BIOA01H3 Lecture Notes - Lecture 5: Cadherin, Desmosome, Active Transport

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Cytoskeleton, cell junctions, extracellular matrix lec 5. Cytoskeleton is composed of microfilaments, microtubules, and intermediate filaments. If (cid:272)ells do(cid:374)"t ha(cid:448)e a(cid:272)ti(cid:374) (cid:894)lo(cid:272)ated u(cid:374)der plas(cid:373)a (cid:373)e(cid:373)(cid:271)ra(cid:374)e(cid:895), the(cid:455) (cid:449)ould (cid:271)e u(cid:374)a(cid:271)le to: organize proteins across the cytoplasmic membrane, maintain shape, and connect to neighboring cells. Microfilaments and microtubules cause movement by: small motor proteins called kinesin and dynein motor proteins associate with microtubules. Cargo moves from inside to outside of cell: the energy for this movement is driven by conformational changes (i. e. changes in 3d shape) in the motor proteins and is powered by atp. Ki(cid:374)esi(cid:374) (cid:373)otor protei(cid:374)s use atp to: carr(cid:455) (cid:448)esi(cid:272)les alo(cid:374)g a (cid:373)i(cid:272)rotu(cid:271)ule (cid:449)ithi(cid:374) a (cid:272)ell i(cid:374) a (cid:373)i(cid:374)us-to-plus dire(cid:272)tio(cid:374). In epithelial cells this anchoring results in structural continuity/strength to the tissue: allows skin to withstand the daily stresses, genetic defects in intermediate filaments can result in skin that is easily damaged.

Related Questions

1)Describe the directions in which the two motor proteins, kinesin and dynein, travel along a microtubule. Which of the two proteins moves materials towards the Golgi and which moves materials away from the Golgi? Lastly, what is the speed of kinesin dependent on?

2)What are microfilaments crucial for? How do they self-assemble? Which end do they prefer to elongate from?

3)Describe what types of filaments are in each of the bands of the sarcomere. As a muscle fiber is shortened, describe what happens to each of the bands in the sarcomere as the Z lines move inwards.

4)Describe the role of calcium ions in muscle contraction.

5)List the various types of actin-binding proteins

6) A. What are 3 functions of the cytoskeleton?

B.What are the three filaments that compose the cytoskeleton, and what are they composed?

7)How do they see the internal structures of cells in the microscope? What do proteins get labeled with?

8)Myosin II action (Figure 9.61) differs from that of kinesin (Figure 9.15) in that one of the kinesin heads is always in contact with a microtubule, whereas both myosin heads become completely detached from the actin filament. How are these differences correlated with the two types of motor activities in which these proteins engage?

9)If a myofibril were pulled so that the sarcomeres increased in length by approximately 50 percent, what effect would you expect this to have on the contractile ability of the myofibril? Why? What effects would this have on the H, A, and I bands?

10)Because cytoplasmic vesicles are seen to move in both directions within an axon, can you conclude that some microtubules are oriented with their plus end facing the axon terminus and others oriented with the opposite polarity? Why or why not?

1. How does the extracellular matrix affect a cell that it surrounds? (Select all that apply.)

	The cell's shape depends in part on the structure and composition of the extracellular matrix.
	The genes that the cell expresses depend in part on the types of proteins in the extracellular matrix.
	The size that the cell grows to depends in part on the polysaccharides in the extracellular matrix.
	The extracellular matrix has no effect on the cells that it surrounds.
	All of these choices are correct.

2. Which of the following enable(s) the movement of cells?

	microtubules
	microfilaments
	intermediate filaments
	microtubules and microfilaments
	microfilaments and intermediate filaments

3. Microtubules increase in length:

	more quickly at one end than the other.
	by growing outward from the centrosome.
	in cycles, following rapid depolymerization.
	if free tubulin dimers are available.
	All of these choices are correct.

4. Dynamic instability is the rapid assembly and disassembly of:

	microfilaments.
	intermediate filaments.
	microtubules.
	both microfilaments and microtubules.

5. Which one of the following is a characteristic shared by integrins and cadherins?

	Both are peripheral membrane proteins.
	Both facilitate the adhesion of cells to extracellular matrix proteins.
	Both are present in adherens junctions, desmosomes, and hemidesmosomes.
	The cytoplasmic domains of both proteins are connected to the cytoskeleton.

6. Cadherin is an example of a(n):

	motor protein.
	intermediate filament protein.
	cell adhesion molecule.
	extracellular matrix protein.

7. Which is the CORRECT order from lesser to greater complexity for the following?

	organs, tissues, cells
	cells, tissues, organs
	tissues, organs, cells
	cells, organs, tissues

pucebear535

Determine whether each of these statements is true or false and then explain why?

a) Myosin II molecules have two motor domains and a rodlike tail that allows them to assemble into thick filaments with motor domains on either end, which is crucial for the efficient sliding of oppositely oriented actin filaments past each other.

b) When activated by Ca2+ binding, troponin C causes a conformation change in the troponin complex that allows tropomyosin molecules to shift their positions slightly so that the myosin heads can bind to the actin filaments.

c) In most animal cells, minus-end directed microtubule motors deliver their cargo to the periphery of the cell, whereas plus-end directed microtubule motors deliver their cargo to the interior of the cell. (Be sure to name these motors).

d) Both kinesin-1 and myosin II move processively making them suitably adapted for their biological functions.

e) Axonemal dyneins mediate the bending of cilia and eukaryotic flagella.

BIOA01H3 Lecture Notes - Lecture 5: Cadherin, Desmosome, Active Transport

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