Quiz 2

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University of Guelph *

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3010

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Biology

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Feb 20, 2024

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pdf

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Uploaded by rosemary966

Short Answer Question Set 3 (FOR QUIZ #2) 1) When you wake up in the morning and turn on the light, is dopamine release increased or decreased? How does dopamine alter the neuronal activity in the retina? (3 marks) 2) Certain bacteria secrete enzymes that can digest protein or carbohydrate components of the basal lamina. A) Why do you suppose they do so? (1 mark) B) What other cells of the body have evolved specialized abilities to do this? (1 mark) C) What are the 2 main classes of enzymes they secrete? (2 marks) 3) You are interested in integrin activation and perform mutagenesis studies on integrin. You find a mutant form of integrin which you call int-act , because the int-act mutation causes the extracellular domain to exist always in an unfolded state regardless of the presence or absence of ligand. When you determine the sequence of int-act , you find that the mutation is in the intracellular domain of integrin. Explain how this intracellular mutation could affect the conformation of the extracellular domain of integrin (hint be sure to mention talin) (3 marks) 4) The basal lamina is composed of many different types of proteins, one of the most abundant ones being laminin. Laminin contains many binding sites for various proteins. A) name 3 of proteins for which laminin contains binding sites for (1.5 marks) B) Why is it important for laminin to be able to bind to all of these different proteins? (1.5 marks)

5) You are working in a lab and discover a mutant form of fibronectin that has a mutation in the RGD domain. A) What is the function of this domain normally? (1 mark) B) What would be the result of having a mutation that renders the RGD domain non- functional? (2 marks) 6) Sam, the undergraduate working with you in your lab, has just asked for help. You and Sam are investigating the role of the b-catenin protein at adherens junctions. Your adviser has asked you to clone the b-catenin gene by PCR. When Sam took the PCR clone you produced and sequenced it, he found a mutation that would change a conserved arginine to a methionine. When Sam ran the b-catenin protein through some web-based protein domain-finding algorithms, he found that this arginine was a conserved residue in a predicted nuclear-localization signal (NLS) and thus figured it did not matter that much because the b-catenin at adherens junctions must be a cytoplasmic protein. To Sam’s dismay, your adviser was horrified at this news. Explain why a protein localized at an adherens junction might need an NLS. (4 marks) 7) You are a physician with a patient complaining of hearing loss, excessive urination and back pain. You perform a genetic analysis and analyze and urine sample. From the genetics analysis you discover they have a mutation in their type IV collagen gene. From the urine sample you see that they have blood and protein in their urine. Explain how a mutation in type IV collagen could result A) the urine sample (2 marks) B) the hearing loss (1 mark)

8) Collagen chains undergo a series of post-translational modifications. Due to this fact, where in the cell must collagen molecules be translated? (1 mark) To go from pro-alpha chains to procollagen 4 processes must occur, what are they? (2 marks) Which rare amino acids are found in collagen and what is their function? (2 marks) 9) Cells needs to be able to both make the ECM and degrade it, why is that important? (2 marks) 10) The activity of proteases that degrade the ECM components has to be tightly controlled if the fabric of tissues is not to collapse. What are the three basic control mechanisms that facilitate this? BRIEFLY explain each mechanism (3 marks) 11) Your two friends are having an argument. Henry, who works in a lab studying signal transduction, claims that ligand–receptor interactions are higher affinity interactions than those between two cadherin molecules. In contrast, Oliver, who works in a lab studying the cell junctions, claims that the interactions between two cadherin molecules must be stronger, because epithelial tissues can be extremely difficult to pull apart and anchoring junctions are joined by forces that are much stronger than the usually transient interactions of a ligand and a receptor. Who is correct and why? 12) Integrin signalling is bidirectional. Which direction is key in white blood cell migrations? Explain how the Velcro principle works as an advantage for these WBCs. (3 marks)

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13) There are four main type of junctions that link epithelial cells to allow them to respond as a unit. What are these 4 junctions? Briefly explain their function. Give an example of each junction (5 marks) 14) Explain how the homophilic interactions between cadherins facilitates the formation of the neural tube. Start when you only have ectoderm, be sure to include the changes in expression of the various cadherins involved in the process (5 marks)

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