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Biology 224 Chapter 8 (Dr. Brophy) Liberty University
Terms in this set (79)
What is Photosynthesis?
the conversion of light energy to chemical energy
organisms which cannot manufacture their own food from simple Carbon compounds.
organisms which can manufacture their own food from simple Carbon compounds.
The reactants of photosynthesis
Carbon Dioxide, water, light (energy)
The products of photosynthesis
Food (carbohydrates), oxygen
H2O + CO2 = C6H1206 + O2
Light comes in particles termed
Light travels in
the distance from one wave peak to the next.
all forms of Radiant Energy, including the visible spectrum.
Longer wavelengths have ___________ energy.
What is the range of the wavelengths on the visible spectrum?
400 - 700 nm
molecules capable of absorbing some wavelengths (color) of light but not others.
How do pigments produce color?
only the wavelengths not absorbed by a pigment are reflected or transmitted so they can be seen.
Why is blue Blue?
pigment absorbs green, yellow, orange and red, so only blue is reflected (seen).
Why is red Red?
blues and greens and absorbed, orange and red are not, they are transmitted.
Why are leaves green?
blue, orange and red wavelengths are absorbed, so only green is reflected (seen).
What is an Absorption Spectrum used for?
a graph for a pigment, plotting the amount of light absorbed vs. wavelength.
What is the Action Spectrum used for?
a graph for a plant, plotting the photosynthetic activity (action) vs. wavelength.
How does one determine which of the many pigments in plant are the major one(s) used for Photosynthesis?
Compare the Absorption Spectrum of each pigment with the Action Spectrum.
What does a pint do wth the light absorbed?
Structure of Chlorophyll:
Hydrophobic, Hydrocarbon "tail" inserts Chlorophyll into the Thylakoid membrane.
Describe the head of the Chlorophyll.
It has alternating double and single bonds - useful for picking up and giving off extra electrons.
Photosynthesis I and II:
are groups of many copies of Chlorophyll a and b; and Carotene and Xanthophyll as accessory pigments.
How does photosystems arrangement affect light energy?
light energy is passed from pigments tats absorb shorter wave-lengths to those that absorb longer wavelengths.
A pair of _________________ molecules occur in each Photosystem and ultimately receive the energy/ electrons from all the other pigments.
In Photosynthesis I chlorophyll a is
In Photosynthesis II chlorophyll a is
P700 and P680 have special associations with
What does P700 and P680 responsible for?
they pass the high energy electrons generated by the Photosystem absorbing light, to molecules outside the Photosystem.
_______________ enters the plant through the roots, traveling up the steam and to the leaves, through the Xylem in the Vascular Bundles.
How does Carbon Dioxide enter the plant?
from the atmosphere (o.3%) through microscope pores (Stomata) in the underside of leaves.
How does Water enter roots and Carbon Dioxide enter leaf cells?
Noncyclic Photophoshorylation (Light-Dependent Reactions)
Water + Light = NADPH + Oxygen + ATP
Light hits Photosystem I, transferring the energy in the photon to an ____________________ in one of the pigment molecules.
__________________________ are passed to P700 (Reaction Center) which passes them to Feridoxin then NADP Reductase then NADP reducing it to NADPH.
________________________ will run out of electrons and shut down.
Light hits _____________________ transferring the energy in the photon to an electron in a pigment.
In Photosystem II, what happens to energized electrons?
they are passed to P680 (Reaction Center) which passes them to the Redox Chain (Photosynthetic Electron Transport Chain) then to Photosystem I.
electrons passing through Redox Chain used to pump Hydrogen ions from Stroma into Thylakoid's lumen.
Hydrogen ions diffuse down concentration gradient and pass through __________________, making ATP.
ATP Synthase process:
- H+ ions diffuse back into the Stroma through ATP Synthase making ATP.
- ATP Synthase is a multimeric protein.
- It rotates as H+ ions pass, coupling H+ flow with ADP Phosphorylation.
ATP Synthase is a
ATP Synthase consists of a base embedded in the _________________________, a shaft, and a rotating head.
Inner Mitochondrial Membrane
During ATP Synthase, the shaft rotates as ________ pass between the a and c subunits in the base.
During ATP Synthase, the ______________ rotation causes conformational changes in the head.
During ATP Synthase in one conformational, what binds ADP and Phosphate?
During ATP Synthase in the second, __________ and _________ are forced together, making ATP.
ADP and Phosphate
During ATP Synthase in the third, what is released?
___________________ is coupled to ATP Synthesis.
Hydrogen Ion flow
The light absorbed by Photosystem II is used to split __________, generating _______________ gas (diffuses out through the Stomata); ____________ are passed to Photosystem II then the ET chain; and ________________ added to those pumped into the Thylakoid lumen.
water, oxygen, electrons, hydrogen ions
Products of Light - Dependent Reactions:
ATP, NADPH and Oxygen
During Light - Dependent Reactions (Cyclic Photophosphorylation): what energizes electrons in Chlorophyll (PSI)?
What is the difference between Cyclic and Noncyclic phosphorylation?
Electrons not passed to NADP+, but to the Redox Chain (backwards) to make extra ATP only; no NADPH or Oxygen.
The Calvin-Benson Cycle is also known as the
Light- Independent Reactions
What are the two names for the Calvin-Benson Cycle?
- Calvin-Benson Cycle after the co-discovers of the cycle.
- C3 Photosynthesis after the first detectable compound (3PG), a 3-Carbon compound.
The first step in the Calvin- Benson cycle is
CO2 is added to RuBP (Ribulose Biphosphate) to yield 2 molecules of 3PG (3 Phosphoglycerate).
What is the name of the enzyme that helps with step 1 of the Calvin-Benson cycle?
Ribulose Biphosphate Carboxylase - Oxygenase.
The second step in the Calvin- Benson cycle is
Phosphorylation and Reduction of 3PG to G3P using ATP and NADPH.
The third step in the Calvin- Benson cycle is
Regeneration of RuBP from G3P, to continue the cycle.
Net Yield: 6 CO2 entering the cycle will produce
6C of carbohydrate or 1 glucose
Other organic molecules are synthesized from the carbohydrates produced in photosynthesis.
in the absence of CO2 adds O2 to RuBP
What are the products of Photorespiration?
1 molecule of 3PG and 1 molecule of Glycolate which is respired (broken down using O2) but producing no ATP
reduces the pool of cellular carbohydrates when the plant should be storing sugars.
1. hot, dry or still
2. close stomata to prevent water loss
3. low CO2
4. C4 Photosynthesis as a solution to Photorespiration.
How is Oxaloacetate formed?
CO2 is added to PEP by PEP Carboxylase.
Oxaloacetate breaks down to ____________ and _______________ which is then used in C3 Photosynthesis.
Carbon Dioxide "capture" occurs in
What is transferred to Bundle Sheath Cells where it generates CO2 for C3 Photosynthesis?
Net Effect: CO2 is pumped into ___________________ cells.
For the leaf anatomy, the mesophyll cells have
C3 pathway and light-dependent reactions.
Bundle Sheath Cells
What has C4 CO2 pump and light dependent reactions, but no C3 pathway?
What has C3 pathway and are completely surrounded by Mesophyll Cells?
Bundle Sheath Cells
Where is CAM found?
What happens to CAM at night?
CO2 fixed and stored as Oxaloacetate until day
What happens to CAM during the day?
CO2 released for Photosynthesis
What are the advantages of day and night during CAM?
At night: stomata can be open to capture CO2 without losing much water vapor.
During day: stoma are closed to prevent desiccaction.