Different Stars Give off Different types of light or Electromagnetic Waves

The color of plants depends on the spectrum of the star’s light, which astronomers can easily observe. (Our Sun is a type “G” star.)

Wavelength Is the distance between the crests of waves Determines the type of electromagnetic

energy

Is the entire range of electromagnetic energy, or radiation

The longer the wavelength the lower the energy associated with the wave.

Light is a form of electromagnetic energy, which travels in waves

When white light passes through a prism the individual wavelengths are separated out.

Light travels in waves Light is a form of radiant energy Radiant energy is made of tiny packets of

energy called photons The red end of the spectrum has the lowest

energy (longer wavelength) while the blue end is the highest energy (shorter wavelength).

The order of visible light is ROY-G-BIV This is the same order you will see in a

rainbow b/c water droplets in the air act as tiny prisms

Reflect – a small amount of light is reflected off of the leaf. Most leaves reflect the color green, which means that it absorbs all of the other colors or wavelengths.

Absorbed – most of the light is absorbed by plants providing the energy needed for the production of Glucose (photosynthesis)

Transmitted – some light passes through the leaf

Light

ReflectedLight

Chloroplast

Absorbedlight

Granum

Transmittedlight

Figure 10.7

Photosynthesis

includes

of

occur inoccurs in uses

to produce to produce

uses

Lightdependentreactions

Thylakoidmembranes Stroma NADPHATPLight

Energy

ATP NADPH O2 Chloroplasts Glucose

Lightindependent

reactions

Concept Map

Vein

Leaf cross section

Figure 10.3

Mesophyll

CO2 O2Stomata

Chloroplast

Mesophyll

5 µm

Outermembrane

IntermembranespaceInner

membrane

Thylakoidspace

ThylakoidGranumStroma

1 µm

Are located within the palisade layer of the leaf

Stacks of membrane sacs called Thylakoids Contain pigments on the surface

Pigments absorb certain wavelenghts of light

A Stack of Thylakoids is called a Granum

Are molecules that absorb light Chlorophyll, a green pigment, is the

primary absorber for photosynthesis There are two types of cholorophyll

Chlorophyll a Chlorophyll b

Carotenoids, yellow & orange pigments, are those that produce fall colors. Lots of Vitamin A for your eyes!

Chlorophyll is so abundant that the other pigments are not visible so the plant is green…Then why do leaves change color in the fall?

In the fall when the temperature drops plants stop making Chrlorophyll and the Carotenoids and other pigments are left over (that’s why leaves change color in the fall).

The absorption spectra of three types of pigments in chloroplasts

Three different experiments helped reveal which wavelengths of light are photosynthetically important. The results are shown below.

EXPERIMENT

RESULTSA

bso

rptio

n o

f lig

ht

by

chlo

rop

last

pig

me

nts

Chlorophyll a

(a) Absorption spectra. The three curves show the wavelengths of light best absorbed by three types of chloroplast pigments.

Wavelength of light (nm)

Chlorophyll b

Carotenoids

Figure 10.9

The action spectrum of a pigment Profiles the relative effectiveness of different

wavelengths of radiation in driving photosynthesis

Rat

e o

f ph

otos

ynth

esis

(mea

sure

d by

O2 r

elea

se)

Action spectrum. This graph plots the rate of photosynthesis versus wavelength. The resulting action spectrum resembles the absorption spectrum for chlorophyll a but does not match exactly (see part a). This is partly due to the absorption of light by accessory pigments such as chlorophyll b and carotenoids.

(b)

The action spectrum for photosynthesis Was first demonstrated by Theodor W.

Engelmann

400 500 600 700

Aerobic bacteria

Filamentof alga

Engelmann‘s experiment. In 1883, Theodor W. Engelmann illuminated a filamentous alga with light that had been passed through a prism, exposing different segments of the alga to different wavelengths. He used aerobic bacteria, which concentrate near an oxygen source, to determine which segments of the alga were releasing the most O2 and thus photosynthesizing most.Bacteria congregated in greatest numbers around the parts of the alga illuminated with violet-blue or red light. Notice the close match of the bacterial distribution to the action spectrum in part b.

(c)

Light in the violet-blue and red portions of the spectrum are most effective in driving

photosynthesis.

CONCLUSION

Similar- both have two peaks. For both graphs the peak is the higher in the blue end. Both have a valley in the green part of the spectrum.

Different- Chlorophyll B peaks more in blue, whereas chlorophyll a has its peak to the left in violet. (they are at different wavelengths of light)

(2) Any reasonable explanation accepted that connects to the data…Chlorophyll absorbs light in the red and blue ends of the light spectrum but not green. So green is reflected back to our eyes and that is what we see.

(2) reasonable explanation…Reflected and/or transmitted (goes through)

1. Explain why leaves are green. Begin your explanation with white light coming from the sun and ending in your eye. (4)White Light from the sun hits leaf all wavelengths (colors) absorbed but green green reflected to our eyes

X-axis: Wavelength (2) units: nanometers (1)

Y -axis: % absorption (2) Line graph for carotenoids (2) Appropriate title- Absorption of

carotenoids at various wavelengths in the visible light spectrum (2)

Molecules that absorb specific wavelengths of light Chlorophyll absorbs reds & blues and reflects

green Xanthophyll absorbs red, blues, greens &

reflects yellow Carotenoids reflect orange

Green pigment in plants Traps sun’s energy Sunlight energizes electron in chlorophyll

What is beta carotene? Where is it found? What does it do for plants? Why is it beneficial in a human diet? (4 extra credit)Beta-carotene is one of a group of natural chemicals known as carotenes or carotenoids. Carotenes are responsible for the orange color of many fruits and vegetables such as carrots, pumpkins, and sweet potatoes.Beta carotene is converted in the body to vitamin A. It is an antioxidant, like vitamins E and C.

Chlorophyll a Is the main photosynthetic pigment

Chlorophyll b Is an accessory pigment

C

CH

CH2

CC

CC

C

CNNC

H3C

C

CC

C C

C

C

C

N

CC

C

C N

MgH

H3C

H

C CH2CH3

H

CH3C

HHCH2

CH2

CH2

H CH3

C O

O

O

O

O

CH3

CH3

CHO

in chlorophyll a

in chlorophyll b

Porphyrin ring:Light-absorbing“head” of moleculenote magnesiumatom at center

Hydrocarbon tail:interacts with hydrophobicregions of proteins insidethylakoid membranes ofchloroplasts: H atoms notshown

Figure 10.10

Comes from Greek Word “photo” meaning “Light” and “syntithenai” meaning “to put together” Photosynthesis puts together sugar molecules

using water, carbon dioxide, & energy from light.

Light-Dependent Reaction Converts light energy into chemical energy

Light-Independent Reaction Produces simple sugars (glucose)

General Equation 6 CO2 + 6 H2O C6H12O6 + 6 O2

Requires Light = Light Dependent Reaction Sun’s energy energizes an electron in

chlorophyll molecule Electron is passed to nearby protein molecules

in the thylakoid membrane of the chloroplast

When a pigment absorbs light It goes from a ground state to an excited state,

which is unstable

Excitedstate

Ene

rgy

of e

lect

ion

Heat

Photon(fluorescence)

Chlorophyllmolecule

GroundstatePhoton

e–

Figure 10.11 A

If an isolated solution of chlorophyll is illuminated It will fluoresce, giving off light and heat

Figure 10.11 B

Electron from Chlorophyll is passed from protein to protein along an electron transport chain Electrons lose energy (energy changes form) Finally bonded with electron carrier called

NADP+ to form NADPH or ATP Energy is stored for later use

Photosystem II: Clusters of pigments boost e- by absorbing light w/ wavelength of ~680 nm

Photosystem I: Clusters boost e- by absorbing light w/ wavelength of ~760 nm.

Reaction Center: Both PS have it. Energy is passed to a special Chlorophyll a molecule which boosts an e-

A mechanical analogy for the light reactions

MillmakesATP

ATP

e–

e–e–

e–

e–

Pho

ton

Photosystem II Photosystem I

e–

e–

NADPH

Pho

ton

Figure 10.14 

A photosystem Is composed of a reaction center surrounded by

a number of light-harvesting complexes

Primary electionacceptor

Photon

Thylakoid

Light-harvestingcomplexes

Reactioncenter

Photosystem

STROMAT

hyla

koid

mem

bran

e

Transferof energy

Specialchlorophyll amolecules

Pigmentmolecules

THYLAKOID SPACE(INTERIOR OF THYLAKOID)Figure 10.12

e–

Water Electrons from the splitting of water

(photolysis) supply the chlorophyll molecules with the electrons they need

The left over oxygen is given off as gas

The Splitting of Water• Chloroplasts split water into

– Hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules

6 CO2 12 H2OReactants:

Products: C6H12O66 H2O 6 O2

Figure 10.4

Photolysis – Splitting of water with light energy

Hydrogen ions (H+) from water are used to power ATP formation with the electrons

Hydrogen ions (charged particle) actually move from one side of the thylakoid membrane to the other

Chemiosmosis – Coupling the movement of Hydrogen Ions to ATP production

Animation – takes a min. to load…be patient

Animation II – Does not take as long to load but it is not as good

The light reactions and chemiosmosis: the organization of the thylakoid membrane

LIGHTREACTOR

NADP+

ADP

ATP

NADPH

CALVINCYCLE

[CH2O] (sugar)STROMA(Low H+ concentration)

Photosystem II

LIGHT

H2O CO2

Cytochromecomplex

O2

H2O O21

1⁄2

2

Photosystem ILight

THYLAKOID SPACE(High H+ concentration)

STROMA(Low H+ concentration)

Thylakoidmembrane

ATPsynthase

PqPc

Fd

NADP+

reductase

NADPH + H+

NADP+ + 2H+

ToCalvincycle

ADP

PATP

3

H+

2 H++2 H+

2 H+

Figure 10.17

Light-Dependent Pigment Chlorophyll Electron Transport Chain ATP NADPH Photolysis Chemiosmosis

MillmakesATP

ATP

e–

e–e–

e–

e–

Pho

ton

Photosystem II Photosystem I

e–

e–

NADPH

Pho

ton

Figure 10.14 

Converts light into chemical energy (ATP & NADPH are the chemical products). Oxygen is a by-product

Series of Proteins embedded in a membrane that transports electrons to an electron carrier

Adenosine Triphosphate Stores energy in high energy bonds

between phosphates

Made from NADP+; electrons and hydrogen ions

Made during light reaction Stores high energy electrons for use

during light-Independent reaction (Calvin Cycle)

The combination of moving hydrogen ions across a membrane to make ATP

H2O CO2

Light

LIGHT REACTIONS

CALVINCYCLE

Chloroplast

[CH2O](sugar)

NADPH

NADP

ADP

+ P

O2Figure 10.5

ATP

LIGHT INDEPENDENT REACTION Also called the Calvin Cycle No Light Required Takes place in the stroma of the chloroplast Takes carbon dioxide & converts into sugar It is a cycle because it ends with a chemical

used in the first step

The Calvin Cycle begins and ends with RuBP

CO2 is added to RuBP; “fixing” the CO2 in a compound

One compound made along the way is PGAL PGAL can be made into sugars or RuBP Calvin Cycle uses ATP & NADPH

The Calvin cycle

(G3P)

Input(Entering one

at a time)CO2

3

Rubisco

Short-livedintermediate

3 P P

3 P P

Ribulose bisphosphate(RuBP)

P

3-Phosphoglycerate

P6 P

6

1,3-Bisphoglycerate

6 NADPH

6 NADPH+

6 P

P6

Glyceraldehyde-3-phosphate(G3P)

6 ATP

3 ATP

3 ADP CALVINCYCLE

P5

P1

G3P(a sugar)Output

LightH2O CO2

LIGHTREACTION

ATP

NADPH

NADP+

ADP

[CH2O] (sugar)

CALVINCYCLE

Figure 10.18

O2

6 ADP

Glucose andother organiccompounds

Phase 1: Carbon fixation

Phase 2:Reduction

Phase 3:Regeneration ofthe CO2 acceptor(RuBP)

Chloroplast – Where the Magic Chloroplast – Where the Magic Happens!Happens!

HH22OO COCO22

OO22 CC66HH1212OO66

Light Light ReactionReaction

Dark ReactionDark Reaction

Light is AdsorbedLight is AdsorbedBy By

ChlorophyllChlorophyll

Which splitsWhich splitswaterwater

ChloroplastChloroplast

ATP andATP andNADPHNADPH22

ADPADPNADPNADP

Calvin CycleCalvin Cycle

EnergyEnergy

Used Energy and is Used Energy and is recycled.recycled.

++

++

6 CO2 + 12 H2O + Light energy C6H12O6 + 6 O2 + 6 H2 O