Botany 102 ( Lab ) - Photosynthesis

8/8/2019 Botany 102 ( Lab ) - Photosynthesis

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Photosynthesis

Is the process by which green plants andautotrophic organisms synthesize food.

Is the combination of carbon dioxide withwater to form carbohydrates.

6CO2 + 12H20 C6H12O6 + 6O2 + 6H2Ochl

light
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Green plants

cyanobacteria Green algae


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Indian pipe

Snow plant

Non-photosynthetic plants

Non-chlorophyllous


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Differences between autotrophs andheterotrophs

Source of energy

Source of buildingmaterials

Organisms

Photoautotrophs Heterotrophs

Sunlight

carbon dioxide

photosynthetic plants

AlgaeCyanobacteria

Food:proteins

carbohydrates

Food

Completely parasitic plants

FungiAnimals; protozoa

Non-photosynthetic parts


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Photosynthesis uses light energy to convert CO2 and H2Ointo sugars


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The processes of photosynthesis and respiration areinterdependent


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Converting light energy to Chemical Energy: The Light Reaction

Chlorophyll is the principal light absorbing molecule of photosynthesis


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PHOTOSYNTHETIC PIGMENTS- are soluble in

organic solvent such as alcohol and acetone.

CH A MAIN PHOTOSYNTHETIC PIGMENTSDARK GREEN

absorbs BLUE-VIOLET AND RED SPECTRUM

CH B ACCESSORY PIGMENTSBLUISH GREEN

CAROTENOIDS ACCESSORY PIGMENTSABSORB BLUE GREEN AND REFLECTSYELLOW OR YELLOW ORANGE

1. CAROTENE ORANGE- antioxidant

2. XANTHOPHYLL YELLOW- oxidizing


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1. The nature of light

The Light-dependent reaction

Action spectrum- a profile of howeffectively different wavelengths oflight promote photosynthesis.


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Absorption spectrum = the range of pigments ability to absorbwavelengths of light.


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PHOTOCHEMICAL REACTION- LIGHT REACTION

Light energy enters photosynthesis at locations called photosystems


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The Light-dependent reaction

The Photosynthetic units

Photosystem I

Photosystem II

Membrane lipidsAntenna chlorophyll moleculesReaction center and primaryelectron acceptor


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Photosynthetic units- 300 molecules of ch a & b andcarotenoids

Photosystem I

With little chl b

P700

Photosystem II

With ch b almost equal to ch a

P680

Each photosystem consists ofthe ff:

1. Antenna chlorophyll molecules

2. Reaction center (Ch a)

3. Series of electrons carriers


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Movement of electrons in the light reactions


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Chemiosmosis and ATP synthesis in the light reactions

H+ ions move back across the membrane causing the release of energy


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Light-dependent reaction(Photochemical Reaction)

1. Produce the reducing agent NADPH

2. Synthesis of ATP

(chemiosmotic phosphorylation)3. Breakdown of water into H+, O2
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Converting CO2 to sugars: The Calvin Cycle

Melvin Calvin, Andrew Benson, and James Bassham- 19531961 won the Nobel Prize in Biochemistry


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Biochemical reactions

Stroma reaction

Calvin Benson Cycle

Conversion of carbon

dioxide to carbohydrates


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The Calvin cycle uses ATP

And NADPH from the light

Reactions to make sugar

Phosphates from CO2


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Anabolic Metabolism

3-phosphoglyceraldehyde

Several types of storagecompound

1. Short-term storage: ATP andNADPH

2. Intermediate-term storage:

glucose and sucrose3. Long-term storage

starch and lipids


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The synthesis ofPolysaccharides

Gluconeogenesis the anabolic synthesis of

glucoseGlucose is polymerized into polysaccharides

1. amyloseis a linear polymer of glucose linked mainly by(14) bonds.

2. amylopectin is a highly branched polymer of glucose

3. celluloseis an organic compound with the formula (C6H10O5)n, apolysaccharide consisting of a linear chain of several hundred to over ten

thousand (14) linked D-glucose units
http://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Glucosehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Glucosehttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Polysaccharidehttp://en.wikipedia.org/wiki/Glucosehttp://en.wikipedia.org/wiki/Glucosehttp://en.wikipedia.org/wiki/Polysaccharidehttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Glucosehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Glucosehttp://en.wikipedia.org/wiki/Polymer


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Rubisco -RuBP Carboxylase

One of the largest and mostcomplex enzymes known

A giant complex of two proteinsubunits

With 8 copies of large protein,each with a molecular wt of 14,000to 15,000 daltons

Total molecular weight of 480,000

daltons

Low substrate specificity bindseither with Oxygen or Carbondioxide depending which one hashigher conc.


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Rubisco and photorespiration.

Rubisco can function ascarboxylase (fixing carbon);oxygenase (fixing oxygen),depending on oxygenconcentration.


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The C4 pathway limits the loss ofcarbon from photorespiration


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These C4 plants are well adapted to (and likely to be foundin) habitats with:

high daytime temperaturesintense sunlight.

Some examples:crabgrasscorn (maize)sugarcane

sorghum


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C4 plants are more efficient than C3 plants.

High light intensity, high temperature, and loc CO2.


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CAM plants store CO2 in a C4 acid at night for use

in the Calvin Cycle during the day.


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These adaptations also enable theirowners to thrive in conditions of:

high daytime temperatures intense sunlight low soil moisture.

Some examples of CAM plants:

cacti Bryophyllum the pineapple and all epiphytic

bromeliads sedums

the "ice plant" that grows in sandyparts of the scrub forest biome
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