Photosynthesis Part 1Pages 108 to 111

Autotrophs Name some common producers

› Plants, algae, some protists, cyanobacteria Define photoautotroph

› An organism that uses light energy to produce food

Define chemoautotroph› An organism that uses chemical energy to

produce food

Fig. 10-2

(a) Plants

(c) Unicellular protist10 µm

1.5 µm

40 µm(d) Cyanobacteria

(e) Purple sulfur bacteria

(b) Multicellular alga

Location of photosynthesis State the organelle of photosynthesis

› Chloroplast Where are chloroplasts concentrated in

plants?› The green tissue on the interior of the leaf› Mesolphyll

Fig. 10-3a

5 µm

Mesophyll cell

Stomata CO2 O2

Chloroplast

Mesophyll

VeinLeaf cross section

Gas Exchange Explain how gases are exchanged

between the plant and the environment.› Stoma are openings in the epidermis of

leaves› Guard cells surround the stoma and they

regulate the opening & closing of the stoma

› When open, CO2 can enter while O2 and H2O can exit

Fig. 10-3b

1 µm

ThylakoidSpace (lumen)

Chloroplast

GranumIntermembranespace

Innermembrane

Outermembrane

Stroma

Thylakoid

Structure of the

chloroplast

Thylakoid is site of

light reactions

Stroma is site of Calvin Cycle

Plants produce O2 by splitting H2O

1950’s – scientists used heavy isotope of oxygen (18O) to follow oxygen through photosynthesis.

Tagged oxygen of CO2 and found no tagged O2 given off

Tagged O2 of H2O and found tagged O2 given off

Reactants:

Fig. 10-4

6 CO2

Products:

12 H2O

6 O26 H2OC6H12O6

Photosynthesis is a Redox Reaction

Equation› 6CO2 + 6H2O Light C6H12O6 + 6O2

Redox reaction of photosynthesis› Oxidized:

H2O to O2

› Reduced: CO2 to C6H12O6

Overview of Photosynthesis Photosynthesis consists of the light

reactions (photo – absorbs light energy) and the Calvin cycle (synthesis – makes sugar)

2 stages of photosynthesis

Light ReactionsCalvin Cycle

Takes place in the thylakoids Split H2O Release O2 Reduce NADP+ to NADPH Produce ATP via photophosphorylation

Takes place in the stroma Forms sugar using

› CO2 from atmosphere› ATP and NADPH from light reactions

Starts with carbon fixation

Light

Fig. 10-5-4

H2O

Chloroplast

LightReactions

NADP+

PADP

i+

ATP

NADPH

O2

CalvinCycle

CO2

[CH2O](sugar)