cell differentiation 1

what are specialised cell types?

the fact that cells are different

What is cell differentiation?

• the process by which unspecialised cells become specific cell types
  -in the embryo (development)

• and continuing through life (tissue homeostasis)

how many different cell types is there?

• around 200 main types
• other sources say up to 600
• depends how you define a cell

how do cells differ?

• different macromolecules (lipids

What type of cells are found in the adrenal gland?

Chromaffin cells

What do chromaffin cells in the adrenal gland synthesize?

Epinephrine (adrenaline)

What happens when chromaffin cells are stimulated?

They rapidly release vesicles containing adrenaline.

What do chromaffin cells contain to convert tyrosine?

Proteins to convert tyrosine to epinephrine.

what are housekeeping and specialised proteins?

• the human genome codes for around 17

what is a housekeeping cell?

• proteins found in most cell types
• needed for essential cell function

what is a specialised cell?

• proteins specific to particular cell types
• for luxury functions such as epinephrine pathway enzymes

what are some examples of housekeeping cells?

• phosphofructokinase (glycolysis)
• RNA polymerase 2
• actin

how does cell differentiation in the embryo development occur?

• the egg divides to give many cells (initially unspecialised) which differentiate into their various cell types
• they must be highly organised across the embryo (cell signalling influences and coordinates cell differentiation)

what is cell fate determination?

the fate the cell obtains at the end of the process

what are cell lineages?

process that allows you to trace their origins

what are lineage restrictions?

the more specialised

what is developmental potency?

the first are pluripotent and differentiate to any

what is cell differentiation in early embryogenesis?

• fertilised egg forms blastocyst
• then forms tissues
• some blastocytes form trophectoderm to form placenta
• progressive process
• tissues formed are ectoderm

what are the intermediate states of differentiation?

progenitor cells or precursor cells

what does cell differentiation end in?

terminal differentiation which is usually irreversible

what is the first thing that a fertilised egg forms before it starts to differentiate?

a blastocyst - human embryo

what are the 2 things that a blastocyst can form?

• trophectoderm --> Placenta
• Germ layers

what are the 3 germ layers?

• ectoderm
• mesoderm
• endoderm

what are mesoderm cells?

they intermediates that don't exist in the final organ

how are mesoderm cells more differentiated?

• specific proteins
• characteristic cell behaviour - shape changes causing invagination (GASTRULATION)
• restricted future differentiation potential

what des invaginate mean?

the cells move into the embryo

what is gastrulation?

the formation of germ layers by invagination

how is haematopoiesis an example of cell differentiation?

• bone marrow consists of proliferating multipotent cells
• follows the same 4 previous rules as before
• multipotent haemopoietic stem cells can differentiate into any cell
• endoderm develops into several internal organs

what is the experiment carried out in the 1970s to see whether the nucleus of a differentiated cell can lead to development of a new organism?

• culture sample of skin cells
• take nucleus from the skin cells
• destroy the nucleus of the unfertilised egg by UV
• transfer the nucleus from the skin cell into the egg
• embryo should form
• proves that the genes are not lost

what is gene constancy?

when all cells in a multicellular organism have a full complement of genes

what was the important conclusion gathered from the 1970s experiment?

• cells are specialised because of differences in gene activity rather than gene content
• differential gene expression

how is expression of genes regulated?

• switched on or off
• different levels of activity in different cells
• much gene regulation in development is at the level of transcription
• transcription factors regulate steps
• in cells that don't require the proteins

what is a gene pattern?

the cell-type specific distribution of proteins and their mRNAs

what does control of gene expression in a cell determine?

• their protein content
• their morphology and function
• their behaviour during development