Cell Biology III

Question 1

What are the three secretory pathways?

Answer 1

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

Question 2

Exocytosis secretes what types of products?

Answer 2

1) Proteins and enzymes
2) Hormones
3) Neurotransmitters

Question 3

In exocytosis, where are the secretory vesicles formed?

Answer 3

Golgi complex

Question 4

In exocytosis, what do the secretory vesicles fuse with?

Answer 4

Plasma membrane

Question 5

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

Answer 5

COPs (COat Proteins)

Question 6

What are the two pathways specific to exocytosis?

Answer 6

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

Question 7

What is the definition of constitutive exocytosis?

Answer 7

Continuous secretion - no storage involved

Question 8

What is the definition of regulated exocytosis?

Answer 8

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

Question 9

What molecules are required for exocytosis?

Answer 9

Calcium and ATP

Question 10

Calcium and ATP are required for what secretory pathway?

Answer 10

Exocytosis

Question 11

What is porocytosis?

Answer 11

Quantal release of neurotransmitters

Question 12

Quantal release of neurotransmitters is characteristic of what secretory pathway?

Answer 12

Porocytosis

Question 13

What three characteristics define exosomes and exosome-like vesicles?

Answer 13

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)

Question 14

Where are ribosomes synthesized?

Answer 14

Nucleolus

Question 15

Where are the proteins in ribosomes synthesized?

Answer 15

Cytoplasm

Question 16

What are two ways ribosomes are present in the cytoplasm?

Answer 16

1) Individual granules (subunits)

2) Polyribosomes (mRNA + ribosomes)

Question 17

What are two characteristics of polyribosomes?

Answer 17

1) Free in the cytoplasm

2) Bound to the ER to form rER

Question 18

Are ribosomes found in mature erythrocytes?

Answer 18

No

Question 19

Are polyribosomes found in immature erythrocytes?

Answer 19

Yes

Question 20

What role do polyribosomes have in immature erythrocytes?

Answer 20

Hemoglobin synthesis

Question 21

Where are mitochondrial and peroxisomal proteins synthesized?

Answer 21

Cytoplasm

Question 22

Is the rER basophilic or eosinophilic?

Answer 22

Basophilic

Question 23

The rER is continuous with what other organelle?

Answer 23

Nuclear envelope

Question 24

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

Answer 24

A lot of rER

Question 25

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

Answer 25

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

Question 26

What is the definition of ER stress?

Answer 26

Accumulation of unfolded / misfolded proteins in the ER cisterna

Question 27

What are the four steps in the Unfolded Protein Response?

Answer 27

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

Question 28

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

Answer 28

Mutant protein aggregates in ER

Question 29

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

Answer 29

Alpha-1-antitrypsin deficiency

Question 30

Does the sER appear acidophilic or basophilic?

Answer 30

Acidophilic

Question 31

Why does the sER appear acidophilic?

Answer 31

Lacks basophilic polyribosomes

Question 32

What are the functions of the sER?

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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

Answer 34

Von Gierke disease

Question 35

What is the presentation in von Gierke disease?

Answer 35

Glycogen accumulation in the cytoplasm and nucleus of affected cells

Question 36

What are the symptoms of von Gierke disease?

Answer 36

1) Liver enlargement 2) Hypoglycemia 3) Increased lactate

Question 37

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

Answer 37

Increase

Question 38

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

Answer 38

Protracted use of certain drugs and alcohol

Question 39

Where does phospholipid synthesis occur?

Answer 39

Principally in cytosolic lipid monolayer

Question 40

What molecule is synthesized primarily in the cytosolic lipid monolayer?

Answer 40

Phospholipids

Question 41

What happens if phospholipid translocators are defective?

Answer 41

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

Question 42

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

Answer 42

Storage, release, and uptake of calcium

Question 43

What organelle is implicated in the development of malignant hyperthermia?

Answer 43

sER

Question 44

The sER is implicated in the development of what condition?

Answer 44

Malignant hyperthermia

Question 45

What receptor is mutated in malignant hyperthermia?

Answer 45

Ryanodine-1 receptors

Question 46

Ryanodine-1 receptors are mutated in what condition?

Answer 46

Malignant hyperthermia

Question 47

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

Answer 47

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

Question 48

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

Answer 48

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)

Question 49

What agent is administered to counteract malignant hyperthermia?

Answer 49

Dantrolene

Question 50

How does Dantrolene interact with ryanodine-1 receptors?

Answer 50

Inhibits SR release of Ca 2+ into cytoplasm