1. Apoptosis Aims: Must be able to define the term apoptosis.
Should be able to outline the stages of apoptosis.
Could be able to explain the purposes of apoptosis.

2. Basics Apoptosis – Programmed cell death.
A balance is needed between cell replication and cell death.
If the balance is not regulated then uncontrolled increase in cells = TUMOUR.
If a tumour continues to grow and invades healthy tissue = MALIGNANT = CANCER.
Too LITTLE apoptosis can lead to CANCER.
Too MUCH apoptosis can lead to DEGENERATIVE diseases e.g. Alzheimer’s.

3. In Detail Apoptosis and Necrosis are different.
Necrosis occurs if the cell is damaged causing damage to the membrane resulting in cells swelling then bursting.
Apoptosis is controlled as cells respond to signals from one of two signal pathways:
Mitochondrial pathway
Death receptor pathway

4. Mitochondrial Pathway
Signals from inside the cell.
If serious damage occurs inside the cell OR if the cell is infected with a virus.
Proteins on the surface of the mitochondria are activated.
Mitochondrial membrane breaks.
Sequence of events triggered including the cutting DNA with the use of enzymes (CASPASES).

5. Death Receptor Pathway
Signals from outside the cell.
Could be triggered because:
Cell not developed fully – E.g. embryonic brain cells
More cells than are needed – uses energy to keep cells alive e.g. immune cells
No longer useful – E.g. T and B cells after recovering from a disease. Cells between fingers and toes in embryonic development.

6. The Process
Cells receive message from outside using death receptors in cell membranes or from the breakdown of the mitochondrial membrane.
Many different caspases activated within the cell.
Message sent to phagocytes in the area.
Signalled cells begin to shrink and develop small bumps (BLEBS) on surface.
Caspases enter through nuclear pores, DNA and proteins in nucleus are degraded, mitochondria break down.
Other organelles preserved in membrane enclosed fragments.
Phagocytes engulf fragments. Secrete cytokines that inhibit inflammation.

7. Diagram Cell Shrinkage chromatin condensation
Apoptosis activated by intrinsic or extrinsic pathway
Diagram
Normal Cell
Nuclear collapse
Lysis of apoptotic bodies
Apoptotic body formation

8. Video
Apoptosis

9. Activity
Answer the questions from p213 in Biozone books.