1. Photosynthesis Using the sun to make useful forms of energy
Sunlight plays a much larger role in our sustenance than we may expect: all the food we eat and all the fossil fuel we use is a product of photosynthesis, which is the process that converts energy in sunlight to chemical forms of energy that can be used by biological systems

2. Photosynthesis 6 CO2 + 6H2O + light energy C6H12O6 + 6O2
Photosynthesis is the conversion of light energy into chemical energy by living organisms.
How can sunlight be the source of energy for virtually every living thing?
General Equation: chlorophyll
6 CO2 + 6H2O + light energy C6H12O6 + 6O2
Photosynthesis Song
Why is chlorophyll above the arrow, instead of being part of the equation? Chlorophyll absorbs light energy and begins the process of photosynthesis.

3. Photosynthetic Organisms
Plants, algae, some protists, and cyanobacteria all contain chlorophyll
Chlorophyll
Absorbs light energy and begins photosynthesis
Chlorophyll a: blue-green
Chlorophyll b: yellow-green
Composed of porphyrin ring and long hydrocarbon tail
All photosynthetic organism use chlorophyll a as the primary pigment
Several types of chlorophyll are found in photosynthetic organisms
Depends on wavelength of light they absorb – chlorophyll a absorbs best at blue and red and reflects at blue-green
Chlorophyll B absorbs best at blue-green and orange, so it reflects a yellowish green
Chlorophyll a is also used in commercial products as a dye – cleverly named natural green

4. Chlorophyll Chlorophyll a contains –CH3 at R
Chlorophyll b contains –COH at R R
Porphyrin contains magnesium ion surrounded by hydrocarbon ring with alternating single and double bonds.
Delocalized electrons (meaning not associated with a single atom) absorb light energy and begin photosynthetic process
Chlorophyll a contains –CH3 (methyl) at R
Chlorophyll b contains –COH (aldehyde) at R
Porphyrin ring
Mg ion in centre, surrounded by hydrocarbon ring. This ring contains the electrons that absorb light energy
Phytol Chain
Hydrocarbon tail anchors the molecule to a membrane

5. Prokaryotic Autotrophs: Cyanobacteria
Largest group of photosynthetic prokaryotes
Unicellular, but grow in colonies
Live in different environments: oceans, freshwater lakes, rivers, on rocks and soil
Dense blooms produce toxins that pose environmental hazard
First organisms to use sunlight in the production of organic compounds from water and CO2
Contain chlorophyll a to carry out photosynthesis and d : photosynthetic pigments called phycobilins
Closely related to chloroplasts
 endosymbiotic theory
- Another example of photosynthetic organisms
- These are the autotrophs formerly known as blue-green algae – kind of like the artist ‘prince’
Grow rapidly in nutrient rich water and know to create cyanobacterial blooms – which could be toxic
Dense blooms usually occur in water that is rich in nitrates/phosphates usually caused by fertilizer run off from homes or farms
Produced oxygen on a large scale, therefore paved the way for heterotrophs on Earth
Endosymbiotic theory states that larger cells (probably ancestral to today’s eukaryotes) engulfed ancestors of cyanobacteria to create a mutually beneficial relationship – That is cyanobacteria were spared from the harsh environmental conditions and the host benefited from the food that these photosynthetic organelles produced
QUESTION: What other organelle might be a product of endosymbiosis (discussed in cell resp)? – mitochondria
Since they are prokaryotes – do not possess membrane bound organelles

6. Eukaryotic Autotrophs: Algae, Protists, Plants
Contain chlorophyll within chloroplasts
Chloroplasts give leaves, stems characteristic green colour
Leaves are the primary photosynthetic organs of most plants
To undergo photosynthesis, a plant cell must contain chlorophyll and obtain carbon dioxide, water and light energy from its environment
- In order to photosynthesize, plant cells must contain chlorophyll, which is green pigment, therefore plants can only photosynthesize within the green structures- such as stems, and especially leaves

7. Leaves: The Photosynthetic Organs of Plants
Waxy and water resistant, protection
Allows light to pass to mesophyll
Vascular bundle – transport water, minerals, carbohydrates
Chloroplasts are abundant, location of most of photosynthesis
Main function of leaves is photosynthesis
Cross-section of a leaf
Starting from the top
QUESTION about cuticle: what would be the consequence of temperature rising past a given optimal temperature?  denaturing of enzymes
The cuticle prevents against water loss and in addition protects the leaf from absorption of excessive light
Chloroplasts are abundant in spongy and mesophyll layers – most photosynthesis occurs here.
Guard cells are descriptively named as they guard or protect plants by opening or closing openings in the leaves in order to exchange gases and allow water vapour to escape, however if too much water is lost, the cells become flaccid and the stomata are closed
QUESTION: Why would plants have evolved with stomata on the bottom of the leaves? – increase SA for absorption, prevent water loss from the elements like wind, beads of water can act like a magnifying glass and scorch the leaves.
Vascular bundles are the same as veins – composed of xylem and phloem cells QUESTION what do each of those cells carry and where?
Regulate exchange of CO2 and O2, allow water to escape by transpiration
Create openings called stomata (sing. stoma)

8. Transpiration and Photosynthesis
Transpiration is the evaporation of water from leaves
creates a “transpiration pull” that helps to move water, minerals and other substances upward
produces an evaporative cooling effect that prevents overheating
Conditions that promote transpiration cause guard cells to reduce size of stomata
Why would water need to move upward in a plant? Assists with transport of water, minerals and other substances from roots (where absorbed) to leaves (where used)
in combination of protection from waxy cuticle, the process of transpiration allows for a cooling effect – literally letting off some steam
WHAT are some conditions that would promote transpiration? – sunny, warm, dry, windy weather

9. Plants are the only photosynthetic organisms to have leaves (and not all plants have leaves). A leaf may be viewed as a solar collector crammed full of photosynthetic cells.

10. Opening and Closing Stomata
In addition to transpiration stomata allow CO2 to diffuse into air spaces within the leaf’s mesophyll layers
Guard cells control the size of stomata
Stomata would be opening, guard cells around

11. Open and Closed Stomata
When K+ ions diffuse out of the guard cells, water also moves out by osmosis and the guard cells become flaccid and the stomata closes. Stomata are usually closed during the night.
Terminal attachment
Radial cellulose microfibrils
When K+ ions diffuse into the guard cells, water also moves in by osmosis and the guard cells swell, opening the stomata. Stomata are usually open during the day.
The size of the guard cell changes when water moves, by osmosis (low solute concn  high solute concn), into or out of the cell
The direction of osmosis follows the diffusion of potassium ions across the guard cell membrane
While potassium ions diffuse passively through membranes, their movement is coupled with the active transport of H+ions through membrane associated proton pumps therefore changes in size of stomata are dependent on the availability of ATP

12. Chloroplasts The Evolution of Organelles
Photosynthesis factories of plants and algae
Protein-rich semiliquid material in the interior of chloroplast
Lamellae- unstacked thylakoids between grana
Membrane bound, flattened sacs that stack to form granum (columns)
Chlorophyll embedded in thylakoid membranes