12/1/14

Objective: Photosynthesis

Do Now

If you reversed the equation for photosynthesis, what would it look like?

What is photosynthesis?

6CO2 + 6H2O + light ------> C6H12O6 + 6O2

What do you notice about this equation?

Where does photosynthesis occur?

• chloroplast: organelle where photosynthesis takes place

• chlorophyll: chemical compound that gives green color

– stomata: pores found on surface of leaf that allows gas and liquid exchange

– CO2 enters; O2 exits

Structures of the Chloroplast

• stroma: thick fluid in inner membrane

• thylakoids: many disk-shaped sacs

• grana:stacks of thylakoids

• The electromagnetic spectrum is the entire range of electromagnetic energy, or radiation

The Nature of Sunlight

Like other electromagnetic energy, light travels in waves

• Wavelength is the distance between crests of waves

• Wavelength determines the type of electromagnetic energy

• Visible light consists of wavelengths (including those that drive photosynthesis) that produce colors we can see

Pigments

• pigments: a substances color due to chemical compounds– Light can be absorbed,

transmitted or reflected

• A chloroplast’s pigments absorb blue-violet and red-orange very well

• Does not absorb green– Reflected or transmitted

Paper Chromatography• Used to observe pigments in

a green leaf• chlorophyll a: absorbs

mainly blue-violet and red-orange and reflects mostly green– Major role in photosynthesis

• chlorophyll b: “helper” pigment absorbs mainly blue and orange and reflects yellow-green.- carotenoids: “helper”- absorbs mainly blue-green and reflects yellow-orange

Ex. carotein

DirectionsCut out the chloroplast and label the stroma, thylakoid, and granum. Then cut out the reactants and products and paste them either entering or leaving the chloroplast. Answer the following questions:

1.Write the reaction for photosynthesis.2.What organisms undergo photosynthesis?3.In what organelle does photosynthesis occur?4.When do plants do photosynthesis?5.Why might plants help regulate the global climate?6.What would happen if a dust cloud blocked out the sun for 100 years?

Photosystems

• photosystems: clusters of chlorophyll and other molecules in the thylakoid– Each contain a few hundred pigment molecules– Acts like a solar panel

Light

Fig. 10-5-1

H2O

Chloroplast

LightReactions

NADP+

P

ADP

i+

Light

Fig. 10-5-2

H2O

Chloroplast

LightReactions

NADP+

P

ADP

i+

ATP

NADPH

O2

Light

Fig. 10-5-3

H2O

Chloroplast

LightReactions

NADP+

P

ADP

i+

ATP

NADPH

O2

CalvinCycle

CO2

Light

Fig. 10-5-4

H2O

Chloroplast

LightReactions

NADP+

P

ADP

i+

ATP

NADPH

O2

CalvinCycle

CO2

[CH2O]

(sugar)

The Light Reactions• Require sunlight• 1. Chlorophyll molecules(in

thylakoid) capture light energy

• 2. Captured energy used to split water into oxygen and hydrogen

• 3. Water’s electrons and H+ ions are used to make NADPH and ATP

• 5. Oxygen is a bi-product and released through stomata

The Calvin Cycle

• “Light- independent reactions” occur in the stroma

• Makes sugar from CO2 and H+ and electrons carried by NADPH

• ATP from light reactions provides energy to power the cycle.