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The summary equation of photosynthesis including the

source and fate of the reactants and products.

How leaf and chloroplast anatomy relates to

photosynthesis.

How photosystems convert solar energy to chemical

energy.

How linear electron flow in the light reactions results in

the formation of ATP, NADPH, and O2.

How chemiosmosis generates ATP in the light reactions.

How the Calvin Cycle uses the energy molecules of the

light reactions to produce G3P.

The metabolic adaptations of C4 and CAM plants to arid,

dry regions.

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Chloroplasts

• _________________

• _________________

fluid-filled interior

• _________________

• _________________

Thylakoid membrane contains

• chlorophyll molecules

• electron transport chain

• ATP synthase

H+ gradient built up within

thylakoid sac

H+H+

H+

H+

H+H+

H+H+

H+H+

H+

outer membrane inner membrane

thylakoidgranum

stroma

thylakoid

chloroplast

ATP

Plants and other autotrophs are

producers of biosphere

____________________: use light E to

make organic molecules

____________________: consume organic

molecules from other organisms for E

and carbon

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________________: sites of photosynthesis

in plants

Thylakoid space

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Sites of Photosynthesis

• _______________: chloroplasts mainly found in these cells of leaf

• ____________: pores in leaf (CO2 enter/O2 exits)

• ____________: green pigment in _____________ membranes of chloroplasts

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6CO2 + 6H2O + Light Energy C6H12O6 + 6O2

____________ Reaction:

_______ is split ___ transferred with H+ to ____ sugar

Remember: OILRIG

Oxidation: lose e-

Reduction: gain e-

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Reactants:

Products:

6 CO2 12 H2O

C6H12O6 6 H2O 6 O2

Evidence that chloroplasts split water molecules

enabled researchers to track atoms through

photosynthesis (C.B. van Niel)

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“photo” “synthesis”

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Nature of sunlight

Light = Energy = ______________ radiation

__________ wavelength (λ): ____________ E

Visible light - detected by human eye

Light: reflected, transmitted or absorbed

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_______________________ like in cellular respiration

• proteins in organelle membrane

• __________________

______________

• proton (H+)

gradient across

inner membrane find the double membrane!

• ATP synthase

enzyme

H+H+

H+H+

H+H+

H+H+

H+H+

H+

H+H+

H+H+

H+H+

H+H+

H+H+

H+ATP

thylakoidchloroplast

Mitochondria transfer chemical energy from food molecules

into chemical energy of ATP

use electron carrier ___________

ETC of Respiration

generate H2O

ETC of Photosynthesis Chloroplasts transform light energy

into chemical energy of ATP

use electron carrier ___________

generate O2

moves the electrons

runs the pump

pumps the protons

builds the gradient

drives the flow of protons

through ATP synthase

bonds Pi to ADP

generates the ATP

… that evolution built

sunlight breakdown of C6H12O6

respirationphotosynthesis

H+

ADP + Pi

H+H+

H+

H+ H+

H+H+

H+

ATP

Chlorophylls & other pigments

• embedded in thylakoid membrane

• arranged in a “photosystem” collection of molecules

• structure-function relationship

How does thismolecular structurefit its function?

The spectrum of color

ROYGBIV

Interaction of light with chloroplasts

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Pigments absorb different λ of light

chlorophyll – absorb violet-blue/red light,

reflect green

chlorophyll ___ (blue-green): light reaction,

converts solar to chemical E

chlorophyll ___ (yellow-green): conveys E to

chlorophyll a

_______________ (yellow, orange): photoprotection,

broaden color spectrum for photosynthesis

Types: xanthophyll (yellow) & carotenes (orange)

_______________ (red, purple, blue):

photoprotection, antioxidants19

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1. Which color/wavelength of light provides the MOST energy to plants?

2. Why do most pigments have greater absorbance of shorter wavelengths of light

vs. longer wavelengths?

3. Why would a plant not have pigments to capture ALL wavelengths of light?

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4. Why do most plants appear green?

5. If a plant contained mostly carotenoids, what color would you expect

them to appear?

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Action Spectrum: plots rate of photosynthesis vs. wavelength

(absorption of chlorophylls a, b, & carotenoids combined)

Engelmann: used bacteria to measure rate of photosynthesis in algae; established action spectrum

Which wavelengths of light are most effective in driving photosynthesis?

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Photosystems of photosynthesis

• 2 photosystems in thylakoid membrane– collections of chlorophyll molecules

– act as light-gathering molecules

– _________________• __________________

• P680 = absorbs 680nm wavelength red light

– _________________• __________________

• P700 = absorbs 700nm wavelength red light

reaction

center

antenna

pigments

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Summary:

1. Light energy splits ______ to _____

releasing high energy electrons (e-)

2. Movement of e- used to generate ______

3. Electrons end up on NADP+, reducing it

to ________________

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Electrons in chlorophyll molecules are excited by absorption of light

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Photosystem: reaction center & light-harvesting complexes (__________ + ___________)

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Two routes for electron flow:

A. __________ (noncyclic) electron flow

B. __________ electron flow

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1. Chlorophyll excited by light absorption

2. E passed to reaction center of

_______________(protein + chlorophyll __)

3. e- captured by _________________________

• Redox reaction e- transfer

• e- prevented from losing E (drop to

ground state)

4. ______is split to replace e- ___ formed

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5. e- passed to __________________ via ___

6. E transfer pumps ___ to thylakoid space

7. _____ produced by ___________________

8. e- moves from PS I’s primary electron

acceptor to 2nd ETC

9. NADP+ reduced to NADPH

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Mechanical analogy for the light reactions33

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Proton motive force generated by:

(1) H+ from water

(2) H+ pumped across by cytochrome

(3) Removal of H+ from stroma when NADP+ is reduced

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Occurs in the ____________

Uses ____, ________, _______

Produces 3-C sugar ________

(glyceraldehyde-3-phosphate)

Three phases:

1. ___________ fixation

2. Reduction

3. Regeneration of _____ (CO2 acceptor)

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Phase 1: 3 CO2 + ________ (5-C sugar ribulose bisphosphate)• Catalyzed by enzyme ______________ (RuBPcarboxylase)

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Phase 2: Use ______ and ________to produce 1 net ____

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Phase 3: Use _______to regenerate _______

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Alternative mechanisms of carbon fixation have evolved in hot, arid climates

Problem for C3 plants

• Hot or dry days

– _________________________________

– _______________

• gain H2O = stomates open

• lose H2O = stomates close

– adaptation to living on land, but…

creates PROBLEMS! 42

When stomates close…

xylem

(water)

phloem

(sugars)

H2OO2 CO2

CO2

O2

• Closed stomates lead to…

– ______build up from light reactions

– ______is depleted in Calvin cycle

• causes problems in Calvin Cycle

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Photorespiration

• Metabolic pathway which:

– Uses _____ & produces _____

– Uses ATP

– No ____________ production (rubisco binds ______ breakdown of RuBP)

• Occurs on hot, dry bright days when stomata close (conserve H2O)

• Why? Early atmosphere: low O2, high CO2?

Alternative mechanisms of carbon fixation have evolved in hot, arid climates

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Evolutionary Adaptations

1. Problem with C3 Plants:

– CO2 fixed to 3-C compound in Calvin cycle

– Ex. Rice, wheat, soybeans

– Hot, dry days:

» partially close stomata, _____CO2

» ____ Photorespiration

» ____photosynthetic output (no sugars made)

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Evolutionary Adaptations

2. C4 Plants:

– CO2 fixed to 4-C compound

– Ex. corn, sugarcane, grass

– Hot, dry days stomata close

– 2 cell types = ____________ & _________________cells

» mesophyll : _______________________fixes CO2 (4-C), pump CO2 to bundle sheath

» bundle sheath: CO2 used in Calvin cycle

– 2 stages of photosynthesis are _________________ separated

– ____photorespiration, ____sugar production

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C4 Leaf Anatomy

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3. CAM Plants:

• Crassulacean acid metabolism (CAM)

• NIGHT: stomata open CO2 enters converts to

________________, stored in ________________ cells

• DAY: stomata _______ light reactions supply ATP,

NADPH; CO2 released from organic acids for

Calvin cycle

• Ex. cacti, pineapples, succulent (H2O-storing)

plants

• 2 stages of photosynthesis are ___________________

separated

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C3 C4 CAM

C fixation &

Calvin together

C fixation &

Calvin in different

______

C fixation &

Calvin at different

_________

Rubisco PEP carboxylase Organic acid

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Plant:• ____________ for respiration

• Cellulose

Global:• ______ Production

• ______ source

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Photosynthesis

Light

Reaction

Light

ENERGY

______

split

organic

molecules

____

released

____

regenerate

________

photophosphorylation

ATP_____________

energized

electrons

Calvin

Cycle

________

______

fixed to

RuBP

C3

phosphorylated

and reduced

G3P

________

& other

carbs

stored in in which

involves both

Reduce

NADP+ to

using

in process

called

to form

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RESPIRATION PHOTOSYNTHESIS

Plants + Animals

Needs O2 and food

Produces CO2, H2O and

ATP, NADH

Occurs in mitochondria

membrane & matrix

Oxidative phosphorylation

Proton gradient across

membrane

Plants

Needs CO2, H2O, sunlight

Produces glucose, O2 and

ATP, NADPH

Occurs in chloroplast

thylakoid membrane &

stroma

Photorespiration

Proton gradient across

membrane

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