Cell Death: Necrosis and Apoptosis

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Questions and Answers

What is the result of the release of cytochrome C from the mitochondrial membrane?

Formation of a pro-apoptotic protein complex

Activation of anti-apoptotic Bcl-2 proteins

Formation of the apoptosome and activation of the caspase cascade (correct)

Blockage of pro-apoptotic Bcl-2 proteins

What is the function of pro-apoptotic Bcl-2 proteins?

To activate the caspase cascade

To promote the release of cytochrome C from the mitochondrial membrane (correct)

To block the action of anti-apoptotic Bcl-2 proteins

To inhibit the formation of pores in the outer mitochondrial membrane

What is the role of the mitochondria in apoptosis?

To inhibit the formation of the apoptosome

To activate the caspase cascade

To prevent cell death

To regulate the formation of pores in the outer mitochondrial membrane (correct)

What is the result of the balance between pro-apoptotic and anti-apoptotic Bcl-2 proteins?

Regulation of pore formation in the outer mitochondrial membrane Signup and view all the answers

What is the molecular weight of the complete apoptosome?

700 KDa Signup and view all the answers

What is the role of Apaf-1 in the apoptotic pathway?

To form a multi-protein complex with cytochrome C Signup and view all the answers

What is the result of the activation of the caspase cascade?

Destruction of the cell Signup and view all the answers

What is the function of anti-apoptotic Bcl-2 proteins?

To block the action of pro-apoptotic Bcl-2 proteins Signup and view all the answers

What is essential for normal health and development?

Apoptosis Signup and view all the answers

What is the primary function of apoptosis in the immune system?

To destroy self-reacting immune cells and virus infected cells Signup and view all the answers

What is the estimated number of cells that die through apoptosis per day in an average adult?

Between 50 and 70 billion Signup and view all the answers

Which of the following is NOT a function of apoptosis?

Stimulating inflammatory response Signup and view all the answers

What is the role of cytochrome C in apoptosis?

It is an essential component of the electron transport chain Signup and view all the answers

What is the main difference between necrosis and apoptosis?

Necrosis is a disease-associated process, while apoptosis is an essential part of normal health and development Signup and view all the answers

What is the role of initiator caspases in apoptosis?

They activate other caspases Signup and view all the answers

How often is the entire body weight of cells replaced through apoptosis?

Every 1 year Signup and view all the answers

What is the function of effector caspases in apoptosis?

They break down cellular components such as the cytoskeleton and DNA Signup and view all the answers

How do cancer cells often become resistant to apoptosis?

By having defects in the apoptosis pathways Signup and view all the answers

What is the primary function of apoptosis in embryo development?

Sculpting tissue Signup and view all the answers

What is the role of effector caspases in the apoptotic cascade?

Breaking down cellular components Signup and view all the answers

What is the consequence of defects in the apoptosis pathways in cancer cells?

Resistance to apoptosis Signup and view all the answers

What is the estimated daily rate of cell death through apoptosis in an average adult?

Between 5 and 7 billion cells Signup and view all the answers

What is the function of the intrinsic pathway in apoptosis?

Releasing cytochrome C from the mitochondria Signup and view all the answers

What is the role of cytochrome C in the apoptotic cascade?

Participating in the electron transport chain Signup and view all the answers

What is the primary function of initiator caspases in the apoptotic cascade?

Activating other caspases Signup and view all the answers

What is the role of apoptosis in homeostasis?

Counter-balancing cell division and removing old or damaged cells Signup and view all the answers

How often is the body's cell population completely replaced through apoptosis?

Every year Signup and view all the answers

What is the primary location of anti-apoptotic Bcl-2 proteins?

Mitochondrial outer membrane Signup and view all the answers

Which of the following is a characteristic of the complete apoptosome?

It consists of 7 molecules of each protein with a combined molecular weight of 700 KDa Signup and view all the answers

What is the direct consequence of the formation of large pores in the outer mitochondrial membrane?

Release of cytochrome C into the cytosol Signup and view all the answers

What is the role of pro-caspase 9 in the apoptotic pathway?

It is a type of initiator caspase Signup and view all the answers

What is the ultimate consequence of the activation of the caspase cascade?

The cell undergoes programmed cell death Signup and view all the answers

What is the site of action of Bcl-2 proteins in the regulation of apoptosis?

Mitochondrial outer membrane Signup and view all the answers

What is the requirement for the formation of the apoptosome?

Cytochrome C, Apaf-1, pro-caspase 9, and ATP Signup and view all the answers

What is the direct consequence of the release of cytochrome C from the inner mitochondrial membrane?

Formation of the apoptosome and activation of the caspase cascade Signup and view all the answers

What is the primary role of the mitochondria in the regulation of apoptosis?

To act as a checkpoint in the process of apoptosis Signup and view all the answers

Study Notes

Apoptosis

Apoptosis is a type of programmed cell death essential for normal health and development.
It is an essential part of various biological processes, including:
- Embryo development: sculpting tissue
- Immune system: destroying self-reacting immune cells and virus-infected cells
- Homeostasis: counter-balance to cell division and removal of old or damaged cells
- Cancer: radiotherapy and most chemotherapy drugs work by inducing apoptosis

Cellular Death

There are two main ways cells can die:
- Necrosis: associated with disease
- Apoptosis: an essential part of normal health and development

Apoptosis Process

The mitochondria play a central role in the regulation of apoptosis.
Bcl-2 proteins act on the mitochondria to regulate the formation of pores in the outer mitochondrial membrane.
The result depends on the balance between pro-apoptotic and anti-apoptotic Bcl-2 proteins.
Release of cytochrome C from the inner mitochondrial membrane to the cytosol leads to the formation of the apoptosome and activation of the caspase cascade.
The caspases are responsible for the destruction of the cell.

Apoptosome Formation

Pores form in the outer mitochondrial membrane, allowing the release of cytochrome C into the cytosol.
Cytochrome C binds to other cytosolic proteins to form a multi-protein complex called the apoptosome.
The formation of the apoptosome requires:
- Cytochrome C
- Apaf-1
- Pro-caspase 9
- ATP
There are 7 molecules of each protein in the complete apoptosome with a combined molecular weight of 700 KDa.

Caspases

Caspases are a family of 12 proteases that exist as inactive proenzymes in cells.
Following activation by cleavage, they can activate other caspases in a cascade.
There are two types of apoptotic caspases:
- Initiator caspases: activate other caspases
- Effector caspases: break down cellular components such as the cytoskeleton and DNA

Pathways for Triggering Apoptosis

There are two main pathways for triggering apoptosis:
- Receptors mediated
- Mitochondria mediated (intrinsic pathway)
The intrinsic pathway can be activated via the mitochondria by a variety of cell stresses, such as:
- Free radical damage
- DNA damage
- Viral infection
- Loss of survival signals

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Description

Learn about the two main types of cell death: necrosis and apoptosis. Understand the role of apoptosis in normal health and development, and how it differs from necrosis associated with disease.