Photosynthesis

Photosynthesis  Photosynthesis: ability of plant to capture light energy and turn it into the chemical energy of organic food molecules. (i.e. how plants make their food)  ‘photo’ = light; ‘synthesis’ = to make (to make with light)  Occurs in plant chloroplasts

Chloroplast review  Thylakoid membrane contains chlorophylls  Chlorophyll = green pigment in chloroplasts that absorbs light  Starch granules are present in the stroma of the chloroplast Granum (stacks of thylakoids) Thylakoids Stroma Lamellae

Photosynthesis (continued)  Produce glucose and ATP  Involves a series of enzyme-controlled reactions, and can be summarized as: CO 2 + water  Glucose + oxygen + water

The phases  Photosynthesis consists of 2 phases: 1.The Light dependent phase: need light 2.The Light independent Phase/Dark Phase: Does not need light

The Light reaction/ Light Phase  Occurs in the grana of the chloroplast  Light energy (trapped by chloroplast) is used in two ways: 1. Make ATP: Light + ADP + P  ATP ATP produced directly from light captured by chlorophyll (light energizes e - in chlorophyll molecule and the e - gets passed down an electron transport chain)

2. Split water into hydrogen and oxygen Light + water + NADP  NADPH 2 + Oxygen  NADP (nicotinamide adenine dinucleotide phosphate) = hydrogen carrier molecule  Oxygen produced diffuses out of cell (waste) _____________________________________ LIGHT REACTIONS: - Convert light energy  chemical energy (NADPH 2 and ATP) (NADPH 2 and ATP) - These energy-rich compounds are used in the Dark Reactions…

The phases  Photosynthesis consists of 2 phases: 1.The Light dependent phase: need light 2.The Light independent Phase/Dark Phase: Does not need light (OK, I kinda lied…the H from the light phase is needed here…)

The Light independent Phase/ Dark Phase  Also called Calvin cycle/ Carbon fixation stage  Occurs in the stroma of the chloroplast  Uses the ATP and Hydrogen produced in the Light Phase (ATP and H travels from the grana to the stroma) CO 2 + ATP + Hydrogen  G-3-P + water (G-3-P = Glyceraldehyde-3-phosphate)

 G-3-P is converted into: - Carbohydrate (glucose or sucrose) - Amino acid - lipid  Glucose formed is often turned into insoluble starch (granules in stroma) Dark reaction (continued)

Summary

I Need a Little Light By Ross Durand copyright I need a little light So I can store energy I need a little light So I can make ATP I need a little light I’m gonna make some food It’s outta sight And I need a little light Been sittin here in this chloroplast, feeling green the whole day through Yeah, I’m a little thylakoid, just waitin’ for something to do I’m gonna move some electrons through a chain and pump some hydrogen in But it’s been dark all night and you can see the state I’m in

I need a little light So I can store energy I need a little light So I can make ATP I need a little light I’m gonna make some food It’s outta sight And I need a little light When the electrons leave that chain they’re gonna join NADP (plus) And that high concentration of hydrogen’s gonna want outside of me Gonna go through a special protein that’s gonna kick some ATP out That’s what movin these electrons is really all about

I need a little light So I can store energy I need a little light So I can make ATP I need a little light I’m gonna make some food It’s outta sight And I need a little light The ATP and NADPH are gonna make a cycle go round At the end of the calvin cycle glucose can be found You gotta put in 6 pieces of CO2 to make that precious food And use up the products of the thylakoid, darn this system’s good

I need a little light So I can store energy I need a little light So I can make ATP I need a little light I’m gonna make some food It’s outta sight And I need a little light There’s one other thing that I need besides light It’s good old water You see that chlorophyll that loses those electrons – needs to get some back And that’s what the water does Now the whole reason that electron move was because of the light

I need a little light So I can store energy I need a little light So I can make ATP I need a little light I’m gonna make some food It’s outta sight And I need a little light

Factors affecting Photosynthesis 1.Light wavelength: chlorophyll absorbs all wavelengths of light except green (red and blue absorbed the most).  rate of photosynthesis with red and blue light 2.Light intensity:  light intensity   rate of Photosynthesis 3.[Carbon dioxide]: photosynthesis limited by rate of CO 2 absorption 4.Temperature:  temp   rate (until 40 ° C) e.g. plants grow faster in glasshouse

Factors affecting Photosynthesis (continued) 5.Water:  water   rate of photosynthesis 6.[Chlorophyll]: magnesium needed for a functional chlorophyll. Low Mg soil  less chlorophyll. Plants often turn yellow from lack of chlorophyll (growth rate very slow in these plants)

 animations/content/harvestinglight.html animations/content/harvestinglight.html animations/content/harvestinglight.html

Mini Quiz 1.Photosynthesis consists of 2 phases – what are the two phases called? 2.The light reaction occurs within the ________ (structure) in the ____________ (organelle) 3.CO 2 + H 2 O  _______ + _______ + H 2 O 4.How is the light energy captured from chlorophyll used? (2 ways) 5.What is the name of the hydrogen carrier molecule in the light reaction? Light and Dark Phases/ Light dependent phase and Light independent phase Grana Chloroplast Glucose Oxygen To make ATP and to split water into hydrogen and oxygen NADP

Respiration and Photosynthesis sheet  Use the resources provided to you (books, laptops, me…) to complete the sheet as a summary/review.  Good sites to go to (for in-depth info)   cool.co.uk/topic_index.asp?subject_id=3&d=0  gher/biology/cell_biology/index.shtml