Cell biology III Flashcards Preview

Year 1 Cell Biology > Cell biology III > Flashcards

Flashcards in Cell biology III Deck (50):
1

What are the three secretory pathways?

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

2

Exocytosis secretes what types of products?

1) Proteins and enzymes2) Hormones3) Neurotransmitters

3

In exocytosis, where are the secretory vesicles formed?

Golgi complex

4

In exocytosis, what do the secretory vesicles fuse with?

Plasma membrane

5

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

COPs (COat Proteins)

6

What are the two pathways specific to exocytosis?

1) Constitutive - continuous secretory process - no storage involved2) Regulated - secretory product is stored in secretory vesicles until a signal causes secretion

7

What is the definition of constitutive exocytosis?

Continuous secretion - no storage involved

8

What is the definition of regulated exocytosis?

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

9

What molecules are required for exocytosis?

Calcium and ATP

10

Calcium and ATP are required for what secretory pathway?

Exocytosis

11

What is porocytosis?

Quantal release of neurotransmitters

12

Quantal release of neurotransmitters is characteristic of what secretory pathway?

Porocytosis

13

What three characteristics define exosomes and exosome-like vesicles?

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)

14

Where are ribosomes synthesized?

Nucleolus

15

Where are the proteins in ribosomes synthesized?

Cytoplasm

16

What are two ways ribosomes are present in the cytoplasm?

1) Individual granules (subunits)2) Polyribosomes (mRNA + ribosomes)

17

What are two characteristics of polyribosomes?

1) Free in the cytoplasm2) Bound to the ER to form rER

18

Are ribosomes found in mature erythrocytes?

No

19

Are polyribosomes found in immature erythrocytes?

Yes

20

What role do polyribosomes have in immature erythrocytes?

Hemoglobin synthesis

21

Where are mitochondrial and peroxisomal proteins synthesized?

Cytoplasm

22

Is the rER basophilic or eosinophilic?

Basophilic

23

The rER is continuous with what other organelle?

Nuclear envelope

24

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

A lot of rER

25

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

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

26

What is the definition of ER stress?

Accumulation of unfolded / misfolded proteins in the ER cisterna

27

What are the four steps in the Unfolded Protein Response?

1) Chaperone synthesis2) Decreased synthesis of protein3) Export from ER to cytoplasm for proteasomal degradation4) Activation of caspases - apoptosis

28

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

Mutant protein aggregates in ER

29

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

Alpha-1-antitrypsin deficiency

30

Does the sER appear acidophilic or basophilic?

Acidophilic

31

Why does the sER appear acidophilic?

Lacks basophilic polyribosomes

32

What are the functions of the sER?

1) Cholesterol synthesis via HMG-CoA reductase2) Steroid synthesis3) Synthesis of phospholipids4) Glycogenolysis

33

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

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

34

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

Von Gierke disease

35

What is the presentation in von Gierke disease?

Glycogen accumulation in the cytoplasm and nucleus of affected cells

36

What are the symptoms of von Gierke disease?

1) Liver enlargement2) Hypoglycemia3) Increased lactate

37

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

Increase

38

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

Protracted use of certain drugs and alcohol

39

Where does phospholipid synthesis occur?

Principally in cytosolic lipid monolayer

40

What molecule is synthesized primarily in the cytosolic lipid monolayer?

Phospholipids

41

What happens if phospholipid translocators are defective?

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

42

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

Storage, release, and uptake of calcium

43

What organelle is implicated in the development of malignant hyperthermia?

sER

44

The sER is implicated in the development of what condition?

Malignant hyperthermia

45

What receptor is mutated in malignant hyperthermia?

Ryanodine-1 receptors

46

Ryanodine-1 receptors are mutated in what condition?

Malignant hyperthermia

47

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

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

48

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

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

What agent is administered to counteract malignant hyperthermia?

Dantrolene

50

How does Dantrolene interact with ryanodine-1 receptors?

Inhibits SR release of Ca 2+ into cytoplasm