Introduction to Photosynthesis Main Objectives: 1.Discuss energy flow through living systems 2.Identify the parts of a leaf 3.Outline the process of photosynthesis Overview: Plants convert the energy of sunlight into the energy of chemical bonds of carbohydrates

Importance of Photosynthesis Provides energy for plants Provides energy for animals that eat plants Provides energy for animals that eat animals that ate plants Provides energy for organisms that break down all of the above Provides the energy for most ecosystems on earth

But that’s not all.. Gives us food [more efficiently than meat] Provides wood, paper, other wood based products Provides cotton, hemp, linen, other fibers Is the original source of energy in coal and oil Photosynthesis consumes Carbon Dioxide And Produces Oxygen

History Jan Van Helmont Found the mass of a pot of soil and a seedling. Watered the seedling for five years. Found the mass again Concluded that the increase in mass came from water

History Joseph Priestly Found that a candle goes out when placed in a jar. However, the candle keeps burning if a sprig of mint is also placed in the jar. Concluded that plants produce [Oxygen]

History Jan Ingenhousz Showed that Priestley’s experiment only works in the light. Concludes that light is necessary for plants to produce oxygen

CO 2 +H 2 0C(H 2 O)+ O 2 Photosynthesis Respiration Sun Entropy The BIG Picture

Leaf Structure

Cuticle: Waxy layer waterproofing upper leaves. Upper epidermis: Upper layer of cells. No chloroplasts. Protection. Palisade Mesophyll: Tightly packed upper layer of chloroplast containing cells. Spongy Mesophyll: Lower layer of chloroplast containing cells. Air spaces around them. Lower Epidermis: Lower external layer of cells in leaf. Vascular Bundle: Bundle of many vessels (xylem and phloem) for transport. Xylem: Living vascular system carrying water & minerals throughout plant. Phloem: Living vascular system carrying dissolved sugars and organic compounds throughout plant.

Leaf Structure Guard Cells: 2 cells surrounding stomata that control rate of gas & water exchange. Stomata: Opening between guard cells for gas & water exchange.

Light Mostly violet, blue and red wavelengths from the visible spectrum

Pigments Substances that absorb certain wavelengths of light and reflect other wavelengths Thus they are colored Examples: Chlorophyll (a and b) – green Carotene – red/orange Xanthophylls - yellow

Energy Storing Compounds Energy trapped by molecules can be used to lift electrons to a higher energy level. From that higher energy level the electrons can fall down to their original energy level and do work along the way. Example – a solar cell that powers a calculator The high-energy electrons can be bound to an electron carrier. Nicotinamide Adenine Dinucleotide Phosphate NADP+ accepts a pair of high energy electrons and a Hydrogen ion to become NADPH

And of Course ATP – Adenosine Triphosphate Energy storing compound used by every living cell Provides the energy for almost all cellular functions

Light Reactions Energy from sunlight is trapped, water molecules are split, NADPH and ATP are formed, O 2 is given off as a waste gas

Calvin Cycle = Dark Reactions Products from the light reactions are used to produce carbohydrates