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Photosynthesis (Outline) 1. Overview of photosynthesis 2. Producers, consumers, and decomposers of the ecosystem (source of carbon and energy) (Autotrophs: photo-autotrophs, chemo-autotrophs, electro-autotrophs, and heterotrophs) 3. Plant structures: organ, tissue, cells, sub-cellular organelle, and molecules. 4. Visible Light and its wavelengths 5. Overview of the two pathways of photosynthesis Light reactions: Substrates, products, cellular components and their location Calvin cycle: Substrates, products, cellular components and their location 6. Specifics of the Light reactions and the Calvin Cycle -Light Reactions: The light receptors (Pigments), Photosystems, Location within chloroplast, Photophosphorylation, Flow of energy -The Calvin cycle: Energy molecules, Carbon source, RuBp, G3P 7. Comparison of chemiosmosis in respiration and photosynthesis 8. Photorespiration Role of Rubisco Challenge to plants on hot dry days Adaptations of C4 and CAM plants
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Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

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Page 1: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Photosynthesis (Outline)1. Overview of photosynthesis2. Producers, consumers, and decomposers of the ecosystem (source of carbon and

energy) (Autotrophs: photo-autotrophs, chemo-autotrophs, electro-autotrophs, and heterotrophs)

3. Plant structures: organ, tissue, cells, sub-cellular organelle, and molecules.4. Visible Light and its wavelengths5. Overview of the two pathways of photosynthesis

Light reactions: Substrates, products, cellular components and their location Calvin cycle: Substrates, products, cellular components and their location

6. Specifics of the Light reactions and the Calvin Cycle-Light Reactions: The light receptors (Pigments), Photosystems, Location withinchloroplast, Photophosphorylation, Flow of energy-The Calvin cycle: Energy molecules, Carbon source, RuBp, G3P

7. Comparison of chemiosmosis in respiration and photosynthesis8. Photorespiration

Role of RubiscoChallenge to plants on hot dry days Adaptations of C4 and CAM plants

Page 2: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Photosynthesis

Life on the surface of Earth is powered by solar energy that is converted into chemical energy in organic molecules, for use in cellular respiration

Light energy

6 CO2 + 6 H2O

Carbon dioxide Water

C6H12O6+

Glucose6 O2

Oxygen gas

Page 3: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Producers of the ecosystemAutotrophs

Produce their own food and sustain themselves without eating other organisms

Bacteria Algae Plants

Page 4: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Types of autotrophs based on energy source • Photoautotrophs solar energy• Chemoautotrophs chemical energy of inorganic substances.

Bacteria can uniquely oxidize sulfur and ammonia• Electrolithoautotrophs (newly discovered bacteria)

• electrons directly from electric currents are passed through biologic nanowires to heavy metals, not to O2, and are then used to turn CO2 into carbon skeletons

• Several bacterial species with varied mechanisms are found in more common places (mud)

Page 5: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Geothermal Ventshttps://www.youtube.com/watch?v=D69hGvCsWgA

Electric bacteriahttp://www.extremetech.com/extreme/186537-biologists-discover-electric-bacteria-that-eat-pure-electrons-rather-than-sugar-redefining-the-tenacity-of-life

https://www.newscientist.com/article/dn25894-meet-the-electric-life-forms-that-live-on-pure-energy/

Page 6: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Heterot rophs

– consumers and decomposers of the biosphere.

– completely dependent on autotrophs

Page 7: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Leaf Cross Section

Leaf

Mesophyll

Mesophyll Cell

Vein StomaCO2 O2

Chloroplast

Chloroplast

Grana Stroma

TEM

9,75

Stroma

Granum ThylakoidThylakoidspace

Outer membrane InnermembraneIntermembrane space

LM 2

,600

×

In plants, photosynthesis takes place in green leaves

Mesophyll Stoma

Page 8: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.
Page 9: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Necessary components for Photosynthesis

1.Light 2.Chloroplast

Thylakoids (stacked as grana)The light Reactions

StromaThe Calvin Cycle

Chloroplast

Grana Stroma

TEM

9,75

Stroma

Granum Thylakoid Thylakoidspace

Outer membrane

Inner membrane

Intermembrane space

Page 10: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Light as a source of energy- Solar radiation received by Earth.- Visible light consists of photons of different

wavelengths making up the colors of the rainbow.

Increasing energy

103 nm 106 nm10–5 nm 10–3 nm 1 nm 1 m 103 m

Gamma rays

X-rays UV Infrared Micro-waves

Radio waves

Visible light

380 400 500 600 700 750Wavelength (nm)

650nm

http://science.hq.nasa.gov/kids/imagers/ems/index.html

Page 11: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Light

CO2H2O Chloroplast

LIGHT REACTIONS

(in thylakoids) CALVIN CYCLE

(in stroma)

NADP+

ADP+ Pi

ATP

NADPH

O2 Sugar

An Overview of Photosynthesis

Page 12: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

The Light reactions- Converts light energy to chemical energy (ATP & NADPH)- Produces O2 from breakdown of water

The Calvin cycle- uses ATP & NADPH from light reaction to assemble sugar

molecules from CO2

Page 13: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Chloroplasts split water into hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules during the light reaction

Page 14: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Specific details of the Light reactions: The Light Receptors

• Photosynthetic Pigments• Different pigments absorb different

wavelengths• Wavelengths that are not absorbed are

reflected or transmitted• Pigments are present within photosystems

Page 15: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

LightReflected light

Chloroplast

Absorbed light

Granum

Page 16: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Light-capturing Pigments: Chlorophyll

In chlorophyll an electron from magnesium in the

porphyrin ring that is excited.

CH3 in chlorophyll aCHO in chlorophyll b

Porphyrin ring: light-absorbing “head” of molecule; note magnesium atom at center

Hydrocarbon tail: interacts with hydrophobicregions of proteins inside thylakoid membranes of chloroplasts; H atoms not shown

Page 17: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

I. Chlorophyll aparticipates directly in the light reactions

II. Accessory photosynthetic pigments.

Photosynthetic Pigments

Page 18: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

1. Chlorophyll bdifferent absorption spectrumfunnels the energy from these wavelengths to chlorophyll a.

2. Carotenoidsfunnel the energy from other wavelengths to chlorophyll aparticipate in photoprotection against excessive light.

Chemistry of autumn leaf color http://chemistry.about.com/library/weekly/aa082602a.htm

II. Accessory Pigments

Page 19: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

H2O

LIGHT REACTIONS

ATP

NADPH

Chloroplast

Light

O2

NADP+

ADP+ Pi

CO2

CALVIN CYCLE

[CH2O](sugar)

Leaf Cross Section

Leaf

Mesophyll

Vein StomaCO2 O2

Chloroplast

Page 20: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Chloroplast Components• Light reactions:- Structures: Thylakoid membrane

- Photosystems II & I- Photosynthetic pigments- Electron acceptor

- Electron transport chain- ATP Synthase- Electron transport chain- NADP + Reductase

- Energy and chemical factors: light, Water, ADP +Pi, NADP+

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html#

Page 21: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Light-capturing Pigments: Chlorophyll

In chlorophyll, an electron from magnesium in the

porphyrin ring that is excited.

CH3 in chlorophyll aCHO in chlorophyll b

Porphyrin ring: light-absorbing “head” of molecule; note magnesium atom at center

Hydrocarbon tail: interacts with hydrophobicregions of proteins inside thylakoid membranes of chloroplasts; H atoms not shown

Page 22: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Thylakoid

PhotonLight-harvesting

complexes

Photosystem

Reaction center

STROMA

Primary electron acceptor

e–

Transfer of energy

Special chlorophyll a molecules

Pigment molecules

THYLAKOID SPACE (INTERIOR OF THYLAKOID)

Thyl

akoi

dm

embr

ane

Photosystem consists of a

reaction center surrounded by light-harvesting

complexes

Page 23: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Two types of photosystems that work togetherto use light energy to generate ATP and NADPH.

• Photosystem II• Photosystem I

Page 24: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Splitting of waterhttp://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html#

e–

Mill makes

ATP

e–

ATP

Photosystem II Photosystem I

NADPHe–

e–e–

e–

e–

Page 25: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

STROMA(Low H+ concentration)

Light

Photosystem II ytochromeCcomplex Light

2 H+

Photosystem INADP+

reductaseFd

PcPq

H2O THYLAKOID SPACE(High H+ concentration)

1/2O2+2 H+ 2 H+

NADP+ + 2H+

NADPH+ H+

To Calvin cycle

STROMA(Low H+ concentration)

Thylakoid membrane ATP

synthaseATP

ADP+P

H+i

[CH2O] (sugar)O2

NADPH

LIGHT REACTIONS

ATP

LightNADP+

ADP

CO2H2O

CALVIN CYCLE

Page 26: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Light P680

e–

Photosystem II (PS II)

Primary acceptor

Ener

gyof

elec

tron

s

[CH2O] (sugar)

NADPH

LIGHT REACTIONS

ATP

NADP+ ADP

CALVIN CYCLE

LightH2O CO2

O2

e–

e–

2 H+

+1/2 O2

H2OPq

Cytochrome complex

Pc

ATP

P700

e–

Primary acceptor

Photosystem I (PS I)

ee––

NADP+

reductase

Fd

NADP+

+ 2 H+

NADPH+ H+

Light

Electron Flow during the light reaction

Page 27: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

A Comparison of Chemiosmosis in Chloroplasts and Mitochondria

• Chloroplasts and mitochondria generate ATP by chemiosmosis, using different sources of energy

• Mitochondria transfer chemical energy from food to ATP; chloroplasts transform light energy into the chemical energy of ATP

Page 28: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

MITOCHONDRION STRUCTURE

Intermembranespace

MembraneElectron transport

chain

Mitochondrion Chloroplast

CHLOROPLAST STRUCTURE

Thylakoid space

Stroma

ATP

Matrix

ATPsynthase

Key

H+ Diffusion

ADP + P

H+

i

Higher [H+] Lower [H+]

Page 29: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

O2

Page 30: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

The Calvin Cycle• Uses ATP and NADPH• CO2 enters the cycle and leaves as a 3C

sugar, glyceraldehyde-3-phosphate (G3P).

• Regenerates RuBP

Page 31: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

The Calvin Cycle

Page 32: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

LightNADP+

ADP+ P i

CO2H2O

Light reactions Calvin cycle

RuBP

G3PATP

Photosystem II Electron transport

chain Photosystem I

O2

Chloroplast

NADPH

3-Phosphoglycerate

Starch (storage)

Amino acids Fatty acids

Sucrose (export)

Page 33: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Leaf Cross Section

Leaf

Mesophyll

VeinStoma

CO2 O2

Chloroplast

• Terrestrial plants face dehydration.• The stomata close to limit loss of water.• This limits amount of CO2 while O2 production continues• A wasteful process called photorespiration• On a hot dry day photorespiration drains 50% of the carbon

that could be fixed by the Calvin Cycle.

Challenge to plants in hot and dry area

Page 34: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Photorespiration

Rubisco can use both O2 and CO2 as substrates and can catalyze a wasteful reaction known as photorespiration when O2is the substrate.

O2 and organic fuel are consumed without producing sugar

Photorespiration is an evolutionary relic

Page 35: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

• In most plants (C3 plants), initial fixation of CO2, via rubisco, forms a three-carbon compound

• In C3 plants, a drop in CO2 and rise in O2 whenstomata close on hot dry days divert the Calvincycle to photorespiration

• C3 leaf anatomyLeaf Cross Section

Leaf

Mesophyll

VeinStoma

CO2 O2

Chloroplast

Page 36: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Some plants have special adaptationsto save water and limit “Photorespiration” by separating CO2 fixation from sugar formation

1. C4 plants (spatial separation) corn,sugar cane

2. CAM plants (temporal separation) succulents (cacti and pineapple)

Page 37: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

Photosyntheticcells of C4 plantleaf

Mesophyll cell

Bundle-sheath cell

Vein(vascular tissue)

C4 leaf anatomy

StomaBundle-sheath cell

Pyruvate (3 C) CO2

Sugar

Vascular tissue

CALVIN CYCLE

Oxaloacetate (4 CP)EP (3 C)ADPATPMalate (4 C)

CO2PEP carboxylaseMesophyllcell

C4 leaf anatomy and the C4 pathway

Page 38: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

• C4 plants minimize the cost of photorespiration by incorporating CO2 into four-carbon compounds in mesophyll cells

• These four-carbon compounds are exported tobundle-sheath cells, where they release CO2 for use in the Calvin cycle

C4 Plants

Sugarcane

C4 plant

CALVIN CYCLE

3-C sugar

CO2

4-C compound

CO2Mesophyll cell

Bundle-sheath cell

Page 39: Photosynthesis (Outline) - San Diego Miramar Collegefaculty.sdmiramar.edu/bhaidar/bhaidar 210A web uploads/Bio 210A... · Photosynthesis (Outline) 1. Overview of photosynthesis 2.

• CAM plants open their stomata at night, incorporating CO2 into organic acids.

Stomata close during the day, and CO2 is released from organic acids are used in the Calvin cycle

CAM Plants

CAM plant

Day

CALVIN CYCLE

3-C sugar

CO2

4-C compound

Night

Pineapple

CO2