Chapter 3

 Plants, algae, some protists, some bacteria capture about 5% of Sun’s energy.  Absorb CO2, water, and radiant energy  chemical potential energy (glucose)

 Plants, algae, some protists, and cyanpbacteria.  Contain green-coloured pigment called _____________________: absorbs light energy and begins the process of photosynthesis.  Chlorophyll a (blue-green) (contains –CH3) at position –R  Primary light-absorbing pigment  Chlorophyll b (yellow-green) (contains –COH at –R)

 Contains a porphyrin ring attached to a long HC tail.  Porphyrin: contains a magnesium atom at center surrounded by a HC ring with – and = bonds.  Delocalized electrons in single-double bonds absorb light energy.  Different functional groups affect type of light energy molecules can absorb.

 “blue-green algae”: largest group of photosynthesizing prokaryotes.  Evolved between 2.5 and 3.4 billion y.a.  Probably the first organisms to use sunlight in the production of organic compounds.  Produced oxygen: paved way for heterotrophic life on Earth.  Unicellular, but may grow in visible colonies

 Live in oceans, freshwater lakes and rivers, rocks, and soil... And polar bear fur.  Rocks? Cyanobacteria + fungi  lichens  Cyanobacterial blooms: rapid-growing colonies in water rich in nitrates and phosphates (fertilizer, detergent runoff from homes, farms, industry)  May be toxic to fish, birds, humans, and other mammals.  Produce toxin called microcystin.

 Endosymbiosis: ancestor of cyanobacteria engulfed by ancestor of today’s eukaryotic cells.  Mutually beneficial relationship.  Cyanobacteria protected from harsh environment  Eukaryotic host obtained food molecules from bacterium  Cyanobacteria lack membrane-bound organelles: have infoldings of cell membrane used as sites of photosynthesis and respiration.

 Algae, some protists, plant cells:  Contain chlorophyll within chloroplasts.  Leaves, stems, unripened fruit: green!  Chloroplasts: possible ancestors of _______________.

 Thin and broad, or thin and narrow  Structure and arrangement on stems and branches maximizes SA exposed to sunlight  Limits distance that gases need to travel to reach chloroplasts.

 Cuticle: waxy water-resistant coating  Protection against excessive absorbtion of light and evaporation of water.  Epidermis: transparent  Mesophyll: abundant with chlorplasts  Guard cells: create microscopic openings called stomata  Regulate the exchange of CO2 and O2 with atmosphere  Allow water to escape by transpiration  Vascular bundles: ‘veins’  Transport water and minerals from roots and leaves and carry carbs from leaves to roots.

 Stomata: responsible for more than 85% of water lost by plant.  Two ways transpiration assists in photosynthesis:  Creates ‘transpiration pull’ that helps move water, minerals, and other substances from roots  leaves.  Prevents leaves from heating to temperatures that could inhibit or denature enzymes.  Stomata open and close depending on environmental conditions.  Closed:________________________________  Open:_________________________________

 Guard cells control the size of a stoma by changing their shape in response to changes in environmental conditions.  Open: guard cells turgid (swollen)  Day-time: when photosynthesis can occur (light energy)  need of CO 2 (diffusion) and H 2 O (transpiration pull)  Closed: guard cells flaccid (limp)  Night-time: when photosynthesis cannot occur (limited light energy).

 Photosynthetic factories of plants and algae.  Have own DNA and can replicate by fission.  Two-membranes  Stroma: protein-rich semiliquid material in the ‘middle’  Thylakoids: membrane-bound sacs that form columns.  About per...  Grana: column of thylakoids.  About 60 in each chloroplast  Lamallae: connection between thylakoids.  Thylakoid Lumen: inside of the thylakoid  fluid-filled.

 Pg. 145 #1,2,3,4,5,6,7