Explore (Day 2)

Cellular Activities In Plants

Anacharis: A Light-Dark Comparison

Explore: Cellular Activities In Plants

DiscussionWe will review the results of our light/dark experiment.

Predict the results we no longer have the evidence to show so lets discuss what you think happened.

Please take notes in your lab notebooks!

Explore: Cellular Activities In Plants

Stop and Think Stop and Think Questions (page 325) #1-2.

1. We saw water turn from green to yellow with carbon dioxide added to BTB. Do you think the process in your body that caused the color change is the same process in the Anacharis? Why or Why not?

2. How did light affect the oxygen levels in the solutions? Why do you think the oxygen levels changed?

This should have been completed as homework over the weekend, right?

Explore: Cellular Activities In Plants

In-Class TaskFor each of the conclusions below, discuss the evidence we have to support it.

1) Plants give off O2.

2) Plants also do BOTH: give and take in CO2.

3) Plants in light have an increase in the gas exchange (more O2 is given off and more CO2 is taken in).

Explore: Cellular Activities In Plants

Conclusions You Should Have Drawn…

• Plants give off O2. Plants also do BOTH: give and take in CO2.

• When CO2 increases, the amount of carbonic acid increases and pH decreases.

• Bromothymol blue helps us confirm the information gained from the pH measurements. BTB turns greenish, then yellow when CO2 is present. The more intense the yellow color, the more CO2 present.

• Plants in light have an increase in the gas exchange (more O2 is given off and more CO2 is present).

Part II Stored Starch: Background

Lugol’s Iodine

• Is an indicator for the presence of starch

• Turns blue-black in the presence of starch

• Used in chapter 6

• Used now to compare starch content of different

leaves

Chlorophyll

• Is green

• Makes it difficult to see other colors

• Can be removed from an object by boiling in 95%

alcohol. This process also removes the other

pigments.

This Geranium leaf had a small portion covered by black,

non-absorbent, paper for several weeks.

That portion of the leaf was NOT able to photosynthesize.

Process

• Put 250 mL of 95% ethyl alcohol in a beaker

• Bring to a boil under a fume hood

• Add leaves and boil until white (because the pigments

are removed).

• Place leaf in a dish and cover with Lugol’s iodine.

• Wait ~ 3 minutes to observe whether starch is present

or absent.

• Turns blue-black in the presence of starch

• We used Lugol’s in chapter 6

• Used now to compare starch content of different

leaves

VIDEO TOO LARGE TO INCLUDE ON WEBSITE

The covered portion of the leaf was NOT able to photosynthesize.

It also did NOT have starch in the leaf.

This leads us to believe that photosynthesis is required for starch production!

More testing would confirm this to be true.

HomeworkBegin Explain: Converting Sunlight into Sugar

Read:• Answer the “Reflect and Connect” from

previous slide (page 326)

• Energy (page 327-329)

• Making Carbon Compounds, Energy Currency of Cells (page 330-333)

• Cornell Notes in Science Notebook

TomorrowBegin Explain: Converting Sunlight into Sugar

• Class tomorrow:

• We will work on the new “Stop and Think” and “Reflect and Connect”.

• You will have the first ½ to answer the questions with your partner.

• The second ½ we will go over the answers

• Come prepared with science notebooks