Cytoskeleton and Cilia Flashcards
What is the cytoskeleton ?
An intricate network of protein filaments that extends throughout the cytoplasm
What are the roles of the cytoskeleton ?
- Strength and support to cell
- Allows cell shape changes
- Cell movement (sperm)
- Cell contraction
- Wound healing
- Cell division
- Interaction with other cells
- Organisation of cell interior
What causes epidermolysis bullosa?
Caused by defects in keratin and also collagen
What causes progeria ?
Caused by defects in nuclear lamin
What are the three types of cytoskeleton filaments of eukaryotic cells?
- Intermediate filaments
- Microtubules
- Actin microfilaments
What is the main role of the IFs?
To provide tensile strength
What are the main IFs proteins ?
Keratin and lamin
What are desmosomes ?
Contacts points between epithelial cells
How are cells connected to the basal laminate?
Via hemisdesmosomes
What do desmosomes do?
They spread the stress points on a cell, to minimise damage to mechanical strain
What secondary structure does keratin have ?
Alpha helix
What is the basic unit of keratin composed of?
2 tetramers
How many tetramers make up an IF filament ?
8
Where does keratin usually make up the IFs?
Epithelia Tongue Skin Gut Nails Hair
Note - cytoplasmic IFs
What is pemphigus ?
It is an autoimmune condition where the body’s own antibodies attack the desmosomes which causes the contact between epithelial cells to loosen
What type of IF is lamin?
Nuclear
What is the role of lamin?
To provide attachment sites for DNA-binding chromatin
How is the process of disassembly and assembly of lamin controlled ?
By protein phosphorylation of lamin
What are the proteins that add and remove phosphates ?
Add - kinases
Remove - phosphatases
What are microtubules made up of?
Tubulin proteins
Where are microtubules anchored ?
Centrosome - close to the nucleus
What are microtubules important for ?
- Cell division
- Anchoring organelles like mitochondria
- Intracellular transport
How many tubulin filaments are there in a microtubule?
13 - with alpha and beta tubulin molecules
How could you describe the microtubules?
Hollow, polar structure
Microtubules can grow and shrink independently of each other. What is this referred to as?
Dynamic instability
How are microtubules regulated ?
G-proteins
Tubulin bind to GTP
What happens when the GTP is hydrolysed to GDP?
The microtubule shrinks again
Are tubulin polymers stable or unstable in cells?
Unstable
Where is the minus end of the microtubule?
At the centrosome, growing out the the plus end
Why do cilia rely on microtubules?
For movement
What is the protein that allows the microtubules to move and bend?
Dynein
What is a condition that is caused by defective cilia?
Karatagener’s syndrome
Hearing loss
What are actin filaments involved in?
Cell crawling
Phagocytosis
Cell division
How are actin filaments stabilised ?
Actin binding proteins
Are actin filaments polarised ?
Yes
The growing actin strand will be bound to _______ and the shrinking strand will be bound to ________
ATP
ADP
