You should now be able to

Chapter 10 Photosynthesis1. Describe the structure of a chloroplast
2. Describe the relationship between an action
spectrum and an absorption spectrum
3. Trace the movement of electrons in linear electron
flow
flow
oxidative phosphorylation in mitochondria and
photophosphorylation in chloroplasts
6. Describe the role of ATP and NADPH in the Calvin
cycle
producers of biosphere Autotrophs () “self feeders” make
their own food. Autotrophs sustain
themselves without eating anything derived
from other organisms.
molecules
carbon
the biosphere.
• stomata: ()pores in leaf (CO2 enter/O2
exits)
Chloroplasts (): sites of
mesophyll, the interior tissue (layers) of the
leaf.
chloroplasts
membranes of thylakoids (connected sacs);
thylakoids may be stacked in columns called
grana.
fluid region.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Chloroplasts
Light Reactions convert Solar Energy to the Chemical Energy of ATP and NADPH
• Chloroplasts are solar-
powered chemical factories.
• Their thylakoids transform
NADPH.
1 µm
• Photosynthesis consists of the light reactions (the photo
part) and Calvin cycle (the synthesis part)
• The light reactions (in the thylakoids):
– Split H2O
– Release O2
• The Calvin cycle (in the stroma) forms sugar from CO2,
using ATP and NADPH
incorporating CO2 into organic molecules
Reactants:
Products:
Evidence that chloroplasts split water molecules
enabled researchers to track atoms through
photosynthesis (C.B. van Niel)
“photo” “synthesis”
also called electromagnetic radiation.
in rhythmic waves.
waves.
electromagnetic energy.
• The electromagnetic spectrum is the
entire range of electromagnetic energy, or
radiation.
that produce colors we can see.
• Light also behaves as though it consists of
discrete energy particles, called photons.
Photosynthetic Pigments: The Light Receptors
• Pigments are substances that absorb
visible light.
reflected or transmitted.
reflects green light. We see reflected
light. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Nature of sunlight
Visible light - detected by human eye
Light: reflected, transmitted or absorbed
Electromagnetic Spectrum
wavelengths.
pigments and measures the fraction of
light transmitted at each wavelength.
• Transmitted light is light that is not
absorbed.
• An absorption spectrum is a graph plotting a
pigment’s light absorption vs. wavelength.
• The absorption spectrum of chlorophyll a suggests
that violet-blue and red light work best for
photosynthesis.
of different wavelengths of radiation in driving a
process such as photosynthesis.
the spectrum used for photosynthesis.
• Accessory pigments called carotenoids absorb
excessive light that would damage chlorophyll.
Pigments absorb different λ of light
chlorophyll – absorb violet-blue/red light, reflect
green
chlorophyll b (yellow-green): conveys E to
chlorophyll a
Types: xanthophyll (yellow) & carotenes
antioxidants
• When a pigment absorbs light, it goes
from a ground state to an excited state,
which is unstable.
afterglow called fluorescence.
and heat.
Electrons in chlorophyll molecules are excited by absorption of light
Apply Leaf Pigments to Chromatography Paper
Paper Chromatography
Warm-Up 1. What pigments are found in spinach leaves?
2. Based on the color of the pigments, what wavelengths of visible light are absorbed by each of these pigments? (see Figure 10.7 in textbook for help)
Which wavelengths of light are best absorbed by each pigment shown in the graph?
A Photosystem: A Reaction-Center Complex Associated with Light-Harvesting Complexes
• A photosystem consists of a
reaction-center complex (a type of
protein complex) surrounded by light-
harvesting complexes.
to the reaction center.
chloroplasts split H2O into hydrogen and
oxygen.
chloroplasts incorporate the hydrogen
• Photosynthesis is a redox process in
which H2O is oxidized to O2 and CO2 is
reduced to C6 H12 O6
The Two Stages of Photosynthesis: A Preview
• Photosynthesis consists of the light
reactions (the photo part) and Calvin
cycle (the synthesis part)
– Split H2O
– Release O2
Linear Electron Flow: Non-Cyclic Flow is Normal.
• During the light reactions, there are two possible routes for electron flow: cyclic and linear (non-cyclic).
• Linear electron flow, non-cyclic
Non-cyclic flow involves both
ATP and NADPH using light energy.
1. Chlorophyll excited by light absorption
2. E passed to reaction center of Photosystem II
(protein + chlorophyll a)
• Redox reaction → e- transfer
state)
Two routes for electron flow:
A. Linear (noncyclic) electron flow
B. Cyclic electron flow
7. ATP produced by photophosphorylation
8. e- moves from PS I’s primary electron
acceptor to 2nd ETC
• ATP and NADPH are produced on the
side facing the stroma where the Calvin
cycle takes place.
ATP and increase the potential energy
of electrons by moving them from H2O
to NADPH.
in the Light Reactions.
A Comparison of Chemiosmosis in
Chloroplasts and Mitochondria • Chloroplasts and mitochondria generate ATP by chemiosmosis,
but use different sources of energy
• Mitochondria transfer chemical energy from food to ATP;
chloroplasts transform light energy into the chemical energy of
ATP
chloroplasts and mitochondria but also shows similarities
• In mitochondria, protons are pumped to the intermembrane
space and drive ATP synthesis as they diffuse back into the
mitochondrial matrix
• In chloroplasts, protons are pumped into the thylakoid space
and drive ATP synthesis as they diffuse back into the stroma
© 2011 Pearson Education, Inc.
(1) H+ from water
(3) Removal of H+ from stroma when NADP+ is reduced
A Comparison of Photo and Oxidative Phosphorylation
Similarities: Both use
1. Chemiosmotic processes –
2. Both use similar electron carriers such as
cytochromes
4. Both use ATP synthase to produce ATP
from ADP
2) H+ pumped OUT into H+ pumped INTO
the intermembrane lumen of thylakoid
space
4) Final e- acceptor is O2 final e- acceptor is
NADP+
I and produces ATP, but not NADPH
• No oxygen is released
satisfying the higher demand in the Calvin
cycle.
() forms sugar from CO2, using ATP and
NADPH
fixation, incorporating CO2 into organic
molecules
• Carbon enters the cycle as CO2 and leaves as a
sugar named glyceraldehyde-3-phospate (G3P)
• For net synthesis of 1 G3P, the cycle must take
place three times, fixing 3 molecules of CO2
• The Calvin cycle has three phases:
– Carbon fixation (CO2 attaches to RuBP
catalyzed by rubisco)
– Reduction “sugar making”
Concept 10.3: The Calvin cycle uses the chemical
energy of ATP and NADPH to reduce CO2 to sugar • The Calvin cycle, like the citric acid cycle, regenerates its
starting material after molecules enter and leave the cycle
• The cycle builds sugar from smaller molecules by using ATP
(ANABOLIC!) and the reducing power of electrons carried by
NADPH
• Carbon enters the cycle as CO2 and leaves as a sugar named
glyceraldehyde 3-phospate (G3P)
• For net synthesis of 1 G3P, the cycle must take place three
times, fixing 3 molecules of CO2
• The Calvin cycle has 3 phases:
1. Carbon fixation (catalyzed by rubisco)
2. Reduction
© 2011 Pearson Education, Inc.
Figure 10.UN07
Figure 10.UN05
gets stored as chemical energy in organic
compounds
• Plants store excess sugar as starch in
structures such as roots, tubers, seeds, and
fruits
produces the O2 in our atmosphere and
removes CO2!
Photorespiration ()
→ breakdown of RuBP)
stomata close (conserve H2O)
CO2?
Photosynthesis
Light
Reaction
Light
ENERGY
H2O
split
organic
molecules
O2
evolved
ETC
regenerate
RuBP
photophosphorylation
• Photosynthesis is highly endergonic.
• Cell resp is exergonic.
electron flow.
electron/H+ carrier molecule. Cell resp
uses NAD+. NAD has one less
phosphate group.
Now hit them with light…what happens?
However, this is only an INDIRECT method of measuring CO2 rate…why?
They will float after some amount of time because O2 is being produced by photosynthesis.
Cell Respiration is occurring, using some of the O2 and producing CO2 gas as so you are

You should now be able to

Documents

Transcript of You should now be able to