Introduction/Basic Info

Photosynthesis

PhotosynthesisEssential for all life on earthAutotrophs

Consumers

Photosynthesis

Glucose (only an example)Respiration

CO2

PhotosynthesisSo how do we actually see different

colors?The wavelength of the light will

determine the color of the light

PhotosynthesisWhen light waves are absorbed from

this region of the visible spectrum it can be used by a plant

Green leaves look green because they have a pigment that does not absorb green light, it reflects it

Photosynthesis

PhotosynthesisThe main light absorbing pigment in green plants is

chrorophyll—found inside the chloroplasts

Like a mitochondrion, the structure of the chlorophyll is directly related its function (common theme in bio)

Have their on DNA in a ring, ribosomes (70S), an inner and outer membranes

Only actual green structures in a plant

Photosynthesisstarch granuleRibosomes in

stroma

Stoma lamellae

PhotosynthesisChlorphyll is a green pigment

Reflects green wavelengths of light, in the middle of the VS, absorbs non-green wavelengths

Blue and red regions are absorbed the most

Absorption spectra show which wavelengths are absorbed as a function of O2 production

Photosynthesis

PhotosynthesisTwo stages of photosynthesis: light

independent and light dependent

Different sets of reactions used in each stage

Light dependent produces ATP and allows photolysis to occur (O2 is a waste product)

Light independent allows for carbon fixation

Photosynthesis—Light dependent

Chlorophyll, and other pigments, absorb light from the sun (or other source)

Energy from absorbed wavelengths produces ATP

Light also used to split water into H2 and O2 (photolysis)

Released O2 is source of aerobic respiration; ATP and H2 used by the plant

Photosynthesis—Light dependent

light

water

H+

O2

electrons

H2

Chlorophyll and other

photosynthetic pigments

Light dependent

reactions

ATP

• ATP production very similar to that of respiration w/ most energy being acquired via an electron transport chain

ATP and H2 generated from light dependent stage used to covert CO2 and H2O into organic compounds (like glucose)

This carbon fixation…turning inorganic to organic

Fixation requires energy—all comes from sun

Photosynthesis—Light independent

6CO2 + 6H2O C6H12O6 + 6O2

Photosynthesis6CO2 + 6H2O C6H12O6 + 6O2C6H12O6 + 6O2 6CO2 + 6H2O

RESPIRATION!!!!

Plants do both…photosynthesis and respiration

Respiration occurs at a slow, steady rate, regardless of light/dark = small yields of ATP. Why?

No muscle, large movement, or other energy requiring processes…less ATP needed vs animals

Photosynthesis-rates

Photosynthesis does not occur at such a steady rate

Greatly affected by intensity of light, temperature, and CO2 levels

Can be measured directly via CO2 intake and O2 production amounts IF adjusted to account for respiration

Biomass (amount of plant/size) is an indirect method of measuring rate of photosynthesis—indirect b/c a lot of other potential factors

Photosynthesis-rates

0

Day 1 Night 1 Day 2 Night 2

O2 released+ Photosynthesis

RespirationO2 taken in--

Photosynthesis-rates

Light intensity—varies inversely with the square of the distance (farther away, less intense)

Rate

of

ph

oto

syn

thesi

s

intensity

Enzymes at max rate

Photosynthesis-rates

Temperature

Rate

of

ph

oto

syn

thesi

s

Temp

Enzymes and other proteins begin to get denatured

Photosynthesis-rates

CO2 concentration

Rate

of

ph

oto

syn

thesi

s

CO2

Plateaus unless light intensity or temp. go up