Photosynthesis Chapter 7. Environment as a System Observations: Energy flows from sun to earth...
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Transcript of Photosynthesis Chapter 7. Environment as a System Observations: Energy flows from sun to earth...
Photosynthesis
Chapter 7
Environment as a System
• Observations:• Energy flows
• from sun to earth
• Matter cycles• within the four
spheres of earth
• Energy - the capacity to do work• Matter - everything that takes up space and has mass
Energy QualityLow Quality Energy
• Diffused, dispersed, or low in temperature• Difficult to gather and use for productive purposes• Example: heat stored in the oceans
High Quality Energy• Intense, concentrated, or high in temperature• Useful in carrying out work• Example: high-voltage electrical energy
Many of our most common energy sources are low-quality and must be concentrated or transformed into high-quality sources before they are useful to us.
The Energy “Rules”
• The first law of thermodynamics • energy cannot be created or destroyed, but can just
be transformed
• The second law of thermodynamics • when energy is transformed from one kind to
another, it is degraded; thus less energy is available to do work.
• recognizes the principle of entropy - the tendency of all natural systems to go from a state of order toward a state of increasing disorder
• Some energy transformations are more efficient than others, but none are 100% efficient.
The Carbon Cycle
2-5
http://cdiac.esd.ornl.gov/Carbon Dioxide Information Analysis Center
How well does CO2 predict global temperature?
Earth’s Energy Source
• Sun’s Reactions• gravity of sun pulls hydrogen gases
together• with increased pressure, heat, &
density, hydrogen atoms fuse together• Nuclear Fusion
• 4H --> He + particles + ENERGY• Energy emitted as
• Electromagnetic Radiation• transmitted in various wavelengths
Radiation Emitted by the Sun
Electromagnetic Radiation (from Sun)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Gammarays
Long wavelengths
Radio waves
0.01 nm 10 cm
Radi
ation
inte
nsity
Short wavelengths
X rays Ultraviolet
Visiblelight
0.4 μm 0.7 μm
Infrared
Terrestrial radiation(exaggerated about 100,000 ×)
Microwaves
0.1 nm 1 nm 10 nm 0.1 μm 1 μm 10 μm 100 μm 1 mm 1 cm
Wavelength
Solar radiation
Two ways to view this question:1. Absorption spectrum
wavelengths pigments absorb
2. Action spectrumwavelengths pigments use
What light is USED in photosynthesis?
Location of Photosynthesis
• What membranes are present in chloroplast?
• Why additional membranes?
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lightenergy Energized
chlorophyllWater
H2OChlorophyll
Light-dependentreactions
High-energymolecules
Light-independentreactions
OxygenO2
Carbondioxide
CO2
Carbohydrates(CH2O)
Reactions of Photosynthesis
I. Energy-transduction reactions (light or photochemical reactions)
light energy chemical energy
ATP
NADPH
visible spectrum
II. Carbon-fixation reactions (dark or biochemical reactions)
carbon dioxide glucose
CO2 C6H12O6
simple compound complex organic compound
plants use photosynthesis to convert solar energy into energy rich biochemical compounds
Metabolism
• sum of the vast array of chemical reactions that occur in an organism
• step-by-step sequences: metabolic pathways
catabolism• oxidation reactions - loss of electrons• downhill reactions that release energy
anabolism• reduction reactions - gain of electrons• uphill reactions that require a net input of
energy
Cellular Energy
• Adenosine triphosphate (ATP)• energy release
• when terminal phosphate group is cleaved from molecule
• energy storage• when terminal phosphate group is replaced
Adenosine
P PP
ATPAdenosine
PP
ADP
energyP
Reaction Basics
• NADP • nicotinamide adenine dinucleotide
phosphate• primary electron acceptor in photosynthesis• temporary high-energy storage molecule
NADPH
NADP+
(reduced form)
(oxidized form)
oxidationreduction
I. Energy-transduction reactions
• transfer of electrons from light to reduce NADP+ into NADPH
• electron flow (also known as electron transport) creates ATP from ADP + P
• occurs within thylakoid membrane of chloroplast
Chloroplast Structure
I. Energy-transduction reactions
machinery for reactions1. photosystem
a. reaction-center molecule (a special chlorophyll a molecule) which receives electrons from light
b. electron acceptor which receives electrons from reaction center
c. antenna complex of 250-400 pigment molecules that gather and funnel light energy to the reaction center molecule
2. electron transport chain• molecules that move electrons from high to low energy
levels
3. ATP Synthasea. proton pump to make ATP from ADP + P
(photophosphorylation)b. runs off of the H+ gradient between thylakoid lumen and
stromac. also called chemiosmotic coupling
photosystem
electron-transport chain
ATP synthase complex
thylakoid membrane PSIPSII
ea eae - transport chain
ATP synthase
stroma
thylakoid lumen
e- transport chain
NADPH NADP+
2H+
ADP + P
ATP
2H20 2H++O2
photolysis
2e-+
2H+
I. Energy-transduction reactions
I. Energy-transduction reactions
1. Electrons are produced from what compound in the energy-transduction reactions?
2. Electrons end up in which molecule?
3. Which photosystem is “first” in the energy-transduction reactions?
4. What is the name of the process that produces ATP?
5. ATP ends up in which location of the chloroplast?
6. Oxygen is produced in which location of the chloroplast?
7. Compared to the stroma, the thyllakoid lumen is __________ (acidic, basic)
I. Energy-transduction reactions
Uneven distribution of PS II and I. Characterize for me…
Noncylic electron flow and photophosphorylation
Cyclic photophosphorylation
• How is it cyclic?• How does it differ from
noncyclic photophosphyorylation?
• How is it phosphorylation?
• How is it photophyosphorylation?
• What organisms have this?
• What purpose does it serve?
II. Carbon Fixation Reactions
• produce a complex organic compound (C6H12O6) from a simple compound (CO2)
CO2 C6H12O6
• occur in stroma of chloroplast • use energy from photochemical
reactions• are a set of cyclical reactions known as
the Calvin Cycle
Carbon-fixation reactions
Calvin Cycle (C3 pathway)
carbon dioxideCO2
rubisco
1. Carbon Fixation
glucoseC6H12O6
2. Generation of PGAL
(reduction)3. Regeneration of carbon fixing
compound (RuBP)
Calvin cycle: initial carbon fixation
Calvin cycle: reduction of PGA into PGAL
Calvin cycle summary
Carbohydrate basics
made as PGAL in
photosynthesishexose
(glucose or
fructose)
transported as sucrose
stored as
starch
converted to
(glucose-fructose)
Fate of hexose
• converted to sucrose for transport• stored as starch for storage• made into cellulose for cell wall
material• used in respiration for energy• enters metabolic pathways to
generate other organic compounds
Connection of two photosynthetic reactions
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Lightenergy Energized
chlorophyllWater
H2OChlorophyll
Light-dependentreactions
High-energymolecules
Light-independentreactions
OxygenO2
Carbondioxide
CO2
Carbohydrates(CH2O)
Initial carbon fixation in Calvin cycle (C3)
For this reaction, name the:1. enzyme2. substrate3. product
•Enzyme•rubisco (ribulose 1,5-bisphosphate carboxylase)
•Substrate•RuBP (ribulose 1,5-bisphosphate)
•Product•First stable product is PGA (3-phosphoglycerate)
Problems with the Calvin Cycle
1. photorespiration • efficiency of rubisco
• rubisco is best named:ribulose 1,5-bisphosphate carboxylase/oxygenase
• CO2 + RuBP --> 2 PGA• O2 + RuBP --> phosphoglycolic acid + PGA• phosphoglycolic acid leaves the Calvin Cycle
• How common is photorespiration?• atmosphere: 21 % O2, 0.039% CO2
• estimates that as much as 1/2 fixed C is lost
Photorespiration
Salvage of phosphoglycolate
Problems with the Calvin Cycle
2. Transpiration• CO2 in
• water vapor out
• Solutions:• additions to the basic plan
• C4 Photosynthesis • CAM (Crassulacean Acid Metabolism)
C4 Photosynthesis – one solution
• spatial separation of: • initial carbon fixation• Calvin cycle
C4 leaf anatomy
C4 photosynthesisInitial carbon fixation• Enzyme
• PEP carboxylase• Substrate
• PEP (phosphoenolpyruvate)• Product
• Oxaloacetate (a 4C organic acid)• quickly converted to malate or aspartate
(other 4C organic acids)• NOT AN OXYGENASE!
• thus unaffected by O2 concentration
• temporal separation of: • initial carbon fixation• Calvin cycle
CAM photosynthesis – another solution
Crassulacean Acid Metabolism
Crassulacean Acid Metabolism (CAM)
Comparisons of solutions:
Comparisons of Efficiency
C3 C4 CAM
optimum temp (°C) 15-25 30-47 35
loss gH2O/gCO2 fixed 400-500 250-300 50-100
CO2:ATP:NADPH 1:3:2 1:5:2 1:6.5:2
1. What energy does the sun release that is used for photosynthesis?
A. visible lightB. ultra-violet (UV) lightC. infra-redD. Choices A & BE. Choices A, B & C
2. What chemical is responsible for capturing light energy?
A. cytochromeB. phytochromeC. chlorophyllD. hemoglobinE. bilirubin
3. How did scientists determine what wavelengths of light are used in photosynthesis?
A. determined color of plant leafB. determined which wavelengths
were absorbed by plant pigmentsC. determined which wavelengths
were used in photosynthesisD. Choices B & C are correctE. Choices A, B and C are correct
4. What wavelengths of light are used in photosynthesis?
A. whiteB. redC. blueD. greenE. B and C
5. What energy is PRODUCED in the energy transduction reactions of photosynthesis?
A. lightB. glucoseC. ATPD. NADPHE. both C and D
6. What happens to the energy produced in the energy transduction reactions of photosynthesis?
A. stored and used later in cellular respiration
B. all is lost as heatC. drives the carbon fixation
reactionsD. used to make more chlorophyll
7. Reduction is electron gain.
TrueFalse
8. Reduction is often seen in chemical formulas by the addition of hydrogen.
TrueFalse
9. The functional machinery for the energy transduction reactions is located in which membrane?
A. inner chloroplast membraneB. outer chloroplast
membraneC. plasma membraneD. thylakoid membraneE. nuclear membrane
10. The basic machinery for photosynthesis is the
A. chloroplastB. photosystemC. chlorophyllD. antennae complexE. the Bricker BS phenomenon
11. When studying the energy transduction reactions, the flow of _______ is important to track.
A. neutronsB. atomsC. electronsD. hydrogen ionsE. both C and D
12. What happens to the energy produced in the energy transduction reactions of photosynthesis?
A. stored and used later in cellular respiration
B. all is lost as heatC. drives the carbon fixation
reactionsD. used to make more chlorophyll
13. What is meant by carbon fixation?
A. carbon dioxide is made and released
B. glucose is used as energyC. oxygen is generatedD. carbon dioxide is converted to
glucoseE. ATP is generated
14. Photorespiration is a “bad process” for plants.
TrueFalse
15. Transpiration is a unavoidable consequence of photosynthesis.
TrueFalse
Ecosystem Structure
Results of Energy Conversions
Producers
Primary Consumers (herbivores)
Secondary Consumers (carnivores)
Tertiary Consumers (top carnivores)