Upload
joleen-perkins
View
215
Download
0
Tags:
Embed Size (px)
Citation preview
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.
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
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?
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
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 Synthase• proton pump to make ATP from ADP + P
(photophosphorylation)• runs off of the H+ gradient between thylakoid lumen and
stroma• also called chemiosmotic coupling
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. Light-dependent 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)
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
Light-independent reactions
Calvin Cycle
carbon dioxideCO2
rubisco
1. Carbon Fixation
glucoseC6H12O6
2. Generation of PGAL
(reduction)3. Regeneration of carbon fixing
compound (RuBP)
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
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)
• 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 better 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, 0.036% CO2
• estimates that as much as 1/2 fixed C is lost
Problems with the Calvin Cycle
2. Transpiration• CO2 in
• water vapor out
• Solutions:• additions to the basic plan
• C4 Photosynthesis
• CAM (Crassulacean Acid Metabolism)
Initial 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