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Energy Metabolism: Photosynthesis (Environmental and Internal Factors…
Energy Metabolism: Photosynthesis
Energy and Reducing Powers
Reducing Power
Oxidized , not all electrons carried at once
oxidized reaction increases + charge
oxidized compounds (most part) great deal of O2
NAD+ and NADP+ oxidizing agents. take away e-
reduced, electrons added
reduction reaction, decreases + charge
reduced compounds, contain hydrogen
NADH and NADPH reducing agents, add e-
tendency to + or - e- is redox potential :star:
other electron carriers
Plastoquinones
hydrophobic
dissolve easy in lipid component
limited movemnet
plastocyanin
contains metal atom, copper
loosely associated with chloroplast membranes
Cytochromes
intrinsic membrane proteins
limited movement
contains metal atom, iron
Energy carriers
Two ways light is transferred from pigments
let pigments makes several smaller intermediates
easier to control, includes ATP and guanosine triphosphate
ATP/ energy is converted to ADP by metabolic reactions
3 ways ADP phosphorylated back to ATP
substrate-level phosphorylation
oxidation phosphorylation
photophosphorylation
pigments allowed to enter every reaction necessary
Photosynthesis
The Stroma Reactions
Calvin/Benson cycle or C3 cycle
conversion of CO2 to Carbohydrates
an Acceptor molecule (ribulos 1,5-biphosphate; RuBP reacts with CO2
molecules bind with an enzyme and are torn apart
3-phosphoglycerate (PGA) is formed
enzyme which carries out reaction is RuBP carboxylase (RUBISCO)
make up 30% of protein in a leaf
crucial to production of food
first step of stroma reactions is carboxylation only
ATP donated energy to convert PGA to 1,3 diphosphoglycerate
then reduced by NADPH to 3-phosphoglyceraldehyde (PAGL)
rest of reaction is complex, but PAGL can be made ino almost anything plant needs : :tada:
carbon reduced and energized
Anabolic Metabolism
anabolism/ anabolic reactions= build up of larger molecules in cytoplasm
numerous anabolic pathways to stores energy
intermediate term storage= simple sugar glucose and disaccharide glucose
long term storage= starch and lipids
short term storage=ATP and NADPH
Synthesis of Polysaccharides
the anabolic synthesis of glucose is gluconeogenesis
part of PAGL transported to cytoplasm, converted to dihydroxyacetone phosphate
condenses to form fructose-1,6-biphosphate.
minus one phosphate = fructose-6-phosphate
rearranged to form glucose-6-phosphate
both polymerized into polysaccharides amylose, amylopectin, or cellulose
amylose and amylopectin are components of starch
Light dependent reactions
nature of pigments
light that is not absorbed, (color humans see)
in plants, allows them to acquire energy
plants usually only absorb red and blue light
chlorophyll , does not use high energy quanta= too much energy : :fire:
when energy is absorbed, e- is activated
goes from ground to excited state
photochemical processes
absorption spectrum
what is absorbed
action spectrum
effective energy
release of light by pigment is fluorescence
accessory pigments
absorb wavelengths, not absorbed by chlorophyll
a
chlorophyll
b
and carotenoids common accessory pigments
resonance allows chlorophyll
b
to be absorbed
pigments held and harvested by proteins in thykloid membrane
entire set of 300 chlorophyll+caroentiods+ proteins= antenna complex
transferred to reaction center to donate excited e-
pigments and carriers work together in granule called photosynthetic unit
photosystem 1
called P700 because its absorbs red light best (700nm)
electron acceptor Fx absorbs e- from P700 becomes reducing agent
passed to ferredoxin in thylakoid membrane
passed to enzyme ferredoxin-NADP+ reductase
reduced NADP+ to NADPH
takes 2 e- to another NADP+
together an efficient system, moves to electron transport chain from here
nature of light
electromagnetic radiation spectrum
includes gamma rays and X-Rays : :check:
contains quanta or photons
measured in wavelengths (nm)
long= infrared, microwave, radar, and radio :<3:
low amounts of energy
humans more sensitive to long wavelengths
short = cosmic and gamma rays and ultraviolet light :warning:
large amounts of energy
Photosystem 2
Plastocyanin donates e- to chlorophyll
a
Plastocyanin recieves new e- from cytochrome molecule
called cytochrome b6/f complex
gets more e- from Q (quinone), then phaeophytin
called P680
creates a circle of electron sharing
molecule gets e- from water
uses H+ and discards O2
synthesis of ATP
created by process called chemiosmotic phosphorylation
important structures include
grana, hold thylakiod in a region
frets, thylakoids between grana
stroma, liquid surrounding thylakoid system
thylakoid lumen, holds crucial enyzmes and electron carriers
concentration of protons inside thylakoid lumen and outside forces protons out
flow into channels with sets of enzymes
turn ADP and Phosphate to ATP
called ATP synthetase
2 more items...
noncylic electron transport
creates ATP without making extra NADPH, making proper ratios of both
electrons flow smoothly from water to NADPH
Environmental and Internal Factors
Crassulacean Acid Metabolism
2nd metabolic adaptation to conserve water
almost the same as C4 with production of oxaloacetate, and reduce to malate
CO2 is stored in the acids as stomata closes during hottest parts of the day and opens at night
not very effective to use when stomata is opened at night
has to wait until morning to begin photosynthesis again
is selectively advantageous in very hot and dry climates
very critical as most plants would die in such harsh and dry conditions
in moist climates, not very useful as they are not able to photosynthesis all day
conserves water during C3 metabolism where lots of H2O would be wasted in such a climate
cacti make up a majority of this type of metabolism
Leaf Structure
dry climates have excellent water absorption leaves with tightly packed cells
cylindrical leaves minimize water loss but slow photosynthesis
tropical places have great CO2 absobtion but bad at water retaining
C4 metabolism
ratio of water loss by absorption of CO2
RuBP carboxylase will sometimes bind to O2 instead of CO2
Forms PGA and phosphoglycate
breaks down to 2 CO2 molecules
called photorespiration
30% of ATP and NADPH reduced when this happens due to photorespiration
to combat the inefficiency some plants developed C4 metabolism
plant must have Kranz anatomy
contains enzyme called PEP (phosphoenolpyruvate) carboxylase
as CO2 concentration lowers PEP carboxylase continues production as usual
leads to H2O loss very limited good for plant
still needs RuBP carboxylase to carry out reaction
PEP carboxylase adds CO2 to produce oxaloacetate (has 4 carbons)
2 more items...
benefits depends on the environment
Light
quantity of light
more open an area is (including cloud cover), the more sunlight plants receive
plants at the equator receive intense sunlight
shadow of mountain and canyon plants receive little sunlight
plants near the pole receive very little due to scattered atmosphere
refers to light intensity, affected by many factors
intensity of light changes during the day, affecting photosynthesis
adequate water, light, and nutrients= 30% faster photosynthesis speed :check:
too intense of light can damage plant :no_entry:
sufficient light but low CO2= slow photosynthesis :no_entry:
when doing tests, shape and size of plant are crucial as well as correct growing conditions
sufficient air quality but low light slows photosynthesis :no_entry:
Duration of Light
plants at the poles can have 24hr days of sun or 0hr. days of sun depending on season
refers to the number of hours a plant gets of light
plants at equator receive 12hr. of light each day no matter season
middle latitudes vary upon season
summers receive longer duration of direct sunlight
winters receive less duration of direct sunlight
Quality of sunlight
sunlight is pure white
ground appears as red early, thought to have little effect on photosynthesis
at noon, more blue light transmitted upward, suggesting all other colors blocked
allows efficient amounts of light to pass through atmosphere
trees absorb red and blue lights by chlorophyll
low level plants rely on other wavelengths to reach them using chlorophyll
b
atmosphere appears blue as blue light is deflected upward
colors and wavelengths light contains
three important parts: quality, quantity and duration