Cell Division, Mitosis, Apoptosis and Stem Cells

Flashcards about cell division, mitosis, apoptosis and stem cells

What is cytokinesis?

Cytokinesis is the division of the cytoplasm of two cells to form two daughter cells

What is binary fission?

Binary fission is a form of asexual reproduction as it does not involve gametes

What does the G1 checkpoint check for?

Checks for sufficient proteins for cell replication, DNA intact and correct and conditions are favourable for Mitosis

What is checked in the S phase checkpoint?

DNA is replicated correctly during S phase

What are the stages of interphase?

G1, S and G2 phases

What happens during the G1 phase?

Increases cell volume, synthesizes requirements of S phase (mostly proteins), replicating organelles, regulatory checkpoint at end of the phase

What happens during the S phase?

DNA is replicated

What happens during the G2 phase?

Increased volume of cytosol, synthesizing proteins for mitosis, regular checkpoints during this phase

What is the G0 phase?

Phase utilised by non-replicating cells

How are chromosomes made?

DNA is wound around histones (proteins) to make nucleosomes, these complexes keep winding tighter to create chromosomes

What are the phases of mitosis?

Prophase, Metaphase, Anaphase and Telophase

What happens during prophase?

The nuclear envelope disintegrates, DNA condenses to form chromosomes, centrioles move to opposite ends of the cell and spindle fibres extend between them

What happens during metaphase?

Chromosomes line up at the equator, microtubules bind to sister chromatids and spindle fibres attach to the centromeres

What happens during anaphase?

Spindle fibres retract, sister chromatids are pulled apart and move to either side of the cell

What happens during telophase?

Chromosomes uncoil (return to DNA strands), nuclear envelope reforms and spindle fibres degenerate

What is Cytokinesis?

The process of dividing the contents of the cytoplasm including the organelles equally among the new daughter cells

What is apoptosis?

Programmed cell death

Why does apoptosis occur?

Remove old cells to maintain balance with new cells, unneeded cells and active immune cells after infection has been eliminated

How is apoptosis activated?

Internal (Intrinsic or Mitochondrial pathway) or external (Extrinsic or Death Receptor Pathway)

What are caspases?

Enzymes that break down structural and regulatory proteins in the cell or initiate other enzymes involved in apoptosis

What initiates intrinsic pathway (Mitochondrial pathway)?

DNA damage, organelle stress/ damage or removal of growth factor

What activates Extrinsic pathway?

Immune Cell binds onto the Death receptor via the FAS (death ligand)

What is the function of anti-apoptotic proteins?

Prevents programmed cell death these maintain integrity of the mitochondrial membrane

What is the function of Pro-apoptotic?

Activates apoptosis by blocking the anti-apoptotic protein BCL-2 from binding to the mitochondrial binding sites

What happens if errors occur in the checkpoints of the cell cycle?

If errors occur in the G1, G2 or M checkpoints of the cell cycle, the cell should repair itself or undergo apoptosis

What are tumors?

Uncontrolled cell growth producing abnormal amount of cells (cells clump together)

What is necrosis?

Accidental, passive tissue death due to environmental changes or damage

What are stem cells?

Stem cells are undifferentiated cells with the potential to differentiate into various specialized cell with a specific function

What are the level of stem cell potency?

Totipotent, Pluripotent, Multipotent

What are Totipotent stem cells?

Stem cells that can differentiate into any type of cell

What are Pluripotent stem cells?

Stem cells that can differentiate into multiple cells

What are Multipotent stem cells?

Stem cells that can differentiate into a limited number of specialised cell types belonging to a specific tissue or organ