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Chapter 8
I. Energy and Life
•
•
•
Energy = ability to do work
w/o energy life would cease
A. Autotrophs and Heterotrophs
–
Originally most all energy comes from
________
Plants and some other organisms use the sun’s
energy to produce____________.
food
sun
– ________________make their own food.
– _________________obtain energy from food
they consumer
– Some obtain energy as decomposers
– There are several forms of energyradiant(light),electrical,chemical,mechanical
autotrophs
heterotrophs
B. Chemical Energy and ATP
–
–
When electrons in bonds are shifted from
higher to lower energy
levels,_______________is released as heat
and light
___________________is one of the principal
chemical compounds used to store and release
energy
The extra
energy
Adenosine triphosphate
The 3 Phosphate groups are
the key to ATP’s ability to
store and release energy
1) Storing energy
•
_______________________is a compound that
looks a lot like ATP,except it has 2 phosphate
groups and this difference is the key to storing
energy.When a cell has energy available it can
store small amounts by adding a phosphate to
ADP,making ATP (think of ATP like a fully
charged battery)
Adenosine
diphosphate (ADP)
2) Releasing Energy
•
Energy stored in ATP is released by breaking the
bond between the 2nd and 3rd
phosphates,releasing energy as needed.This can
power such things as _______________across
the membrane of the cell,protein synthesis and
muscle contraction
Active transport
• ATP is exceptionally useful as the
_____________________________.
Basic energy source of all cells
C. Using Biochemical Energy
– For active transport---____________________________that
pumps Na+ out of cell and K+ into the
cell.ATP keeps the pump working and
keep ions balanced
A sodium-potassium pumpa membrane protein
• ATP powers synthesis of
proteins,__________________ and responses to
_____________________.
Nucleic acids
Chemical signals @
cell surface
• Cells only have a small amount of ATP,to
last seconds…..not good for long term
storage(1 molecule glucose stores 90 x
the chemical energy of ATP ).Cells can
regenerate ATP from ADP as needed by
the energy in foods like glucose
D. Heterotrophs and Autotrophs
_____________________________get
s food from eating or ingesting othersmay eat autotrophs or other
heterotrophs---includes fungi
________________________make
their own food/primarily by
photosynthesis-which uses light to
convert CO2 and H2O into carb’s and
O2
• autotrophs
heterotrophs
II .Photosynthesis:An Overview
–
Plants use the energy of sunlight to convert
water and CO2 into sugars and starches,as
well as O2
A. Investigating Photosynthesis
– Centuries ago the simple question was did
the increase in tree’s mass come from
soil,water or air?
•
•
1) Van Helmont’s Experiment1600’s-Belgian physician did an experiment to
see if the soil caused plants to grow,by trying
to grow w/o soil….he concluded most of the
gain in mass was from water…..this accounts
for ½ the products of photosynthesis.
2) Priestly’s Experiment
–
–
Candle w/jar over it-concluded that air
enabled it to burn
He put a sprig of a plant under the jar and
waited a few days,…The candle could burn
briefly under the jar…So he concluded the
plant ________________________
Produced oxygen
3) Jan Ingenhoutz
• —showed the plant produced oxygen only if
exposed to light
» In conclusion to all 3 experiments,it is
concluded that plants exposed to CO2
and light and water,produce O2 and
carb’s
B. The Photosynthesis Equation
light
• 6 CO2 + 6 H2O--- C6H12O6 + O2
• Plants use the sugars to produce complex
carb’s such as _______
starches
C. Light and pigments
•
•
•
Photosynthesis also requires light and Chlorophyll
(found in Chloroplasts)
White light is a mixture of different wavelengths
of light---seen as __________
Plants gather the sun’s energy with light
absorbing molecules called____________.
Color
pigments
• The principal plant pigment
is__________________.-chlorophyll a and b
• Chlorophyll absorbs light well in the blue-violet and
red regions,but not well in the
_______________region,which is reflected by
leaves
green
Chlorophyll
• Contain red and orange pigments like
_________________,that absorb light in other
regions
• When chlorophyll absorbs light,much of the energy
is transferred directly to electrons in
Chlorophyll ,raising _________________________which make photosynthesis work!!!
carotenes
The energy levels
• Chloroplasts contain pigments in membranes called
____________________/a stack= 1 granum ;plural
are grana
• Fluid portion of chloroplast is called stroma
• A large portion of light absorbed by the chloroplast
transfers directly to electrons in the chlorophyll
molecule itself .By raising energy levels , light can
produce steady supply of high energy electrons---the
key to photosynthesis
Thylakoids
• D. High Energy Electrons
• The high energy electrons produced by
chlorophyll are highly reactive and
need a special carrier(think of “hot
potato “ analogy )
• Electron carriers= compounds that
accept a pair of high energy electrons
and transfer them/along w/ most of
energy to another molecule
Figure 8-5 Chlorophyll Light
Absorption
Section 8-2
Absorption of Light by
Chlorophyll a and Chlorophyll b
Chlorophyll b
Chlorophyll a
V
Go to
Section:
B
G
YO
R
III. The Reactions of
Photosynthesis
• A. Inside a Chloroplast
– Photosynthesis takes place in the
_____________.
– The chloroplasts contain saclike membranes
called _________________ which are arranged
in stacks known as ________________
chloroplasts
THYLAKOIDS
grana
– Proteins in the Thylakoid membrane organize
chlorophyll and other pigments into clusters
known as ___________________-These are
the light –collecting units of the chloroplast
– Light dependent reaction happens in
_____________________.
photosystems
Thylakoid
membrane
• Light-independent (Calvin-cycle) reaction happens in
_____________-region outside thylakoid membranes
stroma
Figure 8-7 Photosynthesis: An
Overview
Section 8-3
water
CO2
Light
Chloroplast
Chloroplast
NADP+
ADP + P
LightDependent
Reactions
Calvin
Cycle
ATP
NADPH
O2
Go to
Section:
Sugars
B. Electron Carriers
•
When sunlight excites electrons in chlorophyll,the
electrons gain a great deal of energy…..They
require a carrier---__________________by electron
transport chain
– ________nicotinamide adenine dinucleotide
phosphate-accepts 2 high energy electrons
along w/ a H+,converting it into __________.This
is one way some of energy of sunlight is trapped
in chemical form
Compound that can
accept a pair of high
energy electrons and
transfer w/ most of the
energy to another
molecule
NADP+
NADPH
• ______________________-then becomes
an electron carrier
NADPH
C. Light –Dependent Reactions
– Require light
– Light is used to produce ATP and NADPH
Figure 8-10 Light-Dependent
Reactions
Section 8-3
Photosystem II
Hydrogen
Ion Movement
Chloroplast
ATP synthase
Inner
Thylakoid
Space
Thylakoid
Membrane
Stroma
Electron
Transport Chain
Go to
Section:
Photosystem I
ATP Formation
– 1-Photosynthesis begins when pigments in
photosystem II absorb light.Energy is
absorbed by high energy electrons and
passed on to electron transport
chain.New electrons come from the
water (water is required in these reactions
to provide source of electrons and H+
ions),and O2 is released into air-as a
BYPRODUCT
– 2-High –energy electrons move from
electron transport chain from
photosystem II to photosystem I(simply
discovered before photosystemII).Energy
from electrons is used by molecules in
electron transport chain to transport H+
ions from stroma into the inner thylakoid
space.
– 3--Pigments in ___________________use
energy from light to regenerate
electrons.NADP+ picks up high energy
electrons,along w/ H+ ions,at outer
surface of thylakoid membrane…+ H+
ion=NADPH/Photosystems are clusters of
chlorophyll and protein and are essential to
light dependent reaction.They absorb light
and make high energy electrons that are
passed onto high energy electron carriers in
thylakoid membrane.
Photosystem I
•
As electrons pass from chlorophyll to
NADP+,more________________are pumped
along the membrane….Eventually ,the inside of
the membrane fills w/ H+ ions……outside of
membrane is
_______________________charged…The
difference in charges (a gradient)produces
energy for ATP….This is why H+ ions are so
important.
4-
H+ ions
negatively
•
5--H+
ions cannot cross membrane
directly…..But, the membrane contains a protein
called __________that goes across the
membrane and allows H+ ions to pass through
it.(produced by gradient)As H+ passes through
,ATP synthase,the protein rotates,binding w/
ADP and a phosphate group to
make_________________ So….. light-dependent
part makes high energy electrons and also ATP.
ATP synthase
ATP
• Electron transport chain= series of
electron carriers proteins that move
electrons during reactions fueled by
ATP.At end of chain electrons pass to
photosystem I
• Pigments in photosystem I use energy
from light to reenergize
electrons/NADP+
NADPH
D. The Calvin Cycle
–
–
–
The ATP and NADPH from light-dependent
part are not stable enough to store energy for
more than a few moments….these are used in
_____________to make high energy
compounds that can last a long time----it
makes ________________.
Absorb CO2 and use ATP and NADPH to make
high energy sugars
Does not require light so is called
______________________
sugars
Calvin Cycle
Light-independent
Figure 8-11 Calvin Cycle
CO2 Enters the Cycle
Energy Input
ChloropIast
5-Carbon
Molecules
Regenerated
6-Carbon Sugar
Produced
Sugars and other compounds
Go to
Section:
•
•
6 CO2 molecules enter from the
atmosphere.They combine w/ 6
____________________.The result is 12 3-C
molecules.
2) 12 3-C molecules convert to higher energy
forms….The energy for this comes from ATP and
____________________.
1)
5-Carbon
atoms
High energy electrons from
NADPH
• 3)
2 3-C molecules removed from cycle…these
are used to
produce__________________________________
_______________________________________
needed for plant metabolism and growth
Building blocks of
Sugars,lipids,amino
acids and other
compounds-other
macromolecules
•
•
4) Remaining 10 3-C are converted back into 6
5-C molecules.They combine w/ 6 new CO2
molecules to begin cycle again.
***** 2 sets of photosynthetic reactions work
together-light-dependent traps energy of
sunlight in ____________ and light –independent
reactions(Calvin Cycle) use that chemical energy
to produce stable,high energy sugars from CO2
and water….also O2 is produced
Chemical form
E.Factors affecting Photosynthesis
•
•
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Water supply
Temperature---affects enzymes
Light intensity----it does reach a maximum-or
optimal level of light,depending on plant type--eg.conifers only photosynthesize on
__________________________.
Warm.sunny days
• Photosynthesis Under Extreme
Conditions
• To conserve water,most plants under
bright light close openings in leaves
that normally take in CO2-keeps plants
from drying out, but CO2 levels fall low
and photosynthesis slows down
• However,some plants have adapted to
such bright light and hot conditions
• C4 plants-specialized chemical
pathway to capture even low amounts
of CO2 for Calvin cycle(1st compound
made has 4 C’s)/requires extra ATPinclude crops like corn,sugarcane,and
sorghum
• CAM plants-plants adapted to dry
climate get CO2 while minimizing water
loss-family CRASSULACEAE(CRASSULACEAEN ACID
METABOLISM)-CO2 becomes part of
organic acids-Admit air into leaves only
at night-During day leaves sealed tightrelease CO2,allowing carb
production(pineapple trees, many cacti
,ice plants)