The Cell, Cell Structure and DNA

We have been learning a lot about the cell.
Student (age 11) notebook page
 We have sketched them...
Student (age 8) edible cell
(mitochondria: Canadian Bacon and Provolone cheese cut to shape, Golgi body-mozzarella cheese shreds, Nucleus- Pepperoni with black olive nucleolus, ER-Provolone, ribosome- Provolone with bacon bits around the edges, lysomes-black olives, centrioles-celery, cytoplasm-pizza sauce, cell membrane-pizza crust.)
and made edible models of them. I just put out an assortment of pizza toppings and let them go at it.

Cell Structure
The problem with making this type of cell model, however, is that this is flat and doesn't show the cell's shape, or structural support. Cells have structural support systems just like the bones that support our bodies. We made models that show the cell's shape or structural support, using the instructions from Highhill Homeschool.
Cell support systems are made from three main components, microtubules, made from pipe cleaners, actin filaments, represented by strands of embroidery floss and intermediate filament, represented by yarn.

Begin by inserting the pipe cleaners into the straws to create the microtubules.
Make two small circles out of pipe cleaners.
Attach one end of each of the microtubules (pipe cleaners) to a pipe cleaner circle.
Attach the opposite ends to the second pipe cleaner circle.

Attach the actin filaments (strands of embroidery floss) to one of the end pipe cleaner circles. Tie the embroidery floss so that the two circular structures are pulled together, holding the cell in a spherical shape. The outward pushing force of the microtubules is then counteracted by the actin filaments.
The intermediate filament (yarn) is woven around the microtubules to hold the cell in shape.
All of the components of the structure have a bit of flexibility which allows them to be squished or change shape when they are inside our bodies.

Edible DNA Model

We have made models of DNA out of pipe cleaners and beads before, but when I saw these instructions for making an edible model of DNA, I thought it was time for a review of the basic DNA structure and the rules of base pairing.

A molecule of DNA (DeoxyriboNucleic Acid) is composed of two backbones and four types of chemical bases.  The backbone is formed by a chain of alternating phosphates and sugars.  Each 
sugar molecule in the backbone provides an attachment site for one of the chemical bases.  The four types of chemical bases are:  adenine, thymine, cytosine and guanine.  They usually are represented by their first letters: A, T, C and G.  The bases form pairs in a very specific way: A always pairs with T, and C always pairs with G.  A pair of bases is connected by hydrogen bonds.  Each base in the pair is also connected to a sugar compound in the DNA backbone.

A DNA molecule is often compared to a ladder, with the two backbones forming the sides of the ladder and the base pairs forming the steps, or rungs.  However, instead of a straight ladder, DNA looks like a twisted ladder, known as a double helix (“double” for the two backbones).  The DNA sequence is the consecutive order of bases on one side, or strand, of the twisted ladder.  The other strand has a complementary sequence determined by the base pairing rules. The specific matching of the base pairs, A with T and C with G, provides a way for exact copies of DNA to be made. DNA replication is an important part of the cell division process.  Before a cell divides, it first duplicates its DNA so that the new cell will have the same genetic information.  The specific base pair matching during replication ensures that exact DNA copies are made.
To make an edible model, you will need:

2 pieces of licorice
12 toothpicks
9 pink marshmallows
9 yellow marshmallows
9 green marshmallows
9 orange marshmallows
optional: 5 paperclips, Masking Tape

Assemble one side of your DNA molecule. A piece of licorice will form the backbone and marshmallows will be the chemical bases. Place a marshmallow on the end of a toothpick so that the point of the toothpick goes all the way through.
Anchor the toothpick into the licorice backbone. Match the chemical base pairs. Place the color marshmallow for the matching chemical base on the other end of each toothpick. 
Remember that A always pairs with T and C always pairs with G!  

Attach the other backbone so your model looks like a ladder. Carefully twist your DNA 
molecule so that it looks like a double helix. If you wish, you can make flags to label the parts of your DNA out of paper clips and tape.

You can always eat it when you are done!

related posts:
  • Exploring Creation with Human Anatomy and Physiology, Jeannie Fulbright and Brooke Ryan, MD
  • Exploring Creation with Biology, Jay Wile and Marilyn Durnell

inspiration and resources:

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