WEEK 6 (Intermediate Filaments) Flashcards
Intermediate Filaments lack polarity (TRUE/FALSE)
TRUE
Explanation: Unlike microtubules and microfilaments, intermediate filaments lack polarity and both ends of the filaments are same in nature
Intermediate filaments tend to be less sensitive to ___________________
Chemicals
Vimentin is a _______________
Intermediate Filament
Epidermolysis bullosa simplex is caused by the deficiency of _______________ polypeptide
Keratin
Aggregation of neurofilaments leads to ______________________
Neurodegenerative disorders
Explanation: Neurofilaments are intermediate filaments that constitute mature neuronal cells. Aggregation of these neurofilaments blocks axonal transport associated with neurodegenerative disorders
Microfilaments are mostly involved in ___________ processes
Motile
Microfilaments are composed of globular subunits of ____________
Actin
The identification of actin filaments in a cell can be done by using the protein ______________
Myosin
The faster growing end of the microfilament is the plus-end (TRUE/FALSE)
TRUE
The drug cytochalasin blocks the __________________
Plus-end of microfilaments
(preventing polymerisation there)
Latrunculin blocks the _________________
Actin monomers
(prevents their polymerisation)
The head of the myosin binds the _________________________
Actin Filament
Titin is the largest protein discovery till date (TRUE/FALSE)
TRUE
Which type of cytoskeletal element is described as tough, ropelike fibers composed of a variety of related proteins like Keratin?
Intermediate Filaments
What are the functions of the Cytoskeleton?
- Controls cell shape
- Maintains intracellular organisation
- Involved in cell movement
What are the properties of Intermediate Filaments?
- Great tensile strength
- Enable cells to withstand mechanical stress when cells are stretched
- Toughest & most durable of the cytoskeletal filaments
- Survive concentrated salt solutions & nonionic detergents
Why are intermediate filaments called “intermediate”
In smooth muscle cells where they were first discovered, the diameter was between the thinner actin filaments and thicker myosin filaments
What are the four major classes of Intermediate Filaments?
- Keratin Filaments
- Vimentin and Vimentin-related filaments
- Neurofilaments
- Nuclear lamins
Which intermediate filaments are cytoplasmic?
- Keratin Filaments
- Vimentin and Vimentin-related filaments
- Neurofilaments
Which intermediate filament is nuclear?
Nuclear lamins
Where are intermediate filaments present in large numbers?
- Nerve cell axons
- Muscle cells
- Epithelial cells
What is the difference between central rod domains and terminal domains in different intermediate filaments?
CENTRAL ROD DOMAINS = all similar in size and amino acid sequence
TERMINAL DOMAINS = vary greatly in both size and amino acid sequence
Describe the structure of Intermediate filaments
Intermediate filament monomer consists of an A-HELICAL CENTRAL ROD DOMAIN with UNSTRUCTURED REGIONS at either end -> Pairs of monomers associate to dorm a DIMER and two dimers line up to form a STAGGERED, ANTIPARALLEL TETRAMER -> Tetramers pack together into a HELICAL ARRAY containing EIGHT TETRAMER STRANDS -> Assemble into a ROPE LIKE INTERMEDIATE FILAMENT
What are Neurofilaments?
Intermediate filaments that are found along the axons of vertebrate neurons
What are the functions of Neurofilaments?
Provide strength and stability to the long axons that nerve cells use to transmit information
What is Amyotrophic Lateral Sclerosis (ALS)?
ALS (also known as LOU GEHRIG’S DISEASE) is a progressive motor neuron disease that is associated with an abnormal accumulation of neurofilaments in cell bodies and axons of motor neurons. It affects movement such as chewing, walking & talking.
RISK FACTORS:
- Most common between 55 & 75
- Males
- Caucasians & Non-hispanics
- Military veterans
SYMPTOMS:
- Axon degeneration
- Muscle weakness
- Muscle Atrophy
- Brain loses its ability to initiate and control voluntary movements
CURE:
There is no cure
What happens in motor neuron disease?
As motor neurons degenerate and die, they stop sending messages to the muscles -> the muscles weaken, start to twitch (FASCICULATIONS) and waste away (ATROPHY) -> The brain loses its ability to initiate and control voluntary movements
What are Early symptoms of Amyotrophic Lateral Sclerosis (ALS)?
- Muscle twitches in the arm, leg, shoulder or tongue
- Muscle cramps
- Tight and stiff muscles (spaticity)
- Muscle weakness affecting an arm, a leg, the neck or diaphragm
- Slurred and nasal speech
- Difficulty chewing or swallowing