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Photosynthesis
Chapter 10
56
Biology
12th Grade
10/18/2012

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Term
Autotrophic Nutrition
Definition
inorganic raw materials > organic molecules
producers
Term
Photoautotrophs
Definition
use light energy to synthesize organic molecules
Term
Chemoautotrophs
Definition
Use inorganic substances (sulfur, ammonia, etc.) to synthesize organic compounds. Only bacteria.
Term
Heterotrophic Nutrition
Definition
acquiring organic molecules from compounds produced by other organisms
consumers
Term
Chloroplasts
Definition
sites of photosynthesis, found in leaves
Term
Mesophyll
Definition
green tissue in the leaf's interior
Term
Stomata
Definition
pores in a leaf through which CO2 and O2 pass
Term
Stroma
Definition
viscous fluid outside the thylakoids
Term
Summary Equation of Photosynthesis
Definition
Light Energy + 6CO2 + 12 H2O > C6H12O6 + 6O2
Van Neil discovered that the O2 produced by plants came from H2O and not CO2
Term
Two steps of Photosynthesis
Definition
light reactions
Calvin cycle
Term
Is photosynthesis endergonic or exergonic?
Definition
endergonic (not spontaneous)
Term
Light Reactions
Definition
convert light to chemical energy through synthesis of ATP and NADPH, occur in thylakoid membrane, give off O2
Term
Calvin Cycle
Definition
carbon-fixation reactions that reduce atmospheric CO2 to a carbohydrate, occur in the stroma, requires the products of light reactions: NADPH for reducing power and ATP for chemical energy
Term
Electromagnetic Radiation
Definition
form of energy that exhibits wavelike behavior as it travels through space
Term
Lamda
Definition
Wavelength
Term
Nu
Definition
Frequency
Term
c =
Definition
the speed of light
3.0 * 10^8 m/s
Frequency(Wavelength)
Term
Photoelectric Effect
Definition
Emission of electrons by certain metals when light shines on them. No electrons are emitted if the frequency is below a minimum.
Term
Quantum
Definition
Max Planck, minimum amount of energy that can be lost or gained by an electron.
Term
E =
Definition
energy in Joules
h*nu
(Planck's constant)(frequency)
hc/v
Term
Planck's Constant
Definition
h=6.626*10^-34 J-s
Term
Ground State
Definition
lowest energy state of an atom
Term
Excited State
Definition
state in which an atom has a higher potential energy than its ground state
Term
Colors most effectively absorbed by chlorophyll
Definition
blue and red
Term
Pigment
Definition
substance that absorbs visible light
Term
Spectrometer
Definition
instrument used to measure what proportion of a specific wavelength of light is absorbed or transmitted by a pigment
Term
Action Spectrum
Definition
rate of photosynthesis vs. wavelength
Term
chlorophyll a
Definition
light absorbent pigment that participates directly in light reactions. Does most of the photosynthesis.
Term
chlorophyll b
Definition
accessory pigment, yellow-green and similar to chlorophyll a
Term
carotenoids
Definition
accessory pigment, yellow and orange hydrocarbons built into thylakoid membrane
Term
primary electron acceptor
Definition
molecules that trap excited electrons that have absorbed photons
Term
photosystem
Definition
light-harvesting complex of the thylakoid membrane
Term
Photosystems are composed of
Definition
Antenna complex, reaction-center chlorophyll, and primary electron acceptor
Term
Antenna Complex
Definition
several hundreds of pigment molecules that gather light, absorb protons, and pass energy
Term
Reaction-Center Chlorophyll
Definition
one of many chlorophyll molecules that can transfer and excited electron to initiate light reactions
Term
Primary Electron Acceptor
Definition
located near the reaction center; traps excited electrons from the reaction center chlorophyll a
Term
Photosystem I
Definition
Reaction center has specialized chlorophyll (P700)
Term
Photosystem II
Definition
Reaction center has specialized chlorophyll (P680)
Term
Noncyclic Electron Flow
Definition
Photosystems I and II, occurs in thylakoid membrane, passes electrons from water to NADP+, produces ATP, NADPH, and O2)
Term
Cyclic Electron Flow
Definition
Photosystem I, simplest pathway, generates more ATP without NADPH or O2. Excited electrons leave and return to the reaction center.
Term
Chemiosmosis
Definition
coupling of exergonic electron flow down an ETC and endergonic ATP production by electrochemical proton gradient across a membrane.
Term
Similarities of Chemiosmosis in Chloroplasts and Mitochondria
Definition
1. ETC assembled in a membrane translocates proteins across the membrane through a series of carriers that are progressively more electronegative.
2. An ATP synthase complex couples proton diffusion down their gradient to the phosphorylation of ADP
3. The ATP Synthase complexes and some electron carriers are similar.
Term
Differences of Oxidative Phosporylation and Photophosphorylation
Definition
In the ETC:
- Mitochondria transfer chemical energy from food to ATP.
- Chloroplasts transfer chemical energy from light energy.
In Spatial Organization:
- Inner mitochondrial membrane pumps protons from the matrix to the intermembrane space
- Thylakoid membrane pumps protons from the stroma to the thylakoid compartment
Term
The Calvin Cycle
Definition
ATP and NADPH produced by light reactions are used to reduce carbon dioxide to sugar:
3 molecules CO2 -> 1 molecule Sugar (G3P)
Term
Three phases of the Calvin Cycle
Definition
Carbon Fixation
Reduction
Regeneration of CO2 Acceptor (RuBP)
Term
Carbon Fixation
Definition
Each molecule of CO2 is attached to a RuBP catalyzed by rubisco:
3 molecules CO2 ->3 molecules RuBP -> 6 molecules 3-phosphoglycerate
Term
Reduction
Definition
Endergonic two-step reaction, couples ATP hydrolysis with reduction of 6 3-phosphoglycerates to 6 G3Ps. Net gain of 1 G3P because the other 5 are used to regenerate 3 RuBPs.
Term
Regeneration of RuBP
Definition
rearranges carbon skeletons of 5 G3P to 3 RuBP, requires 3 ATp
Term
Photorespiration
Definition
a metabolic pathway that reduces the yield of photosynthesis; consumes oxygen and evolves carbon dioxide but produces no ATP and decreases photosynthetic output.
Occurs because active site of rubsico can accept O2 as well as CO2, reduces organic molecules used in the Calvin cycle
Term
Photorespiration is fostered by
Definition
hot, dry, bright days when plants close stomata to prevent dehydration
Term
C4 Plants
Definition
Precede Calvin cycle with reactions that incorporate CO2 into 4-C compounds. Leaf anatomy segregates the Calvin cycle from the initial incorporation of CO2 into organic compounds because of differing cell types (Bundle-Sheath and Mesophyll)
Term
Bundle-Sheath Cells
Definition
arranged into tightly packed sheaths around the veins of the leaf where the Calvin cycle occurs
Term
Mesophyll Cells
Definition
more loosely arranged between bundle-sheath cells and leaf surface
Term
C4 Pathway
Definition
1. CO2 is added to PEP to form oxaloacetate, a C-4 product, in mesophyll cells using PEP Carboxylase.
2. Oxaloacetate is converted to another 4-C.
3. Mesophyll cells export the 4-C products through plasmodesmata to bundle-sheath cells where CO2 is released and fixed by rubisco in the Calvin cycle
Term
PEP Carboxylase
Definition
C4 Pathway, has an affinity for CO2 but not O2
Term
CAM (Crassulacean Acid Metabolism) Plants
Definition
Avoid photorespiration by opening stomata primarily at night to take up CO2 and incorporate it into organic acids, which are stored in vacuoles of mesophyll cells until daytime when CO2 is released and light reaction can supply ATP and NADPH for the Calvin cycle.
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