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Biology 2382B Lecture Notes - Lecture 9: Interphase, Microtubule-Associated Protein 2, Hemoglobin

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School
Western University
Department
Biology
Course
Biology 2382B
Professor
Robert Cumming

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Document Summary

Cytoskeleton is composed of proteins, actin filaments, microtubules and intermediate filaments. Cytokinesis, mitosis, proteins, chromosomes, cilia/flagella, muscle contraction, adhesion etc. These molecules take up space, there is no empty space in the cell! There is often water, molecules no involved in the direct transport. Red blood cells are filled with hemoglobin, they are not empty. Main proteins are actin filaments, microtubules and intermediate filaments. Actin filaments are 7-9 nm in width. Microtubule dimers are 25 nm in width. Each monomer of tubulin is about 55 kilodaltons. 2 main forms of tubulin that make up the main structure of the microtubule. Made up of alpha () and beta () tubulin monomers to make polymers. When and are translated, they almost immediately bind together and form a dimer, which is stable and it is the basic subunit used to build the microtubule. Whe(cid:374) you depoly(cid:373)erize a (cid:373)i(cid:272)rotu(cid:271)ule, you are depoly(cid:373)erizi(cid:374)g (cid:862)to the di(cid:373)er(cid:863), (cid:449)e never disassemble a dimer.

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Related Questions

1.) Proteins that make up the cytoskeleton play a key role in cellstructure and movement. Select the proteins below that you wouldconsider cytoskeletal proteins:

Answer

A.

ubiquitin
B.

kinases
C.

tubulin
D.

intermediate filaments
E.

phosphatases
F.

actin


2.) Actin or tubulin polymer growth/ disassembly is dependent onthe concenntration of monomer present in the cell. Polymer growthand disassembly can be discussed in terms of monomer on and offrates, respectively. At the critical concentration (Cc):

Answer

A.

all monomer is degraded
B.

momomer on rate > monomer off rate
C.

monomer on rate < monomer off rate
D.

monomer on rate = momomer off rate


3.) Microtubules are subject to dynamic instability. In fact, theregulation of these characteristic governs many cellular processessuch as chomosome segragation during mitosis. Choose the bestexplanation of the concept of dynamic instability.

Answer

A.

This is the concept of GEF recruitment to microtubules to stimulategrowth and GAP recruitment to stimulate disassembly.
B.

Microtubules require GTP to disassemble, GTP hydrolysis results inmicrotubule growth.
C.

Actin filaments alternate between periods of rapid growth anddisassembly that is dependent on GTP binding.
D.

Microtubules alternate between growth and disassembly. This isdependent on the presence of the GTP cap. Microtubules with a GTPcap are stable and favor growth, while loss of the GTP cap resultsin rapid disassembly.


3 separate questions. Thank you in advance!

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

Hello everyone, i'm working on thesepractices multiple choices for my finals. If you know any of theseanswer, please help. i appreciate your time and your help. Thankyou!!!

1. ___ Which of thefollowing statements about the cytoskeleton is false?

(a) The cytoskeletonis made up of three types of protein filament.

(b) The bacterialcytoskeleton is important for cell division and DNAsegregation.

(c) Protein monomersthat are held together with covalent bonds form cytoskeletalfilaments.

(d) The cytoskeleton of acell can change in response to the environment.

2. ___ Which of thestatements below about intermediate filaments is false?

(a) They can stayintact in cells treated with concentrated salt solutions.

(b) They can befound in the cytoplasm and the nucleus.

(c) They can beanchored to the plasma membrane at cell-cell junction.

(d) Each filament is about10 ?m in diameter.

3. ___ Keratins,neurofilaments, and vimentins are all categories of intermediatefilaments. Which of the following properties below is nottrue of these types of intermediate filaments?

(a) They strengthencells against mechanical stress.

(b) Dimers associateby noncovalent bonding to form a tetramer.

(c) They are foundin the cytoplasm.

(d) Phosphorylation causesdisassembly during every mitotic cycle.

4. ___ Which of thefollowing statements about microtubules is true?

(a) Motor proteinsmove in a directional fashion along microtubules by using theinherent structural polarity of a protofilament.

(b) The centromerenucleates the microtubules of the mitotic spindle.

(c) Becausemicrotubules are subject to dynamic instability, they are used onlyfor transient structures in a cell.

(d) ATP hydrolysis by atubulin heterodimer is important for controlling the growth of amicrotubule.

5. ___ Thehydrolysis of GTP to GDP carried out by tubulin molecules________________.

(a) provides theenergy needed for tubulin to polymerize

(b) occurs becausethe pool of free GDP has run out

(c) tips the balancein favor of microtubule assembly

(d) allows the behavior ofmicrotubules called dynamic instability

6. ___ The microtubulesin a cell form a structural framework that can have all thefollowing functions except which of the following?

(a) holding internalorganelles such as the Golgi apparatus in particular positions inthe cell

(b) creating longthin cytoplasmic extensions that protrude from one side of thecell

(c) strengtheningthe plasma membrane

(d) moving materials fromone place to another inside a cell

7. ___ Which of thefollowing statements about organellar movement in the cell isfalse?

(a) Organellesundergo saltatory movement in the cell.

(b) Only themicrotubule cytoskeleton is involved in organellar movement.

(c) Motor proteinsinvolved in organellar movement use ATP hydrolysis for energy.

(d) Organelles areattached to the tail domain of motor proteins.

8. ___ Which of thefollowing statements is correct?

Kinesins and dyneins____________________.

(a) have tails thatbind to the filaments

(b) move along bothmicrotubules and actin filaments

(c) often move inopposite directions to each other

(d) derive their energyfrom GTP hydrolysis

9. ___ Cell movementinvolves the coordination of many events in the cell. Which of thefollowing phenomena are not required for cell motility?

(a) Myosin-mediatedcontraction at the rear of the moving cell.

(b) Integrinassociation with the extracellular environment.

(c) Nucleation ofnew actin filaments.

(d) Release ofCa2+ from the sarcoplasmic reticulum.

10. ___Which of the followingstructures shorten during muscle contraction?

(a) myosinfilaments

(b) flagella

(c) sarcomeres

(d) actin filaments

7. ___ Referring to Figure Q16-29,which of the following statements below is false?

(a) A constitutivelyactive mutant form of PKA in skeletal muscle cells would lead to adecrease in the amount of unphosphorylated phosphorylasekinase.

(b) A constitutivelyactive mutant form of PKA in skeletal muscle cells would notincrease the affinity of adrenaline for the adrenergicreceptor.

(c) A constitutivelyactive mutant form of PKA in skeletal muscle cells would lead to anexcess in the amount of glucose available.

(d) A constitutivelyactive mutant form of PKA in skeletal muscle cells would lead to anexcess in the amount of glycogen available.

8. ___ Match the targetof the G protein with the appropriate signaling outcome.

adenylyl cyclase________ A. cleavageof inositol phospholipids

ion channels_________ B.increase in cAMP levels

phospholipase C_________ C. changes in membranepotential