Lecture 1.2a - Cell injury and cell death 2

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Questions and Answers

What is the primary trigger for the intrinsic pathway of apoptosis?

Inflammation and oxidative stress

Most commonly irreparable DNA damage (correct)

Cells that are a danger, such as tumour cells or virus-infected cells

Hormonal imbalance

What is the primary characteristic of apoptosis?

It results in the destruction of multiple cells

It is a passive process that occurs due to cellular damage

It is an energy-dependent active process (correct)

Lysosomal enzymes are involved in the process

What happens to the nuclear DNA during apoptosis?

It is protected from degradation

It is translocated to the cytoplasm

It is degraded by enzymes (correct)

It is replicated to increase the DNA content

What is the role of the p53 protein in the intrinsic pathway of apoptosis?

It is inactivated, resulting in the outer mitochondrial membrane becoming leaky Signup and view all the answers

What is the final step in the clearance of apoptotic bodies?

Degradation takes place within the phagocytes Signup and view all the answers

What is the primary function of apoptosis during embryogenesis?

To remove excess tissue and sculpt organs Signup and view all the answers

Which of the following is an example of physiological apoptosis?

Hormone-controlled involution of breast gland epithelium after lactation Signup and view all the answers

What is the difference between oncosis/necrosis and apoptosis?

Oncois/necrosis is characterized by cellular swelling, while apoptosis is characterized by cellular shrinkage Signup and view all the answers

What is the role of caspases in apoptosis?

To control and mediate apoptosis by causing cleavage of DNA and proteins Signup and view all the answers

What is the role of TNFalpha in the extrinsic pathway of apoptosis?

It is a cytokine secreted by T killer cells that binds to death receptors Signup and view all the answers

What is the result of cytochrome C release from the mitochondria in the intrinsic pathway of apoptosis?

Activation of caspases Signup and view all the answers

What is the characteristic of apoptosis in terms of the number of cells affected?

It affects a single cell or a small group of cells Signup and view all the answers

What is the initiating signal for the intrinsic pathway of apoptosis?

A signal from within the cell Signup and view all the answers

What is the characteristic of the membrane during apoptosis?

It is maintained, preserving cellular integrity Signup and view all the answers

Study Notes

Apoptosis: Programmed Cell Death

Apoptosis is a programmed cell death, an active process that requires energy
Characterized by shrinkage, induced by a regulated intracellular program
Enzymes are activated to degrade nuclear DNA and proteins, maintaining membrane integrity
Affects a single cell or group of cells, with a characteristic microscopic appearance
Lysosomal enzymes are not involved, and the process is quick, taking only a few hours

Physiological Apoptosis

Occurs to maintain a steady state
During hormone-controlled involution, such as in breast gland epithelium after lactation
During embryogenesis, for removal of tissue and organ sculpting

Pathological Apoptosis

Occurs in cytotoxic T cell killing of virus-infected cells
Removal of neoplastic cells
In response to cell damage, particularly with damaged DNA
In graft vs host disease

Initiation and Execution of Apoptosis

Triggered by two mechanisms: intrinsic and extrinsic pathways
Both pathways result in activation of caspases, enzymes that control and mediate apoptosis
Caspases cause cleavage of DNA and proteins of the cytoskeleton

Intrinsic Pathway

Initiated by signals from within the cell
Triggers include irreparable DNA damage and withdrawal of growth factors or hormones
p53 protein is inactivated, leading to leaky outer mitochondrial membrane
Cytochrome C is released, causing activation of caspases

Extrinsic Pathway

Initiated by extracellular signals
Triggers include cells that are a danger, such as tumor cells or virus-infected cells
One of the signals is TNFalpha, secreted by T killer cells
TNFalpha binds to cell membrane receptor, resulting in activation of caspases

Clearance of Apoptotic Bodies

Both intrinsic and extrinsic pathways cause cells to shrink and break up into apoptotic bodies
Apoptotic bodies express proteins on their surface, allowing recognition by phagocytes or neighboring cells
Finally, degradation takes place within the phagocytes

Apoptotic vs Necrotic Cells

Apoptotic cells: programmed cell death, shrinkage, and maintenance of membrane integrity
Necrotic cells: unprogrammed cell death, cell swelling, and loss of membrane integrity

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Description

Learn about programmed cell death, a regulated intracellular process involving enzyme activation, DNA degradation, and membrane integrity maintenance. Understand the characteristics of apoptosis and its effects on single cells or groups of cells.