Photosynthesis Using light, water and CO2 to make food for over a billion years

Joseph Geissler

Newark Science Park High SchoolMrs. Paulose

Hierarchy Photosynthesis◦Structure of leaf◦Chloroplast◦Thylakoid Membrane ◦Chlorophyll

Photosystems Light vs Dark Reactions Review Questions

Outline

Autotrophs◦ Plants, algae, and many bacteria

Heterotrops◦ Animals, fungi and many bacteria

Aerobic vs Anaerobic ◦ The presence of oxygen vs the absence of oxygen

Energy Source

Cellular Evolution~1,500,000,000 years of anaerobic cells 200,000 years of humans

The earth is 4.6 billion years old(4,600,000,000 years)

The process by which green plants make their own food using carbon dioxide and water in the presence of sun light.

What is Photosynthesis?

6CO2 + 6 H2O + light energy C6H12O6 + 6O2

Hierarchy Photosynthesis

Chlorophyll

Thylakoid Membrane

Palisade Cell

Chloroplast

The Leaf

Structure of Leaf

Palisade Cell

Structure of Chloroplast

Thylakoid Membrane

StromaThylakoid Space

Thylakoid Membrane

Thylakoid Membrane

•Network of flattened disclike sacs (thylakoids) which create a third internal compartment separate from the stroma•The site of the light-capturing systems, the electron-transport chains, and ATP synthase

Stroma

•Interior space of the chloroplasts•Contains metabolic enzymes, as well a special set of ribosomes, RNA and DNA

Light absorbing pigment that plays a central role in photosynthesis

Long hydrophobic tails (in yellow) anchor chlorophyll to the thylakoid membrane

Light is absorbed by electrons within the bond network (in blue)

Chlorophyll are arranged in and around photosystems embedded in the thylakoid membrane

Electrons in chlorophyll molecules interact with photons from light are raised to a higher energy level

Chlorophyll

Photosystems Cartoon

(A) Charge separation generated in pigment-protein complex of a chlorophyll molecule to drive (B) the donation of a high-energy electron to the electron-transport chain

A.

B.

Electron Transport

Classic Model of Photosystems

Direction of electron flow

--Produces high-energy electrons to be propelled along the electron-transport chain--Electron transportation drives H+ pump creating a proton gradient--ATP synthase uses this gradient to drive ATP synthesis (video)

--Finally, the high-energy electron arrives at photosystem I--Here, it will fill a positively charged ‘hole’ which has been left in the reaction center of chlorophyll

Photosystem IIPhotosystem I

Light and Dark Reactions Light reactions (photosynthetic electron-transfer

reactions) Photosystems◦ Energy from sun light excites electrons within chlorophyll,

enabling electrons to move along an electron transport chain in the thylakoid membrane Electrons are obtained from the splitting of water molecules,

which produces O2 as a byproduct

Dark reactions (carbon-fixation reactions) Calvin Cycle◦ ATP and NADPH generated from light reactions serve as a

source of energy and reducing power, respectively, to drive the conversion of CO2 to carbohydrate, such as sucrose These organic molecules can then be exported to other tissues

as a source of energy

High Energy Molecules

ATPGTP

NADH/NADPHFADH2

http://www.biotek.com/resources/articles/nadh-concentrations-fluorescence-absorbance.html

Direct Energy Molecules

Indirect Energy Molecules

Photosystem IIPhotosystem I

ATP Synthase

ATP synthase + ADP + Pi  ATP Synthase + ATP

The ATP Synthase is an enzyme which generates ATP by combining ADP and Pi.

This protein is powered by the movement of H+ down its electrochemical gradient.

Are found in both the stroma of chloroplasts and the inter-membrane space of mitochondria.

http://www.youtube.com/watch?v=PjdPTY1wHdQ

Conditions Properly functioning chloroplasts Properly functioning chlorophyll molecules Well established electron transport chain Optimum exposure to sun light Steady supply of water and nutrients and

CO2 Steady removal of waste products O2

Which of the following is the correct formula which describes photosynthesis?◦ A) O2 + H2O + light C6H12O6 + CO2

◦ B) C6H12O6 + light CO2 + H2O

◦ C) CO2 + O2 + light C6H12O6 + O2

◦ D) CO2 + H2O + light C6H12O6 + O2 + H2O

Balance the equation of your answer

Review Question #1

D) 6 CO2 + 6 H2O → C6H12O6 + 6 O2

Which organelle in plants is the site for photosynthesis?◦ A) Stroma◦ B) Chlorophyll◦ C) Chloroplast◦ D) Mitochondria

Review Question #2

C) Chloroplast, chlorophyll is the light-absorbing green pigment essential in photosynthesis

What gas occupies the intercellular space of the mesoderm on a bright sunny day?◦ A) Nitrogen◦ B) Carbon Dioxide◦ C Hydrogen◦ D) Oxygen

Review Question #3

B) Carbon Dioxide

Which of the following events takes place during light reactions?◦ A) Combination of H and CO2

◦ B) Combination of C and CO2

◦ C) Splitting of H2O

◦ D) Splitting of CO2

Review Question #4

C) Splitting of H2O, Electrons are obtained from the splitting of water molecules, which produces O2 as a byproduct

From where does the low-energy electron responsible for releasing the high-energy electron come from?◦ A) CO2

◦ B) NADPH◦ C) ATP◦ D) H2O◦ E) None of the above

Review Question #6

D) H20