BIOLOGY 2B03 Lecture Notes - Lecture 7: Microtubule Organizing Center, Cyclic Adenosine Monophosphate, Metaphase

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5 Mar 2016

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Microvillus has actin filaments; cilia has microtubules and basal bodies; axons has microtubules and actin. Actin/microfilaments: labelled with an antibody, actin:gfp or with phalloidin molecule: toxin from the death cap mushroom that binds with high affinity and high specificity a. b. Ex of motor protein: myosin: microtubule: labelled with antibody or tubulin:gfp a. b. If, intermediate filaments: labelled with antibody or gfp fusion a. Each type made from different set of proteins. In epithelial cell- actin forms microvilli at apical cell surface; microtubule form networks for intracellular transport; if provide structural support. Establish microvilli, form contractile bundles that form sacromeres for muscle contraction, form filopodia and lamellipodia, and contractile ring for cytokinesis. Organization of actin: contractile bundle, gel-like network and tight-parallel bundles. Filaments are polar; pointed end and barbed + end. Has 4 structural domains with a cleft between domains 2 and 4. F-actin: filament of multiple proteins (made up of g-actin)

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. Kinesin-1 motors can move long distances on microtubule tracks without dissociating. By contrast, myosin II motors in skeletal muscle take only one or a few steps before letting go. What is most likely the difference between these two motors that allow two different types of movement?

A. Differences in length of the stalk of each respective motor allow for differences in step size

B. Differences in ATP versus GTP hydrolysis alter the motor head movement along filaments

C. Actin filaments are smaller in diameter and have less space for movement

D. Binding affinity of the Kinesin-1 motor head to microtubules is high, whereas binding affinity of the myosin II motor head to actin filaments is low

E. Microtubules are larger in diameter and have more space for movement

2. Dynamic instability causes microtubules either to grow or to shrink rapidly. What is the most likely reason for a microtubule to undergo rapid growth?

A. GTP hydrolysis exceeds the rate of heterodimer addition

B. GTP hydrolysis of alpha tubulin causes an outward bend in the heterodimer conformation

C. A low concentration of tubulin heterodimers are in solution

D. Heterodimer addition exceeds the rate of GTP hydrolysis

E. Increased trafficking of microtubule motor proteins favors stability

3. There are no known motor proteins that move on intermediate filaments (IFs). What property of intermediate filaments would most likely explain the lack of motor proteins?

A. Tissue specific expression of IFs prevent a single type of motor protein to evolve over time

B. Lateral bundling of IFs prevent motor movement

C. IFs are less dynamic than microtubules and actin filaments

D. IFs are unpolarized

E. IFs do not bind a nucleotide

4. You discover a mutation that results in less rapid hydrolysis of GTP by the beta-tubulin subunit. What would most likely occur?

A. There would be no change in filament assembly

B. There would be enhanced instability of the microtubule

C. There would be enhanced stability of the microtubule

D. Microtubules would not form

E. There would be enhanced treadmilling

5. Which of the following statements describes common features of cadherins and integrins?

A. They can link to microtubules using specific adapter proteins

B. They mediate heterophillic interactions

C. They achieve high binding affinity through clustering

D. They are responsible for interactions of a cell with the extracellular matrix

E. They are found in the apical plasma membrane of an epithelial cell

6. Intermediate filaments are uniquely non-polar and built by lateral bundling in five steps: 1) synthesis of an alpha-helical monomer, 2) formation of a coiled-coil dimer, 3) formation of a staggered tetramer of two coiled-coil dimers, 4) lateral association of 8 tetramers, and 5) addition of 8 tetramers to a growing filament. At what step is polarity lost?

A. Step 1

B. Step 2

C. Step 3

D. Step 4

E. Step 5

7. Collagenase is an enzyme that breaks peptide bonds in collagen to help destroy extracellular structures. What would be the most likely reason to use collagenase in a cell biology laboratory?

A. Disrupt cadherin interaction with the extracellular matrix

B. Disrupt cell-cell contacts to passage cells in cell culture

C. Dissociate epithelial cells from the underlying basement membrane to separate tissues

D. All of the answers are likely uses for collagenase

E. Lyse cells to expose intracellular proteins and organelles

yellowherring775

The vesicles that transport materials from donor membranes to acceptor membranes include:

	1.	COP-II coated vesicles
	2.	COP-III coated vesicles
	3.	COP-I coated vesicles
	4.	Clathrin coated vesicles

2.5 points

QUESTION 11

During skeletal muscle contraction, the roles of ATP include:

	1.	ATP is not required for forming the crossbridges between myosin and actin filaments.
	2.	ATP is utilized as a structural linker to mediate the interaction between myosin and actin filaments
	3.	Hydrolysis of ATP provides energy for myosin head to move along actin filaments and the binding of ATP to myosin head allows the detachment of myosin fromactin filaments.
	4.	ATP binds to actin filaments to drive the power stroke of myosin head.

2.5 points

QUESTION 12

One of the functions of smooth endoplasmic reticulum is

	1.	Synthesizing steroid hormone in the endocrine cells of the gonad and adrenal cortex
	2.	Serves as the starting point of the biosynthetic pathway
	3.	Synthesizing secretory proteins
	4.	Degrading cell debris

2.5 points

QUESTION 13

The function of COP-II coated vesicles is mainly:

	1.	Transporting materials from endosomes to Golgi complex
	2.	Moving materials from the ER to the ERGIC and Golgi complex.
	3.	Transporting materials from Golgi complex back to endoplasmic reticulum.
	4.	Involved in receptor-mediated endocytosis.

2.5 points

QUESTION 14

Which of the following processes is completed in rough endoplasmic reticulum?

	1.	Chaperones help misfolded proteins fold correctly.
	2.	Proteins that target to nucleus are synthesized in rough endoplasmic reticulum.
	3.	O-linked glycosylation occurs in rough endoplasmic reticulum.
	4.	Misfolded proteins are destructed in rough endoplamic reticulum.

2.5 points

QUESTION 15

Kinesin is the motor protein that coorporates with microtubules. It has the following functions:

	1.	It uses GTP as energy source.
	2.	It can hydrolyze ATP and use the energy to drive cargo along microtubules from minus end to plus end.
	3.	It has a globular head that can act as GTPase
	4.	The tail of kinesin is more diverse and binds to cargo

2.5 points

QUESTION 16

For correct segregation and trafficking, lysosomal proteins are tagged in the cis-Golgi with phosphorylated mannose residues, and then the tagged lysosomal enzymes are recruited to clathrin coated vesicles by mannose 6-phosphate receptors.

True

False

2.5 points

QUESTION 17

The process that specialized cells, such macrophages, engulf relatively large particles is:

	1.	Called pinocytosis
	2.	Called phagocytosis
	3.	Mediated by COP-II coated vesicles
	4.	Called autophagy

2.5 points

QUESTION 18

Proteins synthesized on rough endoplasmic reticulum and smooth endoplasmic reticulum are imported co-translationally to their destinations

True

False

2.5 points

QUESTION 19

Treatment of cells with a drug that promotes microtubule disassembly disperses Golgi complex into separate stacks of membrane compartments, suggesting that:

	1.	Golgi complex is made of microtubules.
	2.	Microtubules are important for the organization of Golgi complex.
	3.	Microtubules are transported into Golgi complex
	4.	Golgi complex is composed of tubulin proteins

2.5 points

QUESTION 20

Which of the following is correct about signal sequence of a secretory protein?

	1.	It is an âaddress codesâ for protein trafficking pathways
	2.	It is usually located at the C-terminus.
	3.	It targets the ribosome and the protein that is being synthesized to endoplasmic reticulum.
	4.	It is removed in Golgi complex.

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BIOLOGY 2B03 Lecture Notes - Lecture 7: Microtubule Organizing Center, Cyclic Adenosine Monophosphate, Metaphase

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