Download Lesson 7 Apoptosis

Apoptosis
• Outline how apoptosis (programmed cell
death) can act as a mechanism to change
body plans.
Syndactyly
Why does this happen?
Apoptosis – what is it?
• Programmed cell death in multicellular
organisms.
• Different to necrosis because all the
contents of the cell are contained.
• Very quick process.
• Highly regulated occurs after about 50
mitotic divisions
1. Enzymes break down the What
cytoskeleton.
happens?
2. Cytoplasm becomes dense with
tightly packed organelles.
3. Cell membrane changes and
blebs (blister like structures)
form.
4. Chromatin condenses and
nuclear envelope breaks up.
5. Cell breaks into vesicles.
6. Vesicles removed by
phagocytosis – cellular debris
disposed of so doesn’t cause
damage.
How is it controlled?
• Controlled by cell signals from inside and
outside of the cell.
– Cytokines (from the immune system)
– Hormones
– Growth factors
– Nitric oxide (makes the IMM more permeable to
H+ so the proton gradient is lost)
Why is it useful?
• Metamorphosis – when tadpoles change into
frogs they lose their tail. The tail cells are
removed by apoptosis.
• Embryo development – to separate fingers
and toes, to remove ineffective T
lymphocytes.
Problems associated with apoptosis
• Not enough apoptosis = tumour formation.
– Hayflick (1962) found that normal body cells divide a
limited umber of times before undergoing apoptosis but
cancer cells are immortal.
• No apoptosis between digits during embryo
development leads to syndactyly – can be
fixed by surgery.
• Too much apoptosis = cell loss and
degeneration (neurodegenerative diseases
such as Parkinson's or Alzheimer's Diseases.)
– Rate of cells dying should balance rate of cells
produced by mitosis.
• http://www.sgul.ac.uk/depts/immunology/~dash/apopto
sis/disease.htm (good website for extra reading)
Plenary
In pairs, devise a concept map which explains
how apoptosis works and why it is important.
http://www.whfreeman.com/kuby/content/anm/cell-deathv06.swf
• Imagine you are a TV doctor responding to
an email enquiry from:
a) a woman with a new baby who has two
webbed toes and if you have time
b) a pregnant woman who has been advised to
eat a lot of vitamin A during pregnancy (this
will require some research).
• Give both women your advice explaining the
science behind what you say.