Photosynthesisor

“How Plants Eat Sunshine”

Plants don’t eat cheeseburgers.

• Where do plants get the food to create the energy they need to grow and reproduce?

PHOTOSYNTHESIS!

What do you already know about Photosynthesis?

• It produces Oxygen.

• It uses CO2.

• It happens in plants.• Uses light.

• Chloroplasts.• Chlorophyll• Starch is produced.

What have we learned in lab?

• Photosynthesis takes place where chlorophyll is present - the green parts

• Photosynthesis produces starch

• Photosynthesis (O2 production) occurs in the light.

How does Photosynthesis work?

• Photosynthesis is the process of TRANSFORMING LIGHT ENERGY into CHEMICAL ENERGY (food, or GLUCOSE).

Light Glucose

BUT HOW??

Let’s look at a plant cell.

Here’s the chloroplast.

Chloroplasts…• Have stacks of thylakoids –a stack of

thylakoids is called grana.

• Have a stroma-

Space

surrounding the

thylakoids

Chloroplasts are GREEN so…

• Sunlight is part of the VISIBLE spectrum

• White light can be separated by wavelengths.

• Wavelengths correspond to different colors.

• The colors you see are being RFLECTED.

• CHLOROPHYLL is the pigment molecule that makes plants green and is responsible for photosynthesis.

• GREEN IS BEING REFLECTED.

• Light that is ABSORBED is used during photosynthesis.

• ALL OTHER LIGHT IS USED FOR PHOTOSYNTHESIS.

Chloroplasts are GREEN so…

The Light Dependent Reaction:uses water and produces O2

Step 1: the ETC (light DEPENDENT reactions)

• An electron Transport Chain (ETC) is an electron conveyer belt.

• Electrons (e-) move down the chain and are picked up and make new molecules.

• The ETC is located in the THYLAKOID MEMBRANE.

Step 1: the ETC(light DEPENDENT reactions)

• Light hits chlorophyll and excites an e-. The e- starts moving down the chain. This leaves an empty space.

Chlorophyll

ETC

e-

• H2O is split. O2 donates an electron to fill the empty space in the chain and diffuses out. H+ stays in the thylakoid,making an H+

gradient.• The OXYGEN

is released!

O- + H+ H+

e-

Step 1: the ETC(light DEPENDENT reactions)

• H+ diffuses out through ATP synthase, to make ATP. http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/

animations.html

H+ H+ H+ H+ H+ H+ H+ H+ H+

ATP!!

ATP Synthase

e-

H+

Step 1: the ETC(light DEPENDENT reactions)

• Electrons are picked up from the ETC and used to take H+ to the CALVIN CYCLE.

Step 1: the ETC(light DEPENDENT reactions)

e-

NADP+e-+H+NADPH

H+ H+ H+ H+ H+ H+ H+ H+ H+

H+ ATP!!

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html#

The CALVIN CYCLE aka

THE DARK REACTIONS:Consume CO2 and produce Glucose

(C6H12O6)

Step 2: The Calvin Cycle(Light INdependent reactions)

• H+ is transferred to the CALVIN CYCLE in the stroma.

Stroma: the dark middle part of the thylakoid.

Step 2: the Calvin Cycle(the DARK reactions)

CO2 diffuses into the chloroplast

And enters the

Calvin Cycle. CALVIN CYCLE

CO2

• H+ enters the Calvin Cycle.• Energy from ATP created during the Light

Dependent Reactions is used to ...

Step 2: the Calvin Cycle(the DARK reactions)

combine 6 molecules of CO2 and 12 H+ to make …

GLUCOSE (C6H12O6)!http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter10/animations.html

Step 2: the Calvin Cycle(the DARK reactions)

CO2

H+

C6H12O6

Step 1 and Step 2:

• http://www.tracy.k12.ca.us/thsadvbio/animations/Photosynthesis.swf

The Bottom Line...

• Photosynthesis occurs in plants.• Photosynthesis uses sunlight to make starch.• Photosynthesis takes place in the chloroplast

using chlorophyll.• Oxygen released from plants comes from

WATER – NOT CO2

• CO2 and H+ (also from water) are used to make C6H12O6.

• Photosynthesis has 2 reactions:

LIGHT DEPENDENT and LIGHT INDEPENDENT.

• Light Dependent Reactions = Thylakoid

• Light INdependent Reactions = Stroma

• CO2 + H2O + ATP SUNLIGHT C6H12O6 + O2

The Bottom Line...

So… why should we save the rainforest?

We need the Oxygen to make our own energy – ATP – during

cellular respiration!

Coming up next in Biology...

How do our cells use Oxygen from plants to make ATP??