Photosynthesis

What is the ultimate source of all energy

How does the energy get from the sun into the foods we eat?

energy

energy

Why do we see colors?

The sun sends downs little The sun sends downs little packets of light energy called:packets of light energy called:

PHOTONSPHOTONS

Why do we see colors?

Photons group together in wavesPhotons group together in waves The waves have different lengthsThe waves have different lengths Each “wavelength” presents Each “wavelength” presents

itself as a coloritself as a colorPhotons

Wavelengths

Why do we see colors?

Plants reflect this colorof light. That’s why

most plants are GREEN

Plant pigments like chlorophyll absorb these colors of light so these colors are not seen.

What colors of light would a plant with purple leaves absorb?

What colors are being absorbed and what colors are being reflected?

Photos courtesy of flowerpictures.net and picturesof.net

Why do we see colors? What do we call the compounds that What do we call the compounds that

absorb and reflect wavelengths of absorb and reflect wavelengths of light?light?

Which compound reflects the green Which compound reflects the green wavelengths thereby making plants wavelengths thereby making plants green?green?

Where would we find this Where would we find this compound?compound?

Chloroplast structure

Disks called GRANA contain the pigmentCHLOROPHYLL.

The liquid portion of a chloroplast is the STROMA

Where do we find chloroplasts?

stoma

Chloroplast containing chlorophyll

Chloroplasts are found in cells of leaves.

Review1.1. What is the ultimate source of What is the ultimate source of

all energy?all energy?

2.2. In what form does light energy In what form does light energy come to the earth?come to the earth?

3.3. What compounds absorbs What compounds absorbs wavelengths?wavelengths?

4.4. How do we see colors? How do we see colors?

5.5. Where in a leaf do we find Where in a leaf do we find pigments?pigments?

What process captures the light energy and uses it to make food?

OVERVIEW OF PHOTOSYNTHESIS

PLANTS TAKE INCO2 AND H2O

PLANTS MAKE GLUCOSE AND OXYGEN

SUNLIGHT PROVIDES THE ENERGY

FOR PHOTOSYNTHESIS

Photosynthesis What is photosynthesis?What is photosynthesis? Photosynthesis is the process Photosynthesis is the process

by which:by which:

water

carbon dioxide

oxygen

glucose

TAKE IN AND USING MAKE

PLANTS(producers)

light

chlorophyll

Photosynthesis 2 steps:2 steps:

Light reactionsLight reactionsDark reactions (aka Calvin cycle)Dark reactions (aka Calvin cycle)

Light Reaction Dark Reaction

Who was Calvin anyway? A member of the faculty A member of the faculty

at UC Berkeley since at UC Berkeley since 1937, Melvin Calvin 1937, Melvin Calvin received the 1961 Nobel received the 1961 Nobel prize in chemistry for prize in chemistry for identifying the path of identifying the path of carbon in carbon in photosynthesis.photosynthesis.

The cycle of reactions in the dark phase of The cycle of reactions in the dark phase of photosynthesis was named after him for photosynthesis was named after him for his work in identifying the processes his work in identifying the processes taking place.taking place.

Photosynthesis Light reaction:Light reaction:

Occurs in the granaOccurs in the granaMustMust have light have light

light

Light Reaction Dark ReactionLIGHT REACTION Dark Reaction

grana(chlorophyll)

Photosynthesis Dark reactions (aka Calvin cycle)Dark reactions (aka Calvin cycle)::

Occurs in the stromaOccurs in the stroma Occurs in the light and darkOccurs in the light and dark

Light Reaction Dark ReactionLight Reaction DARK REACTION

stroma(liquid)

Step 1: Light Reactions

H2O O2

O2

O2

O2

O2

H H

How doesthe O2 leavethe leaf?

ENERGY

light energy reacts with the chlorophyll

water is split by the light energyH is kept for the dark reactionO2 is released

O

H2

Step 2: Dark Reactions AKA: CALVIN CYCLEAKA: CALVIN CYCLE

CO2

CO2

CO2

CO2

HC6H12O6

How does CO2

enter the plant?

H from the water split in the light reaction is present

CO2 enters the chloroplastthe reactants H and CO2 combine

HH + CO2

glucose is the product

Other carbohydrates besides glucose may be made in photosynthesis

Photosynthesis Review Light reactions: H2O split into H2 + O

Dark reactions: H + CO2 = C6H12O6

H2O Light Reaction Dark ReactionC

O 2

C6H12O6

O 2

chlorophyll

Photosynthesis Formula How would this be written as a

chemical equation? What goes in? (the reactants) What comes out? (the products)

H2O Light Reaction Dark ReactionC

O 2C6H12O6

O 2

chlorophyll

H2O CO2 C6H12O6 O2

Photosynthesis Formula What’s wrong with this equation? The number of atoms is not equal on

both sides of the equation.

Balance the equation so that the number of atoms of each element is equal on both sides.

H2O CO2 C6H12O6 O2

one carbon atom reactant

6 carbon atoms product

6 6 6(1)

Now balance it as if TWO glucose molecules were being produced.

Photosynthesis Review What goes in? (the reactants) What comes out? (the products)

H2O Light Reaction Dark Reaction

CO 2

C6H12O6

O 2

chlorophyll

6CO2 + 6H2O 6O2 + C6H12O6

light

chlorophyll