Lab 7: Photosynthesis

10/27/2015

Basics of Photosynthesis

Photosynthesis: process that transforms light energy into chemical energy.

occurs on land and in water

performed by autotrophic plants, algae, and bacteria

Formula of photosynthesis

Inputs: Products:

6 O2oxygen gas

C6H12O6glucose

6 CO2carbon dioxide

6 H2Owater

Formula of cellular respiration: (from last week)Inputs: Products:

6 CO2carbon dioxide

6 H2Owater

6 O2oxygen gas

C6H12O6glucose

Nature Recycles: Photosynthesis and Cellular respiration are opposites: Each one takes the products of the others reactions and uses it for inputs.

6 O2oxygen gas

C6H12O6glucose

6 CO2carbon dioxide

6 H2Owater

Photosynthesis: Road Map

Photosynthesis can be divided into two parts:

1. Light Reactions

2. Dark Reactions

Light reactions: convert solar energy to chemical energy.

Dark reactions: convert chemical energy and carbon dioxide into sugars

Photosynthesis: light reactions(convert solar energy to chemical energy.)

Different colors of light are different wavelengths with different energies.

Inputs:Light and

Water

Products: O2

Chloroplasts are organelles that absorbs light in plant tissue. Green color in chloroplast comes from chlorophyll – light absorbing pigment. thylakoids which are membranous sacs forming stacks called grana.

Chloroplast Thylakoids form stacks called grana

So why are plants green? Chloroplasts and chlorophyll

Photosynthesis: dark reactions / Calvin cycle(convert chemical energy & carbon dioxide into sugars.)

This part is called a dark reaction because it can happen with or without light. Input:

CO2

Product:glucose

Stroma is a thick fluid within chloroplast, this is where enzymes associated with dark reactions occur.

Chloroplast

Photosynthetic PigmentsPart A: 2.

Remember: chlorophyll is a light absorbing pigment. However most chloroplasts contain 4 or more different pigments. These pigments show up as the different colors in fall leaves.

Paper Chromatography:Allows us to separate out each pigment based on molecular size. Smaller pigments travel further up the paper than larger ones. We can identify the pigments by color.

Photosynthesis: Light ReactionPart A: 3.

• As part of the light reaction, oxygen is produced from water.

Volumeter

3% sodium bicarbonate (NaCO3)

2-3 fresh Elodea sprigs, cut end up.

Beaker filled with water – heat absorber

Light source

• Mark the solution front on the glass tube initially and when you first notice movement start timing 10 minutes.

• After 10 minutes mark front again and measure the distance in mm.

water

Photosynthesis: Light ReactionPart A: 3.

• Then carefully pick up tube being sure not to disturbing the stopper or bent tube.

• Wrap the tube in aluminum foil.• Place back into the light.• Wait 10 minutes and mark where the

front is, then measure the distance in mm.

Volumeter

3% sodium bicarbonate (NaCO3)

2-3 fresh Elodea sprigs, cut end up.

Wrap in aluminum foil.

Beaker filled with water – heat absorber

Light source

water

Uptake of Carbon DioxidePart B

Blow into straw

• Add a sprig (or several) of Elodea to one of the test tubes – make sure it is alive!

• Stopper both tubes.

Beaker filled with water and phenol red (red = basic).

CO2 + H2O → H2CO3 → H+ + HCO3−

Yellow = acidic

Uptake of Carbon DioxidePart B

• Monitor any color change over time.

• Swirl the tubes occasionally.

Beaker filled with water – heat absorber

Light source

water

• Place the test tubes in the test tube rack with the tube from Part A.3

To do:• Lab reports• Visual aid for bioethics presentations will be due in 2 weeks

– “Visual aids are due before the beginning of class the week of Nov. 4. So if you have Thursday lab at 12:00 pm on Nov 7, it’s due Thurs, Nov. 7 at 11:59 am. You may email your electronic slide to jerome1.wilson@umconnect.umt.edu. In addition, please bring to class a copy of your visual aid on a thumb drive on the day you present.”

• Research paper topics – due next week on quiz!!• For quiz:

– What are inputs and outputs of cellular respiration? Photosynthesis? Know the formulas!

– What is the purpose of the light reactions? The dark reactions? Why are they called light and dark reactions, respectively?

– What happened to the water in the volumeter in part A 3 when the Elodea was in the light? In the dark? WHY? Be sure your answer to ‘why’ is in terms of the inputs and products of photosynthesis and respiration.

– What happened to the color of the acidified solution in part B when Elodea was photosynthesizing? WHY? Be sure your answer to ‘why’ is in terms of the inputs and products of photosynthesis.