1C Foundations 3 - Organelles Flashcards
Embryologic origin of the tissue just proximal to the pectinate line?
Endoderm
The origin of the tissue just distal to the anal canal?
Surface ectoderm
What is the general amino acid sequence of Nuclear Localization Signals?
4-8 amino acids
Rich in Lysine, Arginine and Proline
What are Nuclear Localization Signals a part of?
Essential component of proteins bound for or residing in the nucleus (e.g. histones)
How are Nuclear Localization Signals transported to the nucleus?
Through recognition by nuclear pores and by ATPase
What happens if there is a single amino acid mutation in Nuclear Localization Signals?
It may prevent nuclear transport of the protein
What regulates the cell cycle?
Tumor suppressor proteins
Cyclins
Cyclin-dependent kinases
Tumor suppressor proteins between G1 and S phase?
Rb
p53
Cancers associated with mutations in the Rb gene?
Retinoblastoma
Osteosarcoma
Tumor suppressor gene and gene product that regulates G2 to M phase?
p53
Cyclin-dependent kinases’ properties?
Constitutive (use ATP to phosphorylase things)
Inactive (must be activated)
Cyclins properties?
Regulatory proteins that control cell cycle events
They activate CDKs and are phase specific?
Cyclins + cyclin-dependent kinases –>?
phosphorylate target proteins to drive the cell cycle
What are cyclins degraded by when their cell-cycle specific job is complete?
Ubiquitin protein ligase
What is ubiquitin?
A protein that marks other proteins for destruction by ubiquitin protein ligase
Ubiquitin is important because?
It degrades cyclins and hence regulate the cell cycle
What does the tumor suppressor p21, p27 and p57 have in common?
They bind to and inactivate cyclin-CDK complexes
Who controls the activation of p21?
p53
Molecular process in which cell moves from G1 to S phase?
Cyclin D binds and activates CDK4. Then CDK4 phosphorylates the Rb protein –> release of Rb protein from transcription factor E2F. With E2F unbound cell is now free to transcribe and synthesize proteins needed for progression through the S phase. Next: Cyclin E binds to CDK2. After this the cell is allowed to move into S phase.
What proteins are needed through S phase?
i.e. they are needed to synthesize DNA
DNA polymerase
Thymidine kinase
Dihydrofolate reductase
Cyclin E
What happens when moving from G2–>M
Cyclin A - CDK2 complex –> mitotic prophase. Also: Cyclin B - CDK1 complex activated by cdc25 –> breakdown of nuclear envelope (specifically nuclear lamin breakdown) and initiation of mitosis.
What is the nuclear lamin?
Like a skeleton framework inside the nucleus.
Type of intermediate filament.
Has to be broken down in order for the nucleus to be able to break down –> division of cell
Rough Endoplasmic Reticulum (RER) is rough because?
It has a lot of ribosomes on it.
What is produced in the RER?
Secretory (exported) proteins
N-linked oligosaccharide addition to many proteins also happen here
Where are cytosolic and organellar proteins synthesized?
Free ribosomes
What are Nissl bodies?
RER of neurons
What does Nissl bodies produce?
Enzymes (e.g. Choline acetyltransferase (ChAT))
ACh
Peptide neurotransmitters
Where in the neuron can you find Nissl bodies?
Dendrite. Not axon
What does Smooth Endoplasmic Reticulum produce?
It has another function as well?
Synthesizes Steroids and detoxifies drugs and poisons
Where do you find a lot of smooth ER?
Liver hepatocytes
Steroid producing cells of the adrenal cortex
Where do you find a lot of RER?
Mucus-secreting goblet cells of the small intestine
Antibody-secreting plasma cells
Where does post-translational modifications take place?
Golgi apparatus
What is the role of Coat protein 2 (COP2) proteins?
Anterograde trafficking.
From ER to cis-Golgi
What is the role of Coat protein 1 (COP1) proteins?
Retrograde trafficking.
From Golgi to ER
What is the role of Clathrin?
Helps transport hydrolase enzymes from trans-Golgi –> lysosomes.
Also: helps in transport from the plasma membrane –> endosomes (in receptor mediated endocytosis)
Golgi Apparatus. Function?
Distribution center of protein and lipids from ER to plasma membrane, lysosomes and secretory vesicles
Post-translational modification of proteins and proteoglycans
What kind of tissue are proteoglycans important in?
Connective tissue
Glycosylation process is where and how?
Golgi.
Core proteins + (e.g. chondroiton sulphate, Heparin suplphate)
Golgi can modify what on asparagine?
N-oligosaccharides
The Golgi apparatus can add what to Serine and Threonine?
O-oligosaccharides
Golgi can can add what to sugars, proteoglycans and tyrosine?
Sulfate groups (“sulfation”)
Golgi can add what to lysosomal enzymes?
mannose-6-phosphate
I-cell Disease
Deficiency in mannose phophorylation.
No mannose-6-phosphate to target lysosomal proteins –> secretion out of cell instead of into lysosomes – > High levels of lysosomal enzymes in plasma.
Death by age 8-
Corneal clouding, coarse facies, Hepatosplenomegaly (HSM), skeletal abnormalities, restricted joint movementm +/- intellectual disability
Similar to Mucoplysaccharidosis like (Hurler or Hunter syndromes)
Function of Chaperones in the ER and Golgi?
Assist in proper folding and transport of polypeptides
Some chaperones are synthesized constantly and are involved in?
Normal intracellular protein trafficking
What is the function of heat shock proteins (also a kind of chaperone). Mention two.
“Rescue” shock-stressed proteins from misfolding (They are sent for degradation).
hsp70 and hsp90
If a protein is unable to be rescued (it’s abnormally folded) what happens?
The heat shock proteins will attach ubiquitin (also a heat shock protein) to them –> degradation
Mention the different types of proteolysis
- Lysosomal degredation (Lysosomal enzymes).
- Proteasomal degradation (Ubiquitin-tagged protein is recognized by ubiquitin-protein-ligase which is a part of the proteosome complex –> destruction of protein).
- Calcium-dependent enzymes
Function of sarcoplasmic reticulum?
Store calcium and help manipulate Ca2+ balance to regulate muscle contraction
Where do you find sarcoplasmic reticulum?
Striated muscle and smooth muscle cells
What does Ca2? trigger?
Muscle contraction and exocytosis of neurotransmitters and hormones
ATP production happens in which organelle?
Mitochondria
ATP happens in which processes?
TCA cycle and Electron transport chain
Mitochondria self-replicate. Why?
They have their own DNA
Mitochondrial DNA comes from mother or father?
Mother
How does the mitochondria relate to Ca2+
It can absorb Ca+ if excess exist in the cytoplasm
Function of the membrane-enclosed organelle peroxisomes?
Beta-oxidation of very long chain fatty acids and branched fatty acids and amino acids.
Synthesis of plasmalogens.
Oxidases and catalase for meatabolizing ethanol and other toxic substances.
What are plasmalogens?
Important phospholipid found in myelin
What is the proteasome?
Barrel-shaped protein complex that degrades damaged and unnecessary proteins tagged for destruction with ubiquitin.
