Photosynthesis

NB pgs 7-11 odd

Pic 8,10

Chemistry Review

• What is an electron?– Negatively charged

particle

• What is a proton?– Positively charged

particle

• Do P and E carry energy?– Yes- they are

charged particles

If the concentration of hydrogen protons (H+) is greater inside a cell than outside the cell, which direction

will the H+ generally flow?

Inside to Outside

• What is the difference between:– ADP and ATP– ATP = Adenosine

Triphosphate

• Why is ATP an energy storing compound?– When bonds are broken

energy is released.– The phosphate bonds

store energy

ATP has an extra phosphate

ATP

• What is the difference between:– ADP and ATP– ATP = Adenosine

Triphosphate

• Why is ATP an energy storing compound?– When bonds are broken

energy is released.– The phosphate bonds

store energy

ATP has an extra phosphate

How Much ATP do Human Cells Use?

• Each cell in the human body is estimated to use between one billion and two billion ATP's per minute!

• With 100 trillion cells in the human body, how much ATP do we need?– Roughly 1 x 1023 molecules. – In the span of twenty-four hours, 100 trillion

cells produce about 441 lbs of ATP.

NADPH

• In addition to ATP being used to release (ATP-ADP) and store (ADP-ATP) energy, a molecule called NADPH is used.

• NADP– Carrier molecule– Moves H+ ions from one reaction to another

(light to dark reaction)– NADP - NADPH

• Nicotinamide adenine dinucleotide phosphate

Why is Photosynthesis Important?

• Heterotrophs obtain their energy from other organisms.

• Whatever we eat can eventually be traced back to producers.

• The Sun provides Earth with energy. We cannot eat the sun…plants “eat” the sun harvesting its energy and passing it on to us.

• Oxygen

• Process by which plants change the energy in sunlight to kinds of energy that can be stored for later use.

6CO2 + 6H2O (+ light energy) →C6H12O6 + 6O2

Carbon Dioxide + Water+ (Light) = Glucose + Oxygen

Yes….you will need to know this!

What is Photosynthesis?

All in the Chloroplast

• 2 Main Steps

Light Reaction-Needs light-Thylakoid membrane-Converts light energy to chemical energy (ATP and NADPH)

Dark Reaction (Calvin Cycle)

-No light needed (but must have ATP and NADPH)-Stroma-Converts CO2 to sugar

Photosynthesis Basics

Light Reactions

Where do the light reactions occur?

Thylakoid

Label

D

E

F

A

B

C

A

Light absorbed by chlorophyll

C

E- move through “electron transport chain” like hot potatoes passing from one membrane protein to another

ChlorophyllB.

Electrons in chlorophyll get excited

D

As water enters the cell- a water splitting enzyme splits 2 molecules of water into atmospheric O2 and H+

and e-

2H2O → O2 + 4H+

What we breathe

Builds a concentration gradient

H+ concentration

gradient

Where do the e- that get excited

in chlorophyll

come from?

E

After e- pass through electron transport chain (ETC), they help attach a H+ to NADP+ to become NADPH.

NADP+ + H+ → NADPH

What is NADPH?

Molecule that stores energy. This energy will be used later

Energy from H+ used by membrane protein to catalyze the reaction of

ADP → ATP

F.

As H+ builds inside thylakoid, a gradient builds. H+ ions move down concentration gradient

We have created an extra phosphate bond (stored energy)ATP is the second energy storing molecule made.

Let’s Review• The light reactions convert energy from the sun to

chemical energy• Light is absorbed by (green structures) chloroplasts.• Electrons become excited and move like hot potatoes

through the electron transport chain.• At the end of the ETC an energy storing molecule

called NADPH is made• At the same type a concentration of H+ build up in

the thylakoid space. This concentration gradient gives energy to the membrane proteins which catalyze the reaction of ADP to ATP

• Electrons are replaced when the water is split into O2 and H+

Dark Reactions

Where do the dark reactions occur?

Stroma

• Uses energy from the light reactions to change CO2 from the atmosphere into

sugar• Energy needed comes from the ATP and

NADPH (light reactions)

Calvin Cycle

Other C molecules recycle

A carbon in the form of CO2 is attached to a 5C compound to form a 6C compound

The 6C compound is unstable and breaks in half.

One 3C product is used to make glucose and other compounds.

How many ATP molecules are needed in the Calvin Cycle?

9 ATP

How many NADPH molecules are needed in the Calvin Cycle?

6 NADPH