Cells 5

What are the 3 major components of the cytoskeleton?

Microtubules, microfilaments, and intermediate filaments.

What are microtubules made of?

Tubulin subunits.

What are microfilaments made of?

Actin subunits.

What are intermediate filaments made of?

Various proteins including keratins, lamins, and neurofilaments.

What are the major functions of the cytoskeleton?

Maintaining cell shape, positioning organelles, support, and mobility.

Why is the cytoskeleton described as dynamic?

It rapidly disassembles and reassembles.

Why is cytoskeleton dynamism important?

It allows rapid changes in cell shape.

Which cytoskeleton component resists compression?

Microtubules.

Which cytoskeleton component resists tension?

Microfilaments.

Which cytoskeleton component forms relatively permanent structures?

Intermediate filaments.

Which cytoskeleton component is least dynamic?

Intermediate filaments.

What is the organizing center for microtubules called?

The centrosome.

What is the main structural arrangement of microtubules?

Hollow tubes made from tubulin dimers.

What is the main role of microtubules in maintaining cell shape?

Resisting compression.

What cell structures involved in motility are made from microtubules?

Cilia and flagella.

What type of movement do flagella produce?

Snake-like movement.

What type of movement do cilia produce?

Rowing-like movement.

What is an example of flagellar movement in humans?

Sperm cell movement.

What is an example of ciliary function in humans?

Moving fluid/mucus in the respiratory tract.

How do microtubules move organelles within the cell?

ATP-powered motor proteins walk organelles along microtubules.

What powers motor proteins on microtubules?

ATP.

What types of structures are transported along microtubules?

Vesicles and organelles.

What is the structure of microfilaments?

Double chains of actin subunits.

What two arrangements can microfilaments form?

Linear strands and 3D networks.

Where is the cortical network of microfilaments located?

Under the plasma membrane.

What does the cortical microfilament network do?

Makes the membrane region less fluid and helps maintain shape.

Which motor protein interacts with actin?

Myosin.

What important biological process depends on actin-myosin interactions?

Muscle contraction.

What type of cell movement depends on microfilaments?

Amoeboid movement.

What plant process depends on microfilaments?

Cytoplasmic streaming.

Name three proteins that can form intermediate filaments.

Keratins, lamins, and neurofilaments.

Where are keratins found?

Hair and skin.

Where are lamins found?

The nucleus.

Where are neurofilaments found?

Neurons.

What is the structure of intermediate filaments?

Supercoiled cables.

What are the main functions of intermediate filaments?

Maintaining shape and anchoring organelles.

Why can hair remain after cells die?

It contains keratin intermediate filaments.

What are the 3 major types of cell junctions?

Tight junctions, desmosomes, and gap junctions.

What is the main function of tight junctions?

Form seals between neighboring cells.

What do tight junctions prevent?

Movement of fluid across cell layers.

What is the main function of desmosomes?

Strong anchoring between cells.

What do desmosomes act like?

Rivets.

Which cytoskeleton component connects to desmosomes?

Intermediate filaments.

What is meant by “a torn muscle is a torn desmosome”?

Desmosomes help resist mechanical stress between cells.

What is the main function of gap junctions?

Cell-to-cell communication.

What can pass through gap junctions?

Ions and small molecules.

What type of communication occurs through gap junctions?

Rapid intercellular communication.

What is the extracellular matrix (ECM)?

The non-cellular material outside cells in tissues.

Do cells always directly contact each other in tissues?

No, many lie within ECM.

What is the ECM composed of?

Material secreted by cells.

How is the ECM secreted?

Constitutive exocytosis.

What type of molecules make up most ECM proteins?

Glycoproteins.

What is a glycoprotein?

A protein with added carbohydrates.

What is the most abundant ECM glycoprotein?

Collagen.

What is the main function of collagen fibers?

Provide tensile strength.

What are proteoglycans?

Proteins with extensive sugar additions.

What is the role of proteoglycans in the ECM?

Trap water.

Why is water important in the ECM?

It resists compression and helps retain tissue shape.

What attaches cells to the ECM?

Fibronectins.

What are integrins?

Membrane proteins connecting ECM to the cytoskeleton.

Why are integrins important?

They provide communication between the ECM and cell interior.

What happens to collagen and elastin as skin ages?

They break down.

What molecule helps retain moisture and “plump” skin?

Hyaluronic acid.

What type of molecule is hyaluronic acid?

A glycosaminoglycan.

Which cytoskeleton component would you use for muscle contraction?

Microfilaments.

Which cytoskeleton component would you use for moving organelles around animal cells?

Microtubules.

Which cytoskeleton component would you use for a flagellum?

Microtubules.

Which cytoskeleton component provides a more rigid and permanent structure?

Intermediate filaments.

Which junction strongly anchors cells together?

Desmosomes.

Which junction forms continuous seals?

Tight junctions.

Which junction allows ions to move between cells?

Gap junctions.

Which cytoskeleton component is associated with cilia movement?

Microtubules.

Which cytoskeleton component is associated with actin and myosin?

Microfilaments.

Which cytoskeleton component is associated with keratins?

Intermediate filaments.

What are the 4 lecture objectives for Lecture 5?

Identify cytoskeleton components, explain regulation of cell shape, outline cell junction importance, and describe ECM composition and origin.