Cell biology Flashcards
(8 cards)
Outline Cell Division and Differentiation
Cell Division is the process by which a parent cell divides into two or more daughter cells. It is essential for:
Growth and development
Tissue repair and regeneration
Reproduction (in unicellular organisms)
There are two main types:
Mitosis: Produces genetically identical diploid cells for growth and maintenance.
Meiosis: Produces genetically diverse haploid gametes (sperm and eggs).
Cell Differentiation is the process through which a less specialized cell becomes a more specialized cell type. It involves the activation of specific genes and is crucial for forming the various tissues and organs in multicellular organisms. Differentiation enables cells to perform specialized functions, such as neurons transmitting signals or red blood cells carrying oxygen.
Define Mitosis and Meiosis
Mitosis:
A type of cell division resulting in two identical daughter cells.
Occurs in somatic (body) cells.
Functions: Growth, repair, and asexual reproduction.
Phases: Prophase → Metaphase → Anaphase → Telophase → Cytokinesis.
Daughter cells are diploid (2n), genetically identical to the parent cell.
Meiosis:
A type of cell division that reduces the chromosome number by half, producing four non-identical haploid cells (gametes).
Occurs in germ cells (testes and ovaries).
Functions: Sexual reproduction and genetic diversity.
Two rounds of division: Meiosis I and Meiosis II.
Results in haploid (n) cells, each genetically unique due to crossing over and independent assortment.
Define Cell Injury and List the Causes
Cell Injury:
A pathological process where a cell’s ability to maintain homeostasis is compromised, leading to dysfunction or death.
Causes of Cell Injury:
Hypoxia (lack of oxygen) – e.g., due to ischemia.
Physical agents – trauma, temperature extremes, radiation.
Chemical agents and drugs – toxins, poisons, alcohol.
Infectious agents – bacteria, viruses, fungi, parasites.
Immunologic reactions – autoimmune diseases, allergies.
Genetic factors – mutations, chromosomal abnormalities.
Nutritional imbalances – deficiency or excess of nutrients.
Define and explain the following terms: atrophy, hypertrophy, metaplasia, dysplasia and neoplasia
Atrophy:
A decrease in the size and function of a cell, tissue, or organ due to decreased workload, loss of innervation, inadequate nutrition, or aging.
Example: Muscle atrophy due to prolonged immobilization.
Hypertrophy:
An increase in the size of cells, leading to an increase in the size of the organ.
Example: Left ventricular hypertrophy from hypertension.
Metaplasia:
A reversible change where one differentiated cell type is replaced by another, often in response to chronic irritation.
Example: Columnar epithelium of the bronchi changing to squamous epithelium in smokers.
Dysplasia:
Disordered growth and maturation of cells within a tissue, often considered a precancerous condition.
Example: Cervical dysplasia detected on a Pap smear.
Neoplasia:
The process of new, uncontrolled growth of cells not responsive to normal regulatory signals, forming a neoplasm (tumor).
Can be benign (non-cancerous) or malignant (cancerous).
Describe the different forms of cell death i.e. necrosis and apoptosis
Necrosis:
Unregulated cell death due to injury. It often involves swelling, rupture of cell membranes, and inflammation.
Types: Coagulative, liquefactive, caseous, fat, fibrinoid.
Example: Myocardial infarction (coagulative necrosis).
Apoptosis:
Programmed, regulated cell death with no inflammation. It is essential for development and maintaining tissue homeostasis.
Features: Cell shrinkage, chromatin condensation, apoptotic bodies.
Example: Removal of webbing between digits in embryonic development.
Describe How Cancer Cells Differ from Normal Cells.
Differences Between Cancer and Normal Cells:
Uncontrolled division and proliferation.
Lack of differentiation (anaplasia).
Evade apoptosis.
Can invade other tissues (invasiveness).
Capable of metastasis.
Sustain angiogenesis (blood vessel growth).
Genetic instability.
What are the difference between benign and malignant tumours?
Benign Tumours:
Slow growing
Well-differentiated
Encapsulated
Non-invasive
Do not metastasize
Rarely recur
Usually not life-threatening
Malignant Tumours:
Fast growing
Poorly differentiated (anaplastic)
Not encapsulated
Invasive
Can metastasize
Often recur
May be life-threatening
Describe the Role of Oncogenes and Tumour Suppressor Genes.
Oncogenes:
Mutated or overexpressed versions of normal genes (proto-oncogenes) that promote cell division and survival.
Act as “gas pedals” for cell proliferation.
Example: RAS, MYC, HER2.
Tumour Suppressor Genes:
Genes that normally inhibit cell division, repair DNA, or initiate apoptosis.
Loss or mutation leads to unregulated cell growth.
Act as “brakes” in the cell cycle.
Example: TP53 (p53), RB1, BRCA1/2.
Together, mutations in these genes disrupt the balance between cell division and cell death, facilitating tumorigenesis.
