Flashcards in Biochem - Cellular (Cell Cycle, Cell Trafficking, & Select organelles) Deck (41):
In general, what controls transitions between phases of cell cycle? What are 3 factors/substances that regulate this process?
Checkpoints control transitions between phases of cell cycle; This process is regulated by cyclins, cyclin-dependent kinases (CDKs), and tumor suppressors
What is the shortest phase of the cell cycle? What is included in this phase?
Mitosis (shortest phase of cell cycle) includes prophase, metaphase, anaphase, and telphase
Describe the duration of G1 and G0 cell cycle phases.
G1 and G0 are of variable duration
What 2 words describe the normal functionality of CDKs?
Constitutive and inactive
What are Cyclins, and how do they function?
Regulatory proteins that control cell cycle events; Phase specific; Activate CDKs
What must happen to Cyclin-CDK complexes in order for cell cycle to progress?
Must be both activated and inactivated for cell cycle to progress
What are 2 examples of tumor suppressors that function in the cell cycle? What function do they have?
p53 and hypophosphorylated Rb normally inhibit G1-to-S progression
What results from mutations in tumor suppressor genes? Give an example.
Mutations in these genes result in unrestrained cell division (e.g., Li-Fraumeni syndrome)
What defines the permanent cell type?
Remain in G0, regenerate from stem cells
What are 4 examples of permanent cells?
(1) Neurons (2) skeletal and (3) cardiac muscle (4) RBCs
What defines the stable (quiescent) cell type?
Enter G1 from G0, when stimulated
What are 2 examples of stable (quiescent) cells?
(1) Hepatocytes (2) Lymphocytes
What defines the labile cell type?
Never go to G0, divide rapidly with a short G1.
What are 5 examples of labile cells?
(1) Bone marrow (2) Gut epithelium (3) Skin (4) Hair follicles (5) Germ cells
Which cell type is most affected by chemotherapy?
Labile cell type
What are 2 events that occur at/in the rough endoplasmic reticulum?
Site of synthesis of secretory (exported) proteins and of N-linked oligosaccharide addition to many proteins
What are Nissl bodies? What function do they serve?
Nissl bodies (RER in neurons) - synthesize peptide neurotransmitters for secretion
What defines free ribosomes? What function do they serve?
Free ribosomes - unattached to any membrane; site of synthesis of cytosolic and organellar proteins
Give 2 examples of cells that are rich in RER.
Mucus-secreting goblet cells of the small intestine and antibody-secreting plasma cells are rich in RER
What is the function of smooth endoplasmic reticulum?
Site of steroid synthesis and detoxification of drugs and poisons
How does smooth endoplasmic reticulum differ from rough endoplasmic reticulum in its appearance?
Lacks surface ribosome
Give 2 examples of cells that rich in SER.
Liver hepatocytes and steroid hormone-producing cells of the adrenal cortex and gonad are rich in SER.
What function does the golgi serve?
Golgi is the distribution center for proteins and lipids from the ER to the vesicles and plasma membrane
How does the golgi modify asparagine?
Modifies N-oligosaccharides on asparagine
How does the golgi modify serine? What other amino acid is modified by the golgi in the same way?
Modifies O-oligosaccharides on serine and threonine
How does the golgi modify certain proteins, and for what reason?
Adds mannose-6-phosphate to proteins for trafficking to lysosomes
What are endosomes, and what function do they serve?
Endosomes are sorting centers for material from outside the cell or from the Golgi, sending it to lysosomes for destruction or back to the membrane/Golgi for further use
What does the I in I-cell disease stand for? What kind of disorder is it?
I-cell disease (inclusion cell disease) - inherited lysosomal storage disorder
What is the defect in I-cell disease, and what cellular effect(s) does it have?
Defect in phosphotransferase => Failure of the Golgi to phosphorylate mannose residues (i.e., decreased mannose-6-phosphate) on glycoproteins => Proteins are secreted extracellularly rather than delivered to lysosomes
What are 4 signs/symptoms that result from I-cell disease?
Results in coarse facial features, clouded corneas, restricted joint movement, and high plasma levels of lysosomal enzymes
What is often the prognosis/outcome of I-cell disease?
Often fatal in childhood
What is SRP? What function does it serve?
Signal recognition peptide (SRP); Abundant, cytosolic ribonucleoprotein that traffics protein from the ribosome to the RER.
What happens in the event of an absent or dysfunctional SRP?
Absent or dysfunctional SRP => proteins accumulate in the cytosol
Name 3 vesicular trafficking proteins.
(1) COPI (2) COPII (3) Clathrin
What is the function of COPI?
Vesicular trafficking protein; COPI: Golgi => Golgi (retrograde); Golgi => ER
What is the function of COPII?
Vesicular trafficking protein; COPII: Golgi => Golgi (anterograde); ER => Golgi
What is the function of Clathrin?
Vesicular trafficking protein; Clathrin: trans-Golgi => lysosomes; Plasma membrane => endosomes (receptor-mediated endocytosis) [e.g., LDL receptor activity]
Which vesicular trafficking protein is involved in receptor-mediated endocytosis? Give an example of receptor-mediated endocytosis.
Clathrin: trans-Golgi => lysosomes; Plasma membrane => endosomes (receptor-mediated endocytosis) [e.g., LDL receptor activity]
What is the peroxisome, and what function does it serve?
Membrane-enclosed organelle involved in catabolism of very-long-chain fatty acids, branched-chain fatty acids, and amino acids
What is the proteasome, and what function does it serve?
Barrel-shaped protein complex that degrades damaged or ubiquitin-tagged proteins