BCH3021 Lecture Notes - Lecture 3: Intermediate Filament, Cell Adhesion, Cytoskeleton

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25 May 2018

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Lecture 3 – Structural Framework of Cells: Cytoskeleton Structure/Function

and Abnormaalities in Disease

Nature of Cytoskeleton

• Complex network of filaments extending throughout cytoplasm of cells

• Cytoskeletal filaments (3)

o Actin microfilaments

▪ Function: structural support, motility

o Microtubules

▪ Function: cell division, mobility

o Intermediate filaments

▪ Function: support for nuclear membrane, cell adhesion,

structural and shape

• Of all three cytoskeletal filaments which two have major roles in cancer? –

Actin and microtubule filaments

o More involved in dynamics of movement and cell division

o Remodelling actin – allows it to change shape

Actin Microfilaments and Movement

• Actin are helical polymers of protein actin (flexible)

• Dispersed throughout cell – highly concentrated in cortex

o Beneath plasma membrane

o Most abundant protein within eukaryotic

cells

• Use electron microscopy

• Functions

o Provide cell shape

o Participate in cell attachment points

o Allow cell movement

• Structure

o Formation of fibre much more active at

plus end

o Plus and minus end

o Filopodium – movement in one direction

o Excessary proteins help bind actin fibres into specific networks

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Document Summary

Lecture 3 structural framework of cells: cytoskeleton structure/function and abnormaalities in disease. Actin and microtubule filaments: more involved in dynamics of movement and cell division, remodelling actin allows it to change shape. Inhibits acting depolymerisation and blocks cell migration: cytochalasin b. Inhibits cell motility and phagocytosis by inhibiting polymerisation. Intermediate filaments and interaction with plasma membrane: rope like filaments monomeric fibre (8-10nm, extremely strong. Heptad repeat: can identify cellular origin of certain tumours, in tuour cells: lose normal appearance, tumour cells retain however many differentiated properties of cells are derived include. Expression of if proteins: use fluorescent tagged antibodies specific to if proteins determine whether tumor originated in epithelial, mesenchyme or neuronal tissue, epithelial cancers and mesenchymal cancers. Intermediate filament diseases: disruption of keratin networks blistering: epidermis cells bundles of keratin filaments anchored at ends to desmosomes. Intermediate filament family: range of inherited genetic diseases: 70 monomer/genes, keratins.

Related Questions

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

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.

(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.

(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.

(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.

(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

(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

(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.

(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

(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.

(d) Release ofCa²⁺ from the sarcoplasmic reticulum.

10. ___Which of the followingstructures shorten during muscle contraction?

(a) myosinfilaments

(b) flagella

(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

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