biology1-2 mrs. hennings
TRANSCRIPT
CHAPTER 8 PHOTOSYNTHES
ISBiology1-2
Mrs. Hennings
http://www.youtube.com/watch?v=C1_uez5WX1o&feature=related
http://www.youtube.com/watch?v=1gLa5EWn9OI&feature=related
THE ULTIMATE SOURCE OF “E” The Sun is the ultimate source of
energy. Photosynthesis is the process in which
plants capture light energy and change it into chemical energy.
Organisms are classified to how the obtain energy.
TWO MAIN CATEGORIES….Autotrophic organisms- “self feeders” make
their own food. Producers of ecosystems Photoautotroph Chemoautotroph
Heterotrophic organisms- can’t make their own food. They live on compounds made by other living organisms. Consumers of ecosystems. That is
really important
!
That is really
important !
THE ENERGY NEEDS OF LIFE Organisms are endergonic systems
What do we need energy for? synthesis
building biomolecules reproduction movement active transport temperature regulation
WHERE DO WE GET THE ENERGY FROM?
Work of life is done by energy coupling use exergonic (catabolic) reactions to fuel endergonic
(anabolic) reactions
+ + energy
+ energy+
digestion
synthesis
ATP
LIVING ECONOMY Fueling the body’s economy
eat high energy organic molecules food = carbohydrates, lipids, proteins, nucleic acids
break them down digest = catabolism
capture released energy in a form the cell can use Need an energy currency
a way to pass energy aroundneed a short term energy
storage molecule
Whoa! Hot stuff!
ATP
high energy bondsHow efficient!Build once,use many ways
Adenosine TriPhosphate modified nucleotide
nucleotide = adenine + ribose + Pi AMP
AMP + Pi ADP ADP + Pi ATP
adding phosphates is endergonic
HOW DOES ATP STORE ENERGY?
PO–
O–
O
–O PO–
O–
O
–O PO–
O–
O
–OPO–
O–
O
–O PO–
O–
O
–OPO–
O–
O
–O PO–
O–
O
–O PO–
O–
O
–O
Each negative PO4 more difficult to adda lot of stored energy in each bond
most energy stored in 3rd Pi
3rd Pi is hardest group to keep bonded to molecule
Bonding of negative Pi groups is unstablespring-loadedPi groups “pop” off easily & release energy
Instability of its P bonds makes ATP an excellent energy donor
I thinkhe’s a bitunstable…don’t you?
AMPAMPADPATP
HOW DOES ATP TRANSFER ENERGY?
PO–
O–
O
–O PO–
O–
O
–O PO–
O–
O
–O7.3energy+P
O–
O–
O
–O
ATP ADP releases energy
∆G = -7.3 kcal/mole Fuel other reactions Phosphorylation
released Pi can transfer to other molecules destabilizing the other molecules
enzyme that phosphorylates = “kinase”
ADPATP
It’snever thatsimple!
AN EXAMPLE OF PHOSPHORYLATION… Building polymers from monomers
need to destabilize the monomersphosphorylate!
C
H
OH
H
HOC C
H
O
H
C+ H2O++4.2 kcal/mol
C
H
OHC
H
P+ ATP + ADP
H
HOC+ C
H
O
H
CC
H
P+ Pi
“kinase” enzyme
-7.3 kcal/mol
-3.1 kcal/mol
enzyme
H
OHC
H
HOC
synthesis
Can’t store ATP good energy donor,
not good energy storagetoo reactivetransfers Pi too easilyonly short term energy
storage carbohydrates & fats are long term energy storage
ATP / ADP CYCLE
A working muscle recycles over 10 million ATPs per second
Whoa!Pass methe glucose(and O2)!
ATP
ADP Pi+
7.3 kcal/mole
cellularrespiration
THE CROSS SECTION OF A LEAF
CHLOROPLAST ANATOMY
Think about how the structure of this organelle determines its
function!
CHLOROPLASTS Organelles in plants. All green parts of plants have
chloroplasts Leaves is the major place where
photosynthesis happens. Contains chlorophyll- a green pigment
that is used to absorb light energy and drive photosynthesis.
Mainly in spongy mesophyll cells- also in palisade mesophyll cells.
1.5 million chloroplasts per 1 sq meter of leaf surface.
CHLOROPHYLL
Chloroplasts in Elodea leaves!
THYLAKOID ANATOMYIt has a
phospholipid bilayer
membrane around the thylakoid!
PHOTOSYNTHESIS EQUATION
•Where does it come from?
• How does it get into plants?
• What is it used for?
•Where does it come from?
• How does it get into plants?
• What is it used for?
•What provided the building blocks to make it?
• How is it made?
• What is it used for? •Where does it go?
•Where does it come from?
• How does it get out of plants?
• What is it used for?
TWO STEPS OF PHOTOSYNTHESIS Light Dependent: Light Reactions:
Change solar energy into chemical energy. Happens in the thylakoid membrane.
Light Independent: Calvin Cycle: Takes carbon dioxide from air and “fixes” into Calvin cycle. Changes carbon dioxide into sugar. Happens in the stroma.
LIGHT
A LOOK AT LIGHT The spectrum of color
ROYGBIV
LIGHT When light comes into contact with
matter it can be:ReflectedTransmittedAbsorbed- substances that absorb light are
called pigments. Different pigments absorb different wavelengths of light.
LIGHT: ABSORPTION SPECTRA
Photosynthesis gets energy by absorbing wavelengths of lightchlorophyll a
absorbs best in red & blue wavelengths & least in green
other pigments with different structures absorb light of different wavelengths
Why areplants green?
THE LIGHT REACTIONS IN DETAIL
LIGHT REACTIONS
O2
H2O
Energy BuildingReactions
ATP
produces ATP produces
NADPH releases O2 as
a waste product
sunlight
H2O ATP O2lightenergy ++ + NADPH
NADPH
ETC of Photosynthesis Chloroplasts transform
light energy into chemical energy of ATP
use electron carrier NADP+
ETC OF PHOTOSYNTHESIS ETC produces from light energy
ATP & NADPH go to Calvin cycle
PS II absorbs lightexcited electron passes from chlorophyll to
“primary electron acceptor”need to replace electron in chlorophyllenzyme extracts electrons from H2O &
supplies them to chlorophyll splits H2O O combines with another O to form O2
O2 released to atmosphere and we breathe easier!
THE SIMPLE EXPLANATION OF THE LIGHT REACTIONS!
PS II
H2
0
e e e e e PS I
NADP +
O O
H+
H+
H+
H+
PADP
ATP
H+
H+
H+
H+H
+ H+ NADPH
FROM CO2 C6H12O6 CO2 has very little chemical energy
fully oxidized C6H12O6 contains a lot of chemical energy
reducedendergonic
Reduction of CO2 C6H12O6 proceeds in many small uphill steps
each catalyzed by specific enzymeusing energy stored in ATP & NADPH
FROM LIGHT REACTIONS TO CALVIN CYCLE
Calvin cycle chloroplast stroma
Need products of light reactions to drive synthesis reactionsATPNADPH
CALVIN CYCLE
sugarsC6H12O6
CO2
SugarBuildingReactions
ADP
builds sugars
uses ATP & NADPH
recycles ADP & NADP back to make more ATP & NADPH
ATP
NADPH
NADP
CO2C6H12O6 ++ + NADPATP + NADPH ADP
TO G-3-P AND BEYOND! Glyceraldehyde-3-P
end product of Calvin cycleenergy rich 3 carbon sugar“C3 photosynthesis”
G-3-P = important intermediate G-3-P glucose carbohydrates
lipids amino acids nucleic acids
PHOTOSYNTHESIS SUMMARY
Light reactionsproduced ATPproduced NADPHconsumed H2Oproduced O2 as byproduct
Calvin cycleconsumed CO2
produced G3P (sugar) regenerated ADP regenerated NADP
NADPADP
SUMMARY OF PHOTOSYNTHESIS
Where did the CO2 come from? Where did the CO2 go? Where did the H2O come from? Where did the H2O go? Where did the energy come from? What’s the energy used for? What will the C6H12O6 be used for? Where did the O2 come from? Where will the O2 go? What else is involved…not listed in this equation?
6CO2 6H2O C6H12O6 6O2lightenergy + ++
RATE OF PHOTOSYNTHESIS Rate: activity per unit of time. Photosynthesis can be measured by:
How much carbon dioxide is consumed.How much oxygen is produced.How much glucose is produced.
There are 3 main factors that affect the rate: Light intensity Temperature Concentrations of Carbon Dioxide and/or Oxygen
LIGHT INTENSITY
TEMPERATURE
INEFFICIENCY OF RUBISCO: CO2 VS O2
Rubisco in Calvin cyclecarbon fixation enzyme
normally bonds C to RuBP reduction of RuBP building sugars
when O2 concentration is high Rubisco bonds O to RuBP O2 is alternative substrate oxidation of RuBP breakdown sugars
photosynthesis
photorespiration
IMPACT OF PHOTORESPIRATION
Oxidation of RuBPshort circuit of Calvin cycle loss of carbons to CO2
can lose 50% of carbons fixed by Calvin cycle reduces production of photosynthesis
no ATP (energy) produced no C6H12O6 (food) produced
if photorespiration could be reduced, plant would become 50% more efficient
strong selection pressure to evolve alternative systems
REDUCING PHOTORESPIRATION
Separate carbon fixation from Calvin cycleC4 plants
physically separate carbon fixation from actual Calvin cycle
different enzyme to capture CO2
PEP carboxylase stores carbon in 4C compounds different leaf structure
CAM plants separate carbon fixation from actual Calvin cycle by time
of day fix carbon (capture CO2) during night
store carbon in organic acids perform Calvin cycle during day
C4 PLANTS A better way to capture CO2
1st step before Calvin cycle, fix carbon with enzymePEP carboxylase store as 4C compound
adaptation to hot, dry climates have to close stomates a lot different leaf anatomy
sugar cane, corn, other grasses…
COMPARATIVE ANATOMY
Separate reactions in different cells light reactions carbon fixation Calvin cycle
C3 C4
C4 PHOTOSYNTHESIS
CO2O2
CO2
O2
Outer cells light reaction &
carbon fixation pumps CO2 to
inner cells keeps O2 away
from inner cells away from
Rubisco
Inner cells Calvin cycle glucose to veins
Physically separated C fixation from Calvin cycle
CAM (CRASSULACEAN ACID METABOLISM) PLANTS Different adaptation to hot, dry
climates separate carbon fixation from Calvin cycle by time
close stomates during day open stomates during night
at night, open stomates & fix carbon in “storage” compounds organic acids: malic acid, isocitric acid
in day, close stomates & release CO2 from “storage” compounds to Calvin cycle increases concentration of CO2 in cells
succulents, some cacti, pineapple
CAM PLANTS
C4 VS CAM SUMMARY
C4 plants separate 2 steps of C fixation anatomically in 2 different cells
CAM plants separate 2 steps of C fixation temporally at2 different times
solves CO2 / O2 gas exchange vs. H2O loss challenge
SUPPORTING A BIOSPHERE
On global scale, photosynthesis is the most important process for the continuation of life on Eartheach year photosynthesis synthesizes 160
billion tons of carbohydrate heterotrophs are dependent on plants as food
source for fuel & raw materials
REVIEW
PUTTING IT ALL TOGETHER
CO2 H2O C6H12O6 O2lightenergy + ++
SugarBuildingReactions
Energy BuildingReactions
Plants make both:energy
ATP & NADPH
sugars
sunlight
O2
H2O
sugarsC6H12O6
CO2
ADP
ATP
NADPH
NADP
HOW ARE THEY CONNECTED?
glucose + oxygen carbon + water + energydioxide
C6H12O6 6O2 6CO2 6H2O ATP+ + +
Heterotrophs
+ water + energy glucose + oxygencarbondioxide
6CO2 6H2O C6H12O6 6O2lightenergy + ++
Autotrophsmaking energy & organic molecules from light energy
making energy & organic molecules from ingesting organic molecules
exergonic
endergonic
H2O
ENERGY CYCLE
Photosynthesis
Cellular Respiration
sun
glucose O2CO2
plants
animals, plants
ATP
THE END!