Biology 11

What are Stem Cells?

Stem CellsBasically, stem cells are cells that are not

assigned a functional job in the body. (Undifferentiated cells)

We can use stem cells to repair or replace functional cells that are damaged or destroyed.

Some tissues are too complex to reproduce if the need arises, so in some cases, these tissues have stem cells for this purpose. (ie; Bone Marrow)

Types of Stem CellsThere are two types of stem cells:

adult and embryonic stem cells.

Adult stem cells turn into many different cells of the same basic kind.

Embryonic stem cells can turn into almost all of the body's cell types with a few exceptions.

PotencyStem Cells have three different types of potency, based on

the number and types of cells they can differentiate into. There are:

Totipotent These cells are those that have not begun the process of

differentiation. These cells have the capability to differentiate into any type of cell within the body.

Pluripotent Almost as potentent as the previous, , these cells have barely

started the differentiation process and are capable of developing into any other type of body cell.

Multipotent Multipotent stem cells are those cells that have begun the process

of differentiation into general cell type. They can develop into certain type of cells in a particular group or family of cells.

Stem cells are in all of our body and lives, but are far more potent in a fetus than in an adult body.

Some types of stem cells may be able to create all other cells in the body. Others have the potential to repair or replace damaged tissue or cells.

Embryonic Stem Cells are developed from a female egg after it is fertilized by sperm. The process takes 4-5 days.

Stem Cell ControversyThe controversy surrounding stem cell

research led to an intense debate about ethics.

Up until the recent years, the research method mainly focused on Embryonic Stem Cells, which involves taking tissue from an aborted embryo to get proper material to study. This is typically done just days after conception or between the 5th and 9th week.

Stem Cell ControversySince then, researchers have moved on to

more ethical study methods, such as Induced Pluripotent Stem Cells (iPS). iPS are artificially derived from a non-pluripotent cell, such as adult somatic cells.

This is probably an important advancement in stem cell research, since it allows researchers to obtain pluripotent stem cells, which are important in research, without the controversial use of embryos.

ProsStem cell research can potentially help treat a range

of medical problems. It could lead humanity closer to better treatment and possibly cure a number of diseases:Parkinson’s DiseaseAlzheimer’s DiseaseHeart Diseases, Stroke and Diabetes (Type 1)Birth DefectsSpinal Cord InjuriesReplace or Repair Damaged OrgansReduced Risk of Transplantation (You could possibly

get a copy of your own heart in a heart-transplantation in the future

Stem cells may play a major role in cancerBetter treatment of these diseases could also give

significant social benefits for individuals

Cons

"We should not mess with human life.“

"Humans should not be trying to play God“

Some argue that stem cell research in the far future can lead to knowledge on how to clone humans. It is hard to say whether this is true, but we have seen devastating consequences of other research-programs, even with good intentions, such as nuclear research.

Biology 11

Quiz Review

Review QuestionsWhat is Abiogenesis?Who was the first to propose abiogenesis?What is Biogenesis?Who stated that mice could formed from a

dirty shirt?Which scientist put an end to the belief of

Abiogenesis?Which Organelle contains the following:

A plastid usually found in plant cellsContain green chlorophyll where photosynthesis

takes place

Review QuestionsWhich Organelle is this?

What are the differences between plant and animal cells?

What are the three parts of the cell theory?

What is Abiogenesis?Abiogenesis is the belief that living

organisms can be created, or arise, from non living matter.

Aristotle

Who was the first to propose abiogenesis?

What is Biogenesis?Biogenesis is the principle that living

organisms develop from other living organisms and not from non living matter.

Jean van Helmont

Who stated that mice could formed from a dirty shirt?

Which scientist put an end to the belief of Abiogenesis?Louis Pasteur

Chloroplasts

Which Organelle contains the following: •A plastid usually found in plant cells•Contain green chlorophyll where photosynthesis takes place

Which organelle is this?

Mitochondria

What are the differences between plant and animal cells?

Plant Cells Animal Cells

Have chloroplasts and cell Walls

Do Not have chloroplasts and cell

walls

Do not usually have centrioles

Have centrioles

Have a large central vacuole

Do Not have a large central vacuole

What are the three parts of the cell theory?All living things are composed of one or

more cells.

The cell is the basic unit of structure and function of all living things.

All cells arise only from pre-existing cells.

Items to KnowThe Cell TheoryAbiogenesis vs. BiogenesisScientists and their contributionsCell Organelles

Read Pages 10-20 in Text Book for ReviewStudy notes and handouts!