions, the gradient
powers ATP synthase

O2
Electron Transport Chain
Inner
mitochondrial
membrane
Intermembrane space
C
Q
NADH
dehydrogenase
cytochrome
Mitochondrial matrix
cytochrome
Remember the Electron Carriers?
Glycolysis
2 NADH
Time to
break open
the piggybank!
Krebs cycle
8 NADH
2 FADH2
Electron Transport Chain
NADH  NAD+ + H
e
p
intermembrane
space
H+
H+
H  e- + H+
H+
C
2e–
Q
2e–
NADH H
FADH2
NAD+
NADH
dehydrogenase
inner
mitochondrial
membrane
2e–
H
FAD
2H+ +
cytochrome
1
2
O2
H2O
cytochrome
mitochondrial
matrix
What powers the proton (H+) pumps?…
Electronegativity!
H 2O
O2
electrons
are “pulled”
to O2
oxidative phosphorylation
Cellular respiration
2 ATP
+
2 ATP
+
34 ATP
Summary of cellular respiration
C6H12O6 + 6O2








 6CO2 + 6H2O +~34-38 ATP
Where did the glucose come from?
Where did the O2 come from?
Where did the CO2 come from?
Where did the CO2 go?
Where did the H2O come from?
Where did the ATP come from?
What is recycled for use again?
Why do we breathe?
Taking it beyond…
 What is the final electron acceptor in
Electron Transport Chain?
O2
 So what happens if O2 unavailable?
 ETC backs up
nothing to pull electrons down chain
 NADH & FADH2 can’t unload H

 ATP production ceases
 cells run out of energy
Anaerobic respiration
Making ATP without oxygen
 All cells carry out glycolysis: prokaryotes and eukaryotes.
 Eukaryotes and many prokaryotes also carry out oxidative
phosphorylation (remember this requires oxygen).
How can some bacteria carry
out aerobic respiration if they
don't have mitochondria?
FUN FACT: many bacteria have
ETC’s in their cell membranes.
A net of 2 ATP is generated in
glycolysis.
NAD+ must be present available for
this process.
For aerobic organisms this is not a
problem, NAD+ is regenerated during
oxidative phosphorylation (ETC).
Fermentation is the pathway that some
prokaryotes always have to take
(obligate anaerobes). This pathway is
also used by prokaryotes and yeasts
that are facultative anaerobes.
Fermentation is also used by your own
muscles when you are working out
strenuously and gas exchange is not
happening fast enough to replenish
ATP through oxidative
phosphorylation.
Fermentation (anaerobic)
 Alcohol fermentation
 Bacteria (prokaryotes), yeast (eukaryotes)
 wine, bread
 Lactic acid fermentation
 Animals, some fungi (eukaryotes)
 cheese, anaerobic exercise (no O2)
Alcohol fermentation
recycle
NADH
 NADH is recycled back to
NAD+ when pyruvate is
converted to ethanol.
 Alcohol is released into
the organism's
environment as waste.
 Fun fact: Bubbles in beer
and champagne are CO2
released in the
conversion of pyruvate to
alcohol.
recycle
NADH
 NADH is recycled back to
NAD+ when pyruvate is
converted to lactate (enzymecatalyzed)
 Once O2 is available, lactate is
converted back to pyruvate by
the liver
 Cells can then resume aerobic
respiration using pyruvate
(starts Stage 2).
Pyruvate from
cytoplasm
Inner
+
mitochondrial H
membrane
H+
Intermembrane
space
Electron
transport
C system
Q
NADH
Acetyl-CoA
1. Electrons are harvested
and carried to the
transport system.
NADH
Krebs
cycle
e-
e-
FADH2
e-
2. Electrons
provide energy
to pump
protons across
the membrane.
e-
H2O
3. Oxygen joins
with protons to
form water.
1 O
2 +2
2H+
O2
H+
CO2
ATP
Mitochondrial
matrix
H+
ATP
ATP
4. Protons diffuse back in
down their concentration
gradient, driving the
synthesis of ATP.
H+
ATP
synthase
QuickTime™ and a
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are needed to see this picture.
QuickTime™ and a
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are needed to see this picture.
Catalyst: Answer all of the following
questions in your notebook.
 What are the products of pyruvate grooming





for 1 molecule of glucose?
What are the products of the citric acid cycle
for 1 molecule of glucose?
After glycolysis, pyruvate grooming, and the
citric acid cycle, what are your net products?
What is phosphorylation?
What is substrate-level phosphorylation?
What is the main goal for stages 1-3?
Catalyst: Answer all of the following
questions in your notebook
 What is the summary equation for cellular
respiration?
 If oxidation is a loss of electrons (in the form
of hydrogen atoms) and reduction is the gain
of electrons (in the form of hydrogen atoms),


what is oxidized during cellular respiration?
what is reduced during cellular respiration?
 How does glucose get to your cells for
cellular respiration?
 What is the point of cellular respiration?
 What are the net molecular products of
glycolysis?