Photosynthesis

Light Absorption

• Sun gives off visible light (ROYGBIV)• Unabsorbed light reflects to our eyes

– Most green light not absorbed by leaves

• Chlorophyll absorbs sunlight– Absorb mostly reds and blues

Prism

Which color(s) are being reflected?

Yellow

Which color(s) are being absorbed?

Red, Orange, Green, Blue, Indigo, Violet

Which color(s) are being reflected?

Blue

Which color(s) are being absorbed?

Red, Orange, Yellow, Green, Indigo, Violet

Which color(s) are being reflected?

None…Black is the absence of light

Which color(s) are being absorbed?

All….ROYGBIV

Which color(s) are being reflected?

All…ROYGBIV

Which color(s) are being absorbed?

None

Which color(s) are being reflected?

Green

Which color(s) are being absorbed?

Red, Orange, Yellow, Blue, Indigo, Violet

The Chloroplast

• Site of photosynthesis• Thylakoid membranes: light dependent

reactions• Stroma (fluid interior): light independent

reactions

Stomata: pore underneath leaves through which gases enter/exit

Photosynthesis Overview

• Two Stages

• 1) Light Dependent Reactions– Photosystems: groups of

molecules that capture/transfer energy

– Creates: O2, ATP, NADPH

• 2) Light Independent Reactions– Creates: Glucose

Light Dependent Reactions: Photosystem II

Step 1:Chlorophyll absorbs sunlight– Chlorophyll e- become

excited & transfer to thylakoid membrane

› Thylakoid membrane becomes negatively charged

– Starts an electron transport chain

Step 2 & 3:

H2O broken into H+, e-, and O

› e- replace those lost by chlorophyll

› O waste

› H+ pumped inside the thylakoids and accumulate

ee

ee

ee

e e ee e

Thylakoid membrane

Thylakoid membrane becomes negatively charged

chlorophyllchlorophyllee e e

HH

OH

HO

HH

O Oxygen waste is released

Electrons replace those which left chlorophyll

ee

ee

ee

e e ee e

Thylakoid membrane

Thylakoid membrane becomes negatively charged

chlorophyllchlorophyllee e e

Oxygen waste is released

Electrons replace those which left chlorophyll

H

H

H

H

HH

ee

e

e

ee

e

ee

ee

e

e

e

e

The process keeps repeating

The plants takes in water

HH

OH

OH

HO

H

Light Dependent Reactions: Photosystem I

• Chlorophyll absorbs sunlight

– Chlorophyll e- become excited & transfer to thylakoid membrane

› Accumulate with those from photosystem II

e-e-e-e- e-

• NADPH produced (H taxi)› e- causes H+ to

bond with NADP

› NADPH will be used later

• ATP produced› H+ ions diffuse and

bond ADP with Pi

› ATP will be used later

H+

H+

H+

ATP

ATP

e-

e-e-e-e-e-

e- e- e-e- e-

ATP

Light Dependent Summary

• O2, ATP, NADPH created

• NO GLUCOSE CREATED!

Light Independent Reactions (Calvin Cycle)

• Step 1: CO2 bonds with RuBP (5C) molecule to make a 6C molecule

6C molecule

C C C C C CC C C C C

RuBP

CO2 bonds with RuBP

Six carbon molecule is created

• Step 2: 6C molecule splits into two PGAL molecules (3C)

» ATP & NADPH provide the energy

C C C C CC

6C molecule

ADPADP

NADPH (from light dependent cycle) drops off H

H H H

HH H

ATP (from light dependent cycle) provides energy to break the molecule into PGAL

C C C C C C

PGAL

PGAL

ADPADPADPADP

ATP

Step 3:

• Some PGAL (3C) bonds to make glucose (6C)

• Some PGAL recycled to start the cycle over

PGAL

PGAL P

GAL

PGAL

PGAL

PGAL

PGAL

glucose!

glucose!

PGAL bonds with PGAL….to make glucose!

C CCC

C CCC C

C CC

Glucose is used by plant cell mitochondria to create ATP in the process of cellular respiration

PGAL is used to restart the Calvin Cycle

Step 4:

• PGAL (3C) bonds to remake a RuBP (5C) molecule with help of ATP

• CO2 bonds with RuBP (5C) to restart the cycle

PGAL broken apart by ATP

C C C C C C

C C C

C C C

C C C

Unstable C atoms recombine to make RuBP (5C) molecules

RuBP molecules bond with CO2 again

CC

C

C

C

C

C C

C

C

C

C

C

C

C

C C CCCC C CCC

C C CCC

RuBP

RuBP

RuBP

6C moleculeC C C C C C

6C moleculeC C C C C C 6C molecule

C C C C C C

• CO2, ATP, & NADPH create glucose

Light Independent Summary

Your essay question on the next test!

Trace the flow of energy, including ATP, from the sun to your muscles, after eating a green leaf salad.

Kobe Kuiz

• Place these steps in order from start to finish:

A) Electron transport chain creates NADPH and ATP energy

B) 3C molecule broken by ATP into 5C molecule

C) PGAL created when 6C molecule broken down

D) Water broken into H+, e-, and O components

E) Sunlight causes chlorophyll electrons to flow into thylakoid membrane

F) 3C molecule bonds to create glucose

G) CO2 bonds with RuBP

Kobe Kuiz

• Place these steps in order from start to finish:

E) Sunlight causes chlorophyll electrons to flow into thylakoid membrane

D) Water broken into H+, e-, and O components

A) Electron transport chain creates NADPH and ATP energy

G) CO2 bonds with RuBP

C) PGAL created when 6C molecule broken down

F) 3C molecule bonds to create glucose

B) 3C molecule broken by ATP into 5C molecule