2006-2007

Photosynthesis: Life from Light and Air 2006-2007

Energy needs of life All life needs a constant input of energy Animals = Heterotrophs get their energy from “eating others” eat food = other organisms = organic molecules make energy through respiration Plants = Autotrophs get their energy from “self” get their energy from sunlight build organic molecules (food) from CO2 make energy through photosynthesis

+ water + energy  glucose + oxygen Photosynthesis + water + energy  glucose + oxygen carbon dioxide 6CO2 6H2O C6H12O6 6O2 light energy  + This is the equation you are used to seeing, but this is not the whole story…

How do plants live? Photosynthesis Energy building reactions collect sun energy make ATP Sugar building reactions use ATP for energy use CO2 as carbon for new sugars build sugars glucose, cellulose, starch build all other organic molecules proteins, lipids, carbohydrates, DNA store energy for future use starch in seeds & roots

Energy building reactions Sugar building reactions Photosynthesis sun Actually 2 separate reactions Energy building use sunlight make energy (ATP) Sugar building use ATP use CO2 make sugars (C6H12O6) Energy building reactions ADP ATP Sugar building reactions sugar CO2

Chloroplasts absorb sunlight & CO2 Leaf Leaf Chloroplasts Chloroplasts contain Chlorophyll Chloroplast make energy & sugar

Energy Building Reactions H2O + light energy  ATP + O2 H2O makes ATP energy releases oxygen as a waste product sunlight Energy Building Reactions ATP O2

Sugar Building Reactions CO2 +  ATP C6H12O6 + ADP CO2 builds sugars uses ATP cycles ADP back to make more ATP ADP Sugar Building Reactions ATP sugars C6H12O6

Putting it all together CO2 H2O C6H12O6 O2 light energy  + H2O CO2 Plants make both: ATP sugars sunlight ADP Energy Building Reactions Sugar Building Reactions ATP sugars C6H12O6 O2

So what does a plant need? Bring In CO2 H2O light Let Out O2 Move Around sugars leaves shoot roots 6CO2 6H2O C6H12O6 6O2 light energy  +

Leaf Structure xylem (water) phloem (sugar) cuticle epidermis palisades layer spongy layer O2 H2O CO2 stomate guard cell gases in & out water out transpiration O2 H2O CO2

Stomates Function of stomates CO2 in O2 out H2O out guard cell stomate

Xylem carry water up from roots

Phloem: food-conducting cells carry sugars around the plant wherever they are needed new leaves fruit seeds

Putting it all together Making a living… sunlight leaves = solar collectors photosynthesis gases: CO2 in & O2 out stomates = gases in & out H2O roots take in water from soil pulled up by leaf evaporation nutrients roots take in from soil

How are they connected? Respiration  Photosynthesis  glucose + oxygen  carbon + water + energy dioxide C6H12O6 6O2 6CO2 6H2O ATP  + Photosynthesis So, in effect, photosynthesis is respiration run backwards powered by light. Cellular Respiration oxidize C6H12O6  CO2 & produce H2O fall of electrons downhill to O2 exergonic Photosynthesis reduce CO2  C6H12O6 & produce O2 boost electrons uphill by splitting H2O endergonic + water + energy  glucose + oxygen carbon dioxide 6CO2 6H2O C6H12O6 6O2 light energy  +

The Great Circle of Life! sun Energy cycle Photosynthesis plants H2O CO2 glucose O2 animals, plants Cellular Respiration The Great Circle of Life! Where’s Mufasa? ATP

The poetic perspective All of the solid material of every plant was built out of thin air All of the solid material of every animal was built from plant material sun air Then all the cats, dogs, mice, people & elephants… are really strands of air woven together by sunlight!