Cytoskeleton, Lecture 7 Flashcards
What is the cytoskeleton?
The cytoskeleton is a structure that maintains cell shape, internal organization, provides mechanical support for division, and supports movement.
What are general functions of filaments in the cytoskeleton?
Filaments allow cells to maintain and change shape, provide coordinated movement, support intracellular transport, and maintain organelle distribution.
What functions or processes are microtubules involved in?
Microtubules are involved in mitosis, cell motility, intracellular transport, and maintenance of cell shape.
What filament in the cytoskeleton is the largest?
Microtubules are the filaments in the cytoskeleton with the largest diameter.
What monomers are microtubules made of?
Microtubules are made of the protein subunit, tubulin.
Filaments in the cytoskeleton can be described as ‘dynamic’. What does this mean?
Filaments are described as ‘dynamic’ because they can grow or shrink rapidly in length through assembly and disassembly.
Describe what it means by the ‘plus’ and ‘minus’ ends of filaments in the cytoskeleton.
The plus end generally has more assembly and a higher rate of growth, while the minus end has slower growth and more depolymerisation.
What is catastrophe?
Catastrophe is the switch from growth to shrinking.
Describe where assembly and disassembly occurs in the microtubule structure.
Assembly occurs at the positive end via polymerisation of tubulin subunits, while the minus end is anchored to the microtubule organising centre (MTOC).
What are MTOCs (microtubule organising centres)?
MTOCs are structures that anchor microtubules; in eukaryotic dividing cells, the centrosome is a primary MTOC.
What is dynamic instability?
Dynamic instability is the ability of microtubules to grow or shrink rapidly in response to a cell’s needs.
What is dynamic instability dependent on in microtubules?
Dynamic instability is dependent on tubulin concentration and microtubule associated proteins.
What structures do microtubules make up?
Microtubules make up motile structures such as cilia and flagella, and are found in centrioles.
What are motor proteins?
Motor proteins are proteins that walk along a microtubule while transporting a substance, powered by the hydrolysis of ATP.
In what direction of the microtubule do motor proteins work towards?
Kinesin motor proteins move towards the plus end of the microtubule.
In what direction of the microtubule do dynactin motor proteins work towards?
Dynactin proteins move towards the minus end of the microtubule.
What is a type of microfilament found in skeletal muscle cells?
Actin microfilament is present in skeletal muscle cells and functions in the sliding filament model for muscle contraction.
What is the smallest type of filament in the cytoskeleton, in terms of diameter?
Microfilaments are the smallest filament in terms of diameter.
What sub-units make up actin filaments?
Actin filaments are made up of G-actin subunits that polymerise to form F-actin, which twist together to form a helix shape.
What other functions do actin carry out, other than playing a part in the sliding filament model?
Actin supports microvilli structure, forms a cleavage furrow during cell division, and is involved in cytoplasmic contraction.
What is treadmilling?
Treadmilling is the process where assembly and disassembly occur at the same rate, maintaining a constant length of actin filaments.
What are some functions of microfilaments?
Microfilaments determine cell surface shape, control cell locomotion, and serve as tracks for motor proteins in transport and contraction.
Name a motor protein that works along microfilaments.
Myosin is a motor protein that travels along microfilaments towards the plus end.
Name some types of intermediate filaments and where they are found.
Keratin is found in skin and hair cells, while myosin is found in skeletal muscle cells.
What are some functions of intermediate filaments?
Intermediate filaments resist stress and deformation, hold organelles in position, and facilitate network communication.
What is assembly?
Assembly is the addition of subunits to the plus end of filaments in the cytoskeleton.
