location: cytoplasm

morphology: double membrane with inner folds

function: oxidative phosphorylation

location: cytoplasm

morphology: membrane bound sacs

function: destroy carbohydrates, lipids and proteins via hydolyric enzymes

location:near nucleus, in cytoplasm

morphology: studded with ribosomes or not

function: lipid synthesis, detoxification, move proteins to Golgi

location: cytoplasm

morphology: stack of flattened membranes

function: modify and package proteins

location: cytoplasm or on ER

morphology: two subunits

function: assemble amino acids into proteins

There is a highly ordered asymmetric distribution of phospholipids and proteins throughout the inner and outer membranes.

The inner membrane contains: phosphatidylethanolamine and phosphatidylserine

the outer membrane contains: phosphatidylcholine and sphingomyelin

there are four stages to the cell cycle:

Mitosis (M)- physical process of cell division

G₁- after mitosis and before DNA replication

Synthesis (S)- DNA replication

G₂- after DNA replication and before Mitosis

Post-translation modification can alter the protein after it comes out of the ribosome.

(1) exisiting amino acids can be modified

(2) cleavage of initial polypeptide

(3) addition of nonprotein groups

(4) addition of transfer molecule

Checkpoints detect malfunctions, asses certain event completion and allow passage to the next part of the cycle.

-G₁ checkpoint- checks for DNA damage and prevents progression into S-phase if the integrity of the genome is compromised

-S phase checkpoint- monitors the accuracy of DNA replication

-G₂/M phase checkpoint- monitors the accuracy of DNA replication, checks for damages or unreplicated DNA and can block mitosis

-Metaphase checkpoint- functions to ensure that all chromosomes are properly aligned o the spindle apparatus prior to initiating chromosomal separation

P53 is not required for normal cell function, it serves as a molecular policeman. It is a transcription factor that can activate and inhibit gene expression, induced in response to DNA damage that puts the brakes on cell growth and division. It is the most commonly mutated gene in human tumors.

Rb is the protein product of the retinoblastoma susceptibility gene, predisposes individuals to retinoblastomas and other tumors when only one functional copy is present. In its active site, it has antiproliferative effects, inhibiting the cell cycle, it binds transcription factors required for genes needed for cell proliferation, rendering them nonfunctional. In its inactive state it releases the transcription factors which causes activation of gene required for cell cycle progresion. If a cell lacks Rb they have dysregulated cell proliferation which may lead to a malignancy.

Apoptosis is initiated by:

(1) depreivation of survival factors

(2) signals by "death" cytokines

(3) cell damaging stress

Inhibited by:

(1) growth-promoting cytokines

(2) interaction with appropriate extracellular environmental stimuli

Increased apoptosis = myelodysplastic syndromes (ineffective myeloid production), AIDS, Alzheimer's, Parkinson's, MI, stroke, liver disease

  Inhibited apoptosis = acute leukemias, cancer, autoimmune diseases, viral infections

Necrotic cells exhibit a swollen morphology, the organelles accumulate water and lyse because the plasma membrane lost its ability to regulate cation fluxes due to damage or an Inflammatory response. Apoptosis is characterized by cellular shrinking, parts of the cell are phagocytosed