W10 L1 - The Cytoskeleton

Flashcards reviewing key concepts about the cytoskeleton from a lecture.

What are the three main components of the cytoskeleton?

Actin filaments, intermediate filaments, and microtubules.

What is another name for actin filaments?

Microfilaments

Which cytoskeletal filament has the smallest diameter?

Actin filaments.

Which cytoskeletal filament has an intermediate diameter?

Intermediate filaments.

Which cytoskeletal filament has the largest diameter?

Microtubules.

What is the monomeric form of actin called?

Globular actin or G actin.

What does G-actin arrange into?

Actin filament or filamentous actin (F-actin)

What is the diameter of an actin filament?

7 nanometers.

Does an actin filament (F-actin) have a twist?

Yes

What creates structural polarity within an actin filament?

Actin monomers arranging in the same direction.

Which end of the actin filament points toward the plasma membrane?

The plus end.

Which end of the actin filament points towards the nucleus?

The minus end.

What is the cortical actin or cortical cytoskeleton?

A region enriched with actin filaments that lies underneath the plasma membrane.

What is actin treadmilling?

Actin monomers are added to the plus end and dissociate from the minus end.

To which molecule is an actin monomer bound in the cytoplasm?

ATP

What happens to ATP when an actin monomer is incorporated into the plus end?

It gets hydrolyzed into ADP and inorganic phosphate.

Are actin monomers tightly or loosely linked when bound to ADP?

Loosely linked.

What is the name for the motor protein that associates with actin?

Myosin.

What is retrograde actin flow?

The pulling of actin inwards towards the center of the cell by myosin.

What are focal adhesions?

The coupling of the actin cytoskeleton to the extracellular matrix by integrin proteins.

What are the two binding sites of Myosin's head domain?

Actin and ATP

Which domain of myosin varies greatly between classes?

Tail domain.

In which direction do myosins generally move along actin filaments?

Towards the plus end.

What is the exception to the general rule of myosin movement along actin filaments?

Myosin VI, which moves toward the minus end.

What is the function of actin nucleators?

Starting that filament assembly

Which protein is important for generating branched actin filaments?

Arp2/3

Which protein helps create linear actin bundles or filaments?

Formins.

What type of structure does Arp2/3 generate?

Branched actin filaments.

What type of structure does formins generate?

Linear actin filaments.

What is the leading edge of the cell also called?

The lamellipodia.

What are the finger-like projections at the leading edge of the cell called?

Filopodia.

What type of actin filaments are filipodia made of?

Linear actin filaments.

What type of actin filaments is the leading edge made of?

Branched.

What are strong fibers that help the cell in mechanotransduction?

Stress fibers.

What is the function of the cell cortex or cortical actin cytoskeleton?

Provides support and stability to the plasma membrane.

What is another name for a membrane ruffle?

Lamellipodia

What is the building block (dimer) of microtubules?

Alpha and beta tubulin monomers.

What do tubulin dimers arrange into?

Protofilament

How many protofilaments are in a microtubule?

13

What is the diameter of a microtubule?

25 nanometers.

What are the main functions of microtubules?

Positioning organelles within the cell and intracellular transport

What is dynamic instability in the context of microtubules?

They can be present and stable, then suddenly dissociate.

What type of hydrolysis occurs during microtubule formation?

GTP hydrolysis.

To which molecule is beta tubulin bound?

GTP

What happens when GTP hydrolysis is faster than the rate of tubulin dimer addition?

The GTP cap is lost, and the microtubule begins to dissociate.

What are microtubule organising centres?

Regions of the cell from which microtubules grow.

What is the main MTOC in a non-dividing cell?

Centrosome.

What structure protrudes from the poles of the spindle during division?

Microtubules.

What structure do microtubules grow out from in ciliated cells?

Basal bodies.

What is the function of gamma tubulin?

It forms a ring-like structure from which the microtubule will grow outwards.

What is the role of capping proteins in microtubule stability?

Stabilise them

What are the motor proteins associated with microtubules?

Kinesins and dyneins.

Toward which end of the microtubule do kinesins move?

The positive end.

Toward which end of the microtubule do dyneins move?

The minus end.

What structure maintains the position of the golgi apparatus?

Cytoplasmic dynein motor proteins

What type of cargo do kinesins transport in blue?

Endoplasmic reticulum

What are flagella used for?

Moving an entire cell.

What is the function of cilia?

To sweep and move fluid within the body.

What is the arrangement of microtubules in cilia and flagella?

Nine plus two array.

What is the approximate diameter of intermediate filaments?

10 nanometers.

What is the primary function of intermediate filaments?

To withstand mechanical stress

Do intermediate filaments have polarity?

No

What are lamins?

A type of intermediate filament found underneath the inner nuclear membrane.

What is the function of lamins?

Provide support to that nucleus

What are the two classes that make up LINK?

Cash and Sun

What is the name of the disease characterized by accelerated aging?

Hutchinson-Gilford Progeria.

What is the name of the illness caused by mutations within Keratin genes?

Epidermolysis bullosa simplex syndrome.

What does taxol stabilize to treat cancer?

Microtubules

Does taxol stabilize microtubules from polymerizing of depolymerizing?

Depolymerizing

Which cytoskeleton element is responsible for cell crawling?

Actin

What complexes link the nuclear lamina to the cytoskeleton?

LINK complex

What type of cells are sperm and bacteria?

Flagellated

When free within the cytoplasm, what happens to dinein and microtubules?

Dinein will try to walk up and down the microtubule

What element allows for flagella and cilia to bend?

Dinein that are cross-linked with microtubules