Photosynthesis Ch. 8

Photosynthesis Occurs in the Chloroplast Photosynthesis = building glucose by using the sun’s energy Requires sunlight, water, CO2, chlorophyll, Makes glucose (chemical energy) and oxygen (waste product) (chlorophyll) (released) 6CO 2 + 6H 2 O + Light  C 6 H 12 O 6 + 6O 2 REACTANTS PRODUCTS

Composed of 2 main reactions 1. Light-Dependent Reaction –The “light” phase –Light energy (electromagnetic) is absorbed by pigments in the thylakoids –The light excites the electrons in the thylakoids and energy is transferred to the chlorophyll and photosynthesis can begin

1. Light-Dependent Reaction cntd. Electrons continued to be made but how? The water that was absorbed from the roots and needed for photosynthesis is broken down here. The Hydrogen ions are used and the Oxygen atoms are released Chemical energy has now been made (some ATP and NADPH)

2. Light Independent The “synthesis” phase Also know an the Calvin cycle or Dark Reaction Makes glucose from CO 2 and H Occurs in the stroma The CO 2 and NADPH created in the Light Reaction is now converted into Glucose.

Thylakoids H2OH2O e H 2 \ O NADP + H2 C 6 H 12 O 6 CO 2 Stroma Chloroplast

Factors Affecting Photosynthesis Light Intensity –As light intensity increases, photosynthesis increases Carbon Dioxide –As CO 2 increases, photosynthesis increases Temperature –All chemical reactions are dependent on temperature

2 Concerns for plants Getting water & keeping water.Getting water & keeping water. Plants developed roots in order to get water and they developed a cuticle to keep water in the leaves.Plants developed roots in order to get water and they developed a cuticle to keep water in the leaves. –Cuticle: waxy covering that surrounds the leaf and reduces transpiration.

Transpiration Water loss by plants.Water loss by plants. Cuticle was a good AND bad thing because how will plants get CO from the atmosphere?Cuticle was a good AND bad thing because how will plants get CO 2 from the atmosphere?

Stomata Solved the problem!Solved the problem! A stomata is a hole on the underside of a leaf that allows gas exchange. It is surrounded by guard cells.A stomata is a hole on the underside of a leaf that allows gas exchange. It is surrounded by guard cells.

Plants need water for 2 reasons: For photosynthesis and plumps guard cells – open up and allow for gas exchange.For photosynthesis and plumps guard cells – open up and allow for gas exchange. Low water, guard cells may keep stomata closed.Low water, guard cells may keep stomata closed. Stomata are open during the day when photosynthesis is happening.Stomata are open during the day when photosynthesis is happening. Stomata are closed at night when photosynthesis is not happening (& to reduce transpiration.)Stomata are closed at night when photosynthesis is not happening (& to reduce transpiration.)

How fast does a plant photosynthesise? This question is very important to farmers and growers. We can use this apparatus to measure the rate of photosynthesis. How? We might count the oxygen bubbles per minute, or collect the gas given off in one minute and measure its volume. What would happen if we increased the light level? light source oxygen collects test tube water pondweed (Elodea) beaker funnel

Here are some results from the pondweed experiment. What effect does light have on the rate of photosynthesis? What would happen if we put a layer of oil on the water? light levelbubbles of oxygen per minute very high24 high22 medium15 low 7 very low 0 This stops carbon dioxide from the air dissolving in the water.

The Energy Currency for the cell is ___

How well did you do today? Where does photosynthesis take place? A.Chlorophyll B.Chloroplast C.Stroma D.Thylakoids