Everything About Enzymes!! (and a free lab!)

Recently, I was required to attend a system-wide inservice meeting for all the science teachers in our district.  In attendance were science teachers of grades 7 through 12.  These events are fun and interesting, mostly because I have been teaching for 28 years, and it is nice to see science teachers from other schools that I have known for years, but rarely get to see.  After joining up with a group of old acquaintances, the inevitable question came up:  "What have you been doing in your biology classes?"

I responded with, "I have just finished teaching a unit on enzymes to our biology 1 students."  One of the other teachers immediately responded with, "I don't really teach that in my class."

What????  How do you NOT teach about enzymes in a biology class????  As soon as I returned home that day, I promptly sent her all of my teaching materials on enzymes.

Enzymes are the stuff of life.  No cell would be alive without the action of enzymes.  Life in a cell is made possible through the hundreds of chemical reactions that occur there.  If these chemical reactions proceed too slowly, the activities of the cell would come to a screeching halt.  You see, enzymes are biological catalysts. They speed up the chemical reactions of the cell.  Without these enzymes, the reactions of the cell would proceed so slowly that they would be of no use to the cell, and the cell would die.

When is the best time to teach about enzymes?  I begin teaching about enzymes when I teach biochemistry.  When teaching about carbohydrates, lipids, and proteins, it is a natural fit to talk about enzymes as you discuss the structure and functioning of proteins.  I also teach about enzymes when I cover photosynthesis, respiration, replication, transcription, digestion..... This list could go on and on since enzymes are involved in every single biological process!

Be sure to cover all the basic points about enzymes:

• Enzymes are biological catalysts that speed up the chemical reactions of the cell.
• Enzymes are proteins.
• Enzymatic reactions occur faster and at lower temperatures because enzymes lower the activation energy for that chemical reaction.
• Enzymes are never consumed or used up during the reaction. They can do their job over and over again.

• Enzymes are highly specific for just one substrate.  The enzyme has an active site with a unique 3-D shape into which this substrate must fit.  
• Enzymes catalyze both the forward and the reverse of the same reaction.
• Enzymes can be denatured by temperatures and pH levels outside the optimal range for that particular enzyme.

Enzymes are truly amazing proteins that play a vital role inside every living cell.  Please don't leave this out of your curriculum!

Okay.... I did promise you a freebie.  This is a lab that I have done for years, and it remains a favorite with my students year after year.

FREE LAB:

Enzymes Common to Both Plants and Animals

And if you are interested, here are a few other products that I use when teaching about enzymes:

Enzymes, Catalysts, and the Chemical Reactions of the Cell Complete Teaching Bundle of Products
Enzymes and Catalysts PowerPoint with Notes for Teacher and Student
Lab: The Effect of Amylase on Starch

Earth Day 2012

Don't forget that Earth Day is on Sunday, April 22nd.  

My classes on Monday will be packed with Earth Day information and activities.  Here are links to some great sites that will help you plan some teaching lessons for your classes.

The Earth Day Network

When was the first Earth Day and why did it start?

Looking for Earth Day events in your area?

Looking for Earth Day activities for your classroom?  (Games, crafts, facts, activities)

This looks like great fun:  Picnic for the Planet!

More Earth Day Crafts and Games

PlanetPals:  I think this site covers all the bases!

Looking for activities for a particular grade level?  This site has them organized by grade.  Perfect!

Great YouTube video appropriate for all ages

Finally, I'll leave with some of my favorite photos:

The Importance of Environmental Influences on Gene Expression

All students know that their hair color and their eye color is a result of the alleles that they have inherited from their parents. But do your students know that the environment plays a role in the expression of these alleles?

The phenotype of an individual often depends on the influences from the environment. A snowshoe rabbit has white fur in the winter months and brownish fur in the summer months. Why? If the rabbit is white in the winter, it will be camouflaged  and will have a greater chance of survival.  The same is true of a brown rabbit in the summer months.  A particular allele codes for coat color in these rabbits.  During the winter, the snowshoe rabbit will have white fur because these pigment producing genes do not function in cold weather.  When the weather warms in the spring and summer, the genes function to produce pigments and the coat becomes brown.

The million dollar question is this:  Is heredity or environment more important in determining the kinds of traits that appear in the offspring?

I recently had my students explore this very question in a laboratory activity. Students were given 10 corn seeds to plant.  Half of the students were asked to leave their container of planted seeds near a window in our lab.  The other half of the class was asked to place their container of corn seeds in complete darkness.   The seeds were watered as needed and left to grow.

The trait the students were asked to observe was the color of the stem and leaves.  Did the seeds grow into plants with green stems or into plants that were albino?  Stems are green due to the production of chlorophyll. Chlorophyll production is controlled by a dominant allele.  The absence of a dominant allele results in a plant that is albino.

The students were given seeds that were the offspring of heterozygous parents.  Therefore, it is expected that 3/4ths of the seeds will grow into corn plants that are green, and 1/4th of the seeds will grow into plants that are white or albino.

After allowing the seeds to grow into seedlings, students return to the lab to count their offspring.

In the above photos, both trays of corn were grown in the light.  As you can see, some of the plants have green stems, while other plants have albino stems.  Class data was tabulated and we were very close to the expected 3:1 ratio of green to albino stems.

Take a look at the plants in the photo to the right.  The plants on the right side of the photo were grown in complete darkness.  All of these plants are termed albino.  The expected 3:1 ratio was not supported.  100% of the plants grew into albino plants.  What is the difference between the albino plants grown in the light and the albinos grown in the dark?   The albino plants that were grown in the light are albino due to their genetics.  These plants have two recessive alleles for chlorophyll production.  Without the dominant allele, chlorophyll production is not possible.  The albino plants that were grown in complete darkness are albino because of their environment.  Some of these plants may have the dominant allele, but in the absence of sunlight, the dominant allele is not expressed.  

To make this argument just a bit stronger, all students were asked to let their seedlings continue to grow for another 24 hours, and all trays of seedlings were left in the light.  Plants that were initially grown in the dark, were left in the light for 24 hours.  At the second observation, 3/4ths of these albinos had developed chlorophyll and were green.

So back to the original question...... Is heredity or the environment more important in gene expression?  Every student in my class now knows that having the dominant allele is not always enough for the trait to be expressed. Sometimes the dominant allele and the proper environmental condition work together in the expression of the trait.

The printable lesson is perfect for traditional classroom settings, and the paperless, digital Google Apps version is perfect for distance learning and 1:1 classrooms. You might want to try this as a "Virtual Lab" for distance learning and 1:1 classrooms.  You can check out the "Virtual Lab Version" by clicking this link.

Give this lab a try.  Your students will love it!

Happy Teaching!

Lab: The Effect of the Environment on Gene Expression

Genetics Practice Problem Worksheets - Set of 7 Worksheets

Genetics PowerPoint with Notes for Teacher and Student

Genetics Complete Unit Bundle of 21 Products

The Giant Corpse Flower

A giant flower that smells of rotting flesh??

Yep, this is the Giant Corpse Flower, or scientifically speaking,  Amorphophallus titanum.  (Appropriate name, huh?)

This recently caught my attention when I was on my daily prowl on the internet searching for fun and interesting bits of science news to share with my students in my biology classroom.   It seems that Cornell University has a giant corpse flower that recently bloomed.  It was only one of 140 plants to bloom in cultivation in recorded history.

As you know, in angiosperms, the flower is the reproductive organ of the plant.  For true land plants reproduction is tricky business.  In order to be adapted to life on land, the plant must find a way to get its sperm to the egg of a different (but of the same species) plant.  Sperm cells are placed inside pollen grains, and then pollen grains must be effectively delivered to nearby flowers.  Pollen can be carried by wind or water, but many plants depend upon the insect pollinators to deliver their sperm cells.  The flower that can best attract these pollinators has the best chance of having its eggs fertilized.

Now back to the giant corpse flower.  This plant produces one of the largest flowers on record.  When it opens, the smell is said to be horrific, mimicking the odor of dead, rotting flesh.  The smell attracts dung beetles and flies that feed on carrion.   When the insects crawl into the flower, their bodies are covered with pollen.  The insects exit the flower, and move on to the next flower, transferring pollen from flower to flower as they go.

The news about the blooming of the flower at Cornell University was perfect timing for me.  I was in the process of teaching angiosperm reproduction to my biology students.  I did a quick YouTube search and found two short, but excellent videos to show my classes.  The first is called "Corpse Flower Blooms at Zoo" and is about a blooming that occurred at the Cleveland Zoo.  It has wonderful photography and my students were captivated by it.

The second video was a clip from The Private Life of Plants by David Attenborough.  This clip is called "The Largest Flower in the World."  This video is just a few minutes longer, and contains information about other plants, as well as the corpse flower.  But anything by Attenborough gets shown in my classroom....I may be his biggest fan!  Now, here is the neatest bit of information about the corpse flower being used in The Private Life of Plants.  Sir David felt that the constant use of the scientific name (Amorphophallus titanum) during his documentary would be inappropriate, so he invented the popular name of "titan arum" to use during the filming of his show.

To wrap up this lengthy post, here are a few fun and interesting facts about the giant corpse flower:

• It is referred to as the corpse flower because it emits an odor resembling dead, rotting flesh.
• Flowers are either male or female.  The female flower opens first.  A few days later the male flower open.  This prevents self-pollination.
• The titan arum grows in the wild only in the equatorial rainforests of Sumatra, Indonesia.
• The plant blooms rarely in the wild, and even less often when cultivated.
• In 2003, the tallest bloom in cultivation was achieved at the Botanical Garden of the University of Bonn in Germany.  The bloom was 2.74 m (8 ft 11 in) high, and was recorded in the Guinness Book of World Records.
• This record was broken in June of 2010 when a flower reached the size of 2.74 m (8 ft 11 in) high in a nursery in New Hampshire.

The Koala "Bear"

I recently had the opportunity to visit the Dallas Zoo.  It was my first visit to Dallas and my first visit to the Dallas Zoo.  It was a wonderful zoo!  Since spring arrived in the south so early this year, all of the vegetation was lush and in bloom.  I have never been to a zoo that had koala "bears", so I made a beeline straight for their enclosure.

I was not disappointed.  The koalas were magnificent!



The koalas are such amazing animals, so I thought I would look up the stats and statistics for them:

• Koalas are often called bears, but this is not correct.  Koalas are marsupials.
• Koalas weigh between 9 and 20 pounds.
• Koala fur is thick and soft and pleasant to touch.
• Koalas can live up to 17 years.
• Koalas spend up to 75% of each day sleeping.  They become active at sunset.
• Koalas survive solely on a diet of eucalyptus leaves.
• Koalas seldon drink water.  The eucalyptus leaves are about 50% water.
• Koalas have a very slow metabolism due to their nutrient poor diet.
• Koalas breed once a year.  The gestation period is only 35 days.
• The baby is born hairless and blind, is less than one inch long and weighs less than one ounce.
• Unaided, the baby must crawl to its mother's pouch, relying only on its sense of smell to do so.
• Once inside the pouch, the baby will remain for 6 months, drinking milk from the mother.

This was my first encounter with the koala.  I watched them for quite some time, and left very satisfied with the experience!

Myths and Misconceptions About Genetics

If you teach genetics, I KNOW you have encountered these misconceptions before!

It is the time of the year that I teach genetics to my students.  It's a great time of the year.... I love teaching genetics and the students love learning about genetics......for the most part!  But have you noticed that even the students that seem to really "get it" will often ask a question that just stops you in your tracks?  You think to yourself, "How in the world did they get so mixed up on the concepts I have been teaching?"

A few weeks ago I noticed a post that Carolina Biological had posted on their facebook page.  It really caught my eye when I read "Five Common Misconceptions in Genetics."  A link was provided with the post, so I quickly clicked on it and began to read.  I am giving complete credit to this article to Crystal Jeter,  Product Developer for Carolina Biological.  Before reading further, click on the link above and read what she had to say.  The article is short and to the point and really packs a punch!  I deal with these five misconceptions EVERY SINGLE YEAR!  (I am in no way affiliated with Carolina Biological, but I am a huge fan of this company!)

I am not going to repeat any of her article here, but if you read it, I am sure you are nodding your head in agreement.  It is so nice to have my frustrations validated!  I am overjoyed to know that these are misconceptions that are very common and I am not the only one who deals with this each year.  Seeing the five misconceptions so neatly outlined in her article will make it much easier to address them in my class.  

I enjoyed her article very much, and I will keep an eye open to her future writings.

Happy Teaching!

Genetics Complete Unit Plan of 21 Products

Genetics PowerPoint With Notes for Teacher and Student

Genetics Practice Problem Worksheets

Red Cabbage pH Indicator in Respiration Labs

A new twist on using cabbage juice?

Most every science teacher is aware that the juice extracted from red cabbage makes an excellent acid/base indicator.  But at our school, we recently used it for a different (but related) purpose.  Our biology classes do a cellular respiration lab in which the students observe the production of carbon dioxide during respiration.  Normally we use phenol red as an indicator.  Our supply of phenol red was running low and we looked for an alternative.  The answer was cabbage juice indicator!!

How was red cabbage used as an indicator of carbon dioxide?  I'll come back to that in a minute.  First, here is a little background about red cabbage......

Background:   Red cabbage contains a natural pH indicator in the form of the pigment, anthocyanin.  It is a water soluble pigment that is commonly found in nature in red cabbage, of course, as well as purple plums, grapes, and apples.  Red cabbage juice will turn a wide variety of colors in the presence of acids and bases.  In a neutral solution, the cabbage is a fairly dark purple color.  In the presence of acids, the cabbage juice will turn red/pink, and in the presence of bases, the cabbage juice turns a greenish-yellow color.

How to Make Cabbage Juice Indicator:  This process is so simple that I usually allow my students to make their own indicator.  Simply chop up a head of red cabbage.  Place a small handful of cabbage leaves into a beaker.  Cover the leaves with water and boil for about 15 minutes.  As the cabbage boils, the pigment will be extracted from the leaves and the water will turn a dark purple color.  Use a slotted spoon to remove the cabbage, or pore the solution through filter paper.  Your indicator is now ready to use!

Our Cellular Respiration Lab:  In order to complete the chemical reactions of cellular respiration, oxygen is required.  Carbon dioxide is released during the reactions and is given off as a waste product.    Although it is very difficult for us to observe the conversion of glucose to ATP, it is possible to observe the gas exchange that must take place in order for respiration to be carried out.   The lab that we do at our school has three objectives:

1.   To observe the release of carbon dioxide during cellular respiration in animals.

2.   To determine if plants carry out the same gas exchange as animals.

3.   To observe, record, and analyze the results of an acid-base indicator.

In the first part of our lab, the student will learn how to use the cabbage juice to indicate the presence of carbon dioxide.  (See above photo.)  Carbon dioxide and water will react to form carbonic acid.  Since our breath and carbonated beverages contain carbon dioxide, the color change from dark purple to pinkish/red indicates the formation of carbonic acid.

In the second part of the lab, we want the student to determine if plants also give off carbon dioxide during cellular respiration.  As you can see in the above photo, the first tube serves as a control, the second tube contains germinating seeds, which have a high rate of respiration, and the third tube contains dry seeds, which are alive, but dormant.  The photo clearly shows that the germinating peas are releasing carbon dioxide.  (Since the peas are not photosynthetic, they are not consuming carbon dioxide.)  In the tube containing the dry peas, there is a very slight color change that does not show clearly in this photo.  The dry seeds do carry out cellular respiration, but at a very slow rate.  The results seen in the above photo were obtained after allowing the tubes to sit for just 24 hours.

This lab is easy to set up, easy to clean up, and best of all, our students really enjoy doing it.

Happy Teaching!

Click image to view product on TpT.