Lecture 7 Review

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Questions and Answers

What is a primary function of the components of the cytoskeleton?

Transmitting electrical signals

Energy production in cells

Facilitating cell division

Providing shape and structure to cells (correct)

Which internal structure is responsible for moving organelles along microtubules?

Cytoplasm

Ribosome

Plasma membrane

Molecular motors (correct)

How do myosins use actin filaments in muscle cells?

To perform mechanical work (correct)

To store genetic material

To secure cell membranes

To synthesize proteins

What is the primary function of kinesin on microtubules?

To transport cargo over long distances Signup and view all the answers

What happens when ADP is bound to the leading head of kinesin?

The affinity of the head for microtubules is low Signup and view all the answers

How does ATP hydrolysis affect kinesin's function?

It induces a conformational change enabling motion Signup and view all the answers

What does the term 'processive' refer to in relation to kinesin?

Its ability to take many steps without releasing from the microtubule Signup and view all the answers

Which of the following statements is true regarding kinesin's heads?

One head is always bound to the microtubule when moving Signup and view all the answers

What causes the myosin head to release from the actin filament?

ATP binding to myosin Signup and view all the answers

What is the role of phosphate in the myosin-actin interaction cycle?

It triggers the power stroke of myosin Signup and view all the answers

Why is the action of myosin described as not processive?

Each motor head operates independently Signup and view all the answers

During muscle contraction, what mechanism leads to the movement of actin filaments?

Sliding filament mechanism Signup and view all the answers

What happens to the myosin head after it has completed the power stroke?

It releases ADP and is ready for another cycle Signup and view all the answers

What happens to organelles when ATP is removed?

They do not move. Signup and view all the answers

What role do motor proteins play in a eukaryotic cell?

They transport organelles along microtubules. Signup and view all the answers

What is the effect of using a non-hydrolyzable ATP analog on motor protein activity?

Motor proteins do not move cargo. Signup and view all the answers

Which of the following correctly describes kinesin's mechanism of movement?

The trailing head binds to ATP causing forward propulsion. Signup and view all the answers

How do kinesin and dynein differ in their cargo transport direction?

Kinesin moves toward the cell periphery, whereas dynein moves towards the cell center. Signup and view all the answers

What structural feature of kinesin contributes to its function?

Coiled-coil dimerization region and ATP-binding sites. Signup and view all the answers

What is the typical distance kinesin moves per cycle of ATP hydrolysis?

16 nm Signup and view all the answers

What is the primary energy source for motor proteins to transport cargo?

ATP hydrolysis. Signup and view all the answers

What is the primary role of actin in interphase cells?

To facilitate cellular movement and changes in shape Signup and view all the answers

What happens to actin monomers during polymerization?

They grow primarily at the plus end while being hydrolyzed to ADP at the minus end Signup and view all the answers

Which of the following statements is true regarding myosin function?

All actin-dependent motors are classified under the myosin family Signup and view all the answers

What characteristic do skeletal muscle cells possess that is not typical of other cell types?

Multinucleate structure Signup and view all the answers

What role do actin-binding proteins play in the behavior of actin filaments?

They control the nucleation and organization of actin filaments Signup and view all the answers

What is the primary role of the centrosome in relation to microtubules?

It organizes microtubules and serves as an MTOC. Signup and view all the answers

Which tubulin dimer is involved in stabilizing the minus ends of microtubules?

g-tubulin Signup and view all the answers

What occurs when GTP bound to b-tubulin is hydrolyzed to GDP?

Microtubules become less stable and may disassemble. Signup and view all the answers

Which of the following best describes the dynamics of microtubules?

Microtubules can dynamically grow and shrink. Signup and view all the answers

What is the effect of Taxol on microtubules?

It stabilizes microtubules and blocks cell division. Signup and view all the answers

What is the maximum speed of outward transport along microtubules in a nerve cell?

5 µm/s Signup and view all the answers

Which of the following statements about microtubule plus and minus ends is true?

The plus end is favored for assembly. Signup and view all the answers

Microtubules are primarily composed of which proteins?

Tubulin dimers Signup and view all the answers

Which condition can lead to the stabilization of microtubule plus ends in cells?

Binding of specific stabilizing proteins Signup and view all the answers

What is the structure of microtubules?

Hollow tubes made of a- and b-tubulin dimers Signup and view all the answers

Study Notes

Prelim 1: Next Monday, Sep 23rd

Exams are taken in class, 12:20 PM - 1:10 PM, via CANVAS.
Check seat assignments by Friday, Sep 20th, through CANVAS/EXAMS, either in the Call Auditorium or Klarman G70.
Complete exam instructions are available on CANVAS/EXAMS.
Students are responsible for reading and following instructions. Failure to follow instructions may result in a zero on the exam and further penalties.
Material covered includes lectures 2-7 and sections 2-4.
Grades are based on material taught in lectures and sections.
A practice exam is available on CANVAS/EXAMS.
BIOMG1350 review sessions are held Saturday/Sunday, 1-4 PM, in Biotech Racker Room G01 (instructions on CANVAS/EXAMS).
A BIOMG1035 review session is scheduled for Sunday, 6-7:30 PM, in Stimson Hall G01.
Office hours with Martin Graef are held Wednesday, 1:30 PM - 2:30 PM, in Biotech 201.

The Cytoskeleton and Molecular Motors

Learning objective: Understanding cytoskeleton components, their arrangement, and how molecular motors use ATP hydrolysis to move organelles along microtubules.
Learning objective: Understanding the structure of actin filaments and how myosins utilize them in muscle contraction.
Today's topics: Cytoskeleton overview, microtubules and their motors, and microfilaments and their motors.
The cytoskeleton consists of three filament systems that support cell shape and structure: microfilaments (actin), microtubules (αβ-tubulin dimers), and intermediate filaments (various).
Different filament systems support different cellular functions including contractile machinery, organization, and transport, and tissue integrity.
Microtubules are hollow tubes of α- and β-tubulin.
Microtubules have a plus end and a minus end, with the plus end favored for assembly and the minus end favored for disassembly.
Microtubules generally grow outward from the microtubule-organizing center (MTOC), like the centrosome.
Microtubules are GTP-binding proteins.
GTP hydrolysis in microtubules allows the dynamic growth and shrinkage of the microtubules.
Microtubules in cells are stabilized at the minus end by y-tubulin complexes.
Taxol is a small molecule that stabilizes microtubules, blocking cell division, and used in cancer chemotherapy.
Microtubules transport cargo along nerve cells, moving in both outward and inward directions.
The movement of cargoes along microtubules relies on ATP hydrolysis by motor proteins.
Motor proteins (e.g., kinesin and dynein) move along microtubules through a cycle of ATP binding and hydrolysis.
Kinesin motors move organelles like ER to the periphery.
Dynein motors move organelles like Golgi towards the center of the cell.
Kinesin is a highly processive motor protein, transporting cargo along microtubules without dissociating from the microtubule.
Myosin molecules associate to form bipolar myosin filaments.
Each myosin head walks along actin filaments in a cycle of ATP hydrolysis and binding, moving the entire myosin filament when phosphate is released.
The sliding filament mechanism of muscle contraction is driven by the interactions of actin and myosin filaments.

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Description

Test your knowledge on the components and functions of the cytoskeleton and motor proteins such as kinesin and myosin. This quiz covers key concepts including organelle movement, muscle contraction, and the role of ATP. Perfect for students studying BIOMG1350 or related courses.