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MCB > MCB6 - Intracellular Transport and Membrane Trafficking I > Flashcards

MCB6 - Intracellular Transport and Membrane Trafficking I Flashcards

1
Q

What type of microscope is required to observe organelles.

A

Transmission electron microscope.

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2
Q

What are cell organelles and why are they necessary.

A

Membrane enclosed compartments to isolate chemical reactions and prevent degradation of molecules by proteolytic machinery such as proteases.

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3
Q

Discuss general role of mitochondria.

A

Produces ATP via oxidative phosphorylation.

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4
Q

Discuss general role of endosome

A

Sorting and transporting of endocytosed material

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5
Q

Discuss general role of Golgi apparatus

A

ModificAtion, sorting and packaging of proteins and lipids for secretion or delivery to another organelle.

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6
Q

Discuss general role of lysosome.

A

Intracellular degradation producing waste material for a cell

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7
Q

Discuss general role of cytosol.

A

Location of protein synthesis, glycolysis and other chemical reactions. Contains cytoskeleton

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8
Q

Discuss general role of peroxisome,

A

Oxidation of toxic molecules

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9
Q

Discuss general role of ribosomes.

A

Protein synthesis either free in cytosol or bound to ER membrane

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10
Q

Discuss general role of nucleus.

A

Storage of genetic material. Production of RNA and DNA

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11
Q

Discuss general role of plasma membrane

A

Controls move,ent of molecules between cytosol and extracellular medium whilst defining interior and exterior of a cell.

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12
Q

Discuss general role of RER

A

Synthesis of proteins and lipids for distribution to other organelles or plasma membrane for secretion.

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13
Q

Discuss structure of nucleus in relation to its function.

A

Nuclear envelope double membrane with putter enveloped continuous with ER allowing continuum of movement of molecules. Nuclear pores aid import and export of molecules e.g. mRNA. Nuclear lamina as intermediate filaments of cytoskeleton on inner membrane to aid cell division.

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14
Q

Discuss structure of endoplasmic reticulum in relation to its function.

A

Interconnected sacs and tubes of membrane with ribosomes studded on outside. Aids protein synthesis. Membrane can pinch off to form transport vesicles. Membrane also used to create tracks for motor proteins to aid movement,

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15
Q

Discuss structure of Golgi apparatus in relation to its function.

A

Stacks of flattened membranes and transport vesicles aiding movement of molecules. Allows modifications to be made as enzymes can easily access the molecules. Located near nucleus and ER for efficient transport of molecules.

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16
Q

Discuss transport vesicle structure and function.

A

Allows the packaging and transport of molecules placed in the transport vesicle. Vital for movement of substances. Constantly formed and broken down.

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17
Q

Discuss structure of mitochondrion and its relation to its function.

A

Outer and inner membrane allowing various chemical reactions to take place. Matrix contains enzymes required for the reactions.

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18
Q

What is the perinuclear space.

A

Space between one and outer membrane of nuclear envelope

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19
Q

What are three types of protein transportation methods in a cell.

A

Gated transport
Transport across membranes
Transport by vesicles

20
Q

Give example of gated transport

A

Nuclear import of proteins

21
Q

Give example of transport across membranes for proteins.

A

Mitochondrial import of proteins.

22
Q

Give example of transport by vesicles

A

Endocytosis and exocytosis.

23
Q

Discuss overview of gated transport for protein transportation.

A

Allows transport of proteins with a selective gate which allows/prevents some molecules from passing.

24
Q

Discuss overview of transport across membrane for protein transportation.

A

Proteins must the transported across various membranes for use as well as movement, secretion, modification etc.

25
Q

Discuss overview of transport by vesicles for protein transport

A

Allows inter organelle transport via transport vesicles. Allows transport of soluble proteins.

26
Q

Define difference between signal and import sequence.

A

Generally the same concept, acts as a stamp on a letter. Depends on context.

27
Q

What is the purpose of a signal or import sequence

A

To tell the protein where it should be translocated to.

28
Q

If proteins do not have a signal sequence where are they most likely to be found

A

In the cytosol .

29
Q

How can a cytosolic protein be translocated to the ER

A

By adding an ER signal sequence to it

30
Q

In which direction does protein translation occur, with regards to terminals.

A

Protein translation occurs from N terminal to C terminal .

31
Q

What type of transport is nuclear import of protein.

A

Gated transport

32
Q

What types of molecules can be transported through nuclear pores.

A

Small water soluble molecules

33
Q

What is the role and structure of the cytosolic fibrils in nuclear import

A

Allows molecules to be transported to be boroughs closer to the nuclear pore. Protein fibrils that stick out as protrusions

34
Q

What is the role of nuclear fibrils in nuclear import of proteins

A

Protein structures that form the nuclear basket and supports structure of the nuclear pore

35
Q

Why is the nucleus not permeable to large molecules

A

Large molecules cannot pass through the nuclear pore.

36
Q

Discuss process by which proteins move into the nucleus via the nuclear pore.

A

Protein synthesised in cytoplasm has nuclear localisation signal added to it. Moves towards nuclear import receptor forming cargo- receptor complex. Interacts with cytosolic fibrils to move towards nuclear pore. Mesh like structure moves cargo receptor complex through pore until nuclear basket is reached. Cargo released by using energy from GTP hydrolysis. Empty nuclear receptor returns for re-use

37
Q

How is the nuclear localisation signal removed from a protein

A

It is not

38
Q

What is the role of chaperone proteins in mitochondrial protein import

A

Prevent backsliding of protein back into the cytosol as it is being fed into the mitochondria

39
Q

What is the role of signal peptidase in mitochondrial import of proteins

A

Cleaves signal sequence from the polypeptide once inside the mitochondria

40
Q

Discuss process by which Proteins are imported into the mitochondria

A

Protein with mitochondrial signal sequence has affinity for protein translocator in outer membrane of mitochondria. Translocator protein diffuses across membrane until protein translocator in inner membrane is reached. Protein is unfolded and begins to be fed into the mitochondrion. Chaperone proteins pull the precursor protein into the mitochondria. Once fully in, chaperone proteins released and signal peptidase cuts signal sequence. Protein becomes folded into mature protein.

41
Q

What is the purpose of a N terminal sequence during protein import into ER.

A

Directs a protein into the ER lumen.

42
Q

Describe process of protein import into ER.

A

Signal recognition particle (SRP) binds to exposed ER signal sequence and ribosome which slows translation. SRP-ribosome complex binds to SRP receptor on ER membrane. SRP released passing ribosome from SRP receptor to protein translocator in ER membrane. Protein synthesis resumes and translocator threads growing chain across lipid bilayer. Signal sequence is cleaved and the translocated polypeptide is released into ER lumen when translation is complete. If stop transfer is present, polypeptide chain grows sideways resulting in another pass in the lipid bilayer.

43
Q

Proteins produced in the cytosol are received by which cell organelles.

A

Mitochondria and nucleus. Not ER or Golgi

44
Q

What is the role of the signal recognition particle.

A

Binds to exposed ER signal sequence and ribosome to initiate protein import into ER.

45
Q

Are start and stop transfer sequences in polypeptide chains hydrophobic or hydrophilic.

A

Hydrophobic.

46
Q

What is a translocation channel and it’s role in protein import into ER.

A

Channel where polypeptide chain is fed through with the hydrophobic start and stop sequences.

MCB (13 decks)

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