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Cell biology > Lecture 10 > Flashcards

Lecture 10 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

three large families

A
  • Myosins - actin +
  • Kinesins - microtubule +
  • Dyneins - microtubule - (move toward center of cell)
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2
Q

motors
heads
tails

A 
heads 
-ATP hydrolysis
-Binds to filament
-Called motor domain
tails 
-Determines the cargo that is bound
-Determines the biological function of motor
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3
Q

Kinesins and myosins similar

A
  • Structurally similar
  • Bind and hydrolyze ATP to facilitate movement
  • Changes in structure associated with ATP hydrolysis
  • -> results in movement
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4
Q

myosin II

A
  • Globular N-terminal head
  • Binds and hydrolyzes ATP to move along actin filaments
  • Walks to +
  • All but one of the myosin family of motors go to + end (VI)
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5
Q

kinesin

A
  • Globular head domains
  • Movement along microtubules toward + end
  • Humans have >40
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6
Q

muscle contraction

A

Due to the movement of myosin motor along actin filaments (in + direction)
Structure of muscle cells and actin allows for this activity

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7
Q

myofibril

A

muscle cells that have become multinucleated and create this structure. allows movement of sarcomeres.

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8
Q

thick filaments

A

Myosins are bound together by their tails into thick filaments
Thick filament is bipolar (motors face both ways)

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9
Q

myosin doesnt move

A

processively, only takes one or a couple steps before letting go. moves based on hydrolysis

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10
Q

contraction

A
  • Brain sends signal
  • Motor neuron triggers AP at muscle cell membrane
  • Releases Ca from sarcoplasmic reticulum
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11
Q

transverse tubules

A

signal when you should contract and when you shouldnt. brain interacts w transverse tubules

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12
Q

what regulates muscle contractions?

A

Ca

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13
Q

z disks made of

A

intermediate filaments

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14
Q

what does Ca do?

myofibril

A
  • made up of sarcomere - has actin
  • Actin has other molecules bound - tropomyosin and troponin
  • Resting state - troponin binds to tropomyosin and pulls it out of the groove - inhibits binding to myosin II (thick filaments)
  • Calcium releases tropomyosin from troponin
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15
Q

tropomyosin binds to actin then

A

blocks the binding of myosin. how to get it out of the way? troponin complex

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16
Q

troponin complex

A

ICT

Ca binds C component and changes confirmation of C. C is bound to I and T. Now it changes the confirmation of I and T.

17
Q

Ca release causes

A

contraction and Ca reuptake into sarcoplasmic reticulum by Calcium ATPase leads to relaxation - both require a lot of ATP

18
Q

rigor mortis

A

when someone dies their body gets stiff. bc myosin head binds to actin when it has no nucleotide

19
Q

when do you have no nucleotides?

A

takes a while (rigor). after 12-18 hours proteins break down so rigor mortis goes away

20
Q

kinesin motor movement

A
  • Start with one head bound and one not bound
  • ATP binding to forward head causes head to be tightly bound (rigor) to microtubule and causes conformational change so that the other head swings past the ATP-bound head
21
Q

note the difference

rigor atp bound for kinesin as compared to

A

non nucleotide bound for myosin

22
Q

1 kinesin has 2 heads

when we’re talking about myosin thick filament,

A

hundreds of heads

23
Q

The time that any given kinesin head is attached

The time that any given myosin head is attached

A

is half the time

is very little of the time

24
Q

kinesins move processively

A

travel for hundreds of cycles without dissociating (it’s always bound by one or the other head)

25
Q

processivity

A

allows few motors to move organelles from one place to another in cells - myosin never operates as a single molecule (always an array)

26
Q

dynein

A
  • Attachment to membranes mediated by large protein complexes
  • Dynein/dynactin complex
  • Tails bind to receptors for motor proteins on organelles
27
Q

dyneins

two classes

A

-Cytoplasmic
-Ciliary or axonemal (cilia and flagella)
Microtubule minus end motors
Largest of motors and fastest

28
Q

cross bridge cycle/contraction

A
  1. myosin head attaches to actin myofilament, forming cross bridge
  2. ADP and Pi are released, myosin head bends to low energy state, pulls actin filament toward M line (power stroke-conf. change).
  3. after ATP binds to myosin head, link bw myosin head and actin weakens, then head detaches
  4. ATP hydrolyzed to ADP and pi. myosin head is cocked forward. energy released during hydrolysis reactivates myosin head.
29
Q

alzheimers disease

A

Characterized by neurofibrillary tangles and plaques
Amyloid precursor protein - receptor for a motor protein (kinesin 1) in neurons
-Defect in APP causes neurons to become clogged
-KIF1A

Cell biology (15 decks)

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