DO NOW:
Answer the following question:
A plant was planted six months ago that weighed 12 oz (including the soil) in the window. Now the plant and soil weigh 22 oz!!! How is this possible? (No soil was added, and wet soil does not account for the answer).
Plants and Light
How do plants get their energy?
Photosynthesis!!! which means?
Using light to make energy.
Photo= light Synthesis= to make
2 Types of organisms…
Autotrophs make their own food
Heterotrophs must obtain food from environment (eat)
What are plants?
Autotrophs!!!
2 Types of Autotrophs…
1)Photoautotrophs-
2)Chemoautotrophs-
organisms that use light to make food
organisms that use chemicals to make food.
plants
bacteria
Photosynthesis in brief…
Plants are autotrophs, relying on photosynthesis to make food (glucose).
What’s required for photosynthesis?Light, CO2, and water…
…sugar and oxygen are given off
Light Energy!!!
Light is a form of radiation, which travels in what are called waves…
Let’s see some examples…
wavelength
Smaller wavelength, but greater frequency…
So…
Sunlight is a mixture of all visible wavelengths…what color is it?
White!!!
White light can be broken down into different colors using a prism, which diffracts the light to form a spectrum.
Spectrum?
A spectrum is simply a distribution of light, arranged in order according to its energy…
Good Ole Roy!!!
How can you remember the colors?
Listed backwards, they spell:
ROY G. BIV
Why are they arranged this way?
It’s due to wavelength…
380 430 500 560 600 750
Why do we see colors?
When we see color, it is due to reflected light.
This dot, absorbs all light, but that in the red end of the spectrum.
Umm Hmm…
Substances that absorb light are called pigments.
Umm, what doesn’t absorb light?
Anything that’s white!!!
Photosynthetic Pigments
By far, the most important pigment in plants, is chlorophyll.
All plants have 2 types of chlorophyll:
chlorophyll a and
chlorophyll bgreen
Other Pigments
Besides chlorophyll, plants have other pigments:
carotene (orange) and
xanthophyll (yellow)
Pigments continued…
Why don’t we see the other pigments?
They’re masked by chlorophyll, which is present in great quantities.
Why are the other pigments there?
They absorb light at different wavelengths than chlorophyll.
Light
ReflectedLight
Chloroplast
Absorbedlight
Granum
Transmittedlight
Figure 10.7
Photosynthesis again…
Where does photosynthesis occur?
Plants!!!
More specifically?
Chloroplasts!!!
Anatomy of a Chloroplast:
Chloroplasts contain flattened sacs of photosynthetic membranes called thylakoids.
A bunch of thylakoids make up grana.
The fluid surrounding the grana is called stroma.
Why are chloroplasts necessary?
Chlorophyll is contained within the grana…
Chlorophyll can absorb energy without stroma present, but it immediately gives off the energy as heat or light.
Necessity of chloroplasts continued.
For chlorophyll to produce food for the plant, all of the enzymes contained within the stroma are necessary.
thylakoid
grana
stroma
Photosynthesis
Overall reaction
6CO2 + 12H2OLight C6H12O6 + 6O2 + 6H2O
Takes place over many steps…
Photosynthesis Dissected:
Divided into 2 types of reactions:
1)Light-dependent reactions
2)Light-independent reactions
Light-dependent reactions
Requires light
Take place in the grana of chloroplast
Store energy in high energy molecules – ATP– NADPH
Light Dependent Reactions
Chlorophyll a and b absorb blue-violet and red-orange light from sun and excite electronsTransfer excited electrons to NADP (carrier) and convert ADP to ATPSome electrons split water called photolysis
Oxygen is released
photosystem II
photosystem I
H2O 2H+ + ½ O2
2e-
2e-
ADPATP 2e-
NADP+ + H+ + 2e- NADPH
Excitedstate
Ene
rgy
of e
lect
ion Heat
Photon(fluorescence)
Chlorophyllmolecule
GroundstatePhoton
e–
Figure 10.11 A
MillmakesATP
ATP
e–
e–e–
e–
e–
Pho
ton
Photosystem II Photosystem I
e–
e–
NADPH
Pho
ton
Figure 10.14
Light-independent Reactions
Energy from the light dependent reactions is used to power the light-independent reactions.
Do not necessarily occur in the dark, but they don’t require light.
Light-independent continued…
Occur in the stroma of the chloroplast
Series of enzyme controlled steps to convert CO2 and H into glucose.
The reaction:
CO2 goes through a process known as carbon fixation.
CO2 reacts with a 5 carbon sugar called ribulose bisphosphate (RuBP), and then enters the Calvin Cycle
Light Independent Reactions
H from NAPH2 from light reactions
Carbon dioxide from environmentRequire products from light reactions so stop shortly after light reactions endWater is also a by-product
Light reactions:• Are carried out by molecules in the thylakoid membranes• Convert light energy to the chemical energy of ATP and NADPH• Split H2O and release O2 to the atmosphere
Calvin cycle reactions:• Take place in the stroma• Use ATP and NADPH to convert CO2 to the sugar G3P• Return ADP, inorganic phosphate, and NADP+ to the light reactions
O2
CO2H2O
Light
Light reaction Calvin cycle
NADP+
ADP
ATP
NADPH
+ P 1
RuBP 3-Phosphoglycerate
Amino acidsFatty acids
Starch(storage)
Sucrose (export)
G3P
Photosystem IIElectron transport chain
Photosystem I
Chloroplast
Figure 10.21
Factors influencing photosynthesis:
There are 3 main factors influencing the rate:
1)Light intensity
2)Temperature
3)Water and mineral availability
4)Carbon dioxide level
Photosynthesis vs Cellular Respiration
In brief, they are exact opposites: photosynthesis stores energy in glucose, respiration releases energy.
Photosynthesis vs Cellular Respiration
Photosynthesis:
6CO2 + 12H2OLight
C6H12O6 + 6O2 + 6H2O
Photosynthesis vs Cellular Respiration
Photosynthesis:
6CO2 + 12H2OLight
C6H12O6 + 6O2 + 6H2O
Respiration:
C6H12O6 + 6O2 + 6H2O 6CO2 + 12H2O
Vein
Leaf cross section
Figure 10.3
Mesophyll
CO2 O2Stomata