Chap 11 Cellular Development, Apoptosis and Cancer

Question 1

What is an embryonic stem cell and adult stem cell?

Answer 1

Embryonic Stem (ES) Cells: isolated from the inner cell mass of blastocysts and can give rise to all of the cells of the human body, except the placenta and other supportive tissues in the womb

Adult stem cells: found in adult tissues; can only produce a limited number of cell types; act as a repair system for the body and maintain turn-over of cells

Question 2

What are the 2 properties of stem cells?

Answer 2

Self-renew - the ability to go through numerous cycles of cell division while maintaining the undifferentiated state

Potency - the capacity to differentiate into specialized cell types

Question 3

List and explain the different levels of potency of stem cells. (give examples)

Answer 3

1. Totipotent: Most versatile. Can give rise to any and all human cells, i.e. can give rise to an entire functional organism. E.g. Fertilized egg cell.
2. Pluripotent: Can give rise to nearly all cells except the placenta. E.g. Embryonic cells.
3. Multipotent: Can give rise to limited range of cells within a tissue type. E.g. multipotent blood (haematopoietic) stem cells can develop into red blood cells, white blood cells or platelets.
4. Oligopotent: Can only give rise to a few cells, e.g. lymphoid cells which can differentiate into T cells, B cells, etc or myeloid cells which can differentiate into erythrocytes (RBCs), neutrophils etc.
5. Unipotent: can produce only their own cell type, but have the property of self-renewal, e.g. skin cells

Question 4

What are the differences in sources of ASC and ESC?

Answer 4

. Embryonic Stem Cells (ESC)
From blastocysts left over from in-vitro fertilization in the laboratory – early stage embryos that would otherwise be discarded from fertility clinics
These embryos are created and exist entirely outside the body
From aborted fetuses

. Adult Stem Cells (ASC)
Are rare cells that can be found in only some developed organs or tissues
Stem cells have been found in the brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, liver and umbilical cord blood

Question 5

Explain the advantages and disadvantages of using ESC.

Answer 5

Offer significantly more promise in curing diseases and injuries- can develop into any kind of cell type or tissue
Can be replicated outside the body in a lab
Pluripotent
Stable. Can undergo many cell divisions
Easy to obtain, but blastocyst is destroyed

Question 6

Explain the advantages and disadvantages of using ASC.

Answer 6

Have been successfully used for some time now and still have great further therapeutic potential
Generally, can only be used to repair the types of organs or tissues from where they came, and not every organ has been shown to contain them (and they are often difficult to obtain)
Cannot grow outside the body and have to be immediately frozen or transplanted into the patient
Multipotent
Less stable. Capacity for self-renewal is limited
Difficult to isolate in adult tissue
Host rejection minimized

Question 7

What are 2 functions of stem cells?

Answer 7

Stem cells can replace diseased or damaged cells that cannot heal or renew themselves,thereby reversing disease and injury

We can test different substances (drugs and chemicals) on stem cells
in vitro (outside the body) drug testing

Question 8

What are some differences between necrosis and apoptosis?

Answer 8

In apoptosis the cell is fragmented into membrane (intact membrane) bound bodies while in necrosis the cell lyses.(membrane breakdown)

In apoptosis energy is required but in necrosis no energy is required.

In apoptosis DNA is fragmented, in necrosis there is random digestion of DNA

In apoptosis no inflammation is produced while in necrosis inflammation is produced.

Question 9

Explain the morphology of apoptotic cells vs necrotic cells

Answer 9

In apoptotic cells it begins with activation of cysteine proteases called caspases.The cell shrinks and develops “blebs” on the surface.DNA and protein in the nucleus degrade,cellular fragmentation occurs and apoptotic bodies are formed.Phagocytosis of apoptotic cell fragments then occurs.

In necrotic cells it begins with the swelling of cytoplasm and mitochondria and ends with total cell lysis.Blebs form and structure of the nucleus changes but there are no organelles in the blobs.The cell breaks and releases cell contents which cause inflammation.

Question 10

What are the 2 functions of apoptosis and give examples.

Answer 10

Enables the body to
Control cell numbers in the normal development and functioning of the organism
Examples:
Removal of tissues between toes and fingers during embryonic development.
Sloughing off of the inner lining of the uterus at the start of menstruation.

 Enables the body to:
Eliminate cells that threaten the organism’s survival
	Examples: 
Cells infected with viruses
Cells with damaged DNA
Cancer cells (misregulated cell cycle)

Question 11

What are the signals for apoptosis?

Answer 11

Damaged DNA

Misfolded Proteins

Increased levels of oxidants

Death activators (molecules that bind to specific receptors on the cell surface and signal the cell to begin the apoptosis program)

Question 12

What genes control apoptosis and how?

Answer 12

Apoptosis is regulated by genes which promote and prevent apoptosis.

Anti-apoptotic genes in the Bcl-2 family
Produce proteins that prevent apoptosis
E.g. Bcl-2, Bcl-xL
Expression of these genes maintains the integrity of the mitochrondrial membrane, preventing apoptosis from occurring

Pro-apoptotic genes in the Bcl-2 family
Produce proteins that cause apoptosis
E.g. Bax, Bak
Expression of these genes leads to destruction of the mitochondria membrane => release of cytochrome C => activation of caspases => Apoptosis