The Cell Division Cycle and Apoptosis Flashcards

Comprehensive vocabulary flashcards covering the eukaryotic cell cycle, its regulation by cyclin-Cdk complexes, specific stages of mitosis, programmed cell death (apoptosis), and the molecular basis of cancer development.

Cell cycle

The process by which cells reproduce by duplicating their DNA/contents and dividing in two.

M phase

The phase of the cell cycle consisting of nuclear division ($mitosis$) and cytoplasmic division ($cytokinesis$).

S phase

The period of the eukaryotic cell cycle dedicated to DNA replication.

$G_1$ phase

The first gap phase where cells increase metabolic activity to increase size and duplicate cell compartments such as mitochondria, golgi, and ribosomes.

$G_2$ phase

The second gap phase in the cell cycle occurring between S phase and M phase.

Interphase

The period of the cell cycle where the cell increases in size and the DNA of the chromosomes is replicated ($G_1$, $S$, and $G_2$ phases).

Checkpoints

Stages in the cell cycle ($G_1$, $G_2$, and M phases) where internal and external conditions are monitored to ensure appropriate sequence and preparation.

$$G_0$$

A state where non-dividing cells, such as neurons and skeletal muscle, completely withdraw from the cell cycle.

Cyclin-dependent protein kinases (Cdk)

Protein kinases that initiate or regulate cell cycle processes using phosphorylation/dephosphorylation switches; they are activated only when bound to cyclins.

Cyclins

Proteins whose concentrations vary throughout the cell cycle to control the timing of Cdk activation.

Wee1

An inhibitory kinase that adds phosphates to M-Cdk, keeping it in an inactive state.

Cdc25

An activating phosphatase that removes inhibitory phosphates from M-Cdk to switch its activity on abruptly at the start of M phase.

p27

A protein that binds to an active cyclin-Cdk complex to render it inactive.

p53

A Cdk inhibitory protein involved in $G_1$ arrest due to DNA damage; it acts as a tumor-suppressor gene.

p21

A Cdk inhibitory protein that works with p53 to stop cells with damaged DNA from progressing through the cell cycle.

Mitogens

Factors that promote the production of the cyclins that stimulate cell division.

Rb

A protein involved in the inhibition of cell proliferation; its inactivation by mutation can lead to excessive cell division.

Cdc6

A protein that, along with ORC and DNA helicase, must be phosphorylated by S-cyclin/Cdk to initiate DNA replication; its degradation prevents re-initiation.

Prophase

The stage of mitosis where duplicated sister chromatids condense and the mitotic spindle assembles between two centrosomes.

Prometaphase

The stage of mitosis starting abruptly with the breakdown of the nuclear envelope, allowing chromosomes to attach to spindle microtubules via kinetochores.

Metaphase

The stage of mitosis where chromosomes are aligned at the equator of the spindle, midway between the spindle poles.

Anaphase

The stage of mitosis where sister chromatids synchronously separate and are pulled toward opposite spindle poles.

Telophase

The final stage of mitosis where chromosomes arrive at the poles and a new nuclear envelope reassembles around each set.

Cytokinesis

The division of the cytoplasm into two daughter cells by a contractile ring of actin and myosin filaments.

Apoptosis

The process of programmed cell death (PCD) characterized by blebbing, cell shrinkage, nuclear fragmentation, and chromatin condensation.

Necrosis

A form of traumatic cell death resulting from acute cellular injury, contrasting with the clean process of apoptosis.

Caspases

Enzymes that mediate the intracellular proteolytic cascade of apoptosis; they exist as initiator and executioner procaspases.

Bax or Bak

Activated molecules that trigger the release of cytochrome c from the mitochondrial intermembrane space during the intrinsic apoptosis pathway.

Apoptosome

A complex assembled from cytochrome c and adaptor proteins that recruits and activates procaspase-9.

Bcl2

A protein that suppresses apoptosis by blocking procaspase activation.

Akt

An activated kinase that promotes cell growth by inhibiting protein degradation and stimulating protein synthesis through Tor.

Metastasis

The process where cancer cells cross cellular barriers to enter the blood stream or lymph and colonize new sites.

Oncogenes

Genes for which gain-of-function mutations (dominant mutations), such as constitutively active Ras, promote cancer.

Tumor-suppressor genes

Genes for which loss-of-function mutations (recessive mutations), such as p53 or Rb, can promote cancer.

Telomerase

A ribonucleoprotein complex needed to replicate chromosome ends (telomeres) and help cells distinguish true ends from DNA breaks.

HeLa cell

The oldest and most commonly used immortal human cell line used in scientific research.

Warburg effect

The observation that cancer cells predominantly produce energy via a high rate of glycolysis followed by lactic acid fermentation in the cytosol.