Chapter 5 - Nutrition Photosynthesis

Autotrophic Nutrition  - Organisms manufacture organic compounds (C 6 H 12 O 6 ) from inorganic raw materials.(CO 2 + H 2 O)  Ex. Chemosynthesis  Ex2: Photosynthesis – converts light energy to chemical energy.  Most Oxygen in air from photosynthesis.

Chloroplasts  Where photosynthesis takes place  Pigment – chlorophyll – traps sunlight –Separate colors/pigments by chromotography

Photosynthetic Equation 6CO H 2 O  C 6 H 12 O 6 + 6O H 2 O Carbon Dioxide + Water  Glucose + Oxygen + Water ***Photosynthesis is the opposite of Respiration*** Photosynthesis: Occurs in plants, during the day, in the chloroplasts Respiration: All organisms, all the time, in the mitochondria

Photosynthesis

Reactions of Photosynthesis 1. Photochemical Reaction (“light reaction”)  Occurs in the grana (chloroplast)  H 2 O is absorbed  Light energy is converted to chemical energy  H 2 O splits – photolysis, oxygen goes into the atmosphere  H2 combines with NADP(enzyme) temporarily  ATP  ADP for energy

Photolysis – Water splitting

2. Carbon-Fixation Reactions (Dark)  Occurs in the stroma (chloroplast)  H 2 and NADP split  H 2 combines with CO 2  H 2 CO 2  PGAL (3 Carbon sugar)  PGAL  C 6 H 12 O 6 (Glucose 6 Carbon sugar)

Structure of a Chloroplast

Photosynthesis takes place in:  Leaves (more surface area)  A little in the stem

Structure of the leaf  Cuticle – (cutin)  Waxy covering of the epidermis  Protects against water loss  Upper & Lower Epidermis  Outer Cell Layer  Palisade layer  Packed with chloroplasts  Most photosynthesis here  Spongy layer  Below palisade layer  Air pockets  Some photosynthesis here

 Mesophyll  2 layers- Palisade & Spongy  Guard Cells  Regulates the size of a stomate ( gas exchange)  Some photosynthesis here  Stomates (stoma)  Openings for gas exchange  Veins  Xylem – transports water  Phloem – transports food (glucose)

Structure of a Leaf

X – Stomate surrounded by guard cell – controls gas exchange

Wavelengths of Light  Why is chlorophyll green?  They absorb red and blue wavelengths and reflect green.  Red and blue light  best for photosynthesis – these colors are absorbed  Green and yellow  worst for photosynthesis - these colors are reflected