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My Packs: (WIZEPREP) (BIO 2382) > Chapter 4: 4.2 Motor Proteins > Flashcards

Chapter 4: 4.2 Motor Proteins Flashcards

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Biology 101 flashcards
1
Q

Define:

Motor proteins

A

A class of proteins capable of moving along a surface

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2
Q

What do motor proteins do in a cell?

A
  • Move along components of the cytoskeleton
  • Transport cellular components throughout the cytoplasm
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3
Q

Where does the energy for movement of motor proteins come from?

A

ATP

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4
Q

Give examples of motor proteins

A
  • Kinesin
  • Myosin
  • Dynein
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5
Q

Define:

Kinesin

A

Moves along microtubules in the (+) direction

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6
Q

Define:

Myosin

A

Moves along actin filaments

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7
Q

Define:

Dynein

A

Moves along microtubules in the (-) direction

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8
Q

What are the three types of movement?

A
  1. Motor proteins “walk” along the cytoskeleton transporting cargo
  2. Motor proteins cause a filament to move
  3. Motor proteins cause a “bend”
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9
Q

Describe:

How motor proteins “walk” along the cytoskeleton transporting cargo

(3 points)

A
  • Head proteins attach to the cytoskeleton
  • Tail proteins attacch to the cargo
  • The head proteins alternate attaching and detaching from the cytoskeleton, taking “steps” forward every time they re-attach
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10
Q

Describe:

How motor proteins cause a filament to move

(3 points)

A
  • Head proteins attach to a filament (e.g. actin filament)
  • Tail proteins are anchored to a surface
  • As the head proteins carry out “walking motion”, the tail remains anchored. The head proteins therefore push the filament along, causing it to move
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11
Q

Describe:

How motor proteins cause a “bend”

A
  • Tails attached to one microtubule
  • Heads attach to another microtubule
  • The two microtubules are held together by a linking protein
  • As the heads carry out their “walking” motion, it causes a bend to form
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12
Q

What are myosins?

A

A family of actin-binding motor proteins that hydrolyze ATP to move along actin filaments towards the plus end of actin filaments

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13
Q

Define:

Myosin I

A

Monomeric form of myosin involved in movement of vesicles and microfilaments

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14
Q

How does Myosin I move?

A

Moves along a microfilament in a repetitive cycle of binding, detachment, and re-binding

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15
Q

Describe:

Myosin I

A
  • Single globular ATPase head domain (binds actin microfilament)
  • Single tail domain (binds cargo)
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16
Q

Define:

Myosin II

A

Form of myosin involved in muscle contraction and cell movement

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17
Q

Myosin II is a dimer, meaning that…

A

Two globular ATPase head domains; tails coiled around each other

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18
Q

Define:

Myosin filament

(In Myosin II)

A

A bipolar filament made from clusters of myosin II molecules bound together by the tail region

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19
Q

Define:

Myofibrils

A

Contractile elements of skeletal muscle fibres, organized into sarcomeres

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20
Q

What is a sarcomere?

A

A contractile unit of a skeletal muscle fibre
* Consists of myosin filaments and actin filaments

21
Q

In sarcomeres:

What are myosin and actin filaments also known as?

A
  • Thick filaments (Myosin filaments)
  • Thin filaments (Actin filaments
22
Q

Describe:

Movement produced by sarcomeres

A

Simulatneous shortening of every sarcomere in a cell results in contraction

23
Q

What happens to myosin heads when a muscle is stimulated to contract?

A

The myosin heads walk along the actin filament in repeated cycles of attachement and detachment

24
Q

What is the cycle that myosin heads undergo during muscle movement?

A
  • Attached
  • Released
  • Cocked
  • Force-Generating
  • Attached
25
Q

Initially, the myosin head is…

A

Attached to an actin microfilament

26
Q

In the released state:

What happens?

A

Myosin head binds to ATP, reducing its affinity for the actin microfilament

27
Q

In the cocked state:

What happens?

A

ATP hydrolysis
* ADP + phosphate
* Causes conformational changes that move the myosin head toward the plus end of the actin microfilaments

28
Q

In the force-generating stage:

What happens?

A

Myosin heads (currently bound to ADP) binds weakly to actin, causing release of the phosphate produced from ATP hydrolysis

29
Q

What occurs between the force-generating stage and attached stage?

A

Power stroke

30
Q

Define:

Power stroke

A

Myosin head releases the ADP and binds actin tightly again, this time closer to the plus end

31
Q

What happens when simultaneous power strokes from multiple myosins occur at once?

A

Brings the actin microfilaments of the sarcomere closer together

32
Q

When multiple power strokes occur simultaneously, what happens to the sarcomere?

A

The sarcomere is shortened
* Causes muscle contraction

33
Q

What is the Sliding-Filament Theory?

A

Thick filaments (myosin) move past thin filaments (actin)

34
Q

In the Sliding-Filament Theory:

  1. What happens to the sarcomeres?
  2. What happens to the filaments?
A
  1. Sarcomeres shorten
  2. Filaments remain same length
35
Q

In the Sliding-Filament Theory:

What does this theory require?

A
  • Actin-myosin binding sites
  • ATP
  • Ca2+
36
Q

What is the role of Ca2+ in muscle contraction?

A

Allows for myosin binding on actin, by shifting the troponin-tropomyosin complex

37
Q

When does the Actin-Myosin ATP Cycle begin?

A

Begins as the myosin head is ready to bind actin once it has hydrolyzed ATP

38
Q

What are the steps of the Actin-Myosin ATP Cycle?

A
  1. Phosphate is released (now, strong bond between actin and myosin is able to form)
  2. Power stroke happens
  3. ADP is released
39
Q

What is the strong bond between actin and myosin formed called?

A

Cross-bridge

40
Q

After the actin-myosin ATP cycle, what state is the muscle in?

A

Contracted state

41
Q

How does the muscle get back into relaxed state?

A

ATP binds myosin again, causes release of actin

42
Q

Explain:

What happens in rigor mortis?

A

Due to the lack of ATP, the muscles are unable to relax

43
Q

How long does the Actin-Myosin ATP Cycle continue for?

A

Will continue as long as Ca2+ and ATP are available

44
Q

What are cilia and flagella comprised of? How do they move?

A
  • Composed largely of microtubules
  • Move through the action of dynein
45
Q

State:

The microtubule arrangement of cilia + flagella

A

9 + 2 arrangement
* 9 fused pairs of microtubules surrounding 2 central microtubules

46
Q

Define:

Cilia

A

Hair-like structures that protrude from the plasma membrane of many eukaryotic cells (e.g. cells in the small intestine)

47
Q

Describe:

How cilia move

A

Beat in a whip-like fashion to move fluid across the cell surface
* Some protists use cilia for locomotion

48
Q

Describe:

Flagella

A

Similar in structure to cilia, but longer
* Main role is in locomotion

49
Q

List:

The differences between cilia and flagella

(5 points)

A

Cilia
* Eukaryotes
* Short, hair-like
* Wave-like movement
* Many per cell

Flagella
* Eukaryotes and Prokaryotes
* Long, thread-like
* Rotational movement
* Few (<10) per cell

My Packs: (WIZEPREP) (BIO 2382) (20 decks)

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