Lecture 1- Epithelial Cells Flashcards
What are the darker regions of the nucleoplasm called and what is it?
Heterochromatin. Regions of condensed DNA which is less active
What is contained in the nucleolus?
- clusters of rRNA genes from the ends of pairs of chromosomes
- synthesised rRNA
- proteins for ribosomal sub-units
- Lots of copies of rRNA genes present because 1 rRNA–> 1 ribosome but 1 mRNA–> many proteins
Where can ribosomes be found?
- free in the cytoplasm –> cytoplasmic proteins
- attached to the RER –> membrane and secretory proteins
What is found on the inside of the nuclear envelope?
The nuclear lamina- cytoskeleton (Intermediate filament) which helps control the assemble/ disassembly of the nuclear envelope in cell division
What shape is the RER, SER and Golgi apparatus?
RER + Golgi: Flattened sacs = cisternae
SER: tubular
What is the function of the SER
- detoxification
- lipid metabolism
- Ca 2+ storage for cell-signalling
Describe the relative orientation of the Golgi apparatus to the cell
Cis face- ER
Trans face- cell periphery
What are peroxisomes?
- Contain many enzymes involved in lipid and O2 metabolism
- Present in such high conc that they crystallise
- enclosed by single membrane
- remove free radicals
Name the three types of filaments making up the cytoskeleton in ascending order of size
1) Microfilaments (5-9nm)
2) Intermediate Filaments (10-15nm)
3) Microtubules (20nm)
Describe the structure of microtubules, their main function
- Polymers of a and B tubular heterodimers
- Involved in cell shape + organelle movement
Where can microtubules be found?
CILLIA & FLAGELLAE
- (9 doublets + 2 singlets arrangement)
- ATP dependent motor proteins distort cilium–> movement
MITOTIC SPINDLE
Where do microtubules originate from in the cell?
The Microtubule Organising Centre (MTOC)
Describe the structure of intermediate filaments
Groups of polymers of filamentous proteins which form rope like filaments
Describe the main function of IF
- provide mechanical strength to cells
Where can IFs be found?
- Desmosome cell-cell adhesions
- Nuclear lamins- stabilise the envelope
- Cells have specific IFs
What are microfilaments made of?
- made of actin
- usually helical
- Monomer= Globular actin (G-actin)
- Microfilament= Filamentous Actin (F-actin)
What are the main functions of microfilaments?
- cell shape
- cells movement (contraction) with the help of accessory proteins
Where can microfilaments be found?
- adhesion belts in epithelia
- bundled near the periphery of cells
- muscles
What are the four main cell groups?
1) Mesenchymal Cells
§ Connective tissue cells: fibroblasts, chondrocytes (cartilage), osteocytes (bone) § Contractile tissue: (skeletal, cardiac, smooth muscle), endothelial lining of blood vessels
2) Haematopoietic cells: blood cells, tissue- resident immune cells, cells from bone marrow
3) Neural Cells:neurones and glial (support) cells
4) Epithelial cells: cells forming continuous layers, line surfaces, separate tissue compartments
What are the names of tumours of the different cell groups?
- Epithelial = carcinoma
- Mesenchymal = sarcoma
- Haematopoietic =leukaemia (bone marrow), lymphoma (lymphocyte)
- Neural = neuroblastoma (neurones), gliomas (glial)
Define the term tissue and what constitutes it
- Tissue: group of cells whose type and organisation are required for its function
- Made of cells, ECM and fluid
What is the Extracellular Matrix?
- Material deposited by cells
- forms insoluble extracellular environment
- fibrillar proteins (collegens, elastins) embeded in hydrated gel (proteoglycans)
What are the two group of junctions and then the four different types of junctions?
- Zonulae (belts) and Maculae (spots)
1) Tight junction (zonula occludent)
2) Adherens junction (Zonula adherens)
3) Desmosomes (Macula adherens)
4) Gap Junction (Macula Communicans)
[5) Synapse]
Describe the tight junction and its main function
- Found on apical lateral membrane
- points where membranes form close contact with adjacent membrane
- To segregate apical and basolateral membrane polarity
- To seal paracellular pathways
