Epithelial cells

Question 1

What happens in the nucleolus?

Answer 1

Ribosomal subunits are synthesised

Question 2

What three types of filament constitute the cytoskeleton?

Answer 2

Microtubules
Intermediate Filaments
Microfilaments

Question 3

What are microtubules made of and what is the diameter of a microtubule?

Answer 3

Alpha and beta tubulin heterodimers

20nm.

Question 4

What are microtubules used for?

Answer 4

Cell shape
Movement of organelles through the cell – involves motor proteins
Involved in spindle fibre formation

Question 5

Describe the organisation of microtubules in cells.

Answer 5

They originate from a point within the cell called the microtubule organising centre (MTOC)

Question 6

Microtubules are an important structural component for which cellular features?

Answer 6

Cilia and flagellae

Question 7

Which component of the cytoskeleton distinguished different cell types?

Answer 7

Intermediate Filaments – different for different cell types

Question 8

What are intermediate filaments usually connected to?

Answer 8

Desmosomes which are connected to cytokeratins

Question 9

Where else are intermediate filaments found than in the cytoplasm and what do IF provide to cells?

Answer 9

Nuclear lamin – on the internal surface of the nuclear envelope – provides support

-Give mechanical strength

Question 10

What are microfilaments made of?

Answer 10

Actin

Question 11

What do microfilaments associate with and what is it involved in?

Answer 11

Adhesion belt and accessory proteins e.g. myosin

Involved in cell shape and cell movement.

Question 12

What is the monomer of microfilaments and where is it found and what structure does it have ?

Answer 12

G-actin (globular actin)

• usually near the periphery of the cell
• helical structure

Question 13

Define ‘Extracellular Matrix’.

Answer 13

The insoluble material found extracellularly.

Question 14

What are the four main types of cell-cell junctions (in order of apical to basal)?

Answer 14

Tight junction
Adhesion belt
Desmosomes
Gap Junctions

Question 15

What is the role of tight junctions?

Answer 15

Seals off the paracellular pathways. Allows polarity. Stops proteins that diffuse through membranes.

Question 16

Describe the structure of the adhesion belt.

Answer 16

It consists of a cadherins, which interact with similar molecules on the adjacent cell and clusters to form these junctions. Actin filaments are bound to the adhesion belt. It is the first to form- Master Junction

Question 17

Describe the structure of desmosomes.

Answer 17

Also involves cadherins interacting to maintain adhesion. Cadherins links to the Intermediate filaments.

Question 18

What is the role of Gap junctions?

Answer 18

Allows transport of small molecules between cells.

Important to communicate between the cells.

Question 19

What are the cancer called when they originate from:

Answer 19

• epithelial cell: carcinomas
• mesenchymal: sarcomas
• heamatopoietic: leukaemias
• neural : neuroblastomas ( from neurone precursors) and gliomas (from glial cells)

Question 20

What does peroxisomes contain?

Answer 20

Contain enzymes involved in lipid and oxygen metabolism e.g. catalases, peroxidases.

Question 21

What is the main function of the nucleolus?

Answer 21

It is the site of ribose production

Question 22

What is mesenchymal cells

Answer 22

connective tissue

Question 23

Which major cytoskeletal component is associated with the desmosome cell-cell junctions in epithelial cells?

Answer 23

Cytokeratins

Question 24

what are the main types of cells and give examples?

Answer 24

Epithelial cells: cells forming continuous layers, these layers line surfaces and separate tissue compartments.

Mesenchymal cells: cells of the connective tissues, e.g. fibroblasts (many tissues), chondrocytes (cartilage), osteocytes (bone), muscle cells (skeletal, cardiac, smooth), the endothelial cells lining blood vessels.

Haematopoietic cells: blood cells and the cells of the bone marrow from which they are derived.

Neural cells: cells of the nervous system having two main types; neurones (carry electrical signals) and glial cells (support cells).

Question 25

what are the two types of endoplasmic reticulum?

Answer 25

rER: exists as flattened sheets which is studded on its outer surface with ribosomes.

sER: more tubular and lacks ribosomes. It has a major function in lipid metabolism.