Chapter 5 - Nutrition

Photosynthesis

Autotrophic Nutrition - Organisms manufacture organic

compounds (C6H12O6) from inorganic raw materials.(CO2 + H2O)

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 Equation6CO2 + 12 H2O C6H12O6 + 6O2 + 6 H2O

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 Photosynthesis1. Photochemical Reaction

(“light reaction”)

Occurs in the grana (chloroplast) H2O is absorbed Light energy is converted to chemical energy H2O 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) H2 and NADP split

H2 combines with CO2

H2 CO2 PGAL (3 Carbon sugar)

PGAL C6H12O6 (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 epidermisProtects against water loss

Upper & Lower EpidermisOuter Cell Layer

Palisade layerPacked with chloroplastsMost photosynthesis here

Spongy layerBelow palisade layerAir pockets Some photosynthesis here

Mesophyll2 layers- Palisade & Spongy

Guard CellsRegulates the size of a stomate ( gas exchange)Some photosynthesis here

Stomates (stoma)Openings for gas exchange

VeinsXylem – transports waterPhloem – 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