Organelles Flashcards
1
Q
Fxns of sER
A
production of lipids and steroids, glycogen metabolism and membrane formation and recycling
2
Q
Sarcoplasmic Reticulim
A
sER in muscle cells, sequester Ca and releases it to produce contraction
3
Q
What enzymes are found in sER?
A
CYP450
4
Q
How can the detoxification function level of the liver be estimated?
A
by the size of its sER
5
Q
Fxn of rER
A
protein synthesis
6
Q
What part of the ER is granular?
A
rough
7
Q
Ergastoplasm
A
portion of rER that has a basophilic stain
8
Q
Nissl bodies
A
large basophilic bodies in nerve cells that are rER and free ribosomes
9
Q
State the number of RNA molecules and proteins foundin the subunits of ribosomes
A
small subunit (40S): 1RNA and 33 proteins large subunit (60S): 3 RNA and 49 proteins
10
Q
When does a ribosome unit form?
A
when protein synthesis begin?
11
Q
What sites are in the small subunit
A
mRNA binding, P site, and A site
12
Q
What type of protein is synthesized in cytoplasmic ribosomes?
A
proteins that remain in cytoplasm
13
Q
How many ribosomes are in polyribosomes?
A
10-20
14
Q
What type of protein is synthesized in rER?
A
proteins to be exported, to be part of an organelle, or for the plasma membrane
15
Q
how are proteins translocated to the lumen of rER when being synthesized?
A
- Signal seq on N terminus interacts with a signal recognition particle 2. a docking protein binds SRP 3. ribisome binds to translocator proteins and SRP-docking protein complex dissociates
16
Q
What enzyme cleaves off signal seq on polypeptide being synthesized and which one digests it?
A
cleaving: signal peptidase and digesting: signal peptide peptidase
17
Q
How are integral proteins synthesized?
A
The polypeptide passes back and forth through the
rER membrane creating the functional domain for its
final membrane function.
18
Q
Chaperones
A
assist in protein folding
19
Q
What are the post translational modifications done to protein in rER?
A
glycosilation, disulfide-bond, hydrogen bond, chaperones
20
Q
What cells is the constitutive pathway of secretion dominant?
A
plasma cells and fibroblasts
21
Q
What is the morpholigical effect of a dominant constitutive pathway?
A
an enlarged rER cisternae?
22
Q
What happens to proteins not properly modified?
A
exported back to cytoplasm and marked for degradation
23
Q
A1AT deficiency (alpha1- antitrypsin)
A
inability of rER to export a mutated protein to Golgi, causes accumulation of defective A1AT within rER cirternae of liver hepatocytes, impaired liver fxn
24
Q
What mediates bidirectional traffic between the RER and Golgi apparatus?
A
Coatomers (COPs)
25
WHat COP mediates transport vesicles
| originating in the Golgi back to rER, as well as retrograde transport between Golgi cisternae?
COP-I
26
What is retrograde transport?
returns proteins mistakenly transferred to Golgi
27
What is responsible of anterograde transport from rER to Golgi?
COP-II
28
In what cells is the Golgi developed?
secretory cells
29
How is golgi seen in LM and EM?
LM: as white and EM: you can see it
30
What is the forming face of the golgi? Convex or concave
cis-golgi, convex
31
What stain can be used with Golgi?
osmium (osmiophilic)
32
What enzymes are in the intermediate compartment of the golgi?
NADPase, and N-acetyl glucosamine (agt)
33
What is the mature face of the golgi? Convex or concave?
trans-golgi, concave
34
Where does thiamin pyrophosphatase activity occur?
trans-golgi
35
Where does mannose phosphorylation occur?
cis-golgi
36
Where is the site of condensing vacuoles and vesicles?
trans golgi or maturing face
37
What is synthesized in the Golgi?
CH component of complez glycoproteins associated with glycosyl transferase. GAGs, glycoproteins, glycoolipids, proteglycans
38
Where in the golgi are proteins for export and the cell membrane are sorted for packaging?
trans golgi
39
What proteins are delivered to the apical plasma membrane from the golgi? What pathway and vesicle is usually used?
extracellular proteins and membrane proteins and constitutive pathway is used, non-clathrin coated viscles
40
What proteins are delivered to the basolateral plasma membrane from the golgi? What pathway and vesicle is usually used?
Proteins with specific sorting signal
attached to them by the TGN. Constitutive pathway uses an unidentified protein associated with an epithelium-specific adaptor protein.
41
What type of transport is present in most polarized epithilial cells?
constitutive pathway with an epithiium-specific adaptor protein
42
What proteins are delivered to the endosomes or lysosomes from the golgi? What pathway and vesicle is usually used?
proteins destined to organelles.
43
What type of endosome do proteins targeted with mannose-9-P go to?
early or late endosomose
44
What proteins are delivered to the apical cytoplasm from the golgi? What pathway and vesicle is usually used?
proteins stored in large vesicles, where they mature and then are released by exocytosis
45
What is the fxn of sorting signals?
determine to what intracellular structure a protein will be delivered from the TGN, once recognized, the protein is sorted first to a lipid raft and then to the appropriate coated transport vesicle
46
What is a sorting signal?
a linear polype[ptide array or carbohydrate molecule
47
Where are early endosomes located in and what is their structure?
plasma membran, tubovesicular where the lumen is separated in cisternae
48
What does the tubular protion of the early endosome contain?
majority of the integral proteins destined for membrane recycling
49
What does the luminal protion of the early endosome contain?
secretory cargo proteins
50
Describe the stable compartment model of endosomes
early and late endosomes are stable cellular
organelles connected by vesicular transport with the cell
exterior and with the Golgi apparatus. Coated vesicles fuse only with the early endosomes because they have specific surface receptors.
51
Describe the maturation model of endosomes
Early endosomes are formed de novo from endocytotic
vesicles, their composition changes as some components are recycled between the cell surface and the Golgi. The
maturation leads to the formation of late endosomes and them to lysosomes.
52
What is the major fxn of early endosomes?
to sort and recycle proteins internalized by encocytic pathways
53
Compare the pH of and early endosome, late endosome, and lysosome
goes from basic to acidic
54
Where are late endosomes located in and what is their structure?
located near Golgi and nucleus, complex structure with onion-like internal membranes
55
How do endosomes become lysosomes?
receive newly synthesized lysosomal enzymes that are targeted via M-6-P receptor
56
What organelles have M-6-P receptors?
early and late endosoemes, lysosomes, and golgi apparatus
57
Synonyme for late endosomes
perylysosomes
58
How many hydrolytic enzymes needed to be considered a lysosome?
50 or more
59
Where are lysosomes present? Abundant?
all cells, macrophages
60
Lysosome Function
intracellular digestion of macromolecules brought int cell by endocytosis and turnover of cellular components
61
What is autophagy?
turnover of cellular components
62
Tay- Sachs disease
```
caused by the absence of one enzyme, a
lysosomal galactosidase (β-hexosaminidase) that catalyzes a step in lysosomal breakdown of gangliosides in neurons. The resulting accumulation of the GM2 ganglioside that is found within concentric lamellated structures in residual bodies of neurons interferes with normal cell function.
```
63
What is the histochemical method used to identify lysosomes?
acid phosphatase
64
Describe the membrane of lysosomes
uniquely resistant to hydrolytic digestion because of its phospholipid structure that has cholesterol and lysobisphosphatidic acid, proton pumps and transport proteins
65
Where are lysososomal membrane proteins synthesize and sorted
synthesis rER and sorting Golgi
66
Describe the constitutive secretory pathway
Proteins secreted to the cell surface >endocytosed > early > late endosomes >lysosomes.
67
Describe the golgi-derived coated vesicle secretory pathway
Proteins exit the Golgi in clathrin-coated vesicles > late
| endosomes > lysosomes.
68
Describe the process in which extracellular large particles are delivered to lysosomes
Extracellular large particles (engulfed by phagocytosis) =>
Phagosome > fuses with a lysosome> phagolysosome.
Function digestion of exogenous material e.g. Bacteria
Identified as Heterophagic vacuole
69
Describe the process in which extracellular small particles are delivered to lysosomes
Extracellular small particles (plasma membrane proteins,
ligan-receptor complex >early/late endosomes >
lysosomes> degradation
70
Describe the process in which intracellular particles are delivered to lysosomes
```
Entire organelles (mitochondria) and
cytoplasmic components are isolated from the cytoplasm by ER membranes > fuses with lysosomes> degraded. Part of normal turnover process of cell organelles. Identified as Autophagosome (vacuole autophagic)
```
71
What is a heterophagic vacuole?
contains extracellular large particles for digestion
72
What is an autophagosome?
contains intracellular particles for digestion
73
What are residual bodies?
undigested residues from both autophagy and heterophagy
74
What are lipofuscin pigments? How are they seen in LM and what method is used?
residual bodies in neurons seen in LM as brownish-gold pigment visible in H&E preparations
75
What are proteasomes?
large cytoplasmic or nuclear protein complexes that destroy abnormal proteins misfolded, short-lived regulatory proteins, TFs, tumor suppressor or tumor promoters
76
Describe polyubiquination
Is the process of marking proteins for degradation by tagging them with multiple ubiquitin molecules (addition of one ubiquitin molecule after the other).
77
What degrades proteins that have been polyubiquinated? how many ubiquitin molecules are needed?
26S proteasome complex... 4
78
What diseases arise from the loss of fxn in polyubiquiniation?
alzheimers and HPV
79
In what cells are mitochondria present?
all except RBCs and terminal keratinocytes... abundant in cells that generate and expend large amounts of energy
80
What type of stain is used for mitochondria?
since they are acidophilic, eosin
81
What does the mitochondrial genome encode for and what is their fxn?
14 enzymes and their are for the oxidative phosphorylation pathway, 2 rRNAs, and 22 tRNAs used for translation of mitochondrial mRNA
82
What is the structure of mitochondrial DNA?
closed and circular
83
In what way are mitochondria independent from the cell?
contain a complete system for protein synthesis and ribosomal synthesis. Also include translocase of the outer membrane and inner membrane (TOM and TIM complexes)
84
Compare and contrast the two mitochondrial membrane
Outer: freely permeable and contains voltage-dependent anion channels that are permeable to uncharged molecules
Inner: rich in cardiolipin which make it impermeable to ions
85
What enzymes does the outer membrane contain?
phospholipase A2, monoamine oxidase, and acetyl coenzyme A
86
What mitochondrial membrane is involved in steroid metabolism?
inner membrane
87
How can you determine the metabolic activity of the cell?
number of mitochondria and number of cristae in each mitochondrion
88
To what membrane are the enzymes of the respiratory chain attached to and where do they project to?
inner membrane and and project their heads into the matrix
89
What are elementary particles?
enzymes of the respiratory chain
90
What are the 3 major functions of the proteins in the membrane forminf the cristae of mitochondria?
oxidation reactions of the respiratory chain, ATP synthase, and transport proteins regulating transport into and out of the matrix
91
What enzymes are found in the intermembrane space of mitochondria?
enzymes that uses ATP: cratine kinase, adenylate kinase, and cyto C
92
What two metabolic processes are in the matrix of mitochondria?
FA B-oxidation and citric acid cycle
93
What are the major products of the mitochondrial membrane?
CO2 and NADH
94
Where is the genetic material of mitochondria stored?
matrix
95
What is the function of mitochondrial granules? What is their composition
they store calcium and other divalent ions, composed of phopholipoprotein
96
How do mitochondria divide?
fission
97
What type of enzymes do peroxisomes have and how many?
oxidative enzymes, 40 or more
98
Do peroxisomes have acid phosphatase?
No
99
Catalase fxn
destroy hydrogen peroxide
100
What is the main product of peroxisomes
hydrogen peroxide
101
What are the major products of FA B-oxidation in peroxisomes?
acetyl CoA and H2O2
102
Where are peroxisome proteins synthesized?
cytoplasmic ribosomes
103
Where are the peorxisomal targetting signal in proteins?
C-terminus
104
What molecule is present in animal peroxisomes but not human?
crystalloid of urate oxidase?
105
In what organs are peroxisome abundant?
Liver and kidney
106
What can change the number of peroxisomes?
increases in response to diet, drugs and hormonal stimulation
107
What is the fxn of liver peroxisomes?
alcohol detoxification
108
Zellweger syndrome
Mos common inherited disease related to peroxisomes fxn. The disorder is caused by a mutation in the gene encoding the receptor for the peroxisome targeting signal that does not recognize the signal Ser-Lys-Leu at the carboxy- terminus of enzymes directed to peroxisomes.
109
What are the fxns of peroxisomes?
Oxidation reactions and synthesis of specialized phospholipids required for nerve cell myelination
110
How do peroxisomes divide?
By fission
111
Where is glycogen stored within the cell? In liver, skeletal muscle?
in cytoplasm as alpha particles in liver and beta particles in skeletal muscle
112
How are peroxisomes seen in TEM?
as black circles
113
How are lipid droplets seen in TEM?
as clear vacuoles since extracted with dehydration
114
in what cells are lipid droplets abundant?
in steroid secreting cells
115
What are lipid storage disease?
When genetic defects of enzymes involved in lipid
| metabolism occur, lipid droplets may accumulate in abnormal locations and in abnormal amounts.
116
What is melanin pigment?
pigment of skin hair and iris, synthesized by melanocytes and stored in melanosome granules, seen as black not perfect circles or ovals
117
What are the contents of lipofuscin pigments?
aggregation of oxidized lipids, phospholipids,
metals, and organic molecules that accumulate within the cells as a result of oxidative degradation of mitochondria
and lysosomal digestion.
118
Why do lipofucsin accumulate?
as a result of cellular aging
