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Energy Metabolism: Photosynthesis (Photosynthesis (Sunlight intensity…
Energy Metabolism: Photosynthesis
Concepts
Environmental and External Factors
Light
Light compensation point
level of illumination + photosynthetic fixation of CO2= respiratory loss
Red and blue are absorbed by chlorophyll
Properties
Quantity
Intensity or brightness
Sunny mt slope vs mt shadow
Near equator receive more light than plants at the poles
Cloudy vs Clear
Duration
Number of hours sunlight available
Quality
Colors and Wavelengths it contains
quanta is absorbed by pigment, electron is activated
raised to higher energy level
ground state
excited state
flourescence
release of light by a pigment
Water
Leaf Structures
#
:
Examples
trichomes
protect from intense light, insects
Colors indicate percentage of sunlight reaching the tree
Algae
Surface of Lakes or Oceans: red or violet absorbed
Deep water: Blue or green absorbed
spines
Closely spaced
Shade for stem
Abundant
prevent chlorophyll being damaged
White wax
protects against sunlight
Protects against excess water loss
strongly reflects UV light
Energy and Reducing Power
ATP
Converted to:
ADP
Phosphate
Guanisine Triphosphate
Phosphorylation of ADP
Substrate-level phosphorylation
Produce high-energy phosphate groups :explode:
Force phosphate on ADP
Makes ATP
Oxidative phosphorylation
#
Late stages of phosphorylation
ADP phosphorylated to ATP
Photophosphorylation
Light energy :
Animals, fungi, etc cannot perform.
Lack pigment and organelles
Only in Chloroplasts
Reducing Power
Organization
Organisms are highly ordered
Sunlight maintains and increases orderliness
Photosynthesis
#
Photoautotrophs
Types
All cyanobacteria
Some bacteria capable of photosynthesis
All green plants
Process
Water
Nitrates, Sulfates, Minerals
Build molecules using CO2
Chlorophyll
#
Green pigment for photosynthesis
does not use high energy quanta
1 more item...
Respiration
Heterotrophs
Types
All completely parasitic plants
All fungi
All Animals
Non-photosynthetic prokaryotes
Process
Some material is used for construction
Rest is respired for energy
Energy comes from organic materials
Holoparasites
Orange Dodder (Cuscuta)
Haustoria
Specialized roots
Enter bodies of photosynthetic plants
Extract sugars, water, minerals
Convert sugars into needed organic compounds
Don't photosynthesize
Entropy in universe increasing
Metabolism
Tissues can change metabolism
Seedlings
Germinating
Heterotrophic
White
Survival
Cotyledons
Endosperms
Emerge to sunlight
Become photoautotrophic
Fruits
Immature
Green
Photosynthetic
Maturation
Chloroplast->Chromoplasts
Chromoplasts
Plastids with pigments other than chlorophyll
Energy=Imported or stored nutrients
Type
Crassulacean Acid Metabolism
Improves conservation of water
Advantageous in hot habitats
first discovered in Crassulacea family
succulent leaves
almost identical to C4
Different how?
Stomata closed during hottest periods
open at night when its cold
coolness reduces transpiration
Not particularly efficient
C4 Metabolism
#
CO2 is absorbed
Transported through
Concentrated in a leaf
Oxygen kept away from RuBP carboxylase
RuBP Carboxylase
fixes 1-12 CO2 molecules/sec
Extremely slow
Sometimes binds to Oxygen
produces phosphoglycolate
acts as an oxygenase
phosphoglycolate transported to perixome and mitochondria
phosphoglycolate is broken down-> 2 CO2 molecules
Enzyme that fixes carbon molecules
Energy and reducing power all lost
Kranz anatomy
Mesophyll
#
not distributed
PEP carboxylase
high affinity and specificity for CO2
binds rapidly, firmly
keeps ration of water lost to CO2 low
produces oxaloacetate
has 4 carbons: HENCE C4
prominent Chlorophyllous sheath of cells
around sheath are mesophyll cells
Photorespiration
Energy wasting process
Exergonic
protects against toxicity of phosphoglycolate
30% of ATP and NADH lost during this process
Photosynthesis
CO2->Carbohydrates :
Sunlight intensity affects photosynthesis
Dim Light=little CO2 absorption
#
Brighter light=Higher CO2 absorption
Slow on overcast days
Faster on clear days
#
Photosynthesis faster at higher concentrations of CO2
#
Saturates leaves
1/4 to 1/2 is all they can use :star:
Water
Stomata remains open during day
Allows CO2 to enter
Stomata close at night
Retains water in the plant
Water Use Efficiency Ratio
H20 lost for every CO2 molecule absorbed
Ideal: Low Ratio
Cyanobacterial Photosynthesis
Chloroplasts-Endosymbiotic Cyanobacteria :silhouettes:
light reactions almost identical to chloroplasts
lack chlorophyll beta
Accessory pigments
Phycobilins
open-chain tetrapyrrole rings
act like carotenoids
absorb wavelengths that chlorophyll cannot
All photosynthetic plants: C3 reactions
#
RuBP
Energized
Reduced
Carboxylated
2 molecules of 3-phosphoglyceraldehyde
Light
Electromagnetic Spectrum
Pigments
Melanin
Chlorophyll a
absorbs only red and some blue light
Chlorophyll b
Energy
Plants cannot store ATP or NADH during day to use at night
not stable enough
cells have too little
CO2 is stored on acids until daytime
photosystems: 1 and 2
transfer electrons from water to NADPH
Electron's energy boosted 2X
Once: P680
Again at : P700
Photosystems Details
Photosystem 1
Energy absorbed in by a pair P700 chlorophyll a molecules
P700, reaction site
raise 2 electrons to an excited energy level
transfer to ferredoxin
strong reducing agent
Photosystem 2
Photosystem 1 loses electrons, so needs to add electrons back
reduces P700
working backward from Photosystem 1
phaeophytin
Chlorophyll a molecule - magnesium
electrons
pass from water to P680
energy is boosted by light
move through the electron transport chain
#
shape: Z scheme
Agents
Oxidizing
NAD+
NADP+
Reducing
NADH
NADPH
redox potential
tendency to accept or donate electrons
only capture 5% energy available
Synthesis of ATP
chemiosmotic phosphorylation
Structures
Aid
Conservation of water
Absorption of CO2
Types
Tropical and Temperate
Standard structure
Spongy Mesophyl
Pros and Cons
Excellent at absorbing carbon
Inefficient water conservation
Terrible for extremely dry habitats
Stomata would have to remain closed
Plants would starve
Palisade Parenchyma
Hot, dry habitats
leaf cells packed closely together
no intercellular space
Pros and Cons
Excellent water conservation
Internal surface area reduces water evaporation
Small SA = difficulty dissolving CO2
Slows photosynthesis
Not always disadvantageous
Cylindrical Leaves
Water conservation
Few stomata are present
Photosynthesis is slowed
Chloroplasts
inner membrane folds inwards
form flattened sacs
called thylakoids
grana
some lie between grana
called frets
stroma: liquid surrounding thylakoid system
thylakoid lumen
enzymes
electron carriers
regions swell and form rounded vesicles
Electron Carriers
Plastoquinones
transport electrons over short distances
pickup 2 electrons, bind 2 protons
have a long hydrocarbon tail
hydrophobic
absorb easily into chloroplast membrane
Plastocyanin
small protein
#
carries electrons on a metal ion
Copper instead of iron
+2 oxidation state
as it picks up electron->+1 oxidation state
short distance along surface
does not travel far
Cytochromes
#
Small proteins
integral to chloroplast's thylakoid membrane
Cofactor Heme
iron atom
carries electrons
cycles between +2 and +3 oxidation states
transport electrons between sites that are very close together
Energy Metabolism: Photosynthesis Continued
noncyclic electron transport
electrons flow smoothly from water to NADPH
Cyclic electron transport
flow of electrons from P700 back to plastoquinone
reactions
Stroma Reactions
Calvin/Benson cycle
conversion of CO2 to carbs
acceptor molecules
RuBP
react with a molecule of CO2
Anabolic Reactions
Gluconeogenesis
large molecules are built from small ones
process occurs in
chloroplasts
amyloplasts
cytosol
Climate Change
Greenhouse effect
Energy trapped in the atmosphere
Greenhouse gas
CO2
Global Warming
Carbon dioxide increasing in the atmosphere
