Term
| What is and how does photosynthesis work? |
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Definition
Process that traps light energy and stores it as chemical energy in bonds of organic molecules(e.g. sugar)
Light energy is used to convert carbon dioxide & water into glucose & oxygen
6 Co2 + 6 H2O + Light Energy C6H12O6 + 6O2
Occurs in: plants, photosynthetic protists and some bacteria |
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Term
| Tell me about the sites of photosynthesis in plants. |
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Definition
Chloroplasts in leaves
Leaf has large surface area
Leaf is thin to allow light to reach chloroplasts
Leaf structure
Cuticle – transparent, waxy, waterproof covering
Prevents evaporation of water
Epidermis – layer of transparent cells inside cuticle
Stomata – pores in epidermis to allow CO2 in
Mesophyll – layers of cells containing
Vascular bundles – veins in leaf
Carry water and nutrients to leaf
Carry sugars out of leaf to other parts of plant |
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Term
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Definition
Located in cells of mesophyll
Small in size
Double membrane organelles containing
Stoma (= fluid)
Grana (= stacks of thylakoids)
Thylakoids (= interconnected membranous sacs)
Contain pigments to absorb light (e.g. Chlorophyll) |
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Term
| What are important Properties of Sunlight? |
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Definition
Sunlight= electromagnetic radiation
Waves of light composed of photons (=energy packets)
Spectrum of wavelengths of light
Ranges from low to very high frequency wavelengths
Visible spectrum of light= colors of the rainbow
Objects reflect or absorb/capture wavelengths of light
Black objects – absorb/Capture all wavelengths
White objects – reflect all wavelengths
Color of object = wavelengths of light in reflects
Ex: Red objects reflect wavelengths of light |
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Term
| Photosynthetic Pigments in Plants are? |
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Definition
Each pigment absorbs a different wavelength of light
Primary pigment of photosynthesis
Chlorophyll a
Absorb violet, blue and red Reflects green
Accessory pigments
Chlorophyll b
Absorbs blue and red-orange Reflects yellow-green
Carotenoids
Absorb blue and green Reflect yellow and orange
Ex: beta-carotene in carrots
Procyanins
Absorb green and yellow Reflect blue and pink |
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Term
| What are the processes of photosynthesis? |
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Definition
involves dozens of individual reactions catalyzed by dozens of enzymes
2 interdependent stages of reactions
Light Reactions (“photo” aspect)
Occur in thylakoids of chloroplast
Conversion of light energy to chemical energy
Formation of ATP and NADPH (=energy- carrier molecules)
Calvin Cycle (“synthesis” aspect)
Occurs in stroma of chloroplast
Capture of carbon from CO2
Synthesis of sugars from carbon
Utilizes energy from ATP and NADPH |
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Term
| Tell me about light reactions. |
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Definition
Conversion of light energy to chemical energy
Occur in thylakoids of chloroplast
Photosystems – cluster of chlorophyll , accessory pigments and proteins
2 Types of photosystems
Photosystem II (PS II)
Produces ATP
Splits H20 molecules to utilize electrons
Photosystem I (PSII)
produces energy for Calvin Cycle
NOTE: PS II occurs before PS I.
Can not occur without light! |
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Term
| What are the photo-system components? |
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Definition
Pigment clusters - chlorophyll b, carotenoids & procyanins
Absorb light energy and transfer to reaction center
Reaction center = specialized chlorophyll a molecules
“excited” by light energy and loses high energy electron
Primary electron acceptor = molecule embedded in complex of proteins
Passes electron from chlorophyll to electron transport system
Electron transport chain (ETC I and II) = series of electron carrier molecules
Pass electron to each other to utilize energy |
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Term
| Photosystem II - Process? |
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Definition
1) Light energy by pigment clusters
2) Pigment clusters transfer light to reaction center
Chlorophyll a molecule becomes excited
Releases energized electron
3) Electron captured by primary electron acceptor
4) Electron passed to first molecule of ETC II
Electron passed down chain from molecule to molecule
Some energy from electron lost along the way
5) Energy harnessed to pump H+ ions into thylakoid
space to generate ATP.
6) Energy depleted electron leaves ETC II & enters PS I reaction center |
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Term
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Definition
6) Light energy absorbed by pigment clusters
Pigment clusters transfer light to reaction center
Chlorophyll molecule becomes excited
Releases energized electron
7)Electron captured by primary electron acceptor
8)Electron passed to first molecule of ETC I
Electron passed down chain from molecule to molecule
9)Electron reaches NADP+ molecule
NADPH energy-carrier molecule formed when 2 energized & 1 H+ combine with NADP+
NADP+ + 2e- +H+ --> NADPH |
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Term
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Definition
Process in which H+ gradient across thylakoid membrane drives ATP synthesis
Active transport (carrier protein) of H+ ions against gradient from stroma into thylakoid space
Utilizes energy liberated during PS II
Results in:
High H+ concentration in thylakoid space
Low H+ concentration in stroma
Flow of H+ ions back across membrane through ATP synthase (=channel protein)
ATP synthase captures liberated energy
Generates formation of ATP from ADP+ phosphate |
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Term
| Electron Flow in Photosynthesis. |
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Definition
H2O e- + H+ ½ O2
Photosystem II
Photosystem I
NADPH
Calvin Cycle |
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Term
| How does the Calvin Cycle work? |
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Definition
Occurs in stroma of chloroplast
Function: convert inorganic CO2 into chemical into organic sugar molecules
Requirements:
CO2 (from atmosphere)
Ribulose bisphosphate (RuBp)
Enzyme
ATP & NADPH (from light reactions)
3 Step Cycle
Carbon fixation
Synthesis of glyceraldehyde-3- phosphate (G3P)
Regeneration of RuBP |
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Term
| Carbon Fixation is and... |
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Definition
Capture of carbon from CO2
Incorporation of carbon into organic molecules
3 Co2+ 3 RuBP unstable 6-carbon molecule
Catalyzed by rubisco enzyme
6-carbon molecule 2 PGA molecules
PGA = phosphoglyceric acid (3-carbon molecule)
PGA molecules used in next step |
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