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C Bio > Chloroplasts & Photosynthesis (23) > Flashcards

Chloroplasts & Photosynthesis (23) Flashcards

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Biology 101 flashcards
1
Q

heterotrophs

A

depend on an external source of organic compounds which were produced abiotically

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2
Q

autotrophs

A

utilize CO2 to manufacture their own organic molecules

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3
Q

chemoautotrophs

A

utilize the energy stored in inorganic molecules (ex: hydrogen sulfide) to convert CO2 into organic compounds

Ex: found around thermal vents

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4
Q

photoautotrophs

A

utilize radiant E of the fun to convert CO2 into organic compounds

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5
Q

what organisms carry out photosynthesis?

A

higher plants

eukaryotic algae

various flagellated protists

variety of prokaryotes (ex: blue-green bacteria)

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6
Q

photosynthesis

A

sunlight is transformed into chemical E & used to form carbs

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7
Q

what is the chemical formula of photosynthesis?

A

6CO2 + 6H2O –> C6H12O6 + 6O2 (coupled with light)

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8
Q

how is light E captured?

A

with pigment molecules including chlorophylls & accessory pigments (carotenes & phycobilins)

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9
Q

cytochromes

A

method plants capture electrons & produces a reducing power in the form of NADPH (plant version of ETC PROs)

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10
Q

NADH is used for _____ & NADPH is used for ______

A

catabolism

anabolism

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11
Q

light rxns

A

photochemical rxns

Products: ATP & NADPH

Occurs in thylakoid membranes of chloroplasts

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12
Q

darks rxns

A

thermochemical rxns

ATP & NADPH are used to synthesize carbs, conversion of CO2 into carbs

Occurs in stroma of chloroplasts

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13
Q

what are the 3 types of membranes of a chloroplast?

A

Outer membrane: freely permeable

Inner membrane: contains transporters which involves the transport in & out of the chloroplast of:
Small molecules like sugars
PROs synthesized in the cytoplasm

Thylakoid membranes

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14
Q

thylakoid membranes

A

enclose a lumen containing a sys of vesicles

System of vesicles are stacked in an array called a grana 

Carry out light rxns 

Contains 4 types of PROs that are embedded in the membranes: 
Photosystem I: includes chlorophyll & carotenoid molecules
Photosystem II: also includes chlorophyll & carotenoid molecules
Cytochromes b & f
ATP synthase
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15
Q

stroma

A

fluid surrounding thylakoid membranes

Contains enzymes involved in dark rxns

Contains the complete chloroplast genome which encodes most of the molecules required for chloroplast function
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16
Q

where are the molecules required for chloroplast function made?

A

stroma of the chloroplast

transcribed in the nucleus & translated in the cytoplasm

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17
Q

chloroplast genome

A

total gene set found within the chloroplast

   Encodes about 100 chloroplast specific PROs 

Uses its own RNA polymerase & ribosomes
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18
Q

how many PROs for the chloroplast are encoded in the nucleus?

A

900

they’re made in the cytoplasm & transported into the chloroplast

19
Q

how do chloroplasts divide?

A

Arise from pre-existing chloroplasts

Chloroplasts pinch themselves into 2 equal parts like bacteria (binary fission)

FtsZ PRO (in chloroplasts & bacteria) polymerize & form a contractile ring on the inside of the chloroplast –> constrict & divide the organelle

There is also a ring on the outside of the chloroplast called the plastid-dividing ring
PROs are derived from the host

20
Q

describe the process of the absorption of light?

A

E from sun is in the form of electromagnetic radiation
Radiation travels in photons

When a photon is absorbed the compound is converted to a higher E state (excited state)

Ground state is re-established in 3 ways:
Dissipated as heat
Re-emitted as a longer wavelength
Transferred to another molecule (occurs in photosynthetic pigments)

21
Q

pigments

A

molecules containing chromophores

22
Q

chromophore

A

chemical group capable of absorbing light of a particular wavelength

23
Q

absorption spectrum

A

plot intensity of light absorbed vs. wavelength

24
Q

action spectrum

A

plot of physiological response vs wavelength

25
Q

what does the action spectrum follow?

A

absorption spectrum of chlorophylls & carotenoids

26
Q

carotenoid

A

long hydrocarbon chains containing alternating double bonds

protects photosynthetic machinery from damage caused by reactive oxygen species

27
Q

how do carotenoids increase their efficiency?

A

absorbing light in regions where the chlorophyll absorbs light inefficiently

28
Q

carotenoids absorb what colour light & of what wavelengths?

A

light blue & green (400-550nm)

29
Q

carotenoids reflect what colour light & of what wavelengths?

A

yellow, orange & red (>550nm, <700nm)

30
Q

how do animals obtain carotenoids?

A

diet

31
Q

how do animals use carotenoids?

A

ornamental colourings:
Pink of flamingos, pigment in feathers
Pink colour of salmon
Red colour of lobsters

Antioxidants –> reduces risk of cancer when consumed carotenoids
Ex: lycopene in tomatoes is linked to reduced lipid peroxidation, reduced heart attacks, improved male fertility & longevity

32
Q

Steps of electron transfers in photosynthesis

A
  1. rxn center chlorophyll P680 absorbs photons & gives up the electrons to the primary electron acceptor (pheophytin)
  2. P680 replenishes its electrons from H2O, H2O is oxidized releasing O2 (photolysis)
  3. Electron is passed from PSII to PSI via the ETC & produces ATP (used in calvin cycle)
  4. P700 chlorophyll uses light to excite the electron to its own primary acceptor
  5. Electron is sent down another chain to create NADPH
  6. NADPH is used in the calvin cycle
33
Q

what are the 2 fates of the excited electrons in PSI?

A

can pass down:

a short electron transport chain to NADP+ to form NADPH

or

back to P700 to form ATP

34
Q

cyclic photophosphorylation

A

electrons are excited, pass down the chain creating ATP & then land back on 9700 to be reused
Electrons move from P700 to ferredoxin & back to P700
Electrons return to ground state
Use PSI only
Formation of ATP

35
Q

noncyclic photophosphorylation

A

electrons aren’t recycled back to ground state, they end up on NADH
Electrons move in a linear path from H2O to NADP+
Electrons don’t return to ground state
Uses PSI & PSII
Formation of: ATP, NADPH & O2

36
Q

Z scheme or pathway steps

A
  1. 2 photosystems acting in series
  2. Electron flow occurs in 3 steps:
    a. B/w H2O & PSII
    b. B/w PSII & PSI Electron transport chain
    c. B/w PSI & NADP+
  3. As electrons flow along Z-pathway, H+ ions are moved from stroma to inner compartment of thylakoids
  4. Important end result is proton gradient proton concentration:
    a. High in lumen of thylakoid
    b. Low in stroma
37
Q

calvin cycle steps

A
  1. Carboxylation
    a. CO2 combines with ribulose-1, 5-bisphosphate (RuBP)
    b. Forms a transient 6-carbon compound
    c. This breaks down to form 2 3-carbon molecules of 3-phosphoglycerate (PGA)
    d. Catalyzed by ribulose-1, 5-bisphosphate carboxylase (“Rubisco”)
  2. ATP and NADPH are used to form (in a couple of steps) glyceraldehyde 3-phosphate (G3P)

some G3P is used to make glucose & some gets cycled to re-make more RuBP

38
Q

what is the most abundant PRO in the world?

A

Rubisco

39
Q

endosymbiotic theory with chloroplasts

A

suggests that chloroplasts started as a photosynthetic bacterium which later got assimilated in a larger cell

40
Q

how do chloroplasts resemble bacteria in structure & composition? (3)

A

own circular genome

double membranes

share highly similar photosynthetic enzymes

41
Q

what are the similarities b/w mitochondria & chloroplasts? (3)

A

Method of replication

Generation of chemical E electron transport coupled to a proton gradient

Similar ATPases

42
Q

what are the diffs b/w mitochondria & chloroplasts? (2)

A

conduct opposing rxns –> one uses glucose (chloroplasts) & the other produces it (mitochondria)

diff electron acceptors

43
Q

Artifical photosynthesis

A

Attempt to replicate the natural process of photosynthesis

Replace fossil fuels

Artificial light rxns hopes to generate H as a new E source

Done in 2 ways:
Cyanobacteria are genetically altered so that they release H instead of using it to make carbs in bioreactors
Engineered enzymes on solar cells

C Bio (30 decks)

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