Bài 21. Quang hợp

Chapter 7 Photosynthesis: Seven things to know
1. General chemical equation (7.3-7.4)
2. Part of the plant cell involved (7.2)
Photosynthesis is composed of 2 processes (7.5)
General description of light reaction (7.6-7.9)
General description of Calvin cycle (7.10)
Importance of ATP and NADPH (7.11)
Alternate pathways (7.12)
Common theme in biology:
Energy processing


Acquiring energy and
transforming it to a form
useful for the organism

Energy: the ability to do
Work


*Photosynthesis

*Cellular Respiration
3
Photosynthetic Organisms are autotrophs/producers
What do plants need to survive?
What are the REACTANTS for photosynthesis?
I. General chemical equation
Photosynthesis: Sun energy to chemical energy
Is this process exergonic or endergonic?
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 of cells containing chloroplasts
Chloroplasts contain chlorophyll pigment



How about H2O?
Cell
8
9
Photosynthesis Overview
Place the following terms in the correct order from BIGGEST to SMALLEST
Thlakoid
Cell
Chloroplast
Mesophyll Tissue
Chlorophyll
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 to G3P to make glucose
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!
13
REDOX Reactions
GER!
14
NADPH

Nicotinamide Adenine Dinucleotide Phosphate

Electron Carrier

Coenzyme

NADP+ + H+  NADPH

IV. General description of light reaction
Capture light energy in the form of a photon with chlorophyll pigment and excite electron in photosystem
Water splits to replace lost electrons
3. Transfer electron to electron transport chain (ETC)
4. Creation of H+ concentration gradient
NADP+ is reduced to NADPH
ATP generated with ATP Synthase
Light
Chloroplast
Thylakoid
Absorbed
light
Transmitted
light
Reflected
light
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Capture light energy in the form of a photon by pigments
Chlorophyll
molecule
Excited state
Ground state
Heat
Photon
Photon
(fluorescence)
e–
+
O2
H2O
1

2
H+
NADP+
H+
NADPH
+ 2
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
H+
ATP synthase
Light
Light
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 or reduced?
What have we done so far?
V. General description of Calvin Cycle (aka Dark Reaction, Light Independent)
Carbon fixation of CO2 and cycling of various carbon products
Use of light reaction products (NADPH & ATP)
Production of G3P (glyceraldehade-3-phosphate) to make glucose


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The Calvin Cycle:
Fixation of CO2
1. CO2 fixation
2. Use of light reaction products
3. Make G3P  glucose
NADPH
ATP
RuBP
3
P
G3P
P
Input:
CO2
1
Rubisco
3
P
Step Carbon fixation
3-PGA
6
P
CALVIN
CYCLE
6
6
6
6
P
Step Reduction
2
2
G3P
5
P
3
3
G3P
1
P
Glucose
and other
compounds
Output:
Step Release of one
molecule of G3P
1
Step Regeneration of RuBP
4
4
ATP
3
3 ADP
NADP+
6 ADP +
Importance of Calvin Cycle
G3P (glyceraldehyde-3-phosphate) can be converted to 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
General chemical equation
Reduced
Oxidized

H2O
NADP+
ADP
P
LIGHT
REACTIONS
(in thylakoids)
Light
Chloroplast
VI. Importance of NADPH and ATP
H2O
ADP
P
LIGHT
REACTIONS
(in thylakoids)
Light
Chloroplast
NADPH
ATP
O2

NADP+
VI. Importance of NADPH and ATP
H2O
ADP
P
LIGHT
REACTIONS
(in thylakoids)
Light
Chloroplast
NADPH
ATP
O2
CALVIN
CYCLE
(in stroma)
Sugar
CO2

NADP+
VII. Alternate pathways
Photorespiration: A wasteful process that produces no ATP or sugars

Occurs in hot, dry climates
Stomata must close to avoid wilting
CO2 decreases and O2 increases

VII. Alternate pathways to avoid photorespiration

C4 plants
Examples: corn, sugarcane
Fix CO2 with alternate carbon molecule in different types of cells
Net productivity about 2-3 times C3 plants

Crassulacean-Acid Metabolism (CAM)
Examples: cacti, jade plants, pineapple
Partition carbon fixation by time of day



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Chloroplast distribution in
C4 vs. C3 Plants
32
CO2 Fixation in a
CAM Plant
You should now be able to
Explain the general chemical equation
Recognize and define reduction and oxidation equations
2.. Identify the parts of the plant cell involved
Identify the 2 processes/stages of photosynthesis and where each occurs
Generally describe the events of the Light Reaction
Generally describe the events of the Calvin cycle
Explain the importance of ATP and NADPH
Describe photorespiration and the need for alternate pathways

Copyright © 2009 Pearson Education, Inc.
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Sun energy
Light Reaction
Calvin Cycle
The electron transport chain
NADPH
Splits to 3 C molecule
ATP
O2 is formed
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http://www.youtube.com/watch?v=Q_1mxZdF2TY&feature=related

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