Section Outline
Section 8-1
8–1 Energy and Life
A. Autotrophs and
Heterotrophs
B. Chemical Energy and ATP
1.Storing Energy
2.Releasing Energy
C. Using Biochemical Energy
Go to
Section:
What is energy?
•The ability to do work.
•Cells require energy for any “work” they do:
– Cell reproduction
– Manufacturing proteins
– Movement of materials between cells
– To allow tissues in muscles to move (animals)
Go to
Section:
Autotrophs and Heterotrophs
•Autotrophs
– Have the ability to generate their own food.
– Base of many food chains
– Plants, bacteria, etc.
•Heterotrophs
– Must obtain food from other source
– Typically the autotrophs
•All organisms must obtain/make food in the form of
sugars
to ultimately be used to create energy.
Go to
Section:
Section Outline
Section 8-2
8–2 Photosynthesis: An
Overview
A. Investigating
Photosynthesis
1. Van Helmont’s
Experiment
2. Priestley’s Experiment
3. Jan Ingenhousz
B. The Photosynthesis
Equation
C. Light and Pigments
Go to
Section:
•Photosynthesis
– the process of using light energy to convert
CO2 and H2O into high energy glucose
Go to
Section:
Photosynthesis: Reactants and Products
Section 8-2
Light Energy
Chloroplast
CO2 + H2O
Go to
Section:
Sugars + O2
Early discoveries
•Jan Van Helmont
– 1643 – discovered plants take in water
•Joseph Priestly
– 1771 – plants release O2
•Jan Igenhousz
– Plants only produce O2 in the presence of light.
Go to
Section:
The Photosynthesis Equation
Go to
Section:
Go to
Section:
Figure 8-7 Photosynthesis: An Overview
Section 8-3
Light
CO2
Chloroplast
Chloroplast
NADP+
ADP + P
LightDependent
Reactions
Calvin
Cycle
ATP
NADPH
O2
Go to
Section:
Sugars
Go to
Section:
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
Light Used in Photosynthesis
• During Photosynthesis, the chlorophyll pigments can
absorb only some wavelengths of the visible light
from the electromagnetic spectrum.
• Visible light consists of the following colors or
wavelengths in order of increasing wavelengths /
decreasing energy:
– Violet, Indigo, Blue, Green, Yellow, Orange and
Red.
• The grana of the chloroplasts absorb mainly blueviolet and red-orange lights.
• Green light is reflected and transmitted by green
plants – hence, they appear green.
Go to
Section:
• Photon
= a discrete packet of light energy.
Light
• The shorter the wavelength, the greater the energy….and viceversa.
Go to
Section:
Pigments
• Chlorophyll – “More like Borophyll”…..Billy Madison
– Main pigments absorbing light for photosynthesis
– Two types:
1. Chlorophyll a – light green
2. Chlorophyll b – dark green
• Accessory pigments
– Found in much smaller quantities
– Xanthophyll - yellow
– Carotene - orange
Go to
Section:
Section Outline
Section 8-3
8–3 The Reactions of Photosynthesis
A. Inside a Chloroplast
B. Electron Carriers
C. Light-Dependent Reactions
D. The Calvin Cycle
E. Factors Affecting Photosynthesis
Go to
Section:
Inside the chloroplast
-Contain thylakoid
- Site of light reaction
- Stacks are called grana
-Space in between is known as
stroma
- Site of Calvin cycle
Go to
Section:
Go to
Section:
Electron carriers
•NADPH
– Electrons are typically carried by molecules, especially when
they are energized
– Because they are negatively charged they are attracted to
positive “things”
– Electrons will combine with NADP+ and H+ to form NADPH
• Called a reduction reaction (NADP+ is reduced)
NADP+
Go to
Section:
+
H+ +2e-
NADPH
Light Reaction overview
• Light reaction – is dependent on light and occurs only
during the day in nature.
– It takes place in the thylakoid membrane of the
chloroplast.
• Light reactions involve
a) Splitting of water to produce oxygen,
b) Energy production (ATP) and
c) Reduction of NADP+ to NADPH.
Go to
Section:
Light reaction….in detail (now the party begins)
•Chlorophyll's role
– Provide electrons to be
“energized”
– Specific wavelengths of light
strikes chlorophyll and energize
electrons to enter into electron
transport chain of light reaction.
Go to
Section:
e-
•Water’s role
– Can chlorophyll run out of electrons?
– Theoretically, yes.
– Water replenishes the supply to chlorophyll so they
can donate electrons to the electron transport chain
– Water is split into H+ (Hey, that looks familiar!) and
O2 (sort of important stuff – wonder where that
goes?!?)
Go to
Section:
So what happens?
1. A specific wavelength of
elight (680 nm) strikes
chlorophyll on the thylakoid
membrane.
2. An electron gets
“energized” and enters into
the electron transport
chain.
3. Electron “hops” from protein
to protein “down hill.”
e4. Energy is released,
provides energy for:
ADP +GoPto
ATP
Section:
So where does the electron go?
•Into another chlorophyll “center” that is losing electrons
when 700 nm of light hits it.
•Those electrons eventually must join up with NADP+
and H+ to form NADPH (also needed by Calvin cycle)
– Electron carriers!
Go to
Section:
Untitled Document
Go to
Section:
How is it made?
•Concentration gradients are established by “pumping”
H+ into the inner thylakoid space (energy comes from
the electron “bouncing down hill”)
•H+ naturally tend to diffuse out
– This is kinetic energy – energy of motion
– ATP synthase uses that energy to put ADP
together with P to make ATP
Go to
Section:
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
Go to
Section:
So what if ATP is made?
•What is it used for?
– To run the Calvin Cycle!
•So does light directly make food for the plant?
– No! Makes the fuel to run the reaction that makes
food for the plant!
Go to
Section:
Summary
•Light hits chlorophyll P680…..
– Electrons energized enter electron transport chain
•Water split………
– Replenishes lost electrons
•Electrons passed “downhill”………
– Releases energy used to “pump” H+ uphill
•P700………..
– Catches electron, 700 nm of light hits it and sends
electrons on down to be picked up by NADP
•NADP…..
– Catches electrons, goes to Calvin Cycle
•H+………
– “Fall” or diffuse through ATP synthase, provides
Go to
Section:energy to make ATP
Go to
Section:
Go to
Section:
Go to
Section:
Go to
Section:
Go to
Section:
Go to
Section:
Calvin Cycle
•Series of reactions that require energy from ATP and
electrons from NADPH
•Starting reactant:
– CO2
•Finished product:
– “G3P” – glyceraldehyde 3-phosphate
•G3P is then later processed into sugars, starches etc.
Go to
Section:
http://ppdb.tc.corne
ll.edu/images/calvi
Go to
ncycle9kj7.jpg
Section:
CARBON FIXATION
(3) CO2 molecules enter
Rubisco attaches the CO2 to RuBP
Go to
Section:
REDUCTION
6 ATP and 6 NADPH used
1 G3P molecule produced
Go to
Section:
Regenerate RuBP
Use 3 more ATP
Go to
Section:
•“PGA”
– Three carbon molecules formed at the beginning
of Calvin
•“G3P”
– Cell converts later to sugars and carbs
•“RuBP”
– What combines with CO2, to keep Calvin going.
Go to
Section:
Video 5
Calvin Cycle
Click the image to play the video segment.
Concept Map
Section 8-3
Photosynthesis
includes
Lightdependent
reactions
Calvin cycle
use
take place in
Energy from
sunlight
Thylakoid
membranes
to produce
ATP
NADPH
Go to
Section:
O2
takes place in
Stroma
uses
ATP
NADPH
of
to produce
Chloroplasts
High-energy
sugars
Now where???
•So what happens with this G3P??
– Converted to sugar based molecules like….
• Glucose/fructose…. – maple syrup anyone?
• Starch – French fries, cornbread, and pasta
• Cellulose – cell wall material – 2 X 4’s, paper,
and Raisin BRAN
– Depends on the needs of the cell at that instance
•Plants generate 200 billion tons of “Carbs” a year
globally!
Go to
– Atkins would be mortified!
Section:
Factors affecting photosynthesis
•Water deficiencies
– Supplies chlorophyll with electrons for light
reaction
•Temperature
– Low temperatures minimize enzyme activity
– Most reactions in photosynthesis enzyme driven
•Light
– Amount of daylight
– Why deciduous trees drop leaves and go dormant
for the winter
Go to
Section:
Alternative methods of photosynthesis
•Tropical plants temporarily fix CO2
by alternate method
– Corn, sugar cane, grasses
– C4 plants (most plants are C3 –
remember PGA?)
•CO2 fixed forms a 4-carbon
molecule instead of PGA, one of the
carbons breaks off, saving an extra
carbon dioxide for the regular Calvin
Cycle
•Why do they feel the need to do so?
– Generates lots of CO2 inside
the leaf for Calvin
– Ok???, So what?
Go to
Section:
Leaf anatomy of plants adapted for
hot/arid conditions (C4 plants)…
O2
C4 pathway
Separate CO2
fixation and sugar
making into two
different cells
Go to
Section:
C3
pathway