07 Photosynthesis

7/31/2019 07 Photosynthesis

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Chapter 7 Photosynthesis: Seven things to know

1. General chemical equation (7.3-7.4)

2. Part of the plant cell involved (7.2)

3. Photosynthesis is composed of 2 processes (7.5)

4. General description of light reaction (7.6-7.9)

5. General description of Calvin cycle (7.10)

6. Importance of ATP and NADPH (7.11)

7. Alternate pathways (7.12)


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Common theme in biology:

Energy processingAcquiring energy andtransforming it to a formuseful for the organism

Energy: the ability to doWork

*Photosynthesis*Cellular Respiration


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3Photosynthetic Organisms are autotrophs/producers

What do plants need to survive?

What are the REACTANTS forphotosynthesis?


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I. General chemical equation

Photosynthesis: Sun energy to chemical energy

Is this process exergonic or endergonic?


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II. Parts of plant cell involved

CO2 enters leaf through stomata

Light is absorbed through the green portions of plants leaves

Mesophyll tissue

Tissue composed ofcells containing chloroplasts

Chloroplasts contain chlorophyll pigment

How about

H2O?


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Cell


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8


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9Photosynthesis Overview


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Place the following terms in the correct order fromBIGGEST to SMALLEST

Thlakoid

Cell

Chloroplast

Mesophyll Tissue

Chlorophyll


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III. Photosynthesis is composed of 2 processes

Light Reaction:

Use light energy to split water; make NADPH and

ATP

Calvin Cycle Reaction:

Incorporate light reaction products; change CO2 toG3P to make glucose


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Oxidation-Reduction

Oxidation-reduction (redox) reactions:

LEO says GER

Lose Electrons = Oxidation

Gain Electrons = Reduction

Both take place at same time

One molecule accepts the electron given up by the other

GER!


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13REDOX Reactions

Transfer ofelectron

NaSodium atomIs oxidized

ClChlorine atomIs reduced

Na+Sodium ion

ClChloride ion

Na Cl ClNa

+

GER!


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14

NADPH

Nicotinamide Adenine Dinucleotide Phosphate

Electron Carrier

Coenzyme

NADP+

+ H+

NADPH


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IV. General description of light reaction

1. Capture light energy in the form of a photon withchlorophyll pigmentand excite electron inphotosystem

2. Water splits to replace lost electrons

3. Transfer electron to electron transport chain (ETC)

4. Creation of H+ concentration gradient

5. NADP+ is reduced to NADPH

6. ATP generated with ATP Synthase


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Light

Chloroplast

Thylakoid

Absorbedlight

Transmitted

light

Reflectedlight


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171. Capture light energy in the form of a photon by pigments


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Chlorophyll

molecule

Excited state

Ground state

Heat

Photon Photon(fluorescence)

e

Is NADP+


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+

O2H2O

12 H

+

NADP+ H+ NADPH

+ 2

H+

H+

H+ H+

H+

H+

H+

H+

H+H+

H+

H+

H+H+

ATP synthase

LightLight

Stroma (low H+concentration)

Thylakoid space(high H+ concentration)

ADP + P ATP

1. Capture light energy

2. Water splits and

releases electron

3. Pass electron down ETC

4. Create H+ gradient

5. NADPH produced

6. ATP produced

Is H2O oxidized

or reduced?

Is NADP+oxidized orreduced?


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What have we done so far?


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V. General description of Calvin Cycle (aka DarkReaction, Light Independent)

1. Carbon fixation of CO2 and cycling of variouscarbon products

2. Use of light reaction products (NADPH & ATP)

3. Production of G3P (glyceraldehade-3-phosphate)to make glucose

22The Cal in C cle:


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22The Calvin Cycle:Fixation of CO2

1. CO2 fixation

2. Use of lightreaction products

3. Make G3P glucose


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NADPH

ATP

RuBP

3

P

G3P

P

Input:

CO2

1

Rubisco

3 P

Step Carbon fixation

3-PGA6 P

CALVINCYCLE

6

6

6

6

P

Step Reduction

2

2

G3P

5 P

3

3

G3P

1 PGlucoseand other

compounds

Output:

Step Release of one

molecule of G3P

1

Step Regeneration of RuBP4

4ATP3

3 ADP

NADP+

6 ADP +


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Importance of Calvin Cycle

G3P (glyceraldehyde-3-phosphate) can be convertedto many other molecules

Glucose phosphate (simple sugar)

Fatty acids and glycerol to make plant oils

Fructose (which with glucose = sucrose)

Starch and cellulose

Amino acids


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General chemical equation

6CO2 + 6H2OSolar energy C6H12O6 + 6O2 (+686 kcal/mol)

Reduced

Oxidized

VI Importance of NADPH and ATP


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H2O

NADP+

ADP

P

LIGHTREACTIONS

(in thylakoids)

Light

Chloroplast

VI. Importance of NADPH and ATP

VI Importance of NADPH and ATP


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H2O

ADP

P

LIGHTREACTIONS

(in thylakoids)

Light

Chloroplast

NADPH

ATP

O2

NADP+

VI. Importance of NADPH and ATP


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H2O

ADP

P

LIGHTREACTIONS

(in thylakoids)

Light

Chloroplast

NADPH

ATP

O2

CALVINCYCLE(in stroma)

Sugar

CO2

NADP+


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VII. Alternate pathways

Photorespiration: A wasteful process that producesno ATP or sugars

Occurs in hot, dry climates

Stomata must close to avoid wilting

CO2 decreases and O2 increases


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VII. Alternate pathways to avoid photorespiration

C4 plants

Examples: corn, sugarcane

Fix CO2 with alternate carbon molecule in different types ofcells

Net productivity about 2-3 times C3 plants

Crassulacean-Acid Metabolism (CAM)

Examples: cacti, jade plants, pineapplePartition carbon fixation by time of day

31Chloroplast distribution in


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31Chloroplast distribution inC4 vs. C3 Plants

32CO Fixation in a


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32CO2 Fixation in aCAM Plant

Y h ld b bl t


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You should now be able to

1. Explain the general chemical equation

1. Recognize and define reduction and oxidation equations

2.. Identify the parts of the plant cell involved

3. Identify the 2 processes/stages of photosynthesis and

where each occurs4. Generally describe the events of the Light Reaction

5. Generally describe the events of the Calvin cycle

6. Explain the importance of ATP and NADPH

7. Describe photorespiration and the need for alternatepathways

Copyright 2009 Pearson Education, Inc.

34


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34Photosynthesis

(a)

(b) (c)

(d) (h)

(e)(f)

(g)

chemiosmosis

sugar(G3P)

by C6H12O6

to produce

using

reduceNADP+ to

are passeddown

and and then

H2O is split

light-excitedelectrons ofchlorophyll

CO2 is fixed toRuBP

in whichin which

to

chemicalenergy

converts

includes both

producing

Sunenergy Light

ReactionCalvinCycle

The

electrontransportchain

NADPH

Splits to 3 Cmolecule

ATP

O2 isformed

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35

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07 Photosynthesis

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