7 - cytoskeleton Flashcards
Three main types of fiber
- Microfilaments: About 7 nm in diameter and are composed of two actin chains twisted around each other. They have a variety of structural and locomotor functions
- Intermediate filaments: 8-10nm in diameter and are made up of a diverse group of proteins. Tend to be permanent fixtures, and are important in maintaining the shape of the cell, as well as maintaining the position of certain organelles
- Microtubules: Straight hollow rods 25nm in diameter and up to 20 microns long, and are constructed from globular proteins called Tubulins
Microfilaments
- known for their role in the contraction of muscle cells where they interact with myosin filaments.
- In addition to cell movement they are important in the maintenance of cell shape.
- Microfilaments perform some structural roles in non-muscle cells, such as the formation of microvilli.
- Most animal cells have a network of actin filaments just below the cell surface termed the Cell Cortex; this cortex supports the plasma membrane and facilitates cell movement.
True or false: many drugs work by targeting the cytoskeleton and the cytoskeleton remains a prime target for the development of new drugs
TRUE
The main role of intermediate filaments is contraction of muscle cells where they interact with myosin filaments. True or false?
FALSE- Intermediate filaments are important in maintaining the shape of the cell and holding organelles in their correct position - it is MICROFILAMENTS that are involved in muscle contraction
T/F?: G actin is a globular protein
TRUE
Which of the following are true?
a) F actin forms when soluble actin monomers polymerise
b) F actin is a soluble filamentous protein
c) F actin is a double right-handed helical molecule
d) F actin has a diameter of 14nm
a and c are true.
b is false because F actin is insoluble.
d is false because F actin has a diameter of 7nm
What is the Cell Cortex?
A network of actin filaments (microfilaments) just below the cell surface which supports the plasma membrane and facilitates cell movement
T/F?: Actin-myosin interactions are responsible for cytokinesis
TRUE - cytokinesis is the separation of daughter cells during mitosis - actin-myosin interactions are responsible for this
T/F?: The acrosome reaction in echinoderm sperm is driven by actin polymerisation
TRUE
T/F?: The movement of myosin along actin filaments requires ATP
TRUE
What are the two type of microtubules?
Axonemal and cytoplasmic
Axonemal microtubules
highly organised and stable, found in cilia, flagella and basal bodies
Cytoplasmic microtubules
more dynamic and loosely organised, found in cytoplasm
T/F?: Microtubules are formed from the polymerisation of tubulin dimers
TRUE
What are the proteins kinesis and cytoplasmic dynein involved in?
The movement of vesicles and small particles along microtubules
In which direction does kinesin and dynein travel along the microtubule?
Kinesin moves from the negative -> positive end.
Cytoplasmic dynein moves from the positive -> negative end
The drug taxol is a microtubule/tubulin binding drug - true or false?
True - the drug taxol is a cancer drug used to treat ovarian cancer, lung cancer and breast cancer.
Taxol binds to microtubules and prevents disassembly so prevents cell division.
What type of transport is the movement of kinesins?
Kinesins move from the negative end of the microtubule to the positive end - this is known as anterograde transport
What type of transport is the movement of cytoplasmic dynein proteins?
Retrograde transport - dyneins move from the positive end of the microtubule to the negative
T/F?: Cilia and flagella have the same lengths but different structures
FALSE - they have different lengths (cilia are around 2-20 microns - shorter whilst flagella are around 10-200 microns long- longer) but they have the SAME structure
Describe the structure of cilia and flagella
They consist of a core of axonemal microtubules ensheathed in an extension of the plasma membrane
T/F?: Cilia and flagella have a 9+2 arrangement of microtubules
TRUE
T/F?: Intermediate filaments are capable of dynamic movement
FALSE - THEY ARE NOT
T/F?: Intermediate filaments are 8-10nm in length and are soluble
FALSE - correct length but they are insoluble
