Foundations Flashcards
How is the cell cycles regulated?
- CDKs
- Cyclins
- Cyclin-CDK complexes
- Tumor suppressors
What is the shortest phase of the cell cycle
mitosis
What are CDKs
they are constitutive and inactive
What are cyclins
regulatory proteins that control cell cycle. They are phase specific and activate CDKs
What is the importance of cyclin-CDK complexes
must be activated and and inactivated for cell cycle to progress. Inactivated by p21, p27, and p57.
What controls p21 activation
p53
What tumor suppressors inhibit G1 to S progression
p53 and hypophosphorylated Rb
What are the different type of cells
- permanent
- stable
- labile
What are examples of permanent cell
Neurons, skeletal/cardiac muscle, RBCs. - remain in Go, regenerate from stem cells
What are examples of stable cells
Hepatocytes, lymphocytes. - enter G1 from Go when stimulated
What are examples of labile cells
bone marrow, gut epithelium, skin, hair follicles, germ cells. - NEVER go to Go, divide rapidly w/ a short G1
What is the role of the Rough ER
- synthesis of secretory proteins and N-linked oligosaccharide addition to proteins
Where in the body are RER found in excess
mucus-secreting goblet cells of small intestine and Ab secreting plasma cells
What are Nissl bodies
RER in neurons. They make enzymes and peptide neurotransmitters
What is the role of free ribosomes
site of synthesis of cytosolic and organellar proteins
What is the role of the SER
steroid synthesis and detoxification of drugs and proteins
What cells are rich in SER
liver hepatocytes and steroid hormone producing cells of the adrenal cortex
How do proteins get into the nucleus
need to have a nuclear localization signal : 4-8 AA sequence rich in L, R, and Proline
What regulates G1 to S phase
- Cyclin D – activated CDK4 –> phosphorylates Rb protein which releases it from the TF E2F which transcribes and synthesizes components needed to progress thru S phase
- Cyclin E - activates CDK2
What regulates G2 to M phase
- Cyclin A - CDK2 complex –> mitotic prophase
2. Cyclin B - CDK1 complex activated by cdc25 = allows breakdown of nuclear envelope and initiation of mitoses
What is the role of the Golgi Appartus
- distribution center for proteins and lipids from the ER to vesicles and plasma membrane
- Modifies N-oliogosaccharides on asparagine
- Adds O-oligosaccharides on serine and threonine
- Adds mannose6-phosphate for trafficking to lyososomes
- glycosylation of proteins
- sulfation of sugars and tyrosines
What are endosomes
sorting centers for material from outside the cell of from the Golgi, sending it to lysosomes for destruction or back to the membrane/Golgi for further use
What is I cell disease
- inherited lysosomal storage disease due to failure of addition of mannose 6-phosphate to lysosome proteins.
What are the clinical manifestations of I cell disease
- coarse facial features
- clouded cornea
- restricted joint movement
- high plasma levels of lysosomal enzymes
often fatal in childhood