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Questions and Answers
Programmed cell death, also known as ______, is crucial for both embryonic development and adult tissues.
Programmed cell death, also known as ______, is crucial for both embryonic development and adult tissues.
apoptosis
During development, the rapid proliferation of embryonic cells leads to the formation of more than ______ differentiated cell types in humans.
During development, the rapid proliferation of embryonic cells leads to the formation of more than ______ differentiated cell types in humans.
200
In multicellular organisms, cell death and cell proliferation are ______ throughout their life cycles.
In multicellular organisms, cell death and cell proliferation are ______ throughout their life cycles.
balanced
Stem cells have the capability to ______ and differentiate into a wide variety of cell types.
Stem cells have the capability to ______ and differentiate into a wide variety of cell types.
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Abnormalities in cell death are linked to a range of illnesses, including cancer and ______ disorders.
Abnormalities in cell death are linked to a range of illnesses, including cancer and ______ disorders.
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In most cases, necrotic cell death leads to an inflammatory response, often involving red 'activated' ______.
In most cases, necrotic cell death leads to an inflammatory response, often involving red 'activated' ______.
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Apoptosis, often referred to as cellular ______, is a programmed cell death process.
Apoptosis, often referred to as cellular ______, is a programmed cell death process.
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During apoptosis, phosphatidylserine becomes expressed on the cell ______, signaling phagocytes to remove the dying cell.
During apoptosis, phosphatidylserine becomes expressed on the cell ______, signaling phagocytes to remove the dying cell.
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Necrosis occurs when cells sustain a structural or chemical ______ that causes them to swell and undergo membrane lysis.
Necrosis occurs when cells sustain a structural or chemical ______ that causes them to swell and undergo membrane lysis.
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Virus-infected cells frequently undergo programmed cell death, thereby preventing the production of new virus ______.
Virus-infected cells frequently undergo programmed cell death, thereby preventing the production of new virus ______.
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Study Notes
Programmed Cell Death (Apoptosis)
- Apoptosis is an active cellular process leading to cell death.
- It's a normal, controlled part of growth and development.
- It's a way for the body to get rid of unwanted or abnormal cells.
- The word "apoptosis" comes from the Greek word for "falling off" (like leaves from a tree).
- It's different from accidental cell death (necrosis).
Animal Development and Cell Death
- Animal development starts with rapid proliferation of embryonic cells.
- These cells differentiate into specialized cell types making up tissues and organs.
- Humans have approximately 1014 cells and over 200 different cell types.
- Development involves a balance between cell proliferation and cell death.
Cell Renewal
- Cell death must be balanced by cell renewal in adult organisms.
- Most tissues contain stem cells that replace lost cells.
- Stem cells' ability to proliferate and differentiate is crucial for replacing damaged tissues.
Apoptosis vs Necrosis
- Apoptosis is a controlled process.
- Necrosis is a process caused by irreversible cell injury.
- Apoptotic cells are removed efficiently and don't trigger inflammation.
- Necrotic cells cause an inflammatory response and a release of contents into the extracellular space.
Programmed Cell Death Pathways
- Two main pathways: intrinsic and extrinsic.
- Intrinsic pathway: triggered by internal signals, DNA damage, or exposure to certain chemicals.
- Extrinsic pathway: triggered by signals from other cells.
Central Regulators of Apoptosis (Bcl-2 Family)
- Bcl-2 family members have different roles in apoptosis.
- Antiapoptotic proteins (e.g., Bcl-2, Bcl-xL) prevent apoptosis.
- Proapoptotic proteins (e.g., Bax, Bak) promote apoptosis.
Apoptosis in Different Scenarios
- Virus-infected cells undergo apoptosis to prevent virus spread.
- DNA damage can trigger apoptosis to eliminate potentially cancerous cells.
- Neuron development involves programmed cell death for proper connections.
- Cell survival is dependent on growth factors, neighboring cell contact, and extracellular matrix.
Apoptosis Mechanisms and Details
- In apoptosis, cells shrink and break into apoptotic bodies.
- Apoptotic bodies are phagocytosed (engulfed) by neighboring cells.
- Phosphatidylserine (PS) expression on the surface of apoptotic cells signals macrophages for removal.
Signs and Signals of Apoptosis
- Cytochrome C release from mitochondria is a key event in the intrinsic pathway.
- Caspases (a family of proteases) are central to the execution of apoptosis.
Intrinsic Pathway
- Initiated by a withdrawal of survival signals from the environment
- Includes factors like lymphokines (e.g., interleukin-2), nerve growth factor, and extracellular matrix.
Extrinsic Pathway
- Initiated by signals from other cells, such as cytotoxic T lymphocytes.
- Involves Fas ligand binding to Fas receptors on the target cell to initiate apoptotic cell death.
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Description
Explore the concept of programmed cell death (apoptosis) and its role in animal development. This quiz covers the importance of balanced cell proliferation and renewal, as well as the differentiation of embryonic cells. Test your understanding of how apoptosis contributes to growth and the maintenance of healthy tissues.
