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L05: Chloroplast Origins

BIOL 153/LBlack Hills State Univ.Ramseys

I. Overview of respirationA. Basic processes

1. Sugar

See 'Chem of Life' lecture

glucose

2. Oxygen

O2

O

O

See 'Chem of Life' lecture

3. ATP

See 'Chem of Life' lecture

4. Water

O

HHH2O

See 'Chem of Life' lecture

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5. Location in cell

Mitochondria(2x membrane-bound organelle)

I. Overview of respirationB. Chemical formula

C6H12O6 + O2 => CO2 + H2O + Energy

I. Overview of respirationB. Chemical formula

C6H12O6 + O2 => CO2 + H2O + Energy

input output

II. Overview of photosynthesisA. Basic processes

1. Carbon dioxideO

O

CCO2

See 'Chem of Life' lecture

2. Water

O

HHH2O

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3. Light energy

Wavelength

4. Sugar

glucose

5. Oxygen

O2

O

O

6. Location in cell

Chloroplast(2x membrane-bound organelle)

II. Overview of photosynthesisB. Chemical formula

CO2 + H2O + Energy => C6H12O6 + O2

II. Overview of photosynthesisB. Chemical formula

CO2 + H2O + Energy => C6H12O6 + O2

input output

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III. Mitochondria and chloroplastsA. Shared features

1. DNA

both have own DNA

haploid circular chromosome, separate from nucleus

2. Membranes

both have their own membranes

3. Porins

both have particular protein pores in membranes

porins found in prokaryote, not eukaryote membranes

4. Reproduction

both replicate themselves by fission

5. Size

both are small and numerous

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Fig. 6-5Raven p. 111

Fig. 6-5Raven p. 111

III. Mitochondria and chloroplastsB. Chloroplasts only

1. Thylakoids and stroma

membrane-bound spaces

2. Pigments

light-sensitive pigments (chlorophylls, carotenoids)

3. Photosynthesis ETS

electron transport chain in thylakoid membrane

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Fig. 7-7Raven p. 128 III. Mitochondria and chloroplasts

C. Other plastids

1. Plastid

general term for chloroplast-like organelles

some plastids no longer perform photosynthesis!

2. Chromoplasts

plastids with diverse carotenoid pigments

chromoplasts lack chlorophyll; give color to tissue

3. Leukoplasts

plastids that synthesize starch, oil, proteins

leukoplasts lack chlorophyll, complex membranes

Chromoplasts Leukoplast

Figs. 3-12, 3-14; Raven p. 47

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IV. Endosymbiotic origin theory A. Endosymbionts

1. Definition

single-celled organisms living insidecells of larger organisms

typically, prokaryote cells inside large eukaryote cell

2. Examples

recently-evolved endosymbionts 'intact' andmay have free-living relatives

Nitrogen-fixing bacteria

convert N2 to more use-able NH3

some nitrogen-fixing bacteria 'infect' roots of plants

Insect bacteriocytes

fat cell with bacteria that assist metabolically

vertical transmission of bacteria (parent-to-offspring); produce essential nutrients for insect host

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Zooxanthellae dinoflagellates

photosynthetic eukaryote living in marine inverts

hosts include corals, jellyfish, clams, sponges...

B. Phagocytosis

cells physical consuming other (smaller) cells

common in protists, certain cells of animals

C. Endosymbiotic theory

1. Free-living prokaryote => endosymbiontin eukaryotic cell

C. Endosymbiotic theory

1. Free-living prokaryote => endosymbiontin eukaryotic cell

2. Endosymbiont => organelle in eukaryotic cell

Fig. 12-13Raven p. 248

Fig. 12-13Raven p. 248

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How do we unravel organelle origins?

look at membranes, and DNA!

V. Chloroplast origins

Chloroplast originson Tree of Life

Chloroplast originson Tree of Life

Free-living cyanobacteria

Cs.Pk.Green Algae Land PlantsRed Algae

Primary chloroplast origin

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Chloroplast originson Tree of Life

Diatoms EuglenoidsBrown Algae

Secondary chloroplast origins

Those crazy dinoflagellates... Chloroplast originson Tree of Life

A. Multiple chloroplast 'captures' 1. Primaryfree-living photosynthetic prokaryote

(ancestor of cyanobacteria)

endosymbiont (ancestor of red algae and green plants)

~1 BYA(one event)

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vast majority of red algae and green plants are (still) photosynthetic! But...

Parasitic plants: Fig. 19-5, 29-13; Raven p. 460, 699

Dodder Corpse Lily Indian Pipe Mistletoe

parasitize other plants; often no longer photosynthetic

• Ancestor of browns/goldens/diatoms: red algae chloroplast

• Euglenoids: green algae chloroplasts

• Some dinoflagellates: red algae chloroplastsOther dinoflagellates: green algae chloroplast

2. Secondary 2. Secondary

• Apicomplexans: red algae chloroplast

once photosynthetic, apicomplexans evolved parasitism; 'apicoplast' (modified chloroplast) facilitates host invasion!

• Plasmodium: malaria • Toxoplasma: toxoplasmosis

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• Babesia: babesiosis B. 'Recent symbioses'

many symbioses partner photosynthetic species with heterotrophic species

Lichens

organism comprised of multicellular fungi + unicellular 'algae'

'algae' may be a cyanobacteria or green algae

Lichens

Coral

cnidarian forming colonies of small polypswith endosymbiont dinoflagellates

dinoflags (zooxanthellae) = 1º carb source for coral Polyps Zooxanthellae

Coral

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Recently developed symbioses

Coral Reef

Sloths + Green Algae

slow-moving arboreal mammal with symbiotic green algae in hair

algae camouflages sloth, provides carbohydrates;feeds moths that provide protein

Sloths + Green Algae