Cell biology of tissues

Question 1

Recall the types of human cells, and recall examples

and

Recall the originating cell type in neoplasms, including carcinoma, sarcoma, lymphoma, leukaemia, neuroblastoma and glioma

Answer 1

Cell types;

1. Epithelial–> Continuous layers that line surfaces and separate tissue compartments.–> as a tumor it is a carcinoma
2. Mesenchymal–>Connective tissue (fibroblasts/chondrocytes/ostercytes/muscle cells/endothelial cells lining blood vessels)–> as a tumor it is a sarcoma
3. Haematopoietic–> Blood cells and cells of the bone marrow–> as a tumor it is Leukaemia (for bone marrow) or Lymphoma (for lymphocytes)
4. Neural–> Nervous system cells (neurons and glial) –> as a tumor it is Neuroblastoma (neurone precursors) or Glioma (glial cells)

Question 2

Recognise the cell organelles, explain their functions

Answer 2

Nucleus;

1. Outer and inner membrane
2. Nucleoplasm
3. Nucleolus; site of production for the ribosomal subunits
4. Chromatin
5. Nuclear envelope (with pores)

Ribosomes;

1. free; synthesize cytoplasmic proteins
2. bound; synthesize packaged proteins

rough Endoplasmatic reticulumn; flattened sheets and on its surface there are ribosomes engaged in protein synthesis

smooth Endoplasmatic reticulumn; more tubular, there are no attached ribosomes and it is used in metabolixm and detoxification

Golgi Apparatus; used in modifying, packaging and sorting macromolecules

1. cis face; towards the endoplasmatic reticulumn
2. trans face; towards the cell periphery

( golgi, ER, nuclear envelope and cytoplasm are examples of dynamic membranes because they exchange membrane vesicles)

Mitochondria;

1. aerobic respiration
2. bacterial evolution

Peroxisomes;

1. encoled by a single membrane and contain enzymes ( might be in high concentrations and therefore crystilize)

Question 3

Summarise the components of the cytoskeleton

Answer 3

1. Microtubules
   
   • 20nm diameter–> polymers of a and b tubulin heterodimers
   • Responsible for ell shape and acts as “tracks” for movement of organelles
   • major component of cilia and flagella
2. Intermediate filaments
   
   • 10-15nm
   • group of intermedious proteins forming a rope-like structure
   • Provide mechanical strength–> cell to cell adhesions (found in nuclear lamins–> involved in stabilizing the envelope)
   • In epithelial – cytokeratin
   • In mesenchymal - vimentin
   • In neurons – neurofilament protein
   • In muscle – desmin
3. Microfilaments
   
   • They are polymers of actin associate with adhesion belts
   • involved in cell movement and shape

Accessory proteins which associate with actin (myosin)

1. Monomer – globular actin
2. Microfilaments – filamentous actin
3. Helical structure

Question 4

Define the term “tissue” and summarise the main components of tissues

Answer 4

Tissue; group or groups of cells whose type, organization and architecture are integral to its function

made up of;

1. cells
2. extracellular matrix
3. fluid

Question 5

Summarise the major types of cell-cell junction in an epithelium.

Answer 5

• Zonula Occludens
  
  1. Tight junctions
  2. Allow polarity to be established by preventing ion diffusion
  3. Many junctions where membranes form close contacts
  4. Block paracellular pathway
• Zonula Adherens
  
  1. Adhesion belt
  2. Cadherins – bind to similar molecules on adjacent cells
  3. Actin cytoskeleton closely associated
• Macula Adherens
  
  1. Cluster of pores formed by membrane proteins
  2. Passage of ions
  3. Relatively small molecules and ions can pass
  4. 1.5nm diameter
• Macula communicans
  
  1. ​​Gap Junction
  2. Permits the exchange of ions and mienrals between adjacent cells