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Homework/Test

Objective: Discuss the functions of proteins in cell metabolism

Standard:  Structure, function, and purpose of organelles

Sub-objectives: cell division, metabolism, genes, mutations, enzymes, and genetic diseases

Question:  Why are proteins so important in the function of cell processes?

Protein Involved In Cell Division Now Found Key To Cell Growth  

HOUSTON -- A research team at The University of Texas M. D. Anderson Cancer Center has found that a single protein known as ARF helps coordinate both growth and division within a cell.

Many PROTEINS have been found in cancer research that are associated with either errant CELL division or with uncontrolled growth, but ARF is the first "master molecule" that seems to be involved in both crucial aspects of the cell cycle, say researchers.  The work helps explain why so many human cancers -- more than 40 percent -- are found to have altered ARF proteins .

The picture of MOLECULE cell processes now painted by the investigators also suggests that drugs might be developed that could mimic normal ARF function, he says.  "In cancer, cells need to grow first, and then divide, and we have found the first protein that can, in a coordinated fashion, put the brakes on both of these steps," says researchers. "This protein, or those associated with it, might offer some new therapeutic strategies to investigate."

ARF and the proteins it has power over are major players in cancer development, say the investigators. ARF is the second most frequently altered protein in cancer development, and it helps manage the tumor suppressor protein p53, which is the most common protein defect associated with cancer. That was already known. Now, this study shows that ARF also controls a protein known as B23, which is found in abnormally high levels in almost every tumor cell -- but, before this work, no one knew both proteins interacted.

In order for a cell to grow, it must produce new proteins. To do that, small round bodies within the Cell known as ribosomes develop, based on instructions from the cell's DNA genetic code, which then guide production of proteins. Putting together ribosome "protein factories" from RNA (decoded DNA) and other molecules is one of the major activities of a cell; without ribosomes, protein production would shut down.

RIBOSOMES are made up of RNA (decoded DNA) and proteins, and it was found that ARF can help limit the production of ribosomes, and hinder growth. It does this by "degrading" or inhibiting the B23 protein, which helps trigger mature formation of the ribosome factory. Without B23, ribosomes cannot form, proteins aren't produced, and a cell cannot grow.  Normal cells do need some amount of B23, but cells that are constantly growing, as cancer cells do, contain high levels of B23, he says.

At this point, researchers do not know whether high levels of B23 imply that ARF proteins are mutated, unable to limit production of ribosomes, or if there is just too little ARF protein to degrade high levels of B23 protein.  "B23 has been found to be highly over-expressed in many tumors, such as in breast and ovarian cancers, but no one knows why that is or how to control it.  Now we at least know that ARF can control B23, and it may mean a drug that mimics ARF could help inhibit the protein and help control cell growth."

Cells that grow often divide, and ARF has a known function in regulating that aspect of the cell cycle.  ARF works in conjunction with the p53 protein, a tumor suppressor that blocks the cell cycle if the cell starts to grow erratically. Abnormally high levels of molecules that signal this kind of growth activates ARF, which in turn allows p53 to accumulate in the cell to halt that growth.

"The importance of ARF is that it can control the two related activities, growth and division, that are key to cancer development.  ARF can inhibit the CELL CYCLE by activating p53 and can also inhibit cell growth by inhibiting B23."

 

Instructions: Number the lines in the article, highlight concepts and terms, and place notes along the margins. (5 pts) Please write all answers except multiple choice on a separate sheet of paper and incorporate the question in your answers.    

  1. Define and write in a sentence all underlined words. (5 pts)
  2. Create a divided page graphic organizer study guide using the CAPITALIZED bold type words. (10 pts.)
  3. Ribosomes produce what?  Circle the best answer.  Cite the sentence in the article, page in the text, or other source.  (5 pts)
    1. DNA
    2. Protiens
    3. Carbohydrates
    4. Cytoplasm                                                                                                                                              
  1. More than 40% of human cancers have this?  Circle the best answer.  Cite the sentence in the article, page in the text, or other source.  (10 pts)
    1.  altered ARF proteins
    2. an excess of carbohydrates
    3. low water supply
    4. non of the above
  1. The most common protein defect associated with cancer is called what?  Circle the best answer.  Cite the sentence in the article, page in the text, or other source.  (10 pts)
    1. an enzyme
    2. an amino acid
    3. a lipid
    4. protein p53
  1. Without ribosomes, protein production would do what?  Circle the best answer.  Cite the sentence in the article, page in the text, or other source.  (10 pts)
    1. hurt the cell
    2. stop
    3. increase
    4. be taken over by another organelle
    5. none of the above
  1. Normal cells need some amounts of protein B23, which cause ribosomes to grow.  Cancer cells however have what?  Cite the sentence in the article, page in the text, or other source.  (10 pts)
    1. have no amount of B23 proteins
    2. have lesser amounts of B 23 protein
    3. have higher amounts of B23 protein
    4. have a mutated B23 protein
  2. What are the two theories about how ARF works in regulating cell production particularly cancer cells? (10 pts.)
  3.  Create a concept map showing how the protein “ARF” works in regards to cell processes (regulating cell production), other proteins or chemicals, and cancer.  Start the concept map with the ARF protein. (30 pts)

                                                        Ex.

ARF

        ↓                  ↓                   ↓

Extra Credit: (2 pts. each)

  1. What does the phrase "master molecule" mean in line 4?
  2. What is meant by the phrase “therapeutic strategies” in line 10?
  3. What is meant by the phrase “over-expressed” as stated in the penultimate paragraph?
  4. What is meant by the phrase “put the brakes on” in line 9?
  5. What does the term “degrading” mean in line 22?

Extra Credit Research Question: Cite your source of information. (15 pts.) Write a one page essay on any type of cancer. Include a graphic organizer (concept map)with your essay.