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MBOC > Membraan biogenese 2 > Flashcards

Membraan biogenese 2 Flashcards

1
Q

Welke membraanlipiden komen voor in eukaryotische cellen, zoals zoogdieren en gist?
Wat is het geschatte percentage van glycerofosfolipiden in lipidenmembranen, en hoe worden ze opgebouwd?

A

In eukaryotische cellen, zoals zoogdieren en gist, komen glycerofosfolipiden (bijvoorbeeld PC, PE, PS, PI), sfingolipiden en sterolen voor in de membranen. Ongeveer 65 mol% van de lipiden in membranen bestaat uit glycerofosfolipiden.

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2
Q

Wat is het belang van sfingolipiden in het plasmamembraan en waarom zijn ze daar sterk verrijkt?
Hoe verschilt de samenstelling van sfingolipiden in vergelijking met glycerofosfolipiden?

A

Sfingolipiden zijn sterk verrijkt in het plasmamembraan vanwege hun verzadigde vetzuurketens, waardoor het membraan stevig en niet te permeabel wordt. Ze vormen ongeveer 10% van de totale membraanlipiden op celniveau.

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3
Q

Welke sterol is het belangrijkste in zoogdiercelmembranen en wat is zijn functie?
Hoe verschilt de samenstelling van lipiden in verschillende membranen van een cel?

A

Cholesterol is het belangrijkste sterol in zoogdiercelmembranen en maakt ongeveer 25% van de totale membraanlipiden uit. Verschillende membranen hebben verschillende lipidehoeveelheden en samenstellingen, waarbij endoplasmatisch reticulum (ER) en mitochondriën de meeste lipiden hebben vanwege hun grootste membraanoppervlak.

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4
Q

Beschrijf het proces van lipidenextractie uit membranen/cellen en de principes achter de twee-fase extractiemethode.
Noem ten minste drie verschillende methoden voor de analyse van lipiden en leg kort uit hoe ze werken.

A

Lipiden worden geëxtraheerd uit membranen/cellen via een chemisch proces met een twee-fase extractiemethode. Analysemethoden omvatten HPLC, TLC, gaschromatografie, en massaspectrometrie.

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5
Q

Wat is de structuur van cardiolipine en waar komt het voornamelijk voor in cellen?
Hoe beïnvloedt het verwijderen van cardiolipine (zoals in het crd1∆ onderzoek) de oxidatieve fosforylering in mitochondriën?

A

Cardiolipine is een lipide met vier vetzuurstaarten, verrijkt in mitochondriën. Het verwijderen van cardiolipine, zoals in het crd1∆ onderzoek, resulteert in verminderde efficiëntie van de oxidatieve fosforylering.

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6
Q

Bespreek twee voorbeelden van specifieke lipide-eiwitinteracties

A

Voorbeelden van specifieke lipide-eiwitinteracties zijn de rol van cardiolipine in mitochondriën, met name in oxidatieve fosforylering, en de binding van cytosolische eiwitten aan fosfo-inositiden.

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7
Q

Hoe kan in vitro reconstitutie van membraaneiwitten in proteoliposomen helpen bij het begrijpen van de functies van cardiolipine?
Leg uit hoe blue native SDS-PAGE wordt gebruikt om membraaneiwitsupercomplexen te detecteren.

A

In vitro reconstitutie van membraaneiwitten in proteoliposomen, blue native SDS-PAGE, en structuuranalyse kunnen inzicht geven in de functies van cardiolipine in oxidatieve fosforylering.

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8
Q

Beschrijf de biosynthese van fosfolipiden vanuit glycerol 3-fosfaat, inclusief de stappen en enzymen betrokken.

A

Fosfolipiden worden gesynthetiseerd vanuit glycerol 3-fosfaat, waarbij PA wordt gevormd en verder kan worden omgezet in andere lipiden zoals DAG, TAG, PI, PS, PE, en PC.

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9
Q

Wat zijn omega-3 en omega-6 vetzuren en hoe verschillen ze in hun biosynthese en functies?

A

Omega-3 en omega-6 vetzuren zijn essentiële vetzuren die niet efficiënt door het lichaam worden gesynthetiseerd. Ze worden verkregen uit voeding, zoals vette vis. Ze spelen een rol bij de synthese van eicosanoïden.

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10
Q

Hoe worden glycerofosfolipiden gesynthetiseerd in gist, en welke metabole relaties bestaan er tussen verschillende membraanlipiden?

A

Glycerofosfolipiden worden gesynthetiseerd in gist door verschillende reacties, waaronder de vorming van cardiolipine, PE, en PC, en kunnen onderling worden omgezet.

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11
Q

Hoe kan de lipidensynthese in levende cellen worden gemeten met radioactieve en stabiele isotopen?
Wat is het belang van dynamic lipidomics bij het bestuderen van lipidensynthese?

A

Lipidensynthese kan worden gemeten door cellen te labelen met radioactieve isotopen zoals [32P]-orthofosfaat of [14C/3H]-acetaat. Massaspectometrie wordt gebruikt voor detectie. De dynamic lipidomics benadert het meten van lipidensynthese op moleculair niveau met stabiele isotopen.

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12
Q

Explain the significance of cardiolipine in the mitochondria and its role in oxidative phosphorylation.

A

Cardiolipin is crucial for the functioning of proteins, particularly in mitochondria. It is a lipid with four fatty acid tails, and its conical shape allows it to play a role in oxidative phosphorylation by facilitating the formation of supercomplexes and maintaining the efficiency of the electron transport chain.

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13
Q

Describe the differences in lipid composition between the plasma membrane and other cellular membranes.

A

The plasma membrane is enriched in sphingolipids and cholesterol, providing stability and reduced permeability. In contrast, endo-/lysosomes contain BMP (bis(mono-acyl-glycerol) phosphate), and mitochondria are rich in cardiolipins, reflecting the diverse lipid compositions across cellular membranes.

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14
Q

Explain the method for lipid extraction from membranes/cells using the two-phase extraction process. What is the significance of each phase?

A

The two-phase extraction process involves using a chloroform/methanol/water mixture to dissolve lipids and proteins. Phase separation occurs, and the lipid-containing chloroform phase (on the bottom) is analyzed. This method is effective due to the differential solubility of lipids in organic solvents versus water.

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15
Q

Discuss the advantages and limitations of using techniques such as HPLC, TLC, gas chromatography, and mass spectrometry in lipid analysis.

A

HPLC and TLC separate lipid classes based on their polar head groups. Gas chromatography analyzes fatty acid composition, while mass spectrometry provides detailed information on lipid molecular species. These techniques collectively offer comprehensive insights into lipid composition.

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16
Q

Elaborate on the function of cardiolipin

A

Cardiolipin is essential for oxidative phosphorylation. Studies on a crd1 knockout in yeast, unable to produce cardiolipin, showed reduced efficiency in oxidative phosphorylation, highlighting the crucial role of cardiolipin in this process.

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17
Q

Explain the metabolic relationships between different classes of glycerophospholipids, focusing on how one class can be converted into another.

A

Phospholipids, such as phosphatidylserine (PS) and phosphatidylethanolamine (PE), play roles in specific lipide-protein interactions. They contribute to membrane structure and participate in signaling pathways.

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18
Q

Provide a detailed explanation of the biosynthetic pathways involved in the synthesis of glycerophospholipids, including the role of glycerol 3-phosphate and key intermediates.

A

Glycerophospholipids exhibit metabolic relationships, with pathways converting phosphatidic acid (PA) into diverse lipids. PA can be converted into diacylglycerol (DAG), which is a precursor for triglyceride (TAG) synthesis, or it can undergo further reactions to produce phosphatidylinositol (PI), phosphatidylserine (PS), and phosphatidylethanolamine (PE).

19
Q

Discuss the outcomes of cellular labeling experiments using [32P]-orthophosphate for an extended duration versus a short duration. How do the results reflect lipid biosynthesis and turnover?

A

Extended labeling with [32P]-orthophosphate reflects steady-state distribution of labeled phospholipids across classes. Short-term labeling followed by cell extraction reveals a dynamic distribution, with rapid turnover, particularly in phosphatidylinositol (PI) and phosphatidylserine (PS).

20
Q

Elaborate on the physiological roles of omega-3 and omega-6 fatty acids, and discuss their sources and potential health implications.

A

Omega-3 and omega-6 fatty acids, derived from essential fatty acids, play crucial roles in health. They are precursors for the synthesis of bioactive lipid mediators and are associated with cardiovascular health. The body cannot synthesize them efficiently, emphasizing their importance in the diet.

21
Q

How can in vitro reconstitution of membrane proteins in proteoliposomes provide molecular insights into the functions of lipids, especially cardiolipin?

A

In vitro reconstitution of membrane proteins in proteoliposomes, particularly with cardiolipin, provides insights into lipid-protein interactions. Cardiolipin has been shown to activate enzymatic activity, such as cytochrome c oxidase and ADP/ATP translocase.

22
Q

Discuss the structural and functional roles of sterols, with a focus on cholesterol, in mammalian cell membranes.

A

Sterols, notably cholesterol in mammalian cell membranes, contribute to membrane rigidity and reduced permeability. The rigid structure of cholesterol organizes unsaturated fatty acids, enhancing membrane order. However, in gel-phase lipids, cholesterol disrupts packing, increasing fluidity.

23
Q

Explain the clinical relevance of lipid-related diseases, using Barth syndrome as an example, and discuss potential therapeutic targets.

A

Barth syndrome, an X-chromosome-linked disorder, exemplifies a mitochondrial-lipid-related disease. Mutations in the tafazzin gene lead to cardiolipin abnormalities, impacting mitochondrial function and resulting in cardiomyopathy. Understanding lipid-related diseases opens avenues for therapeutic interventions.

24
Q

Match the lipid or lipid-related term with its corresponding description.

Cardiolipin
Omega-3 Fatty Acids
Sphingolipids
Phosphatidylserine (PS)

A. Essential fatty acid precursor
B. Key component of mitochondrial membranes
C. Precursor for triglyceride synthesis
D. Lipid involved in membrane stability

A

Cardiolipin = B. Key component of mitochondrial membranes

Omega-3 Fatty Acids = A. Essential fatty acid precursor

Sphingolipids = D. Lipid involved in membrane stability

Phosphatidylserine (PS) = C. Precursor for triglyceride synthesis

25
Q

___________ is a lipid with four fatty acid tails, crucial for oxidative phosphorylation in mitochondria.

A

Cardiolipin

26
Q

The two-phase lipid extraction process involves using a mixture of ___________/___________/___________ to dissolve lipids and proteins.

A

chloroform/methanol/water

27
Q

Glycerophospholipid synthesis starts with glycerol 3-phosphate, and acyl-CoA provides the ___________ chains.

A

fatty acyl

28
Q

True/False: Cardiolipin is a common component of the plasma membrane.

A

F

29
Q

True/False: Sterols, like cholesterol, contribute to increased membrane permeability.

A

F

30
Q

True/False: The body can efficiently synthesize omega-3 and omega-6 fatty acids.

A

F

31
Q

Which statement(s) about phospholipids are correct?

A. They are exclusively found in mitochondrial membranes.
B. They play no role in membrane structure.
C. Phosphatidylserine (PS) participates in specific lipid-protein interactions.

A

C

32
Q

Choose the correct statement(s) about omega-3 fatty acids.

A. They are precursors for bioactive lipid mediators.
B. They are synthesized efficiently by the human body.
C. They have no role in cardiovascular health.

A

A

33
Q

What is the primary function of cardiolipin?

A. Facilitate triglyceride synthesis
B. Enhance membrane fluidity
C. Support oxidative phosphorylation in mitochondria
D. Act as a precursor for cholesterol synthesis

A

C

34
Q

Which analytical technique is commonly used to separate lipid classes based on their polar head groups?

A. Gas Chromatography
B. Mass Spectrometry
C. Thin-Layer Chromatography (TLC)
D. High-Performance Liquid Chromatography (HPLC)

A

D

35
Q

The primary enzyme involved in the synthesis of malonyl-CoA, a precursor for fatty acid synthesis, is ________________.

A

acetyl-CoA carboxylase

36
Q

The lipid class characterized by a rigid structure with four rings, such as cholesterol, is known as ________________.

A

sterol

37
Q

In the biosynthesis of glycerophospholipids, glycerol 3-phosphate is esterified with ________________ to form the lipid backbone.

A

fatty acids

38
Q

True/False: High amounts of cardiolipin are found in the endo-/lysosomes.

A

F

39
Q

True/False: Sphingolipids are enriched in the plasma membrane due to their fluidizing effect.

A

F

40
Q

True/False: Fatty acids can be elongated beyond C16:0 by enzymes called elongases.

A

T

41
Q

Which statement(s) about lipid analysis techniques are correct?

A. Gas chromatography of fatty acid methyl esters provides information on fatty acid tail composition.
B. Mass spectrometry is used for analyzing large datasets on lipid composition.

A

Both true

42
Q

Select the correct statement(s) regarding the functions of cardiolipin:

A. Cardiolipin is important for the functioning of proteins involved in oxidative phosphorylation.
B. Cardiolipin is a major component of the plasma membrane.

A

A = true, B = false

43
Q

What is the role of desaturases in lipid metabolism?

A. Introduce double bonds into saturated fatty acids
B. Convert glycerol into glycerophospholipids
C. Catalyze the esterification of fatty acids with glycerol

A

A

44
Q

Which lipid class is involved in specific lipid-protein interactions, such as binding to cytosolic proteins?

A. Phosphatidylcholine (PC)
B. Phosphatidylethanolamine (PE)
C. Phosphatidylserine (PS)
D. Sphingomyelin (SM)

A

C

MBOC (9 decks)

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