Making energy!
ATP
The Point is to Make ATP!
AP Biology
2005-2006
Chapter 9 Warm-Up
 Define:








AP Biology
Glycolysis
Respiration
Chemiosmosis
Phosphorylation
Fermentation
Electrochemical
gradient
FAD  FADH2
NAD+ NADH
 Explain “glycolysis”.
Where does it occur?
How does it “work”?
Chapter 9 Warm-up
 What is the chemical equation for
cellular respiration?
 Remember OILRIG
In the conversion of glucose and
oxygen to CO2 and H2O, which
molecule is reduced?
 Which is oxidized?
 What happens to the energy that is
released in this redox reaction?

 NAD+ is called a(n) ________________.
AP Biology
Its reduced form is _________.
Chapter 9 Warm-Up
 Why is glycolysis considered an
ancient metabolic process?
 Where in the cell does glycolysis
occur?
 What are the reactants and products of
glycolysis?
 Which has more energy available:
ADP or ATP?
+
 NAD or NADH?
+
 FAD or FADH2?

AP Biology
Chapter 9 Warm-Up
 Where does the Citric Acid Cycle occur in





the cell?
What are the main products of the CAC?
How is the proton gradient generated?
What is the purpose?
Describe how ATP synthase works.
In cellular respiration, how many ATP are
generated through


AP Biology
Substrate-level phosphorylation?
Oxidative phosphorylation?
Chapter 9 Warm-Up
 In fermentation, how is NAD+ recycled?
AP Biology
What you need to know:
 The summary equation of cellular respiration.
 The difference between fermentation and cellular



respiration.
The role of glycolysis in oxidizing glucose to two
molecules of pyruvate.
The process that brings pyruvate from the
cytosol into the mitochondria and introduces it
into the citric acid cycle.
How the process of chemiosmosis utilizes the
electrons from NADH and FADH2 to produce ATP.
AP Biology
Chapter 9.
Cellular Respiration and
Fermentation
AP Biology
What’s the point?
ATP
The Point is to Make ATP!
AP Biology
Harvesting stored energy
 Energy is stored in organic molecules

heterotrophs eat food (organic molecules)
 digest organic molecules
 serve as raw materials for building & fuels for energy
 controlled release of energy
 series of step-by-step enzyme-controlled reactions

“burning” fuels
 carbohydrates, lipids, proteins, nucleic acids
AP Biology
2005-2006
Harvesting energy stored in glucose
 Glucose is the model
respiration

catabolism of glucose to produce ATP
glucose + oxygen  carbon + water + energy
dioxide
C6H12O6 +
6O2
 6CO2 + 6H2O + ATP + heat
combustion = making heat energy
by burning fuels in one step
respiration = making ATP (& less heat)
by burning fuels in many small steps
ATP
fuel
AP Biology
(carbohydrates)
CO2 + H2O + heat
CO2 + H2O + 2005-2006
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-
+
oxidized
+
oxidation
AP Biology
e-
reduced
+
–
ereduction
2005-2006
How do we move electrons in biology?
 Moving electrons

in living systems, electrons do not
move alone
 electrons move as part of H atom
loses e-
gains e-
oxidized
+
+
oxidation
reduced
+
–
H
reduction
H
oxidation
C6H12O6 +
AP Biology
H
6O2
 6CO2 + 6H2O + ATP
reduction
2005-2006
Coupling oxidation & reduction
 Redox reactions in respiration

release energy as breakdown molecules
 break C-C bonds
 strip off electrons from C-H bonds by removing H atoms
 C6H12O6  CO2 = fuel has been oxidized
 electrons attracted to more electronegative atoms
 in biology, the most electronegative atom?
 O2
 O2  H2O = oxygen has been reduced
 release energy to synthesize ATP
oxidation
C6H12O6 +
AP Biology
6O2
 6CO2 + 6H2O + ATP
reduction
2005-2006
Oxidation & reduction
 Oxidation
 Reduction
removing H
 loss of electrons
 releases energy
 exergonic

adding H
 gain of electrons
 stores energy
 endergonic

oxidation
C6H12O6 +
6O2
 6CO2 + 6H2O + ATP
reduction
AP Biology
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. Kreb’s cycle
 4. Electron transport chain
C H O6 +
AP Biology
6 12
6O2
(+ heat)
 6CO2 + 6H2O + ATP 2005-2006
What’s the point?
ATP
The Point is to Make ATP!
AP Biology
Glycolysis
 “sugar splitting”
 Believed to be ancient (early





prokaryotes- no O2 available)
Occurs in cytosol
Partially oxidizes glucose (6C) to 2
pyruvates (3C)
Net gain: 2 ATP and 2 NADH
Also makes 2H2O
No O2 required
AP Biology
Glycolysis
 Breaking down glucose

“glyco – lysis” (splitting sugar)
glucose      pyruvate
2x 3C
6C

most ancient form of energy capture
 starting point for all cellular respiration

inefficient
 generate only 2 ATP for every 1 glucose

in cytosol
 why does that make evolutionary sense?
AP Biology
Evolutionary perspective
 Life on Earth first evolved without
free oxygen (O2) in atmosphere

energy had to be captured from
organic molecules in absence of O2
 Organisms that evolved glycolysis
are ancestors of all modern life

AP Biology
all organisms still utilize
glycolysis
You mean,
I’m related
to them?!
2005-2006
Glycolysis
 Stage 1: Energy Investment Stage

Cell uses ATP to phosphorylate
compounds of glucose
 Stage 2: Energy Payoff Stage
Two 3-C compounds oxidized
 For each glucose molecule:

 2 Net ATP produced by substrate-level
phosphorylation

AP Biology
2 molecules of NAD+  NADH
glucose
C-C-C-C-C-C
Overview
 10 reactions
convert
6C glucose to
two 3C pyruvate
 produce 2 ATP
& 2 NADH
2 ATP
2 ADP

fructose-6P
P-C-C-C-C-C-C-P
DHAP
P-C-C-C
Substrate level
phosphorylation
AP Biology
PGAL
C-C-C-P
pyruvate
C-C-C
2 NAD+
2 NADH
4 ADP
4 ATP
2005-2006
Glycolysis summary
endergonic
invest some ATP
exergonic
harvest a little
more ATP
& a little NADH
AP Biology
Substrate-level Phosphorylation
 In the last step of glycolysis, where
did the P come from to make ATP?
P is transferred
from PEP to ADP
 kinase enzyme
 ADP  ATP
I get it!
The P came
directly from
the substrate!
AP Biology
2005-2006
Energy accounting of glycolysis
2 ATP
2 ADP
glucose      pyruvate
2x 3C
6C
4 ADP
4 ATP
 Net gain = 2 ATP


some energy investment (2 ATP)
small energy return (4 ATP)
 1 6C sugar  2 3C sugars
AP Biology
All that
work! And
that’s all I
get?
Is that all there is?
 Not a lot of energy…

for 1 billon years+ this is how life on
Earth survived
 only harvest 3.5% of energy stored in glucose
 slow growth, slow reproduction
Heck of a
way to make
a living!
AP Biology
We can’t stop there….
 Glycolysis
glucose + 2ADP + 2Pi + 2 NAD+ 
2 pyruvate + 2ATP + 2NADH
 Going to run out of NAD+
 How is NADH recycled to NAD+?


without regenerating NAD+,
energy production would stop
another molecule must
accept H from NADH
NADH
AP Biology
2005-2006
How is NADH recycled to NAD+?
 Another molecule must accept H from NADH

anaerobic respiration
 ethanol fermentation
 lactic acid fermentation

NADH
AP Biology
aerobic respiration
Anaerobic ethanol fermentation
 Bacteria, yeast
pyruvate  ethanol + CO2
3C
NADH
2C
1C
NAD+
 beer, wine, bread
 at ~12% ethanol, kills yeast
 Animals, some fungi
pyruvate  lactic acid
3C
NADH
3C
NAD+
 cheese, yogurt, anaerobic exercise (no O22005-2006
)
AP Biology
Pyruvate is a branching point
Pyruvate
O2
O2
fermentation
Kreb’s cycle
mitochondria
AP Biology
Glycolysis (summary)
AP Biology
What’s the point?
ATP
The Point is to Make ATP!
AP Biology
Mitochondrion Structure
AP Biology
Cellular Respiration
AP Biology
Glycolysis is only the start
AP Biology
3C
1C
Oxidation of pyruvate
 Pyruvate enters mitochondria
[
2x pyruvate    acetyl CoA + CO2
3C
2C
1C
NAD




NADH
3 step oxidation process
releases 1 CO2 (count the carbons!)
reduces NAD  NADH (stores energy)
produces acetyl CoA
 Acetyl CoA enters Krebs cycle

AP Biology
where does CO2 go?
Waiting to
exhale?
]
Pyruvate oxidized to Acetyl CoA
reduction
oxidation
Yield = 2C sugar + CO2 + NADH
AP Biology
Krebs cycle
AP Biology
Count the carbons and electron carriers!
pyruvate
3C
6C
reduction of electron
carriers and
oxidation of sugars
FADH2
4C
AP Biology
citrate
x2
4C
4C
acetyl CoA
6C
4C
NADH
This happens
twice for each
glucose
molecule
2C
ATP
4C
CO2
NADH
5C
CO2
NADH
Whassup?
So we fully
oxidized
glucose
C6H12O6

CO2
& ended up
with 4 ATP!
What’s the
Point?
AP Biology
2005-2006
NADH & FADH2
 Krebs cycle
produces large
quantities of
electron carriers
NADH
 FADH2
 stored energy!
 go to ETC

What’s so
important
about NADH?
AP Biology
2005-2006
Citric Acid Cycle (Krebs)
 Occurs in mitochondrial matrix
 Acetyl CoA→ Citrate→ CO2
 Net gain: 2 ATP, 6 NADH, 2 FADH2

(electron carrier)
ATP produced by substrate-level
phosphorylation
AP Biology
So why the Krebs cycle?
 If the yield is only 2 ATP, then why?

value of NADH & FADH2
 electron carriers
 reduced molecules store energy!
 to be used in the Electron Transport Chain
AP Biology
What’s the point?
ATP
The Point is to Make ATP!
AP Biology
Cellular respiration
AP Biology
ATP accounting so far…
 Glycolysis  2 ATP
 Kreb’s cycle  2 ATP
 Life takes a lot of energy to run, need to
extract more energy than 4 ATP!
There’s got to be a better way!
What’s the
Point?
AP Biology
There is a better way!
 Electron Transport Chain

series of molecules built into inner
mitochondrial membrane
 mostly transport proteins
transport of electrons down ETC linked
to ATP synthesis
 yields ~34 ATP from 1 glucose!
 only in presence of O2 (aerobic)

AP Biology
That
sounds more
like it!
Mitochondria
 Double membrane
outer membrane
 inner membrane

 highly folded cristae*
 fluid-filled space
between membranes =
intermembrane space

matrix
 central fluid-filled space
* form fits function!
AP Biology
Electron Transport Chain
AP Biology
Remember the NADH?
Glycolysis
Kreb’s cycle
PGAL
8 NADH
2 FADH2
2 NADH
AP Biology
2005-2006
Electron Transport Chain
 NADH passes electrons to ETC




AP Biology
H cleaved off NADH & FADH2
electrons stripped from H atoms  H+ (H ions)
electrons passed from one electron carrier to next in
mitochondrial membrane (ETC)
transport proteins in membrane pump H+ across inner
membrane to intermembrane space
But what “pulls” the
electrons down the ETC?
AP Biology
electrons flow
downhill to
O2
Electrons flow downhill
 Electrons move in steps from
carrier to carrier downhill to O2



AP Biology
each carrier more electronegative
controlled oxidation
controlled release of energy
2005-2006
Why the build up H+?
 ATP synthase

enzyme in inner membrane of
mitochondria
ADP + Pi  ATP


only channel permeable to H+
H+ flow down concentration
gradient = provides energy for
ATP synthesis
 molecular power generator!
 flow like water over water wheel
 flowing H+ cause change in
shape of ATP synthase enzyme
 powers bonding of Pi to ADP
 “proton-motive” force
AP Biology
2005-2006
ATP synthesis
 Chemiosmosis couples ETC to ATP synthesis

build up of H+ gradient just so H+ could flow through
ATP synthase enzyme to build ATP
Oxidative
phosphorylation
So that’s
the point!
AP Biology
2005-2006
Summary of cellular respiration
C6H12O6 + 6O2






 6CO2 + 6H2O + ~36 ATP
Where did the glucose come from?
Where did the O2 come from?
Where did the CO2 come from?
Where did the H2O come from?
Where did the ATP come from?
What else is produced that is not listed
in this equation?
 Why do we breathe?
AP Biology
Taking it beyond…
 What is the final electron acceptor in
electron transport chain?
O2
 So what happens if O2 unavailable?
 ETC backs up
 ATP production ceases
 cells run out of energy
 and you die!
AP Biology
What’s the point?
ATP
The Point is to Make ATP!
AP Biology
Any Questions??
AP Biology
Glycolysis
O2 present
Without O22
Fermentation
 Keep glycolysis
going by
regenerating NAD+
 Occurs in cytosol
 No oxygen needed
 Creates ethanol [+
CO2] or lactate
 2 ATP (from
AP Biology
glycolysis)
Respiration
 Release E from



breakdown of food
with O2
Occurs in
mitochondria
O2 required (final
electron acceptor)
Produces CO2, H2O
and up to 32 ATP
Various sources of fuel
 Carbohydrates, fats

and proteins can
ALL be used as fuel
for cellular
respiration
Monomers enter
glycolysis or citric
acid cycle at
different points
AP Biology
aerobic cellular
respiration
(with O2)
ENERGY
anaerobic
(without O2)
glycolysis
(cytosol)
Fermentation
mitochondria
(cytosol)
pyruvate
oxidation
ethanol + CO2
(yeast, some
bacteria)
citric acid
cycle
lactic acid
(animals)
ETC
chemiosmosis
AP
Biology
oxidative
phosphorylation