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Flashcards in Cell IV Deck (113):
1

Where is the principle site of phospholipid synthesis?

CYTOSOLIC layer of sER

2

How do phospholipids get from the sER to anywhere else in the cell?

Phospholipid translocators

3

What is the action of phospholipid translocators?

catalyze the flip-flop of phospholipids from one monolayer to the other

4

Where are phospholipid translocators found?

membrane-bound enzymes in the sER

5

Where is Ca stored?

sER

6

What is the function of atlastin?

a GTPase is involved in constructing and shaping the ER

7

What happens when there is over-expression of atlastin?

increased ER, lack of golgi

8

What happens where there is too little atlastin?

ER becomes fragmented

9

What disease has a deficiency of Atlastin been linked to?

Hereditary spastic paraplegia.

Symptoms include leg stiffness and gait disturbances such as stumbling and tripping. This is due to difficulty in hip flexion and dorsiflexion of the foot.

10

What are proteosomes?

Large proteases that require ATP

11

Where are proteosomes located?

In the cytoplasm and the nucleus

12

What are the three functions of proteosomes?

Proteolysis of:
1. Regulating proteins in cell cycle
2. Malformed, denatured and damaged proteins
3. Antigenic proteins

13

What are the two major types of proteosomes?

Ubiqitin dependent and not (cytosolic is dependent)

14

True or false: prion proteins inhibit proteosomes?

True

15

Defective ubiquitination of proteins is implicated in what disease?

Parkinsons

16

How are proteosomes implicated in cystic fibrosis?

destroy a competent but slow to fold CFTR

17

How can proteosomes contribute to CA?

Inhibition of them decreases the degrading of pro-apoptotic factors

18

Partial inhibition of proetosomes by bortezomib has been effective against what disease? How does this work?

Multiple Myeloma

Inhibits the over destruction of pro-apoptotic factors

19

What is the main function of the Golgi complex?

Functions as a major sorting and distribution center

20

How are proteins sorted in the golgi?

By their 'chemical zip code" (AA or carb attachments)

21

What are the five ways of protein modification in the Golgi?

Glycosylation
Sulfation
Phosphorylation
Oligosaccharides added
Proteolytic cleavage of proteins

22

How are proteins sent out of the golgi?

In vesicles

23

Where is the golgi usually found?

Near the nucleus

24

How many cisternae usually comprise the Golgi?

3-10

25

What is the side of the golgi that faces the nucleus called?

Cis face

26

Where do most of the transport vesicles to the golgi come from?

from the ER

27

How do proteins get to one Golgi stack to the next?

vesicles

28

What is the side of the Golgi that faces the plasma membrane called?

The trans face

29

What is Wilson's disease?

An autosomal recessive disorder caused by a mutation in a protein pump for copper in the trans-Golgi network of liver cells. This results in impaired biliary excretion of copper.
Kayser-Fleicher rings

30

How are proteins inserted into the membrane?

Via a start transfer and stop transfer sequence on the protein

31

Where is Ca stored in the cell?

sER

32

What are three deleterious effects of elevated Ca levels in the cell?

Membrane damage
Nuclear damage
Lower ATP

33

What is the enzymes that flips phospholipids from the cytosolic side to the ER lumen side?

Scramblase

34

What is the enzymes that is required for ER building?

Atlastin

35

Where are proteosomes found?

In the cytoplasm and nucleus

36

True or false: proteosomes are ATP dependent

True

37

What is the transporter of Cu in the Golgi?

ATP7B

38

how are microperforations of skeletal muscles sealed?

Via membrane protein from Golgi in-transporting vesicles containing dysferlin.

39

What is dysferlin transport dependent on?

Cu

40

Deficiency of dysferlin are found in what three diseases?

three types of muscular dystrophy: Miyoshi myopathy, limb-girdle muscular dystrophy type 2b, and distal myopathy tibialis anterior muscle onset

41

What is the protein in the Golgi that holds the Cu?

Ceruloplasm (apoceruloplasm if not bound to Cu)

42

How is Cu excreted from cells

Via transport vesicles that are filled from ATP7B action

43

A defective Cu transporter (ATP7B) leads to what disease?

Wilson's disease

44

What are Kayser-Fleisher rings?

Cu rings around the eye found in Wilson's disease

45

Where is ceruloplasm found?

Golgi

46

What happens to ceruloplasm levels when there is a defective Cu transporter?

Decrease

47

What is the protein that is used in microtears of muscles? What type of diseases are defects of this protein implicated in?

Dysferlin
Muscular dystrophy

48

How is insulin made/secreted? (3 steps)

First made into preproinsulin in the ER, and shipped to golgi.

Golgi forms vesicle with enz to cleave pro part inside.

These vesicles are held in the regulated pathway.

49

What is proinsulinemia?

A disease where mutated proinsulin is sent into the constitutive pathway, but prohormone secreting enzymes are secreted in the regulated pathway. (no insulin produced)

50

What stain is used to show a negative of the Golgi? Why does this work?

A basophilic stain (hematoxylin). Golgi is not charged.

51

How do you get a positive stain of the Golgi?

Use metals

52

Where are the golgi found in nerve cells?

Completely surround the nucleus

53

You see a nucleus that is relatively clear on the EM. What can you infer based on this?

Transcription is taking place at high rates

54

What are endosomes?

dynamic membrane-limited compartments that exist in the cell’s cytoplasm. The organelles are involved in sorting and identifying molecules for recycling or degradation in lysosomes.

55

What are the four types of endsomes?

1. Early endosomes
2. Recycling endosomes
3. Multivesicular bodies
4. Late endosomes

56

Where are early endosomes located?

the cell's periphery

57

What is the pH of early endosomes?

6.2 - 6.5

58

How are endosomes acidified?

H+ ATPases

59

What are multivesicular bodies (MVBs)?

Small membrane bound structures from the early endosome located between the early and late endosome (transporter)

60

What is the pH of the multivesicular bodies?

5-6.2

61

How do MVBs get from the early to late endosome?

Via a microtuble

62

Where do the MVBs eventually go?

Mere with a late endosome or excreted (=exosomes!!)

63

What are late endosomes?

A permature lysosome that receives components for degradtaion from the early endosome.

64

Where are the late endosomes located?

Near the golgi

65

What is the pH of the elate endosomes?

5

66

What is the fate of a late endosome?

become a lysosome or merge with one

67

What is the function of the recyling endosome?

Bring transport molecules (like GLUT4) to the surface plasma membrane in response to a signal (insulin)

68

LDL receptor are endocytozed via clatharin coated pits and turned into what?

Endosomes

69

What happens to the LDL and receptors that are endocytozed (2)?

1. both brought to the early endosome where receptor is taken off of LDL and recycled back.
2. LDL goes to lysosome

70

What is the binding protein for Fe? What is the receptor? What process of endocytosis does the receptor/ligand go through?

1. Transferrin
2. transferrin receptor
3. Clatharin-mediated endocytosis

71

What causes the abnormal bone growth in achondroplasia

lysosomal targeting is disturbed due to a mutation of FGFR3 (fibroblast growth factor receptor). This causes FGFR3 to be recycled to the membrane rather than degraded

72

Why do you want to degrade receptor molecules after they have bound their ligand?

Stop over signalling

73

What is transcytosis?

Receptor and ligand are transported across the cell via endosomes

74

What cells use transcytosis?

Glandular cells

75

What is the signal that is attached to the lysosomal hydrolase precursor?

Mannose

76

How are lysosoms directed to the early endosome?

Mannose phosphate receptor on the last part of the golgi accepts and clatharin coats the vesicle. Now a receptor driven vesicle

77

What are inside of lysosomes?

Lysosomal hydrolases
(ions/molecules)

78

True or false: enzymes are able to only able to destroy a tiny fraction of biological molecules?

False--most are able to be digested

79

In what type of cells are lysosomes primarily found?

professional phagocytic cells such as neutrophils and macrophages

80

How is the acidic nature of the lysosomes maintained?

H+ pumps

81

What is the autophagic pathway?

Pathway where lysosomes degrade defective organelles

82

What are the three types of autophagy?

Macroautophagy
Microautophagy
Chaperone-mediated direct transport

83

True or false: organelles destined for destruction are delivered to the lysoosome inside a membrane?

True

84

What is the term that describes the degradation of outside material such as bacteria?

Heterophagocytosis

85

What happens when sER is no longer needed?

Autophagy of the sER

86

What type of structure are eliminated via macroautophagy?

Organelles

87

What type of structure are eliminated via MICROautophagy?

Proteins, small molecules

88

What molecules are needed to direct proteins to the lysosome?

Chaperones

89

What is a heterophagosome?

Phagosome what has foreign material in it

90

What are residual bodies?

Material that lysosomes cannot digest and leaves undegraded --accumulates

91

What is lipofuscin?

Build up of residual bodies

92

Are lysosomes acidophilic or basophilic?

Acidophilic (H+ in it)

93

What are Heterophagolysosomes?

primary lysosome + heterophagosome

94

What are the two destinies for digested material by lysosomes?

Residual bodies
exocytozed

95

A lysosome that has consistent coloration throughout (on EM) is of what type?

Primary (homogeneous)

96

A lysosome that has inconsistent coloration and a large, darker area (on EM) is of what type?

Secondary (heterogeneous)

97

What is Pompe disease?

Glycogen storage disease due to M6P receptor

98

What is Tay-Sach's disease?

Problem with the breakdown of lipids

99

You're looking at a lysosome through EM and see a whorl effect. You also see a sample from the same tissue using light microscopy and E&M staining, that shows a very large, rounded area in the cell that appears white. What is your diagnosis?

Tay-Sach's disease

100

How do integral membrane proteins establish themselves in the membrane?

1. There are start and stop sequences on the protein that are recognized by a translocator protein that starts and stops translocation of the protein as necessary.
2. a signal peptidase again cuts off the signal sequence

101

What are the four possible fates of endocytozed receptor and ligands? (Give examples of each)

1. Receptor is recycled and ligand is degraded (LDL)
2. Receptor and ligand are recycled (Fe)
3. Receptor and ligand are degraded (EGF)
4. Transcytosis [Receptor and ligand transported across the cell] (IgA)

102

Why would the cell want to degrade receptors? What happens in achondroplasia?

1. To stop signalling
2. FGFR3 is recycled instead of degraded

103

What is the sorting place for all of the receptor/ligands that are endocytozed?

Early endosome

104

What is the enzyme deficiency in Pompe's disease? What accumulates?

alpha-1,4 Glucosidase
Glycogen accumulates

105

What is the enzyme defciency in GM1 gangliosidosis?

GM1 ganglioside beta-galactosidase

106

What is the enzyme that is deficient in Tay-Sach's disease? What accumulates?

Hexosaminidase a subunit
GM2 gangliosides accumulate

107

What is the enzyme that is deficient in Sandhoff (GM2 sphingolipidosis)? What accumulates?

Hexosaminidase beta
GM2 gangliosides globosides

108

What is the defective enzyme in metachromatic leukodystropy? What accumulates?

Arylsulfatase A.
Sulfatide accumulates

109

What is the defective enzyme in Gaucher's disease? What accumulates?

Glucocerebrosidease
Glucocerebrosides accumulate

110

What is the defective enzyme in Hurler disease? What accumulates?

alpha-L-iduronidase

Dematan sulfat, heparan sulfate

111

You are looking at a cell that has intense acidophilia of the cytoplasm, as well as an empty area outside the cell. What type of cell is this?

Osteoclast. (lysosomes are acidophillic)

112

You are looking at a muscle cell at note that there are large white areas where the contractile filaments should be. Using PAS, a sample from the same tissue demonstrates a deep magenta coloration. What is your diagnosis?

Pompe's disease (glycogen accumulating in muscle cells leaves no room for contractile filaments)

113

A low alk phos / bili is indicative of what disease?

Wilson's