BIOLOGY
1111
ENERGY
ACQUIRING PATHWAYS
CHAPTER
7
Northland
Community &Technical College
Instructor Terry Wiseth
ENERGY
ACQUIRING PATHWAYS
modes
of nutrition are based on the sources of carbon for synthesizing glucose
1)
Heterotrophs
2)
Autotrophs
HETEROTROPHS
acquire
carbon and energy from organic compounds
eat
autotrophs, eat each other, and eat organic wastes
ex:
animals, fungi, parasites
AUTOTROPHS
acquire
carbon from carbon dioxide in the atmosphere
A)
photoautotrophs
B)
chemoautotrophs
PHOTOAUTOTROPHS
utilize
sunlight as an energy source for synthesizing glucose
ex:
green plants
CHEMOAUTOTROPHS
able
to extract energy from inorganic sources
ex:
bacteria----sulfur
PHOTOSYNTHESIS
An
energy acquiring pathway performed by photoautotrophs
1)
nature of light
2)
light trapping pigments
3)
chloroplast
4)
light reactions
5)
dark reactions
6)
alternative pathways
7)
carbon cycle
NATURE
OF
LIGHT
White
light consists of all the visible wavelengths of light
A
prism can be used to separate the different wavelengths
Visible
light is one small part of the electromagnetic spectrum
The
longer the wavelength is the more red the color
Infrared
Longer
wavelengths than visible red
The
shorter the wavelength is the more violet the color
Ultraviolet
Shorter
wavelengths than visible violet
Energy
is inversely proportional to the wavelength
Longer
wavelengths have less energy than shorter wavelengths
Ultraviolet
has more energy than infrared
Albert
Einstein developed a particle model of light in 1905
Light
is composed of particles called photons whose
energy can displace protons
PHOTOELECTRIC
EFFECT
Light
energy can force electrons from a compound creating an electrical current
Zinc
exposed to UV light becomes positively charged by the displacement of electrons
LIGHT
TRAPPING PIGMENTS
A
pigment is any substance that absorbs light
Color
of a pigment is determined by the wavelengths of light reflected
Types
of pigments capable of trapping light energy (photons)
1)
Chlorophyll
2)
Carotenoids and Xanthophylls
3)
Anthocyanins
4)
Phycobilins
1)
Chlorophyll - pigment absorbs
wavelengths of light other than green light
Chlorophyll
is a complex molecule
Chlorophyll
a
absorbs
its energy from the Violet and Red wavelengths
Chlorophyll
b
absorbs
its energy from the green wavelength
Origins
of photosynthetic organisms in the sea may account for the presence of both
chlorophyll a and chlorophyll b
Shorter
wavelengths are not able to penetrate much below 5 m deep in the water
Ability
to absorb some energy from the longer more penetrating wavelengths may have inferred an advantage
Energy
absorbed by chlorophyll pigments trigger a chemical reaction
The
chemical reaction is associated with proteins embedded in the chloroplasts inner
membranes
2)
Carotenoids and Xanthophylls
plant
pigments which reflect red, orange and yellow
Absorb
light in the green wavelength
3)
Anthocyanins
Reflect
red and purple wavelengths
Commonly
seen in the color of petals and the skin of fruits
In
the fall of the year Anthocyanins are the by product of biochemical events as
chlorophyll is degraded in order to conserve magnesium (only a part of the
pigment chlorophyll)
Sugars
in the leaf react with proteins to produce Anthocyanins
Exact
color (orange, red, purple) is dependent on the
1)
pH of the sap in the leaves
2)
Weather
Sunlight
Temperature
Moisture
conditions
Cool
weather destroys chlorophyll and encourages the formation of Anthocyanins
Freezing
temperatures kill the leaves before good color develops
Sunny
weather speeds the destruction of the chlorophyll
Dry
weather encourages high sugar concentrations and thus high production of
Anthocyanins
4)
Phycobilins
Plant
pigments which reflect red and blue
Found
In blue-green algae (cyanobacteria) and red algae
CHLOROPLAST
The
organ of function in photosynthesis
two
stages of photosynthesis occur at different sites inside the chloroplast
1)
Thylakoid
compartment (inside the grana)
2)
Stroma
Thylakoids
are stacked like pancakes in stacks known as grana
Stroma
is the areas between the grana
PHOTOSYNTHETIC
FORMULA
|
12H2O
+ 6CO2
|
 |
C6H12O6 + 6O2 + 6H2O
|
glucose
end-product combines at once to form complex carbohydrates
process
occurs inside the chloroplast
PHOTOSYNTHESIS
A)
Light
dependent
reaction
(Light)
B)
Light
independent
reaction
(Dark)
PHOTOSYNTHESIS
1)
Thylakoid compartment (inside the
grana)
1st
stage of photosynthesis
light
dependent reactions
ATP
produced
2)
Stroma
2nd
stage of photosynthesis
light
independent reactions
sugars
assembled
PHOTOSYNTHESIS
A)
Light dependent reaction
energy
from light absorbed
energy
is converted to ATP
water
molecules are split
Oxygen
molecules diffuse out
coenzymes
NADP+ picks up liberated hydrogen and electrons becoming NADPH
H+
ions diffuse out of the grana generating ATP by way of the ATP synthase proteins
This
reaction can be divided into three sub reactions
Oxygen
production from photolysis of the water
molecule
PHOTOSYNTHESIS
1)
Light strikes the P II complex energizing the chlorophyll electrons
2)
The energized electrons leave chlorophyll and are replaced by water which is
split after losing an electron
3)
Free oxygen combines and is released from the chloroplast
4)
Free electrons in the cytochrome complex attract H+ ions into the thylakoid
lumen
5)
A surplus of free H+ ions create a proton gradient inside the thylakoid lumen
6)
Electrons in PS I are boosted to a higher energy level
7)
Free electrons from the cytochrome replace the energized electrons in the PS I
complex
8)
The boosted electron from PS I is given up to NADP+
and H+ to
form NADPH
9)
ADP molecules ready to pick up energy from the synthetase molecule as H+ ions
flow
10)
ATP is formed as the H+ ions
flow across the ATP synthetase from the pressure created by the H+ proton
gradient
11)
Water molecules form from the free H+ ions and free oxygen in the stroma
PHOTOSYNTHESIS
B)
Light
independent reaction
Takes
place in the stroma
“Dark
Reaction”
Process
is able to occur in the absence of light
NADPH
and ATP donate energy to the incorporation of carbon into organic molecules
CO2
acts as a carbon and oxygen source for synthesis of the organic molecule
water
provides hydrogen as delivered by NADPH
LIGHT
INDEPENDENT REACTIONS
These
reactions have two purposes
1)
Capturing carbon
Carbon
fixation
2)
Building glucose
Calvin-Benson
cycle
CARBON
FIXATION
Capturing
(fixing) carbon
Carbon
dioxide diffuses into the stroma from the atmosphere
Carbon
attaches to
RuBP
(Ribulose
Biphosphate)
ALTERNATE
METHODS OF CARBON FIXING
carbon
fixing strategy is dependent on environmental conditions
though
carbon dioxide is abundant in the air, it may not be abundant inside the leaves
of a plant
Carbon
enters the leaf through openings ca
lled
stomata
Stomata
are openings created by specialized cell on the lower epidermis of the leaf
desert
plants and conifers have leaves with thick surface layers that help to restrict
water loss
ex:
cacti, conifer trees
Water
stressed plants do not open their stomata during the day, in order to prevent
excessive water loss
only
open stomata at night, thus carbon dioxide must be fixed at night
CO2
is
stored in the central vacuole to be used the following day when the stomata are
closed
CAM
plants (Crassulacean Acid Metabolism)
C3
PLANTS
C3
plants have only one cell type able to fix carbon
Fix
carbon in
Ribulose
Biphosphate
(RuBP)
which is converted into
Phosphoglycerate
(PGA)
a
3 carbon molecule
C4
PLANTS
C4
plants have two types of cells which are able to fix carbon
more
efficient in hot, dry weather
Fix
carbon in Phosphoenolpyruvate (PEP)
which is converted into oxaloacetic acid (OAA)
a
4 carbon molecule
C4
vs C3 PLANTS
Kentucky
Bluegrass (C3) does well during
spring cool weather only to be overwhelmed during the hot summer by Crabgrass (C4)
CALVIN-BENSON
CYCLE
Building
glucose
A)
carbon attaches to RuBP producing an unstable intermediate
Ribulose
Biphosphate (RuBP) is a 5 carbon sugar with 2 phosphates
attached
B)
this
6 carbon molecule splits into 2 PGA molecules (3 carbon) by the enzyme RuBisCO
C)
ATP donates a phosphate
D)
NADPH donates hydrogen and electrons forming PGAL
most
PGAL is recycled to RuBP to capture more CO2
E)
two PGAL molecules combine to form a 6 carbon sugar phosphate
used
to form sucrose, starch or cellulose
CARBON
CYCLE
0.03%
of the atmospheric air is CO2
Carbon
is cycled between organic compounds produced by photosynthesis and atmospheric
CO2
A
small amount of carbon is trapped in organic deposits
coal,
oil, natural gas
300
million years ago
Now
being returned to atmosphere as
fossil fuel is burned
CHEMOAUTOTROPHS
some
bacteria are able to obtain energy by pulling hydrogen and electrons from:
1)
ammonia (NH4)
ex:
nitrogen fixation
2)
iron compounds
ex:
rust
3)
sulfur compounds
ex:
thermal vents
END
CHAPTER 7