PHOTOSYNTHESISUsing Light to Make Food

Photosynthesis is the most important chemical process on

earth because:• It provides

food for virtually all organisms

• SWEET!!!!

BIG PICTURE: Photosynthesis

Light energy is used to make sugar and other food molecules from carbon dioxide and water

Chemical Reaction

• 6 H2O + 6 CO2 ---------->

C6H12O6+ 6 O2

sunlight

How does this equation compare to the cell respiration one?

Photosynthesis: An Overview of Photosynthesis (click)

7.1 AUTOTROPH• Autotrophs“Self-

feeders”• Make their own food

• Also referred to as: Producers = produce the biosphere’s food supply

Photosynthetic Plants

Diatoms

(microscopic)

Kelp (ocean) Forests (land)

Leaf Structure

1. Stoma (sing.) in leaf lower epidermis

• Is the opening

• carbon dioxide, oxygen. And water in/out

Stomata (pl.)

Leaf CS2. Upper Epidermis

4. Mesophyll-cells containing chloroplasts

3. Lower epidermis

Covers and protects

see stoma –in lower epidermis only

4. Mesophyll

• = Palisade Layer + Spongy Layer

5. Cuticle

Waxy, waterproof coating (to retain H2O)

6. Palisade Layer

• cylindrical cells, vertically oriented, closely packed

7. Spongy Layer

• cells are irregular in shape and loosely packed

O2 ,CO2, H20 vapor go in/out

8. Guard Cells Control Stomata

• Full guard cells (turgid) opens the stoma.

• Flaccid (lost water) guard cells, the stoma closes.

• ANIMATION: Stoma• What causes them to open?

What goes into the stomata?

9. Plant Vein: Xylem + Phloem

Xylem-(blue) carries water

Phloem (thicker cell wall)-(yellow) carries food

10: Air Space Gas Flow Through Leaf

Guard Cells Animations

• LabBench (guard cell animation)

• Another animation of opening and closing of guard cells

http://academic.kellogg.cc.mi.us/herbrandsonc/bio111/animations/0021.swf (really nice)

Water Movement

• LINK: http://www.sciencemag.org/sciext/vis2005/show/transpiration.swf

Draw the Elodea Cell 400X

Leaf CS (cross section)

Photosynthesis in Elodea Lab

See oxygen bubbles coming from the Elodea

What conditions are best?

Elodea Bubbles Movie

• sLowlife Exhibit

7.2

Chloroplast

Chloroplast Diagram• Stroma = thick fluid

between the thylakoids

• thylakoids = disks within the chloroplasts

• granum=stack of thylakoids (grana pl.)

GRANA

• What is the difference between grana and granum?

STROMA

• So what’s the difference between the stoma and the stroma?

• STOMA = opening in lower epidermis

• STROMA = area around thylakoid disks in the chloroplast

Chloroplast DiagramStromal lamella = connect grana D. Outer Membrane

Thylakoid membrane

Thylakoid spaceIntermembrane

Space

Inner Membrane

Chloroplasts TEM

• Note the stacks of thylakoid disks =

grana• Note area between

= stroma

THYLAKOIDS

Photosynthesis

Summary IN

Summary OUT

Nice Little Photosynthesis Movies

• VCAC: Cellular Processes: Photosynthesis: The Movie

• VCAC: Cellular Processes: Photosystem II: The Movie

7.5 Overview of Photosynthesis

What happens here?

• Light Dependent Reaction (LDR)

• Converts light energy to chemical energy + O2

• Light Independent Reaction (LIR)

• Assembles sugar molecules using CO2

Where does energy come from?

•Light Dependent Reaction LDR

•Uses light energy

•Light Independent Reaction LIR

•(Calvin Cycle)

•uses ATP and NADPH (from LDR)

PSI and PSII

• PSI and PSII animation

• Another PSI and PSII animation

Where is it located in the cell?

•LDR•occurs in

thylakoid membranes of chloroplast’s grana

•LIR (aka Calvin cycle)

•occurs in stroma of chloroplast

Final Products of Each?

• LDR

• ATP and NADPH

• Also O2

• LIR

• sugar

NEW VOCAB. WORD

• Carbon fixation =

• incorporation of carbon into an organic molecule (useable)

• EXAMPLE: CO2 into C6H12O6

FIXATION = make in a usable form

LIGHT

• CHLOROPHYLL

Pigments in Plants• Pigments are light-absorbing

molecules

• Different pigments absorb or reflect different colors

Chlorophyll a

• wavelengths absorbed:

blue-violet and red

• Reflects: grass green Wavelength

Chlorophyll b

• Absorbs: blue and orange

• Reflects: yellow-green

•An accessory chlorophyll in plants

Other pigments in plants

• Absorb: blue-green

• Reflect: yellow-orange

Carotenoids-orange

FYI Why do leaves change color?

• As fall comes there

are shorter days of sunlight

• Less photosynthesis means less food for plants.

• Chlorophyll breaks down and exposes the other colors that were there all along, but were masked by the green chlorophyll.

DO WORKSHEET

• “Absorption of Chlorophyll”

• Photosynthesis: The Action Spectrum for Photosynthesis (experiment link)

Chlorophyll a and Chlorophyll b

7.7Electromagnetic

• Photosynthesis: Electromagnetic Energy

• (move the arrow)

#1 What are…

• Fixed quantity (packet) of energy

PHOTONS

WAVES

Distance between crests of two waves

Λ = symbol for wavelength

Light travels as waves and as photons

•

•“Wave-particle theory”

PHOTONS

• Smallest unit of light emitted when an electron jumps to a more excited state

• named by Einstein

light

Shorter the wavelength...

The greater the energy

#2 When an e- in a pigment absorbs a photon...

• Electron goes from “ground state” to “excited state”

Energy from the sun

• ANIMATION:Atomic absorption diagram (how energy causes an electron to jump levels)

#3 Excited State is Very Unstable

• As e- falls back to the ground state it might:

• lose energy as heat• emit light• gives off a photon• IN A CHLOROPHYLL

MOLECULE IT WILL …

PHOTOSYSTEM

Now for photosynthesis

#3 + #4 Chlorophyll passes its photon to:

• A neighboring molecule called the

primary electron acceptor

Reaction Center of Chlorophyll

• Chlorophyll a is the only one that donates to the primary acceptor

CENTER

Pigments in a Photosystem (Light RXN)

reaction center

Figure 7.11Page 122

“Light capturing Antenna”

• Transfer light energy to the reaction center

Going to the ETC

Electron is boosted to a higher energy level

Attaches to an e-acceptor

Then it goes to the ETC

ELECTRON

#4 “Photosystem” = PS

• Antenna

molecules + reaction center

+ primary electron acceptor

Cyclic Electron Flow (Light RXN)

electron acceptor

electron transfer chain

e–

e–

e–

e–

ATP

Electron flow through transfer chain sets up

conditions for ATP formation at other membrane sites.

Figure 7.12Page 122

#5 TWO photosystems: PS I and PS II:absorbs λ(λ = wavelength)PS I -P 700 nmPS II -P 680 nm

Animations

• P700 and P680 Animation

• Making ATP and NADPH (Light Dependent Reaction)

7.8 In light reaction: ETC generates ATP, NADPH, O2

1. Light energy is absorbed2. Electrons excited3. Energy from ETC used to make ATP and NADPH

WATER

#2 PS II: Breaking up water

• The P680 requires an electron, which is taken from a water molecule, breaking the

water into H+ ions and O-2 ions.

• These form the O2 that is released.

• 2 H2O 02 + 4e- + 4H+

What process drives each?

• NADPH forming

• ATP forming

• O2 formation

• Redox and ETC

• Chemiosmosis

• Redox and ETC

NOTE: Final Electron Acceptor is

• NADPH • Not Oxygen (Oxygen is given off)

in Light Reaction of Photosynthesis

Animation

• Making Oxygen (You’ll love the noises)

• (I hate ‘em)

Chemiosmosis Again

• #1 Remember chemiosmosis in cellular respiration, well, here it is again.

7.9 Question #2 PS I: Forming H+ ions to form

ATP• By chemiosmosis

7.9 #3

• There would now be more H+ ions located:

• Came from the stroma and went to the thylakoid interior

7.9 #4

• The H+ ions move through what port to move back into the stroma?

• ATP synthase

#5 Photophosphorylation

• is the process of converting energy from a light-excited electron into the phosphate bond of an ADP molecule into ATP.

• This occurs when the electrons from water are excited by the light in the presence of P680.

CALVIN CYCLE

•Or the LIR

7.10 Dark Reaction (LIR)

Carbon-Fixing Reaction

Calvin Cycle

Light-Independent Reaction

Can the Calvin Cycle also be called the “dark reaction?”

• PEANUT: It does not need light to run, but it can also run during light. So…the “dark cycle” term is not used anymore.

Animation

• Noncyclic photophosphorylation

• (THIS ONE IS MY FAVORITE) Cyclic and Noncyclic Photophosphorylation (first one is very detailed, second one is better for HS)

• Photosynthetic ETC and ATP Synthesis

View Me

• Photosynthetic Electron Transport and ATP Synthesis

7.10 #1 Calvin Cycle• Uses the CO2

(from the atmosphere) and ATP and NADPH (from light reactions) to run the sugar factory

Step 1: Carbon Fixation

• RUBISCO ENZYME combines 3 molecules of CO2 with ribulose bisphosphate (5-C) RuBP makes 6-C

#2 G3P

• “Glyceraldehyde- 3 phosphate”

• the energy-rich molecule made in the Calvin cycle

• it can be used to make glucose or other organic molecules

#3

• The enzyme rubisco combines with CO2 to form 3-C molecule, 3PGA

#4

•It takes 6 turns to make one glucose molecle

Regeneration of RuBP

•Energy from ATP is used to reform RuBP molecules (hey, its recyclable!)

Calvin Cycle

• Occurs in stroma of chloroplasts

7.11 Review of Photosynthesis

Summary: Calvin Cycle

Overall Equation

QUIZ TIME: structures

• The light reactions (LDR) of photosynthesis occur in the __________, and the Calvin cycle (LIR) occus in the __________ of the chloroplast.

ANSWER

• The light reaction occurs in the thylakoid membranes and the dark reaction occurs in the stroma.

Which equation summarizes photosynthesis?

• A. water + starch ---> glucose + glucose + glucose B. water + carbon dioxide ---> oxygen + glucose + water C. glucose + oxygen ---> water + carbon dioxide + ATP D. glucose + glucose ---> maltose + water

ANSWER

• B. water + carbon dioxide ---> oxygen + glucose + water

In what organelle does photosynthesis occur?

• A. the nucleus B. chloroplasts C. the vacuole D. the cell wall

ANSWER

•B. Chloroplast

QUESTION:

• Four identical plants are grown under different colored light bulbs. Under which color will the release of oxygen gas be slowest? A. Green

• B. blue C. orange D. red

ANSWER:

•A. Green

QUIZ TIME

• The reason why ADP + P form ATP in thylakoid membranes is…

• A movement of electrons between photosystem II and photosystem I.

• B oxidation of water • C oxidation of NADPH • D absorption of photons by chloroplast pigments • E higher concentration of H+ inside versus

outside the thylakoid membranes

ANSWER

• E. a higher concentration of H+ ions inside vs. outside the thylakoid membranes

QUIZ TIME

• Water is broken down and the electrons from water pass through photosystem II and photosystem I before adding e- to:

• A carbon dioxide

• B NADP+

• C plastoquinones

• D FAD

• E rubisco

ANSWER

• NADP+ to make higher energy NADPH

QUIZ TIME

• Which of the following would have the smallest effect on the rate of photosynthesis in a green plant? A. carbon dioxide concentration B. light intensity C. oxygen concentration D. water available

ANSWER:

• C. oxygen concentration

QUIZ TIME

• During photosynthetic electron transport, the interior compartment of the thylakoid membranes becomes:

• A. more concentrated with ATP

• B. more concentrated with H+ ions

• C. less concentrated with H+ ions

HINT: Distribution of H+ ions

• Light Rx• more inside

• Dark Rx• Even in and out

ANSWER

•More concentrated with H+ ions

QUIZ TIME

• Which of the following is produced during photosynthesis? A. carbon dioxide B. lactic acidC. DNA D. PGAL

•  

ANSWER

•D. PGAL

QUIZ TIME

• Atmospheric oxygen that is inhaled by animals comes from: A. carbon dioxide molecules split during the light reactions B. carbon dioxide split during the dark reactions C. water molecules split during the light reactions D. water molecules split during the dark reactions

ANSWER

• C. water molecules split during the light reactions

QUIZ TIME

• What change occurs during photosynthesis? A. solar energy is converted to chemical energy B. kinetic energy is converted to chemical energy C. chemical energy is converted to radiant energy D. water is converted to chemical energy

ANSWER

• A. solar energy is converted to chemical energy

Cuticle Epidermis Guard cells Palisade PhloemXylemSpongy MesophyllStomata Bundle Sheath

A=cuticle

B=Upper epidermis

C=Vein

D=Phloem

E=xylem

F=Palisade layer

G=spongy layer

H=guard cell

I=stomata

QUIZ TIME

• The overall source of energy for photosynthesis is:

• A. energy from the sun

• B. energy from ATP

• C. energy when oxygen is produced

ANSWER

• A. energy from the sun

QUIZ TIME

• What three events occur during the light reactions of photosynthesis? –Forming ATP–NADP+ to NADPH

–Fixing CO2

–Releasing O2

ANSWER

–Forming ATP

–NADP+ to NADPH

–Releasing O2

QUIZ TIME

• Which of the following does not happen in photosystem I?–ATP is produced

–electron transport in the thylakoid membranes

–light energy is used

–NADPH is formed

HINT

ANSWER (which is NOT)

• NADPH is formed

QUIZ TIME

• Where does the Calvin Cycle take place?–Thylakoid membranes of

chloroplasts

–Stroma of chloroplasts

–Matrix of mitochondria

–Inner membrane of mitochondria

ANSWER

• Stroma of chloroplasts

QUIZ TIME

• What is the name of the enzyme that causes CO2 to form glucose?–ATPase

–glucosease

–rubisco

ANSWER

• rubisco

QUIZ TIME

• What two high energy compounds are required for this reaction?–ATP

–NADH

–NADPH

–ADP

–FADH

ANSWER

• ATP and NADPH

QUIZ TIME

• What is the name of the process in which carbon dioxide is made into glucose?–Krebs cycle

–Calvin cycle

–Einstein cycle

ANSWER

• CALVIN CYCLE

• (or sometimes the Calvin-Bensen Cycle)

QUIZ TIME

• Which does NOT happen in the Dark Reaction:–using ATP

–using NADPH

–using Carbon Dioxide

–making water

ANSWER

• MAKING WATER

QUIZ TIME

• What are the products of the dark reaction?–ATP

–ADP

–glucose

–CO2

–NADP+

ANSWER

• ADP

• NADP+

• glucose

QUIZ TIME

• The reason why ADP + P form ATP in thylakoid membranes is…

A movement of electrons between photosystem II and photosystem I.

B oxidation of water C oxidation of NADPH D absorption of photons by chloroplast pigments E higher concentration of H+ inside versus outside

the thylakoid membranes

ANSWER

• a higher concentration of H+ ions inside vs. outside the thylakoid membranes

QUIZ TIME

• During photosynthetic electron transport, the interior compartment of the thylakoid membranes becomes:

• A. more concentrated with ATP

• B. more concentrated with H+ ions

• C. less concentrated with H+ ions

ANSWER

• More concentrated with H+ ions

QUIZ TIME

• The overall source of energy for photosynthesis is:

• A. energy from the sun

• B. energy from ATP

• C. energy when oxygen is produced

ANSWER

• A. energy from the sun

QUIZ TIME

• What three events occur during the light reactions of photosynthesis? –Forming ATP–NADP+ to NADPH

–Fixing CO2

–Releasing O2

ANSWER

–Forming ATP

–NADP+ to NADPH

–Releasing O2

QUIZ TIME

• What is the name of the process in which carbon dioxide is made into glucose?–Krebs cycle

–Calvin cycle

–Einstein cycle

ANSWER

• CALVIN CYCLE

• (or sometimes the Calvin-Bensen Cycle)