Transcript Cell Respiration & Photosynthesis PPT

BEST ORGANELLE EVER…?
BEST ORGANELLE EVER…?
Ch 9
Cell Respiration
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Cell Respiration = catabolic, makes ATP,
exergonic (ΔG -686 kcal/mol)
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy
ATP is made and used for energy,
recycled, ATP ↔ ADP
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ADP + P = phosphorylation (common)
P-bond is very energetic
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Redox reaction = transfer of electrons from
reactants to products, energy released
oxidation = loss of e-, reduction = gain of e-
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Figure 9.UN01
becomes oxidized
(loses electron)
becomes reduced
(gains electron)
Figure 9.UN03
becomes oxidized
becomes reduced
Overview
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Electrons are passed “downhill” from:
glucoseNADH  electron transport chain
 oxygen
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In a series of redox reactions
Releases energy, therefore is exergonic
The Key Players
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In resp., transfer of e- uses NAD+ and
electron transport chain
NAD+ = an electron shuttle, is coenzyme and
e- acceptor, converts to NADH, gains 2 eand 1 p+, p165
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WHAT IS ROLE OF OXYGEN IN THESE EXAMPLES?
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Electron transport chain
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Video
Made of e- carrier molecules in the
mitochondrial membrane
electrons slowly get passed down to oxygen
(final electron acceptor) and energy is given
off, p165
Why slow?
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OXIDATION
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Oxygen is HIGHLY electronegative
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Final electron acceptor in respiration
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(6 valence electrons)
Ultimately results as water, also picking up H+ ions
Once a molecule has been oxidized, it has very
little free energy
Process of Cell Respiration in detail
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Phase 1) Glycolysis (what does the word mean?)
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catabolic, glucose is broken into two 3carbon parts, which are converted into two
pyruvate molecules, easy, video
Where: cytosol
anaerobic
uses 2 ATP to start, 4 are released by
substrate level phosphorylation : 2 ATP
NET
2 NAD+ converted (reduced) to 2 NADH
Exergonic: ΔG = -140 kcal/mol
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•Substrate Level Phosphorylation, is
about 10% of the ATP.
• 90% occurs as result of oxidative
phosphyrlation
• occurs during glycolysis and the
citric acid cycle
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Options → If O2 is available – pyruvate moves to a
mitochondrion and the citric acid cycle (a.k.a. the
Krebs cycle) to complete oxidation, if not then
fermentation occurs (we’ll do later)
In Mitochondria
 Pyruvate is converted into acetyl CoA, (3-C into a 2C molecule), makes it reactive, p170
 2 NADH’s made (1 per pyruvate)
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During part 1 of phase 2 (pyruvate oxidation) pyruvate is oxidized and
becomes acetyl coenzyme A, or acetyl CoA
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Phase 2) Krebs Cycle, p.170
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(citric acid, TCA cycle)– catabolic, in
mitochondrial matrix
The CoA on acetyl CoA is removed and the
acetyl group is added to oxaloacetate to
create citrate
energy released, 8 step cycle
For every acetyl CoA (2 per glucose) 
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3 NADH, 1 FADH2, 2 CO2, 1 ATP made (SLP)
most energy is hidden in the electron carriers
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? GTP and GDP
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3) Oxidative Phosphorylation
Electron Transport Chain (ETC)
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Where: inner
mitochondria
Problem – we have
many e- carriers
electronegativity
increases down the
chain so e- are pulled
“downhill” towards
oxygen, the final
acceptor
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What is the ultimate purpose of the electron transport chain? Of the electrons?
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most carriers are
metals or cytochromes
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ATP production
powered by [H+]
gradient, p174
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ATP Synthase 
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Chemiosmosis
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Flow of H+ (osmos = “pushing” H+)
= coupling of rxns to make ATP, p173,
(diffusion & pumps)
e- move down ETC, H+ pumped out into
intermembrane space creating a protonmotive force, H+ diffuse into matrix
through ATP synthase to make ATP
process is enhanced by cristae (folds) in
mitochondria
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Process
ATP by SLP
CoEnzyme
ATP by ETC
Total
Glycolysis
Net 2
2 NADH
4-6
6-8
Oxidation of
pyruvates
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2 NADH
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6
krebs
2
6 NADH
2 FADH2
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4
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TOTAL =
36-38
- range 36-38 because of rounding p176-177
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Resp. is very efficient – 40%
7.3 kcal/mol ATP x 38 ATP/mol
686 kcal/mol glucose
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Fermentation
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anaerobic, makes only 2 ATP, starts after glycolysis if
no oxygen, 2 types
1) alcoholic- 2 pyruvates broken down into 2 CO2 and
ethanol, 2 NADH oxidized to 2 NAD+, replenishes NAD+
 many yeast, and bacteria, do
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2) lactic acid – 2 pyruvates broken down into
lactate
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occurs in muscles when O2 is low
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Fermentation vs Respiration
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both break down pyruvate and use NADH
in ferm. – final electron acceptor is pyruvate,
in resp. it is O2
more energy from respiration, 18 x more ATP
respiration needs O2
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some organisms are
facultative anaerobes=
they can switch back
and forth from aerobic
to anaerobic
What evolved first,
aerobes or anaerobes?
other energy molecules
(ex. fats) can be broken
into parts to go into
glycolysis, p180
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Regulation
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Control of cell respiration is done by feedback
inhibition – too much product inhibits rxn
control at certain enzymes in glycolysis and
krebs
key control enzyme for citric acid cycle (in
glycolysis) is phosphofructokinase
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sensitive to ratios of ATP:ADP:AMP
citrate and ATP are allosteric inhibitors of pfk
ADP and AMP are allosteric activators of pfk
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Review with Bioflix on
MasteringBiology.com
How can sunlight, seen here as a spectrum of colors in a rainbow, power the synthesis of organic substances?
Fun Fact:
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Photosynthesis creates 160 billion metric
tons of carbohydrates per year (or 17 stacks
of our AP text reaching all the way to the sun)
Ch 10
Photosynthesis
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Start with BioFlix on Masteringbiology.com
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Figure 10.2
(b) Multicellular
alga
(a) Plants
(d) Cyanobacteria
(c) Unicellular
protists
10 m
(e) Purple sulfur
1 m
bacteria
40 m
Photosynthesis
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= converts light energy trapped by chloroplasts into
chemical energy stored as sugar
uses CO2 to as carbon source
Endergonic
Anabolic
WAYS OF ENERGY AQUISITION
 Autotroph = organism that makes its own food for
energy
 Photoautotroph= uses light, ex. algae
 Chemoautotroph= uses chemicals, ex. bacteria
 Heterotroph = organism that acquires (eats) its food
for energy, ex. us
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Let’s see this in action with
Bioflix
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Chloropast
where photosynthesis occurs
 contains chlorophyll = green pigment,
absorbs light
 mostly in mesophyll of leaves
 gas exchange through pores (stomata)
 Anatomy of chloroplast:
1) intermembrane space- separates double
membrane
2) thylakoid space- inside the thylakoid
membrane
- thylakoids (sacs in the chloroplast) and
stacks called grana
3) Stroma = fluid-filled space outside the
thylakoids, where sugar is made, only in
eukaryotes
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Does CO2 or H2O get split to give oxygen?
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Van Neil: gave bacteria H2S instead of water
the rxn gave sulfur as a byproduct, so…
splits H2O to give O2, later done with radioactivity
water is split and the electrons are transferred from
water to carbon dioxide, reducing it to sugar
resp. was exergonic, photosynthesis is endergonic,
energy required is light
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Photosynthesis Rxn
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
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Phase 1)
Light Reactions (including the Electron Transport Chain)
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1st stage in photosynthesis, convert light
energy to chemical energy as ATP &
NADPH, p188
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Light = electromagnetic energy
distance it travels = wavelength, ranges
from 380 to 750 nm (visible spectrum)
plants absorb blue and red light best,
reflect green
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1)Light Reactions/Electron Transport Chain
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What is water’s chief purpose?
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Pigments = substances that absorb light,
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each has a specific wavelength it can absorb =
absorption spectrum
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measured with a
spectrophotometer
graph wavelength vs.
rate of photosynthesis
= action spectrum,
p192
main pigments are
chlorophyll a,b,
carotenoids (yellow)
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Structure of chlorphyll
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RESEARCH METHOD: Determining an Absorption Spectrum
TECHNIQUE
Refracting Chlorophyll Photoelectric
solution
tube
White prism
Galvanometer
light
Slit moves to
pass light
of selected
wavelength.
Green
light
High transmittance
(low absorption):
Chlorophyll absorbs
very little green light.
Blue
light
Low transmittance
(high absorption):
Chlorophyll absorbs
most blue light.
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Linear electron flow- passes electrons from water to
NADP+ to make NADPH, uses P680 and P700
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Photons bump electrons’ to
orbital of higher energy level
(photoexcitation). This is
unstable and the electrons want
to drop back down, immediately
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When e- drops back down releases
heat (think of your car’s hood)
Some pigments delay in their giving
off photons as electrons settle back
down…this is fluorescence.
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What color of light would a fluorescing
flask of chlorophyll give off?
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Red-orange…why?
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• photosystem I (P700), and II(P680), video
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Alternate means of generating ATP:
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Cyclic electron flow – simpler, only involves P 700, makes ATP
but no NADPH, nor oxygen
More common in primitive bacteria groups * p195
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vs.
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ETC in respiration vs. photosynthesis
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e- source is organic molecules (sugar) vs.
water
H+ reservoir in intermembrane space vs. into
the thylakoid space
Let’s review
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electrons from water go to NADP+, NADPH
is made to reduce CO2 to sugar
ATP made, O2 is byproduct
pH gradient of 5 inside to 8 in stroma
(1000x H+ inside)
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Phase 2) Calvin Cycle
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2nd stage of photosynthesis, also called dark
rxns., light not directly used here
Where: stroma
carbon source is CO2 and is ultimately reduced to
sugar
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produces 3-C sugar G3P (1/2 a sucrose)
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powered by ATP made from light reaction, uses
NADPH as reducing agent to add electrons to Ccpds, which ultimately become sugar
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p 198*
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(Like citric acid cycle in reverse)
JUST LIKE
RESPIRATION
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Steps
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a) Carbon fixation = CO2 is attached to a 5-C
molecule (RuBP), catalyzed by rubisco (fun
fact: most abundant protein on earth), later
the new 6-C molecule is broken in two
b) Reduction –coupled rxns: 6 ATP to 6 ADP,
used to convert 3PG to G3P, 6 NADPH to 6
NADP+
c) Regeneration of RuBP - uses ATP to make
RuBP
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QUICK
REVIEW
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Similarities of Photo. and resp.
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Similarities of Photo. and resp.
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a) both use ETC via a membrane
b) both make ATP by diffusion of H+ over a
gradient
c) similar electron carriers
d) both are involved in energy conversion
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for mitochondria→ chemical energy from food to ATP
for chloroplast→ light energy into chemical energy
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Differences between Photo. and resp.
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Other types of carbon fixation, p200-201
1) Photorespiration - uses O2, makes no ATP,
so it reduces photosynthetic output by
wasting C
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occurs when O2 is higher in leaf than CO2
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evolutionary relic?
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favored on hot, dry days
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2) C4 plants - 4 carbon intermediate formed at
Calvin cycle
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C3 plants make 3 carbon intermediate,
ex. rice, wheat
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C4 ex. corn, sugarcane
 enhances carbon fixation by minimizing
photorespiration
 PEP carboxylase can fix
carbon efficiently when
Rubisco cannot
 important in hot regions
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3) CAM plants - only open stomata during the
night, opposite of usual
reduces water loss in hot areas, also keeps
CO2 out during the day
ex. cacti, pineapple
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Photosynthesis Free-Response Q,
outline only in 12 min.
A controlled experiment was conducted to analyze the effects of darkness and boiling on the
photosynthetic rate of incubated chloroplast suspensions. The dye reduction technique was used.
Each chloroplast suspension was mixed with DPIP, an electron acceptor that changes from blue to
clear when it is reduced. Each sample was placed individually in a spectrophotometer and the
percent transmittance was recorded. The three samples used were prepared as follows.
• Sample 1 – chloroplast suspension + DPIP
• Sample 2 – chloroplast suspension surrounded by foil wrap to provide a dark environment +
DPIP
• Sample 3 – chloroplast suspension that has been boiled + DPIP
a) On the graph provided, construct and label a graph showing the results for the three
samples.
b) Identify and explain the control or controls for this experiment.
c) The differences in the curves of the graphed data indicate that there were differences in
the number of electrons produced in the three samples during the experiment. Discuss
how electrons are generated in photosynthesis and why the three samples gave different
transmittance results.
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