Apoptosischeck

Definition of Apoptosis: A regulated process of cell death that is essential for development and maintaining tissue homeostasis.
Importance in Development:
- Vital for embryonic development (e.g., separation of fingers and toes).
- Necessary for the attachment of the fetus and placental growth.

Cellular Damage: Cells may trigger apoptosis to eliminate damaged cells (e.g., those that have suffered heat stress).
Immune Response: Cytotoxic T cells induce apoptosis in infected cells to prevent viral replication (e.g., during COVID recovery).
Mitochondrial Stress: Damage to mitochondria can activate apoptosis to prevent mutations and ensure cellular function.

Intrinsic vs. Extrinsic Pathways:
- Intrinsic Pathway: Triggered by internal signals, often related to mitochondrial damage.
- Extrinsic Pathway: Triggered by external signals, such as the activation of death receptors on the cell surface.
Both pathways induce cell death by activating proteases called capases, which then execute the death program by cleaving specific cellular substrates.
Comparison of Necrosis and Apoptosis:
- Necrosis: Passive and uncontrolled, characterized by cell membrane rupture and inflammation.
- Apoptosis: Active, regulated, and neat; leads to the formation of apoptotic bodies that can be cleared by phagocytes.

Cellular Changes During Apoptosis:
- Cell shrinks, condenses, and forms apoptotic bodies.
- Nuclear fragmentation and degradation of cellular components occur.
Role of Caspases: Proteins that execute apoptosis, activated via both intrinsic and extrinsic pathways.
- Activation cascades: Pro-caspase 9 → Caspase 9, which further activates pro-caspase 3 → Caspase 3.

Daily Cellular Maintenance: Approximately 50-70 billion cells undergo apoptosis daily in the human body.
Prevention of Cancer: Regular apoptosis prevents the accumulation of damaged and potentially cancerous cells.

Immortalized Cancer Cells: Cancer cells evade normal apoptotic signals, often activating telomerase, which allows for unlimited division.
Mutation of Genes:
- Proto-oncogenes: Mutations can convert them into oncogenes, promoting uncontrolled cell division.
- Tumor Suppressor Genes: Mutations in genes like p53 can lead to failure in regulating the cell cycle and preventing tumor progression.

Cell Differentiation: The process by which a cell changes into a more specialized cell type, influenced by gene expression.
- Potency: Categories of stem cells based on their ability to differentiate:
  - Totipotent: Can form all cell types, including placental cells.
  - Pluripotent: Can form all body cells, but not placental cells.
  - Multipotent: Can form a limited range of cells.
Examples of Stem Cells:
- Mesenchymal Stem Cells: Can differentiate into bone, cartilage, and fat.
- Hematopoietic Stem Cells: Can form all types of blood cells.

Dolly the Sheep: The first mammal cloned from an adult somatic cell, demonstrating possibilities and ethical concerns of cloning.
Therapeutic Cloning: Using embryonic stem cells for medical therapies, ethical issues arise from the destruction of embryos.
Induced Pluripotent Stem Cells (iPSCs): Conversion of somatic cells back to pluripotent stem cells, enabling potential for patient-specific therapies without ethical concerns of embryo destruction.
- Yamanaka Factors: Transcription factors that induce pluripotency in somatic cells.

Autologous vs. Allogeneic Transplantation:
- Autologous: Using a patient's own stem cells.
- Allogeneic: Using cells from a donor.
Therapeutic Potential: Regenerative medicine for repairing damaged tissues, treating degenerative diseases, and modeling diseases for drug testing.
Risks: Potential for tumor formation (teratomas) and complications in therapy.

Apoptosis*check*