BIOL 130 Lecture Notes - Lecture 15: Endoplasmic Reticulum, Intermediate Filament, Tubulin

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6.6 the cytoskeleton is a network of fibers/proteins that organizes structures and activities in the cell

- cytoskeleton- network of fibers that extend throughout the cytoplasm

- three types of molecular structures- give mechanical support to

cell and maintain its shape

o 1. Microtubules- thickest diameter – made from tubulin α, β

Tubulin dimers

o 2. Microfilaments- thinnest- made from actin

o 3. Intermediate filaments- medium – various proteins

These proteins are dependent on where filament is

ad hat it’s doig

Microtubules- hallow, column of tubulin

Arise from centrosomes dimers

☐Objective- list the functions of microtubules

thik of Disey oorail are’t reliat o diffusio- vesicle can catch a ride on microtubule wait for a

rail

bending- dyneins

- Cytoskeleton roles- give and maintain shape (especially important for animal cells because no

walls) and can move through cell changing shape of cell

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- Cell motility- includes changes in cell location and movements of cell parts

- Motor proteins- interact with cytoskeleton for cell motility

o Vesicles containing neurotransmitter molecules migrate to tips of axons, the long

extensions of nerve cells that release these molecules as chemical signals to adjacent

nerve cells

o Allow neutrophils to hunt bacteria- incredibly dynamic- can move around and break

Microtubules

- All eukaryotic cells have microtubules, hallow rods constructed from protein tubulin

- Each tubulin is a dimer, molecule made up of two subunits (alpha and beta)

- The two ends of a tubule are different- one can accumulate or release tubulin at a much higher

rate than the other thus growing and shrinking during cellular activities (plus end)

- Microtubules guide vesicles from endoplasmic reticulum to the golgi apparatus to the plasma

membrane

- Microtubules are involved in the separation of chromosomes during cell division

- Cilia are stabilized

Centrosomes and Centrioles

- Microtubules grow out from a centrosome (near the nucleus)

- They function as compression-resisting girders \centrosomes have centrioles, each composed of

nine sets of triplet microtubules arranged in a ring

- Cetrioles help orgaize assely i aial ells, ut other eukaryoti ells do’t hae the so

they just do it a different way

☐Objective- List functions of microfilaments

Microfilaments aka actin filaments

- Thin solid rods aka actin filaments because they are built from the globular protein actin

- Microfilaments are to bear tension in the cytoskeleton and dense

- Network of microfilaments give outer cytoplasmic layer of a cell- cortex

- Microfilaments are known for their role in cell motility and thousands of actin filaments are

made of the protein myosin interact to cause contraction of muscle cells

- Pseudopodia- cellular extensions extended by cell

- Cytoplasmic streaming- circular flow of cytoplasm within cells speeds distribution of materials

within large plant cells

- (1) Stabilize microvilli (greater surface area but do not move around like cilia)

- (2) Contract muscles-myosin pulls on actin to contract muscles

- Myosin- protein that can flex/ pull actin filaments

- (3) amoeba extends actin filaments to engulf bacteria

☐Objective- list functions of intermediate filaments

Intermediate Filaments

- Only found in cells of some vertebrae animals

- They bear tension like microfilaments

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Document Summary

Microtubules- thickest diameter made from tubulin (cid:894) , (cid:895) These proteins are dependent on where filament is a(cid:374)d (cid:449)hat it"s doi(cid:374)g. Objective- list the functions of microtubules (cid:894)thi(cid:374)k of dis(cid:374)ey (cid:373)o(cid:374)orail(cid:895) are(cid:374)"t relia(cid:374)t o(cid:374) diffusio(cid:374)- vesicle can catch a ride on microtubule wait for a rail. Cytoskeleton roles- give and maintain shape (especially important for animal cells because no walls) and can move through cell changing shape of cell bending- dyneins. Cell motility- includes changes in cell location and movements of cell parts. All eukaryotic cells have microtubules, hallow rods constructed from protein tubulin. Each tubulin is a dimer, molecule made up of two subunits (alpha and beta) The two ends of a tubule are different- one can accumulate or release tubulin at a much higher rate than the other thus growing and shrinking during cellular activities (plus end) Microtubules guide vesicles from endoplasmic reticulum to the golgi apparatus to the plasma membrane.

Related Questions

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 following structures shortenduring 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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