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MC Biochem 2 > Chpt 19 > Flashcards

Chpt 19 Flashcards

1
Q

Structure of Chloroplast

A

3 membrane layers:

  • Outer
  • Inner
  • Thylakoid-thylakoid membrane organized into stacked (appressed) and unstacked regions (Nonapressed). Stacked regions are called grand

3 compartments:

  • Intermembrane space
  • Stroma
  • Thylakoid lumen
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2
Q

Chloroplast Function

A

1) Photosynthesis-reduces Carbon dioxide to carbohydrates
2) Synthesizes
- amino acids
- fatty acids
- lipids
3) Reduce nitrate (NO2-) to ammonia (NH3)
4) Storage of pigments, starch, and lipids

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3
Q

What do plastids develop from?

A

Proplastids- small undifferentiated organelle present in early plant development

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4
Q

Plastid Development

A

Proplastids->Etioplasts-> Plastids

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5
Q

Plastids are classified by:

A
  • Presence/absence of thylakoid membrane
  • type of pigment
  • type of material stored
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6
Q

Types of plastids?

A

1) Chloroplasts
2) Chromoplasts
3) Leucoplasts

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7
Q

Chlorplasts

  • Presence/absence of thylakoid membrane
  • type of pigment
  • type of material stored
A

TYPE OF Plastid

  • thylakoid membranes
  • pigment-chlorophyll
  • carry out photosynthesis-don’t store anything
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8
Q

Chromoplasts

  • Presence/absence of thylakoid membrane
  • type of pigment
  • type of material stored
A

Type of Plastid

  • lack thylakoid membrane
  • pigment=carotenoids-pigment of flowers
  • functions (other than color) unknown
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9
Q

Leucoplasts

A

Type of plastid

  • lack thylakoid membrane
  • no pigments present
  • storage of energy molecules

2 Types:

1) Amyloplasts
- starch storage
2) Elaioplasts
- lipid storage

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10
Q

Photosynthesis

A

6CO2 + 6H2O ->C6H12O6 + 6O2

1) Light reaction in thylakoid membrane that synthesizes ATP and NADPH
- Photosystem II (PSII)-P680
- Photosystem I (PSI)-P700

Noncyclic flow of electrons (PSII and PSI)-synthesis of ATP and NADPH

Cyclic flow of electrons (PSI only)-synthesis of ATP only

2) Dark Reaction (Calvin cycle) in Stroma
- reduces carbon dioxide to carbohydrates

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11
Q

Complexes of Light Reactions

A

Photosystem II (PSII)

  • PO (plastoquinone)
  • cyt bf (cytochrome bf)
  • PC (plastocyanine)

Photosystem I (PSI)

  • Fd (ferredoxin)
  • Fd-NADP+ reductase
  • ATP synthase
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12
Q

Photosystem II function

A

1) splits water to hydrogen and oxygen
- 4H+ released into thylakoid lumen
- 1 O2 released into thylakoid lumen
- 4 e- used to reduce 2Q to 2QH2
2) energizes electrons using solar energy (Photon)
3) establishes proton gradient which is used to synthesize ATP

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13
Q

Platoquinone function

A

small lipid soluble protein that transfers electrons from PSII to cyt bf
-redox state cycles from plastoquinone (Q) to Plastoquinol (QH2-reduced) back to plastoquinone (Q)

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14
Q

plastocyanine function

A

transfers electrons from cyt bf to PSI

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15
Q

Photosystem I function

A
  • electrons are reenergized by solar energy

- NADP+ reduced to NADPH

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16
Q

Ferredoxin function

A

Transfers one electron from PSI to Fd-NADP+ reductase

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17
Q

Fd-NADP+ reductase function

A

reduces NADP+ to NADPH

  • FAD accepts 1e- and 1H+ from 2 Fd (2e- and 2H+ total)
  • transfers hydride (H-) to NADP+ which picks up H+ from stromal side of thylakoid membrane to synthesize NADPH
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18
Q

ATP synthase function

A

phosphorylates ADP To ATP using energy harnessed from the proton gradient

19
Q

NON cyclic flow of electrons

A

Water-> PSII-> Q-> cyt bf->PC-> PSI-> Fd-> Fd-NADP+ reductase-> NADH

produce NADPH in addition to ATP due to proton gradient
-both ATP and NADPH end up in stroma

20
Q

pH of stroma

A

8

21
Q

Cyclic Flow of electrons

A

PSI-> Fd-> Q-> cyt bf-> PC-> PSI

Produces ONLY ATP (NO NADPH)

22
Q

Chlorophyll a and b

-structure

A

substituted tetrapyrole (like heme)

  • pyrrole-> N complexed to Mg2+
  • conjugated polyene-alternating single/double bonds

Phytol-hydrophobic 20 Carbon tail

Chlorophyll a and b differ by one functional group

  • A-Methyl
  • B- formyl group
23
Q

Chlorophyll a and b

-function

A

captures photon of light in the reaction center

-chlorophyll a and b have different wave lengths of light

24
Q

Carotenoids

-structure

A

conjugated double bond system

25
Q

Carotenoids

-function

A
  • absorb light between 400-500 nm
  • Provides yellow and red colors of fruit and flowers- chlorophylls a and b are destroyed allowing the carotenoids color to show
26
Q

Reaction center

A

pigments (chlorophyl a and b and carotenoids) in/on ct thylakoid membrane absorb photons of light and transfer energy to the reaction center containing a special pair of chlorophyl a molecules

27
Q

Organization of Photosynthetic complexes

A
  • PSII located in stacked regions
  • PSI and ATP synthase located primarily in unstacked regions
  • Cyt bf located in both stacked and unstack regions
  • Plastoquinone (Q) and Plastocyanine (PC) transfer electrons from different regions
28
Q

Photosystem II structure

A

Transmembrane complex of thylakoid membrane

-Contains “special pair” P 680-contains two chlorophyll molecules bond between core subunits D2and D1

29
Q

Photosystem II electron flow

A
  • 2 H2O
  • Mn2+ center
  • P680-> Chlorophyl A-special pair
  • Qa-bound
  • Qb-soluble
30
Q

Heart of Photosystem II is?

A

Manganese Center

31
Q

Mn2+ center Structure

A

contains 4 Manganese-that exist in 4 different oxidation states (2,3,4,5)

  • 1 calcium
  • Tyrosine called Z
32
Q

Mn2+ Center function

A

activates 2 H2O molecules

  • allowing oxidation (electron extraction) by the special pair (P680) forming 1 O2+ 4H+ + 4e-
  • the electrons are moved one at a time

S1->S2->S3->S4->S5->S0

33
Q

How many photons of light is required to form one O2

A

4 photons

34
Q

cytochrome bf

-structure

A 
Transmembrane complex of thylakoid membrane
Four subunits
-cytochrome with two b type hemes
-Rieske center Fe-S protein
-Cytochrome F with a c-type cytochrome

Homologous to complex III it uses THE Q CYCLE

35
Q

cytochrome bf

-function

A

uses energy harvested from electrons to transfer protons into thylakoid lumen

36
Q

Plastocyanin

-structure

A

small, soluble copper containing protein on the luminal side of the thylakoid membrane

37
Q

Photosystem I

-structure

A

Massive transmembrane complex of thylakoid membrane

-contains special pair P700 held between major subunits psaA and psaB

38
Q

Photosystem I electron flow

A

Pc-> P700-chlorophyll A special pair-> Ao-chlorophyll->A1-quinone-> 4Fe-4S-> Fd

39
Q

Ferredoxin Structure

A
  • Soluble protein on stromal side of thylakoid membrane

- contains 2Fe-2S

40
Q

Ferredoxin-NADP+ structure

A

Transmembrane flavoprotein of thylakoid membrane

-Contains FAD as prosthetic group

41
Q

Light Harvesting Complex II (LHC-II)

structure

A

abundant ct membrane protein

binds:

  • 7 chlorophyl a molecules
  • 6 chlorophyl b molecules
  • 2 carotenoid molecules
42
Q

Light harvesting complex II (LHC-II)

-function

A

funnels energy from photons of light to reaction center

43
Q

Calvin cycle (Dark Reaction)

A

Catalyzed by Rubisco (Ribulose bisphosphate carboxylase) and other enzymes

  • occurs in stroma
  • uses ATP and NADPH from light reaction
  • reduces carbon dioxide to carbohydrates

MC Biochem 2 (31 decks)

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