Lecture 1- Epithelial Cells

Question 1

What are the darker regions of the nucleoplasm called and what is it?

Answer 1

Heterochromatin. Regions of condensed DNA which is less active

Question 2

What is contained in the nucleolus?

Answer 2

• 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

Question 3

Where can ribosomes be found?

Answer 3

• free in the cytoplasm –> cytoplasmic proteins

- attached to the RER –> membrane and secretory proteins

Question 4

What is found on the inside of the nuclear envelope?

Answer 4

The nuclear lamina- cytoskeleton (Intermediate filament) which helps control the assemble/ disassembly of the nuclear envelope in cell division

Question 5

What shape is the RER, SER and Golgi apparatus?

Answer 5

RER + Golgi: Flattened sacs = cisternae

SER: tubular

Question 6

What is the function of the SER

Answer 6

• detoxification
• lipid metabolism
• Ca 2+ storage for cell-signalling

Question 7

Describe the relative orientation of the Golgi apparatus to the cell

Answer 7

Cis face- ER

Trans face- cell periphery

Question 8

What are peroxisomes?

Answer 8

• Contain many enzymes involved in lipid and O2 metabolism
• Present in such high conc that they crystallise
• enclosed by single membrane
• remove free radicals

Question 9

Name the three types of filaments making up the cytoskeleton in ascending order of size

Answer 9

1) Microfilaments (5-9nm)
2) Intermediate Filaments (10-15nm)
3) Microtubules (20nm)

Question 10

Describe the structure of microtubules, their main function

Answer 10

• Polymers of a and B tubular heterodimers

- Involved in cell shape + organelle movement

Question 11

Where can microtubules be found?

Answer 11

CILLIA & FLAGELLAE
- (9 doublets + 2 singlets arrangement)
- ATP dependent motor proteins distort cilium–> movement
MITOTIC SPINDLE

Question 12

Where do microtubules originate from in the cell?

Answer 12

The Microtubule Organising Centre (MTOC)

Question 13

Describe the structure of intermediate filaments

Answer 13

Groups of polymers of filamentous proteins which form rope like filaments

Question 14

Describe the main function of IF

Answer 14

• provide mechanical strength to cells

Question 15

Where can IFs be found?

Answer 15

• Desmosome cell-cell adhesions
• Nuclear lamins- stabilise the envelope
• Cells have specific IFs

Question 16

What are microfilaments made of?

Answer 16

• made of actin
• usually helical
• Monomer= Globular actin (G-actin)
• Microfilament= Filamentous Actin (F-actin)

Question 17

What are the main functions of microfilaments?

Answer 17

• cell shape

- cells movement (contraction) with the help of accessory proteins

Question 18

Where can microfilaments be found?

Answer 18

• adhesion belts in epithelia
• bundled near the periphery of cells
• muscles

Question 19

What are the four main cell groups?

Answer 19

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

Question 20

What are the names of tumours of the different cell groups?

Answer 20

• Epithelial = carcinoma
• Mesenchymal = sarcoma
• Haematopoietic =leukaemia (bone marrow), lymphoma (lymphocyte)
• Neural = neuroblastoma (neurones), gliomas (glial)

Question 21

Define the term tissue and what constitutes it

Answer 21

• Tissue: group of cells whose type and organisation are required for its function
• Made of cells, ECM and fluid

Question 22

What is the Extracellular Matrix?

Answer 22

• Material deposited by cells
• forms insoluble extracellular environment
• fibrillar proteins (collegens, elastins) embeded in hydrated gel (proteoglycans)

Question 23

What are the two group of junctions and then the four different types of junctions?

Answer 23

• 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]

Question 24

Describe the tight junction and its main function

Answer 24

• 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

Question 25

Describe the adhesions belt and its main function

Answer 25

• Found basal to the tight junction
• Cadherins adhere membranes together and associate with microfilament skeleton
• To control the assembly of the other junctions

Question 26

Describe desmosomes (spot junction) and its main function

Answer 26

• Scattered throughout the lateral membrane
• cadherin- like molecule adheres membranes
• associated with the IF cytoskeleton
• Provide mechanical continuity between cells

Question 27

Describe gap junctions and their main function

Answer 27

• Clusters of pores from 6 identical subunits in membrane line up with those in the adjacent membrane
• to allow passage of ions and small molecules
• Factors (pH, Ca2+, conc, voltage and signalling molecules) can open + close pores and control intracellular communication
• acts as electrical synapse in cardiac muscle

Question 28

Describe what synapses are and their main function

Answer 28

• found in neural tissue
• button like junctions between neurones/ target cells
• info passed one way by neurotransmitters