PHOTOSYNTHESISHow plants (and some algae and

bacteria) make their own food

video

Recall: Plants use the energy of sunlight and the

green pigment chlorophyll to convert carbon dioxide and water into the sugar glucose.

The Equation What are the reactants or ingredients

necessary to carry out photosynthesis? Carbon Dioxide (CO2) Water (H2O) Solar energy (sun)

What are the products? Glucose (C6H12O6) Oxygen (O6)

So the formula is:CO2 + H2O + sun → C6H12O6 + O2

How can we balance this equation?

666

Heterotrophs vs. Autotrophs

Autotrophs Create their own food from sun or

inorganic chemicals Photoautotrophs

obtain energy from sunlight Chemoautotrophs

obtains its nourishment through the oxidation of inorganic chemical compounds as opposed to photosynthesis

Heterotrophs They need to consume plants– or other

animals that have consumed plants– in order to obtain products such as glucose

Photosynthesis is vital to life on Earth

Animals are not able to create their own food from inorganic compounds. Animals EAT food, which is

then broken down through cellular respiration (the breakdown of glucose to provide energy), which all living cells need to perform.

Cellular respiration produces carbon dioxide and water, which can be used for photosynthesis.

Anatomy of a Leaf

LIGHT DEPENDENT REACTION

The goal: Pass the electrons of water to chlorophyll, and

down the photosystems I and II to make Energy (ATP and NADPH)

Scene: These reactions occur in the thylakoid

membrane stacks (The Grana)

Animation

The Players: Photosystems (PS) II (most

reactive at a wavelength of 680nm) & Photosystem I (most reactive at a wavelength of 700nm) – located in the thylakoid

membranes (grana) inside the chloroplast;

each photosystem contains a few hundred chlorophyll molecules.

Chlorophyll- a green pigment, absorbs the

red and blue wavelengths of sunlight and becomes photoexcited to start photosynthesis.

Electrons- When photoexcited by sunlight,

they leave a chlorophyll molecule in PS II and travel through a series of proteins (called an electron transport chain) to PS I and its electron transport chain.

Water- is split into oxygen, hydrogen,

and electrons in a process called photolysis to replace the electrons lost from PS II.

This is where the oxygen we breathe comes from (a by-product of photosynthesis!)

water is the ultimate source of electrons for photosynthesis!

animation

Electron Transport Chain (ETC)

A group of compounds that pass electrons from one to another via redox reactions coupled with the transfer of protons across a membrane to create a proton gradient that drives ATP synthesis Sort of like a bucket brigade

ATP– Finally, the hydrogen ions (H+)

inside the thylakoid form a proton gradient.

When there are more protons in the inner thylakoid space, they pass back to the stroma through ATP Synthase (an enzyme) which supplies the energy to produce ATP from ADP (this is called chemiosmosis).

ATP Synthase- an enzyme that can

synthesize ATP from ADP and inorganic phosphate by using a concentration gradient

NADPH— Ferredoxin, the last electron

acceptor in the second ETS, "hands" the electrons from PS I to NADP which then adds a H+ from the stroma to form NADPH.

Animation- another overview of the process

Light Dependent Reaction Summed Up

Another animation