BMS 324: Molecular Genetics and Cell Regulation

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Questions and Answers

What is the primary function of cell death in maintaining tissue size?

To destroy cells that are no longer needed (correct)

To maintain a balance between cell growth and division

To produce cells at the same rate as they are destroyed

To regulate the rate of cell migration

What is the characteristic feature of cells undergoing apoptosis?

They shrink and condense (correct)

They swell and burst

They migrate to other tissues

They undergo rapid cell division

What is the role of macrophages in apoptosis?

To produce inflammatory responses

To engulf and digest apoptotic cells (correct)

To stimulate cell growth and division

To regulate cell migration

What is the primary difference between apoptosis and necrosis?

Apoptosis is a programmed process, while necrosis is random Signup and view all the answers

During embryonic development, what is the role of apoptosis in shaping hands and feet?

To eliminate unwanted cells and sculpt structures Signup and view all the answers

What is the consequence of necrotic cell death?

Spilling of cellular contents, leading to inflammation Signup and view all the answers

What is the role of apoptosis as a quality-control process in development?

To eliminate abnormal, misplaced, or nonfunctional cells Signup and view all the answers

What is the likely cause of necrosis?

Energy depletion, leading to metabolic defects Signup and view all the answers

What is the result of apoptotic cells detaching from their neighbors?

They round up and detach from their neighbors Signup and view all the answers

What is the characteristic of the caspase cascade?

It is destructive and self-amplifying but also irreversible Signup and view all the answers

What is the function of the death domain in death receptors?

It is required for the receptors to activate the apoptotic program Signup and view all the answers

What is the role of Fas ligand in the extrinsic pathway of apoptosis?

It activates the Fas death receptors on the surface of target cells Signup and view all the answers

What is the main function of the DISC complex?

It forms a complex with initiator caspases to induce apoptosis Signup and view all the answers

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

It inhibits the activation of the extrinsic pathway Signup and view all the answers

What is the function of the intrinsic pathway of apoptosis?

It is activated by stresses such as DNA damage from inside the cell Signup and view all the answers

What is required for the intrinsic pathway of apoptosis to operate?

At least one of Bax and Bak proteins Signup and view all the answers

What is the result of the activation of the caspase cascade in the extrinsic pathway of apoptosis?

It induces apoptosis by cleaving and activating downstream executioner caspases Signup and view all the answers

What is the role of BH3-only proteins in the intrinsic pathway of apoptosis?

They mediate the inhibition of anti-apoptotic Bcl2 family proteins Signup and view all the answers

What is the function of anti-apoptotic Bcl2 family proteins?

They bind to and inhibit pro-apoptotic Bcl2 family proteins Signup and view all the answers

How do IAPs help control caspases?

They bind to and inhibit activated caspases Signup and view all the answers

What is the role of BIR domains in IAPs?

They enable IAPs to bind to and inhibit activated caspases Signup and view all the answers

Why do insect viruses encode IAP proteins?

To prevent a host cell that is infected by the virus from killing itself by apoptosis Signup and view all the answers

What happens to caspases when they are polyubiquitylated by IAPs?

They are marked for destruction by proteasomes Signup and view all the answers

What is the outcome of activating a caspase cascade?

Cell death Signup and view all the answers

What is the role of IAPs in regulating apoptosis?

To set an inhibitory threshold that caspases must overcome to trigger apoptosis Signup and view all the answers

What is the outcome of deleting the genes that encode IAPs in flies?

Apoptosis is blocked in flies Signup and view all the answers

What is the effect of inactivating one of the two genes that encode IAPs in flies?

All cells in the developing fly embryo undergo apoptosis Signup and view all the answers

What is the role of survival factors in regulating apoptosis?

They bind to cell-surface receptors and activate intracellular signaling pathways that suppress the apoptotic program Signup and view all the answers

Why do nerve cells that receive enough survival signals live?

Because they suppress the apoptotic program Signup and view all the answers

What is the role of Bcl2 family proteins in regulating apoptosis?

They regulate the apoptotic program Signup and view all the answers

How do some survival factors act in Drosophila?

By phosphorylating and inactivating anti-IAP proteins Signup and view all the answers

What is the outcome of deleting the genes that encode XIAP or Smac/Diablo and Omi in mice?

The mice develop normally Signup and view all the answers

What is the process by which phagocytic cells engulf and remove apoptotic cells?

Phagocytosis Signup and view all the answers

What is the main change that occurs on the surface of an apoptotic cell that recruits phagocytic cells?

Flip of phosphatidylserine from the inner to the outer leaflet Signup and view all the answers

What is the consequence of excessive apoptosis in certain diseases?

Tissue damage Signup and view all the answers

What is the function of the Fas death receptor and Fas ligand genes?

To stimulate apoptosis Signup and view all the answers

What is the role of the tumor suppressor protein p53 in cancer development?

To promote apoptosis Signup and view all the answers

What is the effect of p53 dysfunction on cancer cells' response to anticancer drugs?

Decreased sensitivity Signup and view all the answers

What is the consequence of decreased apoptosis in cancer development?

Cancer development Signup and view all the answers

What is the percentage of human cancers in which the p53 gene is mutated?

50% Signup and view all the answers

Study Notes

Cell Death and Apoptosis

The growth, development, and maintenance of multicellular organisms depend on the production of cells and mechanisms to destroy them.
Cell death is not a random process but occurs by a programmed sequence of molecular events.
Apoptosis (programmed cell death) is a process by which cells die and are engulfed by other cells, including macrophages.

Characteristics of Apoptosis

Cells dying by apoptosis undergo characteristic morphological changes: • Shrinkage and condensation • Cytoskeleton collapse • Nuclear envelope disassembly • Nuclear chromatin condensation and fragmentation • Cell surface breakdown into membrane-enclosed fragments (apoptotic bodies)

Contrasting Apoptosis with Necrosis

Apoptosis is distinct from necrosis, a process of cell death caused by acute insults (trauma, lack of blood supply) leading to: • Cell swelling and bursting • Inflammatory response • Energy depletion and metabolic defects • Loss of ionic gradients across the cell membrane

Functional Roles of Apoptosis

Apoptosis helps sculpt body shape during embryonic development
Apoptosis eliminates unwanted cells, including: • Abnormal, misplaced, nonfunctional, or potentially dangerous cells • Cells that form structures that are no longer needed (e.g., tadpole tail)
Apoptosis functions as a quality-control process during development

Regulation of Apoptosis

The caspase cascade is a self-amplifying and irreversible process
Two primary activation mechanisms in mammalian cells: • Extrinsic pathway (death receptors, Fas ligand, and Fas death receptor) • Intrinsic pathway (mitochondrial pathway, Bax, Bak, and anti-apoptotic Bcl2 family proteins)

Intrinsic Pathway of Apoptosis

Cells can activate apoptosis in response to stresses, such as DNA damage
At least one of the Bax and Bak proteins is required for the intrinsic pathway
Anti-apoptotic Bcl2 family proteins (Bcl2 and BclXL) inhibit apoptosis by binding to and inhibiting pro-apoptotic Bcl2 family proteins

Inhibitors of Apoptosis (IAPs) and Anti-IAPs

IAPs bind to and inhibit activated caspases
Some IAPs polyubiquitylate caspases, marking them for destruction by proteasomes
Balance between IAPs and anti-IAPs is crucial for controlling apoptosis

Extracellular Survival Factors and Apoptosis

Most animal cells require continuous signaling from other cells to avoid apoptosis
Survival factors bind to cell-surface receptors, activating intracellular signaling pathways that suppress apoptosis
Some survival factors stimulate the synthesis of anti-apoptotic Bcl2 family proteins or inhibit pro-apoptotic BH3-only proteins

Phagocytic Removal of Apoptotic Cells

Apoptotic cells and their fragments are efficiently eaten by phagocytic cells
Chemical changes on the surface of apoptotic cells, including the exposure of phosphatidylserine, recruit phagocytic cells

Apoptosis and Disease

Excessive or insufficient apoptosis can contribute to various diseases
Examples include autoimmune disease, cancer, and neurodegenerative disorders

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Description

This quiz covers the molecular events of cell death, a programmed sequence necessary for maintaining tissue size in multicellular organisms. Learn about the mechanisms that regulate cell death, an essential process for growth and development.

BMS 324: Molecular Genetics and Cell Regulation - Cell Death

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