Friday, June 13, 2008

Cell Metabolism & Gene Function: Unit 1 Lab Project

The assignment for our first Lab Project was to build a model of cell.
First I will list the parts of the cell represented in the first section and the function of each. Then I will go through each picture that I took and explain which item is representing each part of the cell.

For the DNA replication, transcripton and translation, my representations varies slightly from my cell model, so I will display addtional pictures that walk through those functions explaining how each component is represented as I go.

List of Cell Parts with Functions
Cell (plasma) membrane - The selectively permeable outer boundary of the cell. It separates the inside of the cell from the outside of the cell and regulates what goes into and out of the cell.
Nucleus - Stores the genetic material. Location of DNA replication and transcription.
Nuclear membrane - Double membrane that separates the contents of the nucleuls from the cytoplasm.
Nuclear pores - Allow movement of ribosomal subunits out of the nucleus and proteins into the nucleus.
Endoplasmic reticulum (ER) - Rough ER is studded with ribosomes on the cytomplas side. After production at the ribosomes, proteins enter the rough ER interior for processing and modification. Smooth ER produces phosolipids. There are no ribosomes on the smooth ER.
Golgi apparatus - Receives proteins and phosolipids from the ER for modification.
Lysosomes - Produced by Golgi apparatus. They fuse with endocytic vesicles, digest the contents, and release them into the cytoplasm.
Vesicle - Membrane-bounded sac that stores and transports different substances.
Mitochondria - The powerhouse of the cell. Produces ATP through the process of cellular respiration.
Microtubule - Part of cytoskeleton. Provide support and aid in movement of organelles around the cell.

Description of Model
I started with a bucket covered with material that was white with gold starts for the nucleus. The material represents the nuclear membrane and the gold stars represent the nuclear pores. The nucleus is sitting on top of a half basket, which represents the plasma membrane (the plasma membrane is labeled in a later photo). Next I added the endoplasmic reticulum. For this I used a wide piece of ribbon and used gold beads to represent the ribosomes that stud the rough endoplasmic reticulum. The smooth endoplasmic reticulum is represented by the area of ribbon without the gold beads. The Golgi apparatus is represented by the blue jean material. Next, I added the lysosomes and vesicles which are represented by the clear, red, and pink beads. For the microtubules I used pipe cleaners, and for the mitochondria I used gold ornaments.Lastly, a picture of the entire cell, showing all of the parts described above.

DNA Replication, Transcription, and Translation
A few additional molecules are required to explain these processes.
Chromosome - DNA in a condensed form. When the DNA is in this compact form, it means they have been duplicated and are ready for mitosis or meiosis.
mRNA - DNA is transcribed into mRNA, which then takes the gentic code to the cytoplasm for translation.
rRNA - Combine with proteins to form ribosomes, which are the location of protein synthesis.
tRNA - Carry anticodons and amino acids to mRNA to aid in protein synthesis.
Ribosomes - Composed of rRNA and proteins; location of protein synthesis.

The nucleus is now represented by the half basket. The gold ribbon with green stripes are the chromosomes. The vertical edges of the ribbon represent the sugar phosphate backbone of the DNA double helix, and the green stripes represent the complementary bases.
This picture shows DNA replication. The double helix has unzipped and two new strands of DNA are being formed as complementary bases of the new strand bond with the bases of the original strand.
Next up is DNA transcription. Here you can see the DNA double helix unzipped at the location of transcription. A mRNA molecule is formed as complementary bases line up with one strand of the DNA. The mRNA is represented by the bold ribbon with the red backbone.
Translation is represented in the last photo. The ribosomal subunits have binding locations for both the mRNA and the tRNA. The codon of the mRNA dictates which tRNA will bond next. There is a specific anticodon on the tRNA that will bind with the corresponding codon of the mRNA. On the other end of tRNA is an amino acid. The polypeptide chain grows as the subunit moves along the mRNA.
Through this lab project, I assembled a large scale model of a cell that included the nucleus and nuclear membrane, the ER, the Golgi apparatus, the mitochondria, and the microtubules, lysosomes, and vesicles. I later constructed a model that represented DNA replication, transcription and translation. This assignment held solidify in my mind what all of these parts of the cell do. I can better visualize both the parts and the processes in my mind.

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