Key Area 5
(d) Control of programmed cell death (Apoptosis)
Starter Task
The destruction of cells must be carefully controlled in a multicellular organism in a process called Programmed Cell Death or Apoptosis.
Death of defective cells occurs by apoptosis and is an important step in the prevention of tumour formation.
Click on the pink button to hear more about the association between apoptosis and cancer.
Although we often talk about apoptosis with respect to destroying cells with DNA damage, it is also a necessary and important step throughout growth and development.
Task 80
Rob walked into the class, munching a cheese piece. "Excuse moi Monsier Rob, what might you be doing?!"
"I'm just finishing ma lunch Miss. Be done in a minute".
"Aye, that'll be right". Dr McRobbie swiftly removed poor Rob and continued with her next task.
"While we wait for Rob to finish his sandwich, can you reflect on the videos you've seen and the information you've gained to describe the process of apoptosis. What steps are involved? You might want to do some additional research at this point to gain a deeper understanding of this process".
You should now do the same. Suggested answers are here.
The image above shows the formation of fingers through apoptotic processes during development. In both individuals, a condition called syndactyly is evident due to incomplete apoptosis.
In the image to the right, apoptotic processes have resulted in the formation of a mouse paw during early embryonic development.
Apoptosis for healthy development
Apoptosis is essential during development of multicellular organisms. This serves to remove cells no longer required as development progresses or during metamorphosis in particular organisms. Our hands are not webbed due to apoptotic processes during our development, leading to the formation of discrete digits! Cells may initiate apoptosis in the absence of growth factors.
Triggers of apoptosis
Apoptosis is triggered by cell death signals that can be:
External - e.g. the production of death signal molecules from lymphocytes. These signals bind to a surface receptor protein and trigger a protein cascade within the cytoplasm.
Internal - e.g. DNA damage. These signals cause activation of p53 tumour-suppressor protein.
Both types of death signal result in the activation of caspases - this is a type of protease molecule. Caspases cause the destruction of the cell by triggering the degradation of any protein molecule.
Task 81
"I'm gonae pure greet if this stuff turns up in the exam, Miss", cried Rachelle.
"What?! Of course you won't! Let's take a few minutes to summarise and consolidate then. Watch the video below ("What is apoptosis? University of Dundee) and then, using what you have learned so far, outline the similarities and differences between the intrinsic and extrinsic apoptosis pathways. Try and present this in a clear, concise way in your notes, e.g. a table or flowchart", suggested Dr McRobbie
"Is this some kind of mad magic flowchart that stops me forgetting, Miss?", mocked Rachelle.
"It could be".
Suggested answers are here.
Watch this video from the University of Dundee about Apoptosis. This is an excellent summary of the process to help consolidate your understanding. Perfectly suited to this course! Click the pink button below.
Plenary Task
Here's a kahoot quiz to play to test your knowledge of Topic 1, Key Area 5. You could play in class or have it set as a challenge at home.
Now go to SCHOLAR "5.4 Control of Programmed Cell death (apoptosis)" for consolidation.
Now you have reached the end of Key Area 5, also use SCHOLAR to complete:
5.5 Learning points
5.6 Extended response questions
5.7 End of topic test
Time to create your own content for our online class blog and become a published author! Write a piece that showcases your learning of Key Area 5 on Protein Control of Cell Division.
Your teacher might now issue you with Learner Check 12 to check your learning of Topic 1, Key Area 5.
You have now completed Topic 1!! Take a period of time to consolidate your learning and visit SCHOLAR to attempt "6. Cells and Proteins Test"
