Photosynthesis. Photosynthesis Photosynthesis: ability of plant to capture light energy and turn it into the chemical energy of organic food molecules

PhotosynthesisPhotosynthesis

Photosynthesis Photosynthesis

Photosynthesis: ability of plant to capture Photosynthesis: ability of plant to capture light energy and turn it into the chemical light energy and turn it into the chemical energy of organic food molecules. (i.e. energy of organic food molecules. (i.e. how plants make their foodhow plants make their food))

‘‘photo’ = light; ‘synthesis’ = to make (photo’ = light; ‘synthesis’ = to make (to to make with lightmake with light))

Occurs in plant chloroplastsOccurs in plant chloroplasts

Chloroplast reviewChloroplast review

Thylakoid membrane Thylakoid membrane contains chlorophylls contains chlorophylls

Chlorophyll = green Chlorophyll = green pigment in pigment in chloroplasts that chloroplasts that absorbs lightabsorbs light

Starch granules are Starch granules are present in the stroma present in the stroma of the chloroplastof the chloroplast

Granum (stacks of thylakoids)

ThylakoidsStroma

Lamellae

Photosynthesis Photosynthesis (continued)(continued)

Produce glucose and ATPProduce glucose and ATP Involves a series of enzyme-controlled Involves a series of enzyme-controlled

reactions, and can be summarized as:reactions, and can be summarized as:

COCO22 + water + water Glucose + oxygen + water Glucose + oxygen + water

The phasesThe phases

Photosynthesis consists of 2 phases:Photosynthesis consists of 2 phases:

1.1. The Light dependent phase: need lightThe Light dependent phase: need light

2.2. The Light independent Phase/Dark The Light independent Phase/Dark Phase: Does not need light Phase: Does not need light

The Light reaction/ Light The Light reaction/ Light PhasePhase

Occurs in the Occurs in the granagrana of the chloroplast of the chloroplast Light energy (trapped by chloroplast) is Light energy (trapped by chloroplast) is

used in two ways:used in two ways:

1. 1. Make ATPMake ATP::

Light + ADP + P Light + ADP + P ATP ATP

ATP produced directly from light captured ATP produced directly from light captured by chlorophyll (light energizes eby chlorophyll (light energizes e- - in in chlorophyll molecule and the echlorophyll molecule and the e-- gets passed gets passed down an electron transport chain)down an electron transport chain)

2. 2. Split water into hydrogen and oxygenSplit water into hydrogen and oxygen

Light + water + NADP Light + water + NADP NADPH NADPH22 + Oxygen + Oxygen NADP (nicotinamide adenine dinucleotide NADP (nicotinamide adenine dinucleotide

phosphate) = hydrogen carrier moleculephosphate) = hydrogen carrier molecule Oxygen produced diffuses out of cell (waste)Oxygen produced diffuses out of cell (waste)__________________________________________________________________________LIGHT REACTIONS:LIGHT REACTIONS:- Convert light energy - Convert light energy chemical energy chemical energy

(NADPH(NADPH22 and ATP) and ATP)

- These energy-rich compounds are used in the - These energy-rich compounds are used in the Dark Reactions…Dark Reactions…

The phasesThe phases Photosynthesis consists of 2 phases:Photosynthesis consists of 2 phases:

1.1. The Light dependent phase: need lightThe Light dependent phase: need light

2.2. The Light independent Phase/Dark Phase: The Light independent Phase/Dark Phase: Does not need light Does not need light

(OK, I kinda lied…the H from the light (OK, I kinda lied…the H from the light phase is needed here…)phase is needed here…)

The Light independent The Light independent Phase/ Dark PhasePhase/ Dark Phase

Also called Calvin cycle/ Carbon fixation Also called Calvin cycle/ Carbon fixation stagestage

Occurs in the Occurs in the stromastroma of the chloroplast of the chloroplast Uses the ATP and Hydrogen produced in the Uses the ATP and Hydrogen produced in the

Light Phase (ATP and H travels from the Light Phase (ATP and H travels from the grana to the stroma)grana to the stroma)

COCO22 + ATP + Hydrogen + ATP + Hydrogen G-3-P + water G-3-P + water

(G-3-P = Glyceraldehyde-3-phosphate)(G-3-P = Glyceraldehyde-3-phosphate)

G-3-P is converted into:G-3-P is converted into:

- Carbohydrate (glucose or sucrose)- Carbohydrate (glucose or sucrose)

- Amino acid- Amino acid

- lipid- lipid Glucose formed is often turned into Glucose formed is often turned into

insoluble starch (granules in stroma)insoluble starch (granules in stroma)

Dark reaction (continued)Dark reaction (continued)

SummarySummary

I Need a Little LightI Need a Little LightBy Ross Durand copyright 2003By Ross Durand copyright 2003

http://www.songplanet.com/artists/bands/669/http://www.songplanet.com/artists/bands/669/

I need a little lightSo I can store energyI need a little lightSo I can make ATPI need a little lightI’m gonna make some foodIt’s outta sightAnd I need a little light

Been sittin here in this chloroplast, feeling green the whole day throughYeah, I’m a little thylakoid, just waitin’ for something to doI’m gonna move some electrons through a chainand pump some hydrogen inBut it’s been dark all night and you can see the state I’m in


When the electrons leave that chain they’re gonna When the electrons leave that chain they’re gonna join NADP (plus)join NADP (plus)And that high concentration of hydrogen’s gonna And that high concentration of hydrogen’s gonna want outside of mewant outside of meGonna go through a special protein that’s gonna kick Gonna go through a special protein that’s gonna kick some ATP outsome ATP outThat’s what movin these electrons is really all aboutThat’s what movin these electrons is really all about


The ATP and NADPH are gonna make a cycle go The ATP and NADPH are gonna make a cycle go roundroundAt the end of the calvin cycle glucose can be foundAt the end of the calvin cycle glucose can be foundYou gotta put in 6 pieces of CO2 to make that You gotta put in 6 pieces of CO2 to make that precious foodprecious foodAnd use up the products of the thylakoid, darn this And use up the products of the thylakoid, darn this system’s goodsystem’s good


There’s one other thing that I need besides lightIt’s good old waterYou see that chlorophyll that loses those electrons –

needs to get some backAnd that’s what the water doesNow the whole reason that electron move was because

of the light


Factors affecting PhotosynthesisFactors affecting Photosynthesis

1.1. Light wavelengthLight wavelength: chlorophyll absorbs all : chlorophyll absorbs all wavelengths of light except green (red and wavelengths of light except green (red and blue absorbed the most). blue absorbed the most). rate of rate of photosynthesis with red and blue lightphotosynthesis with red and blue light

2.2. Light intensityLight intensity: : light intensity light intensity rate of rate of PhotosynthesisPhotosynthesis

3.3. [Carbon dioxide]:[Carbon dioxide]: photosynthesis limited by photosynthesis limited by rate of COrate of CO22 absorption absorption

4.4. TemperatureTemperature: : temp temp rate (until 40 rate (until 40° ° C) C) e.g. plants grow faster in glasshousee.g. plants grow faster in glasshouse

Factors affecting Factors affecting Photosynthesis (continued)Photosynthesis (continued)

5.5. Water:Water: water water rate of photosynthesis rate of photosynthesis

6.6. [Chlorophyll]:[Chlorophyll]: magnesium needed for a magnesium needed for a functional chlorophyll. Low Mg soil functional chlorophyll. Low Mg soil less less chlorophyll. Plants often turn yellow from chlorophyll. Plants often turn yellow from lack of chlorophyll (growth rate very slow in lack of chlorophyll (growth rate very slow in these plants)these plants)

http://www.sumanasinc.com/webcontent/http://www.sumanasinc.com/webcontent/animations/content/harvestinglight.htmlanimations/content/harvestinglight.html

Mini QuizMini Quiz1.1. Photosynthesis consists of 2 phases – what are Photosynthesis consists of 2 phases – what are

the two phases called?the two phases called?

2.2. The light reaction occurs within the ________ The light reaction occurs within the ________ (structure) in the ____________ (organelle) (structure) in the ____________ (organelle)

3.3. COCO2 2 + H+ H22O O _______ + _______ + H _______ + _______ + H22OO

4.4. How is the light energy captured from How is the light energy captured from chlorophyll used? (2 ways)chlorophyll used? (2 ways)

5.5. What is the name of the hydrogen carrier What is the name of the hydrogen carrier molecule in the light reaction?molecule in the light reaction?

Light and Dark Phases/ Light dependent phase and Light independent phase

GranaChloroplast

Glucose Oxygen

To make ATP and to split water into hydrogen and oxygen

NADP

Respiration and Respiration and Photosynthesis sheetPhotosynthesis sheet

Use the resources provided to you (books, Use the resources provided to you (books, laptops, me…) to complete the sheet as a laptops, me…) to complete the sheet as a summary/review.summary/review.

Good sites to go to (for in-depth info)Good sites to go to (for in-depth info) http://www.biologymad.com/http://www.biologymad.com/ http://www.s-cool.co.uk/topic_index.asp?http://www.s-cool.co.uk/topic_index.asp?

subject_id=3&d=0subject_id=3&d=0 http://www.bbc.co.uk/scotland/education/bitesize/http://www.bbc.co.uk/scotland/education/bitesize/

higher/biology/cell_biology/index.shtmlhigher/biology/cell_biology/index.shtml

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Photosynthesis. Photosynthesis Photosynthesis: ability of plant to capture light energy and turn it into the chemical energy of organic food molecules