Cell Trafficking Flashcards
G-protein coupled receptors are seven-pass transmembrane receptors. The associate with made of alpha, beta, and gamma sub units.
G-proteins
Signal is the process where a receptor protein changes in response to binding a ligand and activates the second messenger proteins.
transduction
Gs protein stimulates the enzyme .
adenylate cyclase
endocytosis involves proteins such as clathrin to bring target molecules into the cell.
Receptor mediated
Gq protein activates the enzyme .
Phospholipase C
Gi protein inhibits the enzyme .
Adenylate cyclase
The process of is the mechanism that allows cells to bring large amounts of material from inside to outside the cell.
exocytosis
The release of antibodies from white blood cells is an example of , where materials from inside the cell are transported outside the cell in membrane-bound vesicles that fuse with the plasma membrane.
exocytosis
G proteins are bound to when they’re inactive, and guanosine triphosphate (GTP) when a ligand binds.
guanosine diphosphate (GDP)
Endocytosis and exocytosis (are/are not) energy-requiring processes.
are
The transport of neurotransmitters out of nerve cells is an example of , where materials from inside the cell are transported outside the cell.
exocytosis
Phagocytosis and pinocytosis are specific forms of .
endocytosis
is the specific form of endocytosis that involves the intake of small amounts of fluid from outside the cell into the cell.
Pinocytosis
is the specific form of endocytosis that involves the intake of large particles or other cells into the cell.
Phagocytosis
is the mechanism by which macrophages engulf pathogens and cellular debris.
Phagocytosis
The rough endoplasmic reticulum is responsible for which of the following processes?
N-linked glycosylation and protein synthesis
Which of the following proteins is responsible for retrograde transport?
COP I
COPI is a vesicular trafficking protein responsible for retrograde transport. COPII is responsible for anterograde transport.
Mnemonic: The direction of COPI and COPII transport can be remembered with “two (COPII) steps forward, one (COPI) step back.”
I-cell disease is defined as which of the following?
Failure of the Golgi apparatus to phosphorylate mannose residues
I-cell disease is the failure of the Golgi apparatus to phosphorylate mannose residues due to an autosomal recessive inherited lysosomal storage disorder caused by a defect of N-acetylglucosaminyl-1-phosphotransferase.
Key Takeaway:
I-cell disease is an inherited autosomal recessive lysosomal storage disease caused by a defect in N-acetylglucosaminyl-1-phosphotransferase.
Which of the following is capable of trafficking material from both the outside of the cell and from the Golgi apparatus?
Endosome
Endosomes are trafficking compartments for materials from outside the cell or from the Golgi, sending them to lysosomes for destruction or back to the membrane or Golgi for further use.
Key Takeaway:
Endosomes traffic materials from outside the cell or from the Golgi.
Which of the following is most consistent with I-cell disease?
Normal urinalysis
I-cell disease is caused by a defect of N-acetylglucosaminyl-1-phosphotransferase and is consistent with a normal urinalysis and increased serum lysosomal enzymes. The disorder is characterized by the failure of the Golgi to phosphorylate mannose residues, causing a build-up of cellular debris (inclusion bodies) in lysosomes.
Key Takeaway:
I-cell disease classically presents with normal urinalysis.
I-cell disease is caused by defective N-acetylglucosaminyl-1-phosphotransferase
Dysfunctional signal recognition particle results in which of the following?
Protein accumulation in the cytosol
Signal recognition particle (SRP) helps bring nascent protein/ribosome complexes to the rough endoplasmic reticulum. Dysfunctional or absent SRP would therefore result in the cytosolic accumulation of proteins.
Key Takeaway:
Dysfunctional or absent SRP results in protein accumulation in the cytosol.
Which disorder presents with Gottron papules and is classically positive for anti-Jo-1 and anti-SRP antibodies?
Dermatomyositis
Dermatomyositis is positive for anti-Jo-1 and anti-SRP antibodies. On physical exam, one may notice Gottron papules (above) and heliotrope eyelid rash.
Key Takeaway:
Both dermatomyositis and polymyositis are positive for anti-Jo-1 and anti-SRP antibodies.
Only dermatomyositis has cutaneous involvement.
Which of the following is responsible for degrading ubiquitin-tagged proteins?
Proteasome
A proteasome is a barrel-shaped protein complex that degrades ubiquitin-tagged proteins.
Which ability underlies the increased pathogenicity of catalase (+) bacteria?
Peroxide nutralization
Catalase (+) bacteria have increased pathogenicity because they are able to neutralize H2O2 into H2O and O2, leaving phagocytes without reactive oxygen species (ROS) for fighting infections.
Key Takeaway:
Catalase (+) bacteria are more pathogenic because they can degrade H2O2 into H2O and O2.
Adrenoleukodystrophy is caused by which of the following?
ABCD1 gene mutation
Adrenoleukodystrophy is a disorder of β-oxidation due to a mutation of the ABCD1 gene. The mutation results in the decreased import of very-long-chain fatty acids (VLCFAs) and therefore decreased β-oxidation. The result is a buildup of VLCFA in the adrenal glands, the testes, and the white (-leuko-) matter of the brain.
Key Takeaway:
Adrenoleukodystrophy is caused by an ABCD1 gene mutation.
Adrenoleukodystrophy results in increased VLCFAs due to decreased β-oxidation.
Which of the following diseases is characterized by a buildup of phytanic acid due to impaired α-oxidation?
Refsum disease
Phytanic acid is a branched-chain fatty acid that can only be broken down via α-oxidation, not β-oxidation. Refsum disease is a disorder of α-oxidation, thus resulting in a buildup of phytanic acid. Patients can present with ascending polyneuropathy, scaly skin, cataracts, and shortening of the fourth toe.
Key Takeaway:
Phytanic acid is normally broken down via α-oxidation.
Refsum disease, characterized by impaired α-oxidation, results in increased phytanic acid.
A patient with Zellweger syndrome presents with hypotonia and seizures. What is the underlying etiology?
PEX gene mutation
Zellweger syndrome is a disorder of peroxisome biogenesis due to mutated PEX genes. The PEX mutation results in decreased peroxisome biogenesis presenting with hypotonia, seizures, hepatomegaly, and early death.
Key Takeaway:
Zellweger syndrome is caused by PEX mutation.
Zellweger syndrome results in decreased peroxisome biogenesis.
Ubiquitinated proteins are degraded directly by which of the following?
Proteasomes
Ubiquitin is added to misfolded proteins, cell cycle regulators, and anti-apoptotic molecules to mark them for degradation by the proteasome. The ubiquitin-proteasome system degrades endogenous ubiquitinated proteins.
Key Takeaway:
Proteasomes degrade ubiquitinated proteins.
Lewy bodies are composed of which of the following?
α-synuclein proteins
The ubiquitin-proteasome system regulates the degradation of misfolded proteins, cell cycle regulators, and anti-apoptotic molecules. Disruption of this system can result in the formation of Lewy bodies (composed of α-synuclein), stained brown in the image above.
Disorders of Lewy bodies (e.g., Parkinson disease and Lewy body dementia) are characterized by neurodegeneration.
Key Takeaway:
Defects in the ubiquitin-proteasome system have been implicated in disorders of Lewy bodies, such as Parkinson disease and Lewy body dementia.
Lewy bodies are composed of ⍺-synuclein.
Which suffix is used to signify proteasome inhibitors?
-zomib
All small molecular inhibitors target intracellular molecules and end in “-ib”.
Proteasome inhibitors end in the suffix “-zomib”. They are small molecule inhibitors that arrest cells in the G2-M phase of the cell cycle, leading to the accumulation of misfolded proteins as well as apoptosis.
Key Takeaway:
Small molecular inhibitors have the suffix “-ib”.
Proteasome inhibitors (“-zomib”) are small molecule inhibitors that arrest cells in the G2-M phase.
Lewy body deposition in the cerebral cortex is most likely to cause which set of symptoms?
Impaired memory and executive functions
Disruption of the ubiquitin-proteasome system can result in the formation of Lewy bodies (composed of α-synuclein), stained brown in the image above.
Lewy bodies commonly deposit in the following locations:
Brainstem → constipation, depression, and fluctuating blood pressure
Substantia nigra → resting tremor and bradykinesia (i.e., Parkinsonism)
Cerebral cortex → impaired/fluctuating cognition, alertness, and executive function
[Choice D]: Vomiting, loss of balance, and vertigo are classic signs of vestibular disorders.
Key Takeaway:
Lewy bodies are composed of ⍺-synuclein.
Lewy bodies can accumulate in the brainstem, substantia nigra, and cerebral cortex, with different associated symptoms.
