{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

BIO 320 Spring 2008 - Discussion 8 key

BIO 320 Spring 2008 - Discussion 8 key - CELL BIOLOGY(BIO...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
CELL BIOLOGY (BIO 320) SPRING 2008 DISCUSSION SHEET 8 Key _______________________________________________________________________ _ 1. In cells most of the actin subunits are bound to thymosin, which locks actin into a form that cannot hydrolyze its bound ATP and cannot be added to either end of a filament. Thymosin reduces the concentration of free actin subunits to around the critical concentration. Actin subunits are recruited from this inactive pool by profilin, whose activity is regulated so that actin polymerization occurs when and where it is needed. The advantage of such an arrangement is that the cell can maintain a large pool of subunits for explosive growth at sites and times of its choosing. 2. Kinesin molecules need to be highly processive because a small number of kinesin molecules must be able to transport a mitochondrion, for example, all the way down to a nerve axon. Their high processivity translates into high efficiency of transport. By contrast, it is essential for muscle function that myosin II molecules not be processive. Because myosin II motors in skeletal muscle always function as part of a large array, it doesn’t matter that individual motors let go; others will always be bound. In fact, if myosin II is bound to actin tightly enough to be highly processive, it would inhibit muscle contraction, whose speed depends on the low processivity of its motors. 3. Cytochalasin B interferes with actin filament formation, and its effect on the cell demonstrates the importance of actin to cell locomotion. The experiment with colchicine shows that microtubules are required to give the cell a polarity, which then determines the end that becomes the leading edge. In the absence of microtubules, cells still go through the motions normally associated with cell movement, such as the extension of lamellipodia, but in the absence of cell
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern