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Cell Bio I > Cell Biology III > Flashcards

Cell Biology III Flashcards

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1
Q

What are the three secretory pathways?

A

1) Exocytosis (bulk secretion)
2) Porocytosis (quantal secretion)
3) Exosomes and exosome-like vesicles

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2
Q

Exocytosis secretes what types of products?

A

1) Proteins and enzymes
2) Hormones
3) Neurotransmitters

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3
Q

In exocytosis, where are the secretory vesicles formed?

A

Golgi complex

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4
Q

In exocytosis, what do the secretory vesicles fuse with?

A

Plasma membrane

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5
Q

In exocytosis, what molecules are responsible for the intracellular trafficking of vesicles?

A

COPs (COat Proteins)

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6
Q

What are the two pathways specific to exocytosis?

A

1) Constitutive - continuous secretory process - no storage involved
2) Regulated - secretory product is stored in secretory vesicles until a signal causes secretion

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7
Q

What is the definition of constitutive exocytosis?

A

Continuous secretion - no storage involved

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8
Q

What is the definition of regulated exocytosis?

A

Secretory product is stored in secretory vesicles until a signal causes secretion

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9
Q

What molecules are required for exocytosis?

A

Calcium and ATP

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10
Q

Calcium and ATP are required for what secretory pathway?

A

Exocytosis

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11
Q

What is porocytosis?

A

Quantal release of neurotransmitters

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12
Q

Quantal release of neurotransmitters is characteristic of what secretory pathway?

A

Porocytosis

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13
Q

What three characteristics define exosomes and exosome-like vesicles?

A

1) Secretory products are membrane-bound when released into the ECM
2) Discard of unneeded membrane proteins (e.g. TfR)
3) May represent biomarker (e.g. for tumor cells)

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14
Q

Where are ribosomes synthesized?

A

Nucleolus

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15
Q

Where are the proteins in ribosomes synthesized?

A

Cytoplasm

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16
Q

What are two ways ribosomes are present in the cytoplasm?

A

1) Individual granules (subunits)

2) Polyribosomes (mRNA + ribosomes)

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17
Q

What are two characteristics of polyribosomes?

A

1) Free in the cytoplasm

2) Bound to the ER to form rER

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18
Q

Are ribosomes found in mature erythrocytes?

A

No

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19
Q

Are polyribosomes found in immature erythrocytes?

A

Yes

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20
Q

What role do polyribosomes have in immature erythrocytes?

A

Hemoglobin synthesis

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21
Q

Where are mitochondrial and peroxisomal proteins synthesized?

A

Cytoplasm

22
Q

Is the rER basophilic or eosinophilic?

A

Basophilic

23
Q

The rER is continuous with what other organelle?

A

Nuclear envelope

24
Q

What can you expect to see in protein-secreting cells?

A

A lot of rER

25
Q

rER will be a prominent feature of what type of cells?

A

Protein-secreting cells (e.g. pancreatic acinar cells)

26
Q

What is the definition of ER stress?

A

Accumulation of unfolded / misfolded proteins in the ER cisterna

27
Q

What are the four steps in the Unfolded Protein Response?

A

1) Chaperone synthesis
2) Decreased synthesis of protein
3) Export from ER to cytoplasm for proteasomal degradation
4) Activation of caspases - apoptosis

28
Q

In alpha-1-antitrypsin deficiency, what happens in the ER?

A

Mutant protein aggregates in ER

29
Q

What disease is characterized by an aggregation of mutant protein in the ER?

A

Alpha-1-antitrypsin deficiency

30
Q

Does the sER appear acidophilic or basophilic?

A

Acidophilic

31
Q

Why does the sER appear acidophilic?

A

Lacks basophilic polyribosomes

32
Q

What are the functions of the sER?

A

1) Cholesterol synthesis via HMG-CoA reductase
2) Steroid synthesis
3) Synthesis of phospholipids
4) Glycogenolysis

33
Q

Von Gierke disease is due to a defect in what enzyme?

A

Glucose-6-phosphatase (or glucose-6-phosphate transporter)

34
Q

A defect in glucose-6-phosphatase (or glucose-6-phosphate transporter) is the cause of what disease?

A

Von Gierke disease

35
Q

What is the presentation in von Gierke disease?

A

Glycogen accumulation in the cytoplasm and nucleus of affected cells

36
Q

What are the symptoms of von Gierke disease?

A

1) Liver enlargement
2) Hypoglycemia
3) Increased lactate

37
Q

What happens to the volume of the sER in protracted use of certain drugs and alcohol?

A

Increase

38
Q

An increase in sER volume can be seen in what conditions?

A

Protracted use of certain drugs and alcohol

39
Q

Where does phospholipid synthesis occur?

A

Principally in cytosolic lipid monolayer

40
Q

What molecule is synthesized primarily in the cytosolic lipid monolayer?

A

Phospholipids

41
Q

What happens if phospholipid translocators are defective?

A

Cannot catalyze the flip-flop of phospholipids from one monolayer to another - new bilayer could not be synthesized

42
Q

What is an important function of the sER in striated muscle cells?

A

Storage, release, and uptake of calcium

43
Q

What organelle is implicated in the development of malignant hyperthermia?

A

sER

44
Q

The sER is implicated in the development of what condition?

A

Malignant hyperthermia

45
Q

What receptor is mutated in malignant hyperthermia?

A

Ryanodine-1 receptors

46
Q

Ryanodine-1 receptors are mutated in what condition?

A

Malignant hyperthermia

47
Q

In malignant hyperthermia, what does a mutation in ryanodine-1 receptors lead to in the cell?

A

Excessive movement of Ca 2+ from the sarcoplasmic reticulum into the cytoplasm in response to anesthetic (halothane and succinyl choline)

48
Q

What is the cause of hyperthermia in anesthetic-induced malignant hyperthermia?

A

The SR-Ca 2+ pump consumes large quantities of ATP to increase uptake of Ca 2+ (mutated ryanodine-1 receptor pushes Ca 2+ out of SR and into cytoplasm)

49
Q

What agent is administered to counteract malignant hyperthermia?

A

Dantrolene

50
Q

How does Dantrolene interact with ryanodine-1 receptors?

A

Inhibits SR release of Ca 2+ into cytoplasm

Cell Bio I (11 decks)

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