Cell biology and Cell cycle Flashcards
What is the basic unit of life?
The cell is the fundamental structural and functional unit of life. The human body has ~100 trillion cells, each containing a copy of the genome, except mature red blood cells and platelets.
What is the function of the plasma membrane?
Controls the movement of substances in and out of the cell.
Interacts with the extracellular environment.
Composed of a phospholipid bilayer with embedded proteins.
What is the function of mitochondria?
Known as the powerhouse of the cell, producing ATP through cellular respiration.
Contains mitochondrial DNA (mtDNA), inherited only from the mother.
Undergoes fusion (merging) and fission (splitting) based on the cell’s metabolic needs.
Failure to undergo fission can prevent cell division and ATP production.
What are the functions of the nucleus?
Contains DNA, the genetic material of the cell.
Surrounded by a nuclear envelope, a lipid bilayer continuous with the endoplasmic reticulum (ER).
Nuclear pores regulate molecular transport.
The nucleolus is responsible for ribosome biogenesis (making ribosomes).
What is the difference between the rough and smooth endoplasmic reticulum (ER)?
Rough ER (RER):
Studded with ribosomes, involved in protein synthesis.
Smooth ER (SER):
Involved in lipid synthesis, steroid hormone production, detoxification, and calcium storage.
What is the function of the Golgi apparatus?
Part of the endomembrane system.
Modifies, sorts, and packages proteins into vesicles for transport.
What is the role of lysosomes?
Acts as the waste disposal system of the cell.
Contains digestive enzymes to break down unwanted materials, damaged organelles, and invading pathogens.
What is the function of microtubules?
Maintain cell structure along with microfilaments and intermediate filaments.
Involved in movement (cilia and flagella).
Play a role in mitotic spindle formation during cell division.
What are the phases of the cell cycle?
Interphase (90% of the cell cycle):
G1 Phase: Cell growth and organelle duplication.
S Phase: DNA replication.
G2 Phase: DNA repair and preparation for mitosis.
Mitosis (M Phase): Cell division.
What are the key checkpoints in the cell cycle?
G1 Checkpoint:
Ensures the cell has enough nutrients and no DNA damage before entering S phase.
G2 Checkpoint:
Ensures DNA replication is complete and correct before mitosis.
Metaphase Checkpoint:
Ensures all chromosomes are properly attached to spindle fibers before anaphase.
What proteins regulate the cell cycle?
Cyclins and Cyclin-Dependent Kinases (CDKs) regulate cell cycle progression.
Retinoblastoma protein (Rb) controls the G1 checkpoint by binding and inhibiting the transcription factor E2F.
What are the stages of mitosis?
Prophase: Chromosomes condense, mitotic spindle forms.
Prometaphase: Nuclear envelope breaks down.
Metaphase: Chromosomes align along the metaphase plate.
Anaphase: Sister chromatids separate.
Telophase & Cytokinesis: Chromosomes decondense, the nuclear envelope reforms, and the cytoplasm divides.
What are the key differences between mitosis and meiosis?
Feature Mitosis Meiosis
Cell Type Somatic cells Gametes
Number of Divisions 1 2
Genetic Variation No Yes (recombination)
Daughter Cells 2 diploid (2n) 4 haploid (n)
What happens if DNA damage is detected at a checkpoint?
The cell pauses the cycle to repair DNA.
If damage is irreparable, apoptosis (programmed cell death) is triggered.
Mutations in checkpoint proteins (e.g., p53) can lead to cancer.
What role does telomerase play in the cell?
Telomerase extends telomeres, the protective ends of chromosomes.
Found in stem cells, germ cells, and cancer cells (allowing unlimited division).
Most somatic cells lack telomerase, leading to telomere shortening and aging.
What is the difference between apoptosis and necrosis?
Feature Apoptosis Necrosis
Cause Programmed cell death Severe injury or stress
Process Controlled, caspase-dependent Uncontrolled, causes inflammation
Effect No inflammation Triggers inflammation
How do chemotherapy drugs target the cell cycle?
Vincristine & Vinblastine: Inhibit microtubule polymerization, preventing mitotic spindle formation.
Paclitaxel & Docetaxel: Stabilize microtubules, causing metaphase arrest and chromosomal damage.
What is cell senescence and how does it contribute to aging?
Irreversible cell cycle arrest due to telomere shortening, DNA damage, or stress.
Senescent cells secrete inflammatory molecules (SASP), contributing to aging and diseases.
Can act as a tumor suppressor mechanism but may also promote chronic inflammation.
