Download Photosynthesis and Respiration Notes

Today’s Plan:1/26/11
 Bellwork: Test corrections (25 mins)
 Spectroscope and leaf structure (35
mins)
 Begin Notes (the rest of class)
Today’s Plan: 8/18/09
 Bellwork: Themes activity (15 mins)
 Read/Discuss Lab (30 mins)
 Continue notes (the rest of class)
Today’s Plan: 1/26/10
 Bellwork: Go over prelab
questions/Set-up respirometers (20
mins)
 Run Lab (30 mins)
 Notes, continued (the res of class)
Today’s Plan: 1/28/10
 Bellwork: Talk about spec 20s and
pre-lab (15 mins)
 Spec 20 practice/ finish lab 5, etc.
(45 mins)
 Continue with notes (the rest of
class)
Today’s Plan: 1/29/10
 Bellwork: Discuss schedule/fly
demo(10 mins)
 Set-up Flies for AP Lab 6(40 mins)
 Continue Notes (the rest of class)
Today’s Plan: 2/4/10
 Bellwork: Discuss week/calendar (5
mins)
 Finish Spec20/do Part 1 of Lab 4(35
mins)
 Split up/set-up for photosynthesis lab
(10 mins)
 Continue notes (the rest of class)
Today’s Plan: 2/4/10
 Bellwork: Removal of adult flies from
cultures (10 mins)
 Finish Photosynthesis Lab (45 mins)
 Finish Notes on Photosynthesis (the
rest of class)
Today’s Plan: 2/8/10
 Bellwork: Test Q&A (10 mins)
 Photosynthesis and Respiration Test
(as needed)
 Turn in Lab 4 today!
Catabolic Pathways and Energy
 Some molecules have potential energy
because of the arrangement of their atoms
 Breaking these molecules down
(catabolism) releases this energy
 Electron-transfer is responsible for much of
this energy release:Redox rxns
 e- acceptor is reduced
 e- donor is oxidized
 Sometimes, the e- is not completely removed,
but shared differently ex: Oxygen gas to Water
in cellular respiration (Oxygen is reduced)
Figure 9-4
Electrons
pulled farther
from O;
O is oxidized
Electrons
pulled closer
to C;
C is reduced
Potential
energy increases
6 CO2
(carbon dioxide)
6 H2O
(water)
Input of
energy
Glucose
6 O2
(oxygen)
Glucose has four more
CH2O groups like the
one above
Figure 9-1
ATP consists of three phosphate groups, ribose, and adenine.
Adenine
Phosphate groups
Ribose
Energy is released when ATP is hydrolyzed.
ATP
Water
ADP
Inorganic
phosphate
Energy
NAD+
 Hydrogen atoms are good candidates for etransfer as the energy of the electron is
reduced when transferred to other atoms,
like Oxygen
 NAD+ is a coenzyme intermediate that
temporarily accepts Oxygen (step
reactions release more energy than if etransfer happened all at once)
 As Hydrogens are stripped from glucose by
dehydrogenases (2 at a time), 2 e- and 1
p+ get transferred to NAD+ to make
NADH+H+
 Later, in the e- transport chain, the
Hydrogens will be released from the
molecule
Figure 9-7
NAD+
NADH
(electron carrier)
Oxidized
Reduction
Reduced
Oxidation
Nicotinamide
Phosphate
Nicotinamide
Phosphate
Ribose
Phosphate
Oxidized
Adenine
Ribose
Ribose
Phosphate
Reduced
Adenine
Ribose
Cellular Respiration-Overview
 3 steps:
 Glycolysis-glucose is halved to form 2 pyruvate, which
will lose a Carbon and be attached to Coenzyme A
prior to step 2, becoming Acetyl CoA (cytoplasm)
 Kreb’s (Citric Acid) Cycle-For each acetyl CoA, this is a
series of reactions generating 1 ATP (substrate-level
phosphorylation) and Hydrogen carriers
(mitochondrial matrix)
 Electron Transport chain-Hydrogen Carriers will be
stripped of their H+ and e-, causing the synthesis of
mass quantities of ATP-oxidative phosphorylation
(inner mitochondrial membrane)
Figure 9-8
Figure 9-10
Enzyme
ATP
ADP
Phosphorylated
substrate
Glycolysis
 Literally means “sugar-splitting”
 Glucose is cleaved to form pyruvate
 2 ATP are consumed in the process
(during the energy investment phase
at the onset), but 4 ATP are
generated via substrate-level
phosphorylation (during the energy
payoff phase later), yielding a net
gain of 2 ATP
Figure 9-13l
All 10 reactions of
glycolysis occur
in cytosol
GLYCOLYSIS
What goes in:
Glucose
Glucose6-phosphate
Fructose6-phosphate
What comes out:
Glycolysis begins with an energyinvestment phase of 2 ATP
Fructose1,6-bisphosphate
Figure 9-13r
The “2” indicates that glucose
has been split into two 3-carbon sugars
Pyruvate
During the energy payoff phase, 4 ATP are produced for a net
gain of 2 ATP
Figure 9-16
Cristae are sacs of inner
membrane joined to the
rest of the inner membrane
by short tubes
Matrix
Cristae
Inner
membrane
Intermembrane
space
Outer membrane
The Krebs Cycle
 Also called the citric acid cycle
 Once Pyruvate enters the mitochondrion, its carboxyl
group is removed and is oxidized so that NADH are
formed. The remaining molecule is attached to
coenzyme A to become acetyl CoA, which enters the
Krebs cycle
 The point is not so much to produce ATP (only 1 is
produced per acetyl CoA), but to strip the acetyl CoA
of electrons to reduce NAD+ and FAD so that the etransport chain can happen.
 By the end of this, we’re done oxidizing glucose. The
rest of respiration is about generating ATP with our
hydrogen carriers
Figure 9-17
Figure 9-19
The two red
carbons enter
the cycle via
acetyl CoA
THE KREBS CYCLE
Pyruvate
Acetyl CoA
Citrate
Isocitrate
In each turn of the
cycle, the two
blue carbons are
converted to CO2
All 8 reactions of the
Krebs cycle occur in the -Ketoglutarate
mitochondrial matrix,
outside the cristae
Oxaloacetate
In the next cycle, this
red carbon becomes
a blue carbon
Malate
Fumarate
Succinate
Succinyl CoA
Electon Transport Chain (ETC)
 This is a collection of molecules
(flavoprotein, iron-sulfur protein, coenzyme
Q, and cytochromes)embedded in the inner
membrane of the mitochondria
 NADH and FADH2 drop off their Hydrogens,
which pass electrons to these embedded
molecules.
 H+ builds up outside of the membrane
which drives chemiosmosis as it powers the
ATP synthase rotor to generate ATP
 Final e- acceptor is Oxygen
Figure 9-22
The electron transport
chain takes place in the
inner membrane and
cristae of the mitochondrion
FMN: Nucleotide with a flavincontaining group
Fe S: Protein with an ironsulfur group
Cyt: Protein with a heme
group (a cytochrome)
Q: Ubiquinone
Figure 9-25b
The FO unit is the base; the F1 unit is the knob.
THE STRUCTURE OF ATP SYNTHASE
+
+
H+ H+ H
H
Intermembrane
+
H H+
H+ + H+
space
H+
+
H
H+ + H
+
H
H+
H
H+
+
H+ H+ H
H+
Mitochondrial
matrix
FO unit
Stalk
H+
F1 unit
ADP + Pi
ATP
Figure 9-24
Occurs in the inner membrane
of the mitochondrion
Anaerobic respiration
 When Glycolysis occurs, the presence
or absence of oxygen determines
whether or not the Krebs cycle will
proceed.
 In the absence of oxygen,
fermentation occurs in stead
 Less efficient, only 2 ATP produced
 Plants=alcoholic fermentation
 Animals=lactic acid fermentation
Figure 9-27
Fermentation pathways allow cells to regenerate NAD+
for glycolysis.
Fermentation
by-product
Intermediate accepts
electrons from NADH
Lactic acid fermentation occurs in humans.
2 Pyruvate
No intermediate;
pyruvate accepts
electrons from NADH
2 Lactate
Alcohol fermentation occurs in yeast.
2 Pyruvate
2 Ethanol
2 Acetylaldehyde
Versatility of catabolism
 Various other biomolecules can be
metabolized through the processes of
aerobic respiration
 Proteins are broken into amino acids which
can enter any of the steps of this process
 Fats are digested into glycerol and fatty
acids
 Glycerol can go through glycolysis
 Fatty acids go through beta oxidation where
they’re broken into 2-carbon sequences and can
enter the Krebs cycle as Acetyl CoA
Figure 9-29
Anabolic Processes
 Some of the intermediate molecules
from aerobic respiration are used
directly
 Amino acids are also synthesized by
siphoning molecules away from the
Krebs Cycle
 Some AAs, however, are “essential,”
meaning that the body can’t make them
and needs them from food
Figure 9-30
Pathway for synthesis
of RNA, DNA
Fats
Phospholipids
Fatty acids
Glycogen
or starch
Glucose
Pyruvate
Acetyl CoA
GLYCOLYSIS
Lactate
(from fermentation)
KREBS
CYCLE
Several intermediates
used as substrates in
amino acid synthesis
Feedback Regulation
 When ATP drops, the cell works hard to
catabolize fats and carbohydrates to resupply the cell with ATP
 Respiration and heart rate increase to supply
more oxygen
 One enzyme in glycolysis,
Phosphofructokinase, is inhibited by ATP
and stimulated by AMP, so as ATP
accumulates, respiration slows
 It’s also sensitive to citrate from the Krebs
cycle, which allows the rates of glycolysis and
the Krebs cycle to synchronize
Figure 9-20
This step
is regulated
by ATP
These steps are
also regulated via
feedback inhibition,
by ATP and NADH
Citrate
Acetyl CoA
Oxaloacetate
Photosynthesis
 The process where autotrophs convert light
energy from the sun to chemical energy (in
carbohydrates) for the heterotrophs in the
food chain
 Is another redox process, like respiration,
and is responsible for carbon fixation
 Done exclusively in the chloroplast
 Thylakoids-membrane discs that are stacked in
grana (site of the 1st stage of photosynthesis)
 Stroma-fluid that surrounds thylakoids (site of
the 2nd stage of photosynthesis)
Figure 10-2
Leaves contain millions of chloroplasts.
Cell
Chloroplasts
Chloroplasts are highly structured, membrane-rich organelles.
Outer membrane
Inner membrane
Thylakoids
Granum
Stroma
The stages of Photosynthesis
 Light (dependent) Reactions (On the
Thylakoid membrane)
 Is an electron tranport chain that harnesses light
energy into ATP and Hydrogen carriers
 Involves photolysis of water and exciting
chlorophyll molecules
 Calvin Cycle (In the stroma)
 Also called the Dark reactions or LightIndependent Reactions
 This is where carbon fixation occurs and the
sugars are built
About Light and Pigments
 Light occurs in waves along an electromagnetic
spectrum
 Wavelength is the distance between crests of the
wave
 Visible light spectrum lies between 380 and 750 nm
and is responsible for color
 Light can be absorbed, reflected, or transmitted
 Pigments absorb light for photosynthesis, but absorb
best at different wavelengths, which broadens the
spectrum for ps.
 Chlorophyll a-primary pigment for photosynthesis
(blue green)
 Chlorophyll b-accessory pigment (olive green)
 Carotenoids-accessory pigment (yellow and orange)
Figure 10-4
Wavelengths (nm)
Gamma
UltraX-rays
rays
violet
Shorter
wavelength
Infrared
Visible light
Microwaves
Radio
waves
Longer
wavelength
nm
Higher
energy
Lower
energy
Figure 10-6a
Different pigments absorb different wavelengths of light.
Chlorophyll b
Chlorophylls absorb blue and red
light and transmit green light
Chlorophyll a
Carotenoids
Carotenoids absorb blue
and green light and
transmit yellow, orange,
or red light
The Light Reactions

Begins with the excitement of Chlorophyll by photons of light



Photosystem II




A protein complex (reaction center complex) that is surrounded light harvesting
complexes consisting of pigment molecules
As photons are absorbed in the light harvesting complex, the energy is transferred
from pigment to pigment until it reaches a pair of chlorophyll a molecules (P680)
within the reaction center complex
These pigments pass the excited electron to the primary e- acceptor
Photolysis occurs, splitting water to give off Oxygen gas, Hydrogen Ions,
and e-s




An electron gets raised from ground to excited state
Sometimes, with pigments, the e- drops back to ground and releases heat or light
(fluorescence)
The e-s are given to the P680+ pair
The buildup of H+ will eventually drive the synthesis of ATP, just as they did in
the ETC of respiration
The e-s pass through the P680 pair, to the e- acceptor, and then to an ETC to
Photosystem I
Photosystem I



Contains a pair of chlorophyll a called P700 that excite the e- and sends it through
another ETC
At the end of that ETC, NADP+ accepts the electrons to become NADPH
The ATP and NADPH formed here power the Calvin Cycle
Figure 10-11
FLUORESCENCE
or
Electron drops back down to
lower energy level; heat and
fluorescence are emitted.
RESONANCE
or
Energy in electron is transferred to nearby pigment.
Higher
REDUCTION/OXIDATION
Electron is transferred to
a new compound.
Electron
acceptor
Reaction
center
Photon
Photon
Fluorescence
e–
Heat
e–
Lower
Chlorophyll molecule
e–
Chlorophyll molecules in antenna complex
Reaction center
Figure 10-15
4e–
2 NADP+ + 2 H+
Higher
Pheophytin
4e
Ferredoxin
–
PQ
4 Photons
Cytochrome
complex
4 Photons
PC
ATP
produced via
proton-motive force
P680
Photosystem II
4e–
Lower
2 H2O
4 H+ + O 2
P700
Photosystem I
2 NADPH
Cyclic Electron Flow
 This is an alternate path for the light
reactions to take (in photsynthetic
bacteria that don’t have Photosystem
II)
 In this path, Photosystem I is used,
but not Photosystem II
Figure 10-16
e–
Higher
Ferredoxin
PQ
Photon
Cytochrome
complex
PC
ATP
produced via
proton-motive
force
Lower
P700
Photosystem I
The Calvin Cycle
 The ATP and NADPH generated by the Light Reactions
are used here in the stroma
 Occurs in 3 Phases
 Carbon Fixation-Carbon Dioxide is added to RuBP
(Ribulose Bisphosphate), a 5-carbon sugar. This is
catalyzed by RuBP carboxylase
 Reduction-Phosphates from ATP are attached to the
molecule from step 1 and electrons from NADPH are
donated, reducing the molecule to glyceraldehyde-3phosphate (G3P, PGAL), the sugar that will eventually
be converted to glucose (think of it as ½ of a glucose
molecule)
 Regeneration of RuBP-the remaining carbon
backbones are rearranged and phosphorylated by
ATP to form RuBP. This will allow the cycle to start
over again
Figure 10-19
The reaction occurs in a cycle.
The Calvin cycle has three phases.
Carbons are symbolized as
red balls to help you follow
them through the cycle
3 CO2
3 P
P
RuBP
All three phases of the
Calvin cycle take place in
the stroma of chloroplasts
Fixation: 3 RuBP + 3 CO2
Fixation of
carbon dioxide
P
3-phosphoglycerate
6 ATP
3 ATP
6 ADP + 6 Pi
Regeneration of
RuBP from G3P
6 3-phosphoglycerate
Reduction: 6 3-phosphoglycerate + 6 ATP + 6 NADPH
Regeneration: 5 G3P + 3 ATP
3 ADP + 3 Pi
6
6 G3P
3 RuBP
6
5 G3P
Reduction of
3-phosphoglycerate
to G3P
P
G3P
1 G3P
6 NADPH
6 NADP+ + 6 H+
Alternative Mechanisms of Carbon
Fixation


Evolved in plants living in hot, arid environments to help plants
conserve water
Most plants are C3 plants, b/c RuBP contains 3 Carbons




C4 Plants




On hot days, the Stomates are closed to prevent water loss, but this
means less Carbon Dioxide and less Photosynthesis
In that instance, plants switch to photorespiration, which fixes Oxygen
in place of CO2. This, however, is counterproductive as it consumes
ATP
A different mechanism is needed for plants that constantly live in hot
environments
These plants have bundle-sheath cells surrounding their veins
Calvin cycle only occurs in the bundle-sheath cells, but Carbon-fixation
occurs in the mesophyll cells, creating 4C compounds (by PEP
Carboxylase) that are fed to the bundle sheath cells and the Calvin
Cycle through the plasmodesmata
Bundle sheath cells release CO2 back to the mesophyll cells
CAM Plants



Exists in water-storning plants (succulents)
Plants open stomates at night and close them during the day (opposite
of other plants)
Carbon dioxide collected at night are stored as organic acids in a
process called crassulacean acid metabolism (CAM)
Figure 10-21
Leaf surfaces contain stomata.
Leaf surface
Guard cells Pore
Stoma
Carbon dioxide diffuses into leaves through stomata.
Interior of leaf
O2
H2O
Leaf surface
Photosynthetic Extracellular
cells
space
CO2
Stoma
Figure 10-23
C4 plant
Leaf surface
Mesophyll cells contains
PEP carboxylase
Bundle-sheath cells
contain rubisco
Vascular tissue
CO2
Mesophyll
cells
PEP
C4
cycle
C3
compound
C4 compound
Bundle-sheath
cells
CO2
Calvin
RuBP cycle
3PG
Sugar
Vascular
tissue
Figure 10-24
C4 plants
CO2 stored in one cell …
CO2
C4
cycle
Organic
acid
CAM plants
CO2 stored at night …
CO2
C4
cycle
Organic
acid
CO2
CO2
Calvin
cycle
Calvin
cycle
G3P
… and used in another.
G3P
… and used during the day.