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Biology of Plants Exam 2 > Lecture 6: Photosynthesis > Flashcards

Lecture 6: Photosynthesis Flashcards

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1
Q

Photosynthesis

A
  1. main route by which energy enters the biosphere
  2. creation of organic matter
    - high energy organic compounds (like carbohydrates) are made from low-energy, highly abundant, non-toxic inorganic compounds (CO2 & H2O) sing energy from the sun
    - Net equation of two sets of reactions:

6CO2+ 12 H2O -> C6H12O6 + 6O2 + 6H2O

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2
Q

Photosynthetic net equation

A

Net equation of two sets of reactions:

6 CO2 + 12 H2O -> C6H12O6 + 6O2 + 6H2O

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3
Q

Metabolic Chemical Reactions

A
  • chemical reactions either release or require energy
  • exergonic reactions
  • endergonic reactions
  • ATP
  • ADP
  • AMP
  • in metabolic systems you see exergonic and endergonic reactions coupled together
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4
Q

Exergonic reactions

A
  • potential energy of substrates greater than that of products (energy out)
  • (left side of the equation(input) is greater than the right side (products))
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5
Q

Endergonic reactions

A
  • potential energy of substrates is lower than that of products (energy in)
  • (left side is less than the right side of the equation)
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6
Q

ATP

A
  • adenosine triphosphate
  • main energy carrier of cells
  • covalent bonds between phosphate groups contain potential energy
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7
Q

ADP

A

Adenosine diphosphate

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8
Q

AMP

A

Adenosine monophosphate

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9
Q

Redox reactions

A
  • reduction and oxidation happening simultaneously
  • during chemical reactions electrones (e-) may shift energy levels and move from one atom to another creating oxidation-reduction reactions
  • think “LEO the lion goes GER”
  • oxidations and reduction reaction occur in pairs
  • electron transfer is accompanied by H+ transfer
  • electrons and protons are transferred by via electron transport chains made up of electron acceptor molecules, such as NAD+ = nicotinamide adenine dinucleotide; NADP+ = nicotinamide adenine dinucleotide phosphate
  • at each link in chain some energy is lost as heat or to do metabolic work
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10
Q

Oxidation

A

when an atom loses an electron it is oxidized

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11
Q

Reduction

A

when an atom gains an electron it is reduced

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12
Q

Ordered chemical reactions

A
  • in cells chemcial reactions are organized into pathways
  • reactions are catalyzed by enzymes
  • product of one reaction bemoes substrate of another
  • in cyclic pathways the starting molecule of the cycle is always regernated in the last step of the cycle
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13
Q

Where does biomass of the biosphere come from?

A

Annually photosynthetic organisms produce > 250 million metric tons of carbohydrates

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14
Q

Applications to photosynthesis

A
  • photosynthesis captures the energy of visible light
  • the longer the wavelength the less energy it carries
  • visible light has the right amount of energy to excite electrons in organic molecules
  • biomass of the biosphere….it all comes from photosynthetic reactions
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15
Q

Electron states:

GROUND STATE

A
  • the lowest energy state of an electron is the ground state
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16
Q

Electron states:

EXCITED STATE

A
  • when electron absorbs energy (quantum) from visible light it jumps to a higher orbital position and enters an excited state
17
Q

What is an example of molecules that absorb light?

A

Pigments are example of molecules that absorb light

  • Chlorophyll
  • phytochrome
18
Q

3 Potential Paths for Excited Electrons:

A
  • excitation energy converted to light/heat
  • energy passed to another molecule causing it to be excited
  • e- (electron) passed to e- acceptor molecule
19
Q

Pigments:

Chlorophyll a

A
  • is most abundant light-absorbing pigment in cyanobacteria, algae, and chloroplasts of plants
  • when Chlorophyll a absorbs visible light an electron is excited
  • the excited electron is transferred to an electron acceptor molecule
20
Q

Examples of accessory pigments

A
  • Chlorophyll b, carotenoids (a family of pigments), and xanthophylls are examples of accessory pigments
  • the presence of accessory pigments increase the amount of wavelengths of light that can be absorbed by the light, increase the different wavelengths of light that can be absorbed by the plant
21
Q

Chloroplasts****** MAKE SURE THIS IS CORRECT?!????

A
  • Grana -
  • thylakoid membranes - also called lamellae, in the interioir of the chloroplasts and where the light reactions of photosynthesis occur
  • grana stacks - double membranes of thylakoid membranes alternating with sheets of interconnecting stroma thylakoids
22
Q

Light harvesting complex

A
  • pigments in thylakoid membranes absorb photons
  • Chlorophyll b, carotenoids, xanthopyll
  • resonance transfer (????)****
  • reaction center, chlorophyll a dimer
  • chlorophyll molecules transmit energy from excited elctrons in the antenna complex to a reaction center
  • antenna complex - AKA light harvesting complex
23
Q

Light reactions (ADD MORE STUFF AND MAKE SURE THIS IS CORRECT)

A
  • see image
  • the link between the light reactions and the calvin cycle are ATP and NADPH (calvin cycle is where sugars are made)
  • light reactions - light is involved, water is involved, oxygen is released, ATP is made and NADPH is made
  • NADP+ and ADP are made in calvin cycle and shuttled back to the light reactions
  • lower in the diagram indicates lower energy and higher in the diagram indicates higher energy
  • step 4 on diagram is one of most important parts of this
24
Q

Plitolysis (ADD MORE????)

A
  • the splitting of water
25
Q

What is the heart of Photosystem II

A
  • the heart of PS II is P680, a dimer
  • 680 nm is the wavelength of light that 680 is…..??????
26
Q

Pq

A
  • Plastoquinone
  • one of the most important electron acceptor molecules in the (first) ETC
27
Q

Pc

A
  • Plastocyanin
  • one of the most important electron acceptor molecules in the (first) ETC
28
Q

What is the heart of Photosystem I

A
  • the heart of Photosystem I is the dimer p700
29
Q

Fd

A
  • Ferrodoxin
  • contains iron, first important electron acceptor in the second electron transport chain (ETC)
30
Q

NADP+ reductase

A
  • an enzyme that catalyzes the reaction
31
Q

What is produced at the conclusion of the light reactions?

A
  • at conclusion of light reactions ATP and NADPH are created
32
Q

Light reactions: purpose, location, and key reactions

A
  • Location: chloroplast, lamella (aka thylakoid membrane)
  • Purpose: to take light and make usable energy to be utilized by other organisms
  • Key reactions:hydrolysis - splitting of water -donates electron to PS2 then PS2 absorbs light which excites the electrons -> electrons b/c it is excitred can move up the ETC -> looses energy as it goes down ETC (have redox rxns occurring during this) -> redox reactions move the electrons through the ETC -> there it goes into PS1 then it repeats - light is excited
33
Q

Impact of herbicides in the light reactions

A
  • herbicide actions often block amino acid, carotenoid, or lipid biosynthesis or disrupt cell division
  • chemical structure of two herbicides that block photosynthetic electron flow
  • example:
    1. DCMU acts by blocking electron flow at the quionone acceptors of PS2
    2. Paraquat acts by accepting electrons from the early acceptors of PS1 and then reacts with oxygen to form superoxide - a species that is very damaging to chloropast components
34
Q

embedded in thylakoid membrane

A
  • lipid bilayer of cells
  • acidified lumen
  • electrochemical gradient across thylakoid membrane
  • ADP phosphorylated by ATPase
  • NADP+ terminal electron acceptor of PS 1
  • lumen oh thylakoid membrane is where the splitting of water occurs
35
Q

Stroma

A

watery matrix within the chloroplasts

36
Q

Light reactions summary

A
  • link to calvin cycle: ATO and NADPH+ are formed
  • heart of PS1 = dimer P680
  • heart of PS2 = dimer 700
    1. 2 e- excited from PS2 to primary acceptor
    2. splitting of H2O releases O2
    3. ETC - Pq (plastoquinone) -> cytochrome complex -> pc (plastocyanin) -> P700
    4. e- flow provides energy for chemiosmotic synthesis of ATP**
    5. 2 e- excited from PS1 -> primary acceptor
    6. ETC - Fd (ferodoxin) -> NADP+ reductase -> NADPH
37
Q

Herbicide resistant biotypes

A
  • simulated progression of resistant kochia exposed to repeated annual appilcations of herbicide
  • 1 a.a. (amino acid) substitution in D1 protein lowers the binding efficiency of the herbicide and the quinone binding site
38
Q
A
  • simulation assumes an initial seed population of 100,000/m squared with a 1 in 10,000,000 occurrence of resistant biotypes in the intial population, and 90% weed control
  • y-axis title is % resistance in treated population
39
Q

How does selection for herbicide resistance occur?

A
  • herbicide sprayed
  • resistant plant survives and sets seed
  • herbicide is used on weeds with more resistant plants
  • eventually majority resistant

Biology of Plants Exam 2 (5 decks)

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