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Starter

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Cellular Differentiation

Higher Biology Unit 1

Key Area 4 – Cellular Differentiation

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Cellular Differentiation

Learning intentions - to learn about cellular differentiation.

Success Criteria-

  • I can explain how a cell becomes differentiated.
  • I can name the cells that specialised cells differentiate from in plants and animals.
  • I can define pluripotent and multipotent.
  • I can give examples of therapeutic and research uses of stem cells.
  • I can describe some of the ethical issues associated with stem cells.

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Specialised Cells recap

How are the following cells specialised to perform particular functions?

1. Red blood cells

2. Root hair cell

3. Neurone

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Cellular Differentiation

The process by which cells develop more specialised functions.

This is achieved by expressing the genes to produce proteins for that type of cell.

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Selective Gene Expression

Every cell in your body has all the genes necessary for constructing the whole organism.

Genes can be ‘switched on or switched off’

This saves energy in only producing the proteins needed by the cell

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e.g. insulin produced in pancreas cells only, not in brain or heart cells.

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Meristems

In multicellular plants growth is restricted to regions called meristems.

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These are groups of unspecialised plant cells capable of dividing repeatedly throughout the life of the plant (by Mitosis).

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Some of the cells formed remain meristematic and go on to produce new cells while others become differentiated.

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Types of Meristem

Apical meristem at the tip of the root and the shoot – adding length to the plant.

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Lateral meristems allow the stems to thicken.

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Differentiation in Animals

Each human begins life as a fertilised egg (zygote) and divides to become approximately 37.2 trillion cells (37 200 000 000 000)

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With almost 200 different cell types.

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Cellular Differentiation

Learning intentions - to learn about cellular differentiation.

Success Criteria-

  • I can explain how a cell becomes differentiated.
  • I can name the cells that specialised cells differentiate from in plants and animals.
  • I can define pluripotent and multipotent.
  • I can give examples of therapeutic and research uses of stem cells.
  • I can describe some of the ethical issues associated with stem cells.

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Stem Cells

What can you remember?

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Stem Cells

  • Stem cells are cells that can make more of themselves (self-renew) or can become almost any specialised cell.

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  • Stem cells are involved in growth and repair.

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Genetic Control and Specialisation

  • Cells differ because genes can be ‘switched on and off’

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  • When a new cell is produced by mitosis it is non-specialised or undifferentiated.

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  • Specialisation depends on which genes are ‘switched on and off’. The cell only expresses certain genes to produce protein characteristic for that cell.

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Embryonic Stem Cells

Embryonic Stem cells are obtained from in-vitro fertilisation embryos that were not used and are cultured in the lab in order to grow more cells. They cannot self-renew in vivo but can in the right lab conditions.

Embryonic Stem Cells become differentiated to all possible types of specialised cells.

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This is known as PLURIPOTENT

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Tissue (adult) stem cells

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  • Can only form a limited range of cell types. They can differentiate into all of the types of cells found in a particular tissue type.

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  • Main function is to maintain growth and repair of the body.

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  • Are more limited than embryonic stem cells and so are known as MULTIPOTENT.

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Adult/tissue stem cells

Adult stem cells are found at several locations around the body.

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Hematopoietic (blood) stem cells found in the bone marrow give rise to different blood cells.

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Mesenchymal stem cells give rise to bone, cartilage, adipose tissue.

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Starter - on your whiteboards

  • Name 2 types of stem cells
  • Which type of stem cell can be described as multipotent?
  • Which type of stem cell can be described as pluripotent?
  • What is the process by which stem cells divide to make copies of themselves?

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Create a leaflet

Your task……to inform the general public about stem cells and what they can be used for.

  • What are stem cells?
  • How are they collected?
  • What can they be used for?
  • How would this help humans?
  • What are the problems with stem cells?

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Extension

  • Research three therapeutic uses of stem cells.
  • Extension Exam Question:

Write notes on the ethical issues of stem cell use (4 marks)

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Write notes on the ethical issues in stem cell use (4 marks)

  • Use of Embryo Stem Cells
  • Destroys embryo which many believe is unethical
  • Use of induced pluripotent stem cells
  • Not true stem cells, so fewer people have ethical issues
  • Use of nuclear transplant techniques
  • Some believe its unethical to mix human cells and those from another species
  • Others support this as an alternative to embryonic stem cells
  • Some believe this will allow scientists to develop new treatment for diseases/medicine

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Stem Cells in Research

  • Drug discovery – can use stem cells to test new drugs to improve their function, look at disease progression or just to see how the drugs could affect different organs.

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  • To study normal human development – how do they form tissues and organs? How does age impact their function? Having a better understanding of the way the body forms and works helps with better and quicker diagnosis of disease.

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  • Cancer research – cancer cells and stem cells are similar in that they both self-renew. Understanding more about stem cells could help us better understand why cancers develop.

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Therapeutic Uses

Where stem cells are used to repair damaged organs or tissues.

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  • Bone marrow transplants to treat leukemia
  • Repair burned skin
  • Repair damaged cornea.

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Cellular Differentiation

Learning intentions - to learn about cellular differentiation.

Success Criteria-

  • I can explain how a cell becomes differentiated.
  • I can name the cells that specialised cells differentiate from in plants and animals.
  • I can define pluripotent and multipotent.
  • I can give examples of therapeutic and research uses of stem cells.
  • I can describe some of the ethical issues associated with stem cells.

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Ethics

Ethics refers to the moral values and rules that ought to govern human conduct.

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The use of stem cells raises several ethical issues.

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Ethics

https://www.youtube.com/watch?v=nGg31Foz35Y

https://www.youtube.com/watch?v=KspO8HpeYJc

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Traverse - Oracy

The advances made in medicine due to the use of embryonic stem cells outweighs the cost of destroying the embryos to obtain the cells.

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Ethics Debate

The class will be split into 2 groups

  • One group will be arguing FOR stem cell research, the other AGAINST
  • In your groups, you will each have a role depending on which card you are given

In your groups, you will need to gather:

  • An introductory statement e.g. we think stem cell research is wrong.
  • A set of statements ready to argue against the other group - try to anticipate what they might say and have a good statement to argue against them
  • Make sure your statement are backed by evidence - don’t just make things up!
  • A short summary of your group’s views

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Extended response

Write notes on stem cells under the following headings:

i) differentiation of stem cells; 5

ii) therapeutic and research uses of stem cells. 3

8

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  • Stem cells are unspecialised/undifferentiated cells (in animals)
  • Stem cells divide to make more stem cells
  • They differentiate into specialised cells
  • Embryonic stem cells are pluripotent
  • Adult stem cells are multipotent
  • Differentiated cells can only express certain genes
  • To produce proteins characteristic of that type of cell.

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  • Stem cells in research are used to study disease development/test new drugs/study human development.
  • Thearputic use of stem cells includes repair of damaged organs/tissues OR example eg skin graft, corneal repair, bone marrow transplantation.
  • Example of ethical consideration, using embryonic stem cells involves destruction of embryos.

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Bingo

  • Prokaryote
  • Ligase
  • Eukaryote
  • DNA Polymerase
  • Pluripotent
  • Taq polymerase
  • Intron
  • Transcription
  • Multipotent
  • Exon
  • Chromatin
  • Ligase
  • PCR
  • Translation
  • Embryonic
  • Adult
  • Meristem
  • 92-98℃
  • 50-65℃
  • 70-80℃
  • tRNA
  • mRNA
  • rRNA
  • Nucleotide
  • Therapeutic
  • Research
  • ethics

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Use white boards, read out statements to class and they decide True or False.

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Talking point

If we allow spare IVF embryos to be used to make stem cells, should we also create IVF embryos solely for research, or is this treating human embryos as a means to an end?

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Cellular Differentiation

Learning intentions - to learn about cellular differentiation.

Success Criteria-

  • I can explain how a cell becomes differentiated.
  • I can name the cells that specialised cells differentiate from in plants and animals.
  • I can define pluripotent and multipotent.
  • I can give examples of therapeutic and research uses of stem cells.
  • I can describe some of the ethical issues associated with stem cells.

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You should now know…

Glossary: differentiation, pluripotent, multipotent, meristem

    • Definition of ‘meristem’ and ‘stem cell’
    • Describe the process of differentiation into specialised cells from embryonic and tissue (adult) in animals in terms of gene expression.
    • Describe 2 examples of present or future therapeutic uses of stem cells
    • Describe 2 other areas in which stem cell research can be useful
    • Describe the main ethical issues relating to the different types of stem cell use