Pre-Lab #9: Floating Leaf Disks and Photosynthesis AP BIOLOGY Ms. Day

How is photosynthesis divided? Light reactions vs Dark reactions / Calvin Cycle/ Dark cycle

-Creates ATP and NADPH for Calvin Cycle Light Dependent Reactions -Creates ATP and NADPH for Calvin Cycle **water splits and O2 is released! sunlight photolysis THYLAKOID COMPARTMENT second electron transport system H2O NADP+ NADPH e– ATP ATP SYNTHASE PHOTOSYSTEM I PHOTOSYSTEM II ADP + Pi first electron transport system STROMA DPIP! http://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swf

Calvin Cycle - Take place in the stroma of chloroplast. - Uses ATP & NADPH to convert CO2 to sugar

Recall…Fill in the letters of the leaf anatomy B E C D

Leaf Anatomy

In this experiment… You will determine the rate of photosynthesis using the production of oxygen gas in the light reactions. BUT… Remember…Plants need carbon dioxide (CO2) for photosynthesis. Why?

In this experiment… Little disks of spinach leaves (leaf disks) will be used Each disk has many chloroplasts

In this experiment… Air spaces in spongy mesophyll of leaf disks are filled with a sodium bicarbonate solution Solution causes disks to sink in a solution The leaf disks are then exposed to light and the cells undergo photosynthesis.

Why use sodium bicarbonate solution? Sodium biocarbonate solution a baking soda solution that you will make Carbon dioxide (for Calvin cycle) is provided by a baking soda solution.

What happens in air spaces during photosynthesis? oxygen is released into air spaces which changes disks buoyancy causing the disks to rise

What happens in air spaces during photosynthesis?

When is oxygen made in Photosynthesis? Photolysis water splits during light reactions (PS II) Replenishes electrons to P680 chl a

Hypotheses If leaf discs are placed in _(intensity)_ type of light then they will produce ____?____ and they will__(float/sink) ____ because _____________. If leaf discs are placed in the dark then they will not produce ________and they will_________ because ___________ .

Procedure Making the carbon dioxide source for photosynthesis (baking soda solution) Mix 1/8 t () of baking soda and mix it in 300 ml of tap water in one of the beakers provided. USE 0.62 grams

Procedure You need to add soap to baking soda solution Soap = breaks the hydrophobic barrier of the cuticle so the solution can enter the disk

Procedure Making leaf disks  don’t let them dry out! Avoid the veins….WHY? NO chloroplasts

Create a vacuum with your thumb Add small about of solution Create a vacuum with your thumb

You need to get the disks to sink before exposing them to light

Please watch the following videos: https://www.youtube.com/watch?v=ZnY9_wMZZWI 6:45 min https://www.youtube.com/watch?v=vw8baZO89oc 4:22 min