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Immunology > Endomembrane system > Flashcards

Endomembrane system Flashcards

1
Q

Endoplasmic Reticulum

A

-Continuous network of flattened scas, tubules and associated vesicles
-The membrane-bound sacs are called ER cisternae and the space inside them is the ER lumen

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2
Q

Main functions of ER

A

-Biosynthesis of proteins for:
* plasma membrane or into the organelles of the endomembrane system
*Export from the cell
-Lipid synthesis
-Membrane synthesis

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3
Q

Rough ER

A

-Contains ribisomes
-Morphology= flattened sheets
-Function: Biosynthesis and processing of proteins

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4
Q

Smooth ER

A

-No ribisomes
-Morphology= tubular
-Function: Steroid biosynthesis, drug detoxification, carbohydrate metabolism, calcium storage

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5
Q

Protein synthesis for EMS overview

A

Signal recognisiton particle (SRP) recognise and binds the ER signal sequence on the peptide and attaches the ribisome polypeptide complex to the ER membrane

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6
Q

signal sequence

A

-If first amino acids are positively charged, followed by hydrophobic amino acids and then polar aa, it designates that protein to EMS
-signal sequence is 15-30aa

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7
Q

protein synthesis mechanism

A
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8
Q

BLAST to find signal sequence

A

Does not work because signal sequence is never part of finsished protein but is cleaved
-Must use genome

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9
Q

Drug detoxification

A

-Often involves hydroxylation catalysed by cytochrome P450 enzymes
-drugs are usually non-polar and undergo hydroxylation by CYP that add hydroxyl groups to drugs, making them polar and more soluble, allowing the drug to be secreted by urine

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10
Q

Carbohydrate metabolism

A

-The live stores glucose as glycogen in granules associated with smooth ER
-expresses glucose-6-phosphatase to catalyse:
glucose-6-phosphate + H2O-> glucose and P

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11
Q

Calcium storage

A

Sarcoplasmic reticulum is specialised smooth ER in muscle cells
-stores and releases Ca

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12
Q

glogi apparatus

A

-series of flattened membrane-bounded cisternae
-A series of cisternae, usually 3-8, is called a Golgi stack
-Some cells have one large stack and others, especially secretory cells, have hundreds or thousands of stacks

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13
Q

Movement models for golgi

A

-Stationary cisternae mode
-Cisternal maturation model

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14
Q

Stationary cisternae model

A

-Each cisterna in the Golgi stack is a stable structure
-Transport of materials from one cisternae to another is mediated by shuttle vesicles
-These bud off from one cisterna and fuse with the cisterna in a cis-to-trans sequence

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15
Q

Cisternal maturation model

A

-Golgi cisternae are transient compartments
-These gradually change from CGN through medial cisternae to TGN
-Enzymes not needed in later compartments are returned to earlier compartments in vesicles

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16
Q

Glycosilation

A

The addition of carbohydrate side chains (moiety) to proteins to form glycoproteins

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17
Q

N-linked glycosilation

A

Involves the addition of an oligosaccharide to the nitrogen atom of certain asparagine residues

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18
Q

O-linked glycosilation

A

It involves the addition of the oligosaccharide to the oxygen atom on the hydroxyl group of certain serine, threonine and rarely tyrosine residuals

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19
Q

Initial carbohydrate units of golgi

A

All carbohydrate side chains initially have a common core oligosaccharide consisting of two units of N-acetyl glucosamine, 9 mannose units and 3 glucose units

20
Q

Migration through golgi

A
21
Q

Golgi processing

A

-Dolichol phosphate n the ER membrane acts as the carrier of oligosaccharide units for protein glycosilation. In mammals, n=18
-Core oligosaccharide synthesis begins in the cytoplasm as N-acetyl-glucosamine (N) and mannose (M) units are added to the dolichol phosphate
-Translocation of the oligosaccharide from cytosol to ER lumen is catalysed by flippase
-Compeltion of the core oligosaccharide occurs in ER lumen as more M and glucose units are added
Transfer of the completed core oligosaccharide to an asparagine residue of the recipient protein is catalysed by an oligosaccharyl transferase
-Final processing involves the removal of certain glucose and mannose units in ER before transfer of glycoprotein to Golgi

22
Q

golgi processsing overview

A

-Dolichol phosphate
-Core oligosaccharide
-Translocation
-Completion
-Transfer
-Final processing

23
Q

Targeting of soluble lysomal proteins

A

-soluble lysosomal enymes in ER and early Golgi compartments undergo N-glycosylation followed by removal of glucose and mannose units
-Mannose residues on the side chains are phosphorylated within the Golgi complex, forming an oligosaccharide containing mannose-6-phosphate
-This tag ensures delivery of lysosomal proteins to the lysosomes (since they are digestive enzymes, they have to be transported to lysosome specifically)

24
Q

lysosomal targeting mechanism

A
25
Q

Exocytosis

A

The process by which secretory vesicles release their contents outside the cell

26
Q

Endocytosis

A

Process by which cells internalise external materials

27
Q

Secretory pathways

A

Allow proteins to move from the ER through the Golgi to secretory vesicles and secretory granules

28
Q

types of secretion

A

-Constitutive
-Regulated
-Polarised

29
Q

Exocytosis mechanism

A
30
Q

endocytosis mechanism

A
31
Q

Phagocytosis

A

taking up large solid particles (like unicellular organisms)

32
Q

Pinocytosis

A

Taking up large quantities of liquid containg soluble suspended material

33
Q

Phagocytosis mechanism

A

-Bacterium attached to plasma membrane. The plasma membrane forms a pseudopod around the bacterium. The phagocytic vacuole fuses with an early endosome
-The phagocytic vacoule makes transient contact with early and late endosomes during maturation
-Mature lysosome cause bacterium to be broken down by lysosomal hydrolases

34
Q

Rececptor mediated endocytosis

A

-used for specific uptake of nutrients

1.Binding
2.Lateral diffusion
3.Invagination
4.Vesicle formation
5.Uncoating
6.Fusion with early endosome and release of ligand
7a.Transport to late endosome and then to lysosome for digestion
7b. Transport of receptors to cell surface for recycling
7c.Transcytosis

35
Q

Transcytosis use

A

Polarised secretion by moving a substance from one side of cell to other

36
Q

Lysosomes

A

-Contain acid phosphatase and several other hydrolytic enzymes (acid hydrolases)
-Lumenal side of the membrane is coated with glycoproteins to protect the membrane from degradation
-Have an internal acidic environment of (pH 4.0-5.0)
-ATP-dependant proton pumps in the membrane are responsible for an acidic environment

37
Q

Formation of lysomes

A
38
Q

Heterophagic lysome

A

extracellular substances

39
Q

Autophagic substances

A

intracellular substances

40
Q

Autophagy

A

Digestion and recycling of intracellular organelles

41
Q

Peroxisomes

A

Bound by single membranes
-considered part of endomembrane system (+ is they have mebrane from ER and - is they dont have double membrane)
-Defining characteristic is presence of catalase for degrading H2O2

42
Q

essential role of peroxisomes

A

-Hydrogen peroxide metabolism
-Detoxification of harmful compounds
-Oxidation of fatty acids
-Metabolism of nitrogen-containing compounds
-Catabolism of unusual substances (like xenobiotics)

43
Q

E.Constitutive secretion

A

-small intestine cells release mucus as part of their function

44
Q

E.Regulated secretion

A

B cells produce insulin

45
Q

E.Polarised secretion

A

Secretion occurs on specific side of cells like neurotransmitters

Immunology (7 decks)

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