NAME____________________________ DATE______________CLASS_________

Homework/Test/Standard

Objectives:  To understand the structure and function of lipids

Standard: Structure, function, properties of lipids

Sub-objectives:  how lipids affect the nervous system

Pose questions on:  How does the suppression of certain lipids affect nerve cell growth?

Lipids play important role in nervous system development

Blocking a signaling LIPID can keep nerves from developing the arm-like extensions they need to wire the body and may even cause neurons to die, researchers have found.  The researchers hope this piece of the puzzle of how the central nervous system develops in the first place will one day help them repair loss from injury or disease.

It’s already helped them understand the ailments of a spontaneous mouse mutant that has about 20 percent function of the protein that helps the lipid get to the cell surface so it can help axons grow, says Dr. Wen-Cheng Xiong, developmental neurobiologist and corresponding author on the study published in the November issue of Nature Cell Biology.

The mutant mouse is small and has motor neuron degeneration, with tremors, short limbs and a short life, she says. Before this new work, what the blocked lipid transfer protein regulated was still a mystery.  The lipids in question aren’t those measured during an annual physical exam, rather those that help give shape and function to units within cells such as the nucleus and cell powerhouse, or mitochondria, she says.

“Traditionally people didn’t think these lipids were regulated. They thought they were just there,” says Dr. Xiong. “But what we found is this particular lipid is regulated; it’s like a signaling molecule. Especially during axon growth, the dynamic regulation is more dramatic.”

She and her colleagues found the lipid is transferred to the CELL surface at just the right time and place by a protein called phosphatidylinositol transfer protein-a, which humans also have. It’s been known that many proteins can be regulated, especially signaling proteins that enable intracellular chatter. “Now we have found this PROTEIN regulates lipids and lipids also travel,” Dr. Xiong says.

The mouse mutant is a clear example of what can happen when the lipids don’t travel. The researchers also studied a similar mutant chick embryo that had reduced axon growth. For this paper, they added the zebrafish embryo, which forms most of its major organs within the first 24 hours and remains transparent for the first few days of life, to further document the role of these regulated lipids and their transfer protein.

When they injected an agent that blocks expression of a related lipid transport protein, they could see the impact on axon growth and neuron survival. They looked at different levels of suppression, finding the greater the suppression, the greater the resulting defect. “It shows this protein is critical for development,” said Dr. Xiong.

Next they’ll use a version of the transgenic zebrafish that will enable them to watch axon development – or lack of it – in live embryos and in real time.

They also want to look at what happens to the lipid activity in an injury model. They already know some signaling proteins are disturbed.

 

Instructions: Please number the lines in the article, highlight concepts and terms, and place notes along the margins. (5 pts.)

Questions

Please write answers to all the questions, except the multiple choice or fill in the blanks, on a separate sheet of paper and incorporate the question in your answers.

  1. Define and use all underlined words in a sentence. (5 pts.)
  2. Create a divided page graphic organizer study guide using the CAPITALIZED bold type words. (10 pts.) 
  3. The cell’s power house is the_____________________.  Circle the best answer.  Cite the sentence and paragraph in the article, page in the textbook, or other source. (10 pts.)
    1. axons
    2. mitochondria
    3. nerves
    4. proteins

 

 

Standard

  1. Blocking the signaling lipid can keep nerves from ________________________________________. (10 pts.)
    1. receiving stimuli
    2. sending more signals to the brain
    3. sending the wrong signal to the brain
    4. developing arm like extensions called axons
  1. Which of the following substances or compounds are not considered a lipid? (10 pts.)
    1. fatty acids
    2. butter
    3. triglycerides
    4. cholesterol
    5. maltose
  1. A fatty acid lipid with only single bonds along its backbone would be considered ________________. (10 pts.)
    1. unstable
    2. unsaturated
    3. polysaturated
    4. saturated
  1. Which functional group is at the top or  “head” of a single fatty acid? (15 pts.)
    1. methyl group
    2. carboxyl group
    3. carbonyl group
    4. sugar
    5. amino group
  1. Fatty Acidshave both hydrophilic and hydrophobic groups.  Which ends of the

fatty acids are hydrophobic, hydrophilic?  Explain, illustrate, and Describe. (25 pts.)

 

(All other questions must be answered before extra credit can be given.)

Extra Credit:

  1. What is a neuron?
  2. What is an axon?
  3. What is meant by the phrase “block expression of” in paragraph 7?

  Essay Question: (15 pts.) Cite all sources of information.

1.   Write a one page essay about cholesterol and how important it is to our metabolism.  Explain its function, origin,

       and purpose in the body.