Exam 3 Flashcards
The cytoskeleton is a network of protein _____ extending throughout the _______ in all ________ cells
Filaments,
Cytoplasm,
Eukaryotic
Note the two functions of the cytoskeleton:
- Structural framework (scaffold for shape and cytoplasmic organization)
- Movement (for entire cell movement and transport of organelles/other structures thru cytoplasm)
Mostly ______ filaments around the edges of the membrane, mostly ______ connecting to the nucleus radially outward to outer edges, Mostly _______ in between throughout cytoplasm in between
Actin,
Microtubules,
Intermediate filaments
Name the three principal elements/components that make up the cytoskeleton, which are held together and linked to subcellular organelles and plasma membrane by _______
- Actin filaments (8nm)
- Intermediate filaments (10nm)
- Microtubules (25nm)
Accessory proteins
Which principal cytoskeleton element is not involved in cell movement (directly)?
Intermediate filaments
Main function of the intermediate filaments is…
They enable cells to withstand the mechanical stress that occurs when cells are stretched
There are _____ classes of IF’s. _____ in cytoplasm and _____ in the nucleus.
4 classes,
3,
1,
The 3 types of cytoplasmic IF’s and what cells they are found in?
- Keratin filaments (in epithelial cells)
- Vimentin & Vimentin-related filaments (in connective tissue cells, muscle cells, glial cells)
The one class of nuclear IF?
Nuclear Lamins (in all animal cells)
Appearance of IF’s in cell:
IF’s form a network throughout the cytoplasm, surrounding the _____ and extending out to the cell periphery, where they are anchored to the ______. They are also indirectly connected to neighboring cells through a cellular structure called the _____.
nucleus,
plasma membrane
desmosome
Describe the assembly of mature IF’s:
Two _____ ______ wrapped using their central alpha-helical domains to form a _____-______ _____. The two dimers associate in a ______ and ______ fashion to form a tetramer. This thus constitutes a mature IF, in that it does NOT have ______ (one end resembles the other). The NH2 ends will extend out more than the COO- ends.
parallel monomers,
coiled-coil dimer,
staggered and antiparallel,
polarity
Maturation of cytoplasmic IFs results in a ___-____ _____,
_____ ________ then laterally associate and are added to the growing IF. Unlike microfilaments and microtubules, there is no______ ______ and IFs build onto _____ IFs. Thus, the IF network is not very _______.
rope-like structure,
Eight tetramers,
nucleation involved,
preexisting,
dynamic
Two functions of the nuclear lamina:
An IF composed fibrous network that:
1. supports the nuclear membrane
2. provides attachment sites for the chromatin
Intermediate filaments underlying the inner face of the nuclear envelope form the ______ _______
Nuclear lamina
How does the the nuclear lamina differ from the cytoplasmic IFs?
in structure since it forms a meshwork as opposed to a rope-like structure.
The nuclear lamina _____ _____ ______ ______ when the nuclear envelope breaks down. This is regulated by ______ of the lamina to cause disassembly, and _______ to allow for its reformation.
disassembles with each cell division,
phosphorylation,
dephosphorylation
Mutations in nuclear lamin protein are associated with _______ (premature aging in children)
Progeria
Three main functions of microtubules:
- the separation of chromosomes during mitosis
- the intracellular transport of membrane-bound vesicles and organelles
- cell movement
Microtubules are _____, ______ ______ approximately 25 nm in diameter. They are _______ structures that continually undergo ______/_______.
Rigid, hollow rods
Dynamic
Assembly / disassembly
MT’s are composed of a single type of globular protein, called _______, which is a _______ consisting of 2 closely related proteins: 1._______ and 2.________
Tubulin,
Heterodimer,
1. alpha-tubulin
2. beta-tubulin
Dimers of ______ & _______ tubulin (via ________) form a ___________.
Alpha & beta tubulin,
Non-covalent bonding,
Protofilament,
The alpha-tubulin is to _______, and beta-tubulin is for _______. The _______ is considered the growing end (determines direction of movement along MT’s)
minus-end,
plus-end,
plus-end.
