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Cell Biology > week 7: Intracellular compartments > Flashcards

week 7: Intracellular compartments Flashcards

1
Q

Where are proteins made?

A

Made in the cytoplasm then transported to the organelles

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2
Q

What are the 3 mechanisms for protein transportation

A
  1. through nuclear pores
  2. transport across membranes
  3. transport via vesicles through the endomembrane system
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3
Q

what is a signal sequence

A

a specific sequence of amino acids which tells the cell where that protein belongs

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4
Q

what is the transport of proteins through nuclear pores

A
  • nuclear membrane has many pores
  • proteins are trafficked between the nucleus and the cytoplasm through nuclear pores
  • aided by receptor proteins that trap the proteins & delivers them to the pore complex
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5
Q

Do nuclear pores transport fully folded proteins?

A

Yes

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6
Q

How does the transport of protein into the nucleus work?

A

Transport receptors in the cytosol bind to the nuclear signal sequences on the proteins.

receptors interact with the nuclear pore fibrils and direct the protein transport

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7
Q

Does the transport of protein into the nucleus via transport receptors require energy

A

yes

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8
Q

what is the transport of proteins across membranes into organelles?

A

A signal sequence at the N-terminus of the protein allows the protein to enter the mitochondrion

The protein is transported across both the inner and outer membranes, and it is transported in the unfolded state

Chaperone proteins aid this process & help the refolding of the protein once inside the mitochondrion

The signal sequence is removed once the protein is inside the mitochondrion

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9
Q

what are chaperone proteins?

A

they aid in the process of transport of proteins across membranes and help the refolding of the protein once inside the mitochondrion

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10
Q

What is the transport of proteins through the endomembrane system?

A

Proteins travel through vesicles

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11
Q

what is the endoplasmic reticulum

A

serves as an entry point for proteins destined for other parts of the cell.

proteins enter the ER and will move through the cell in membrane-bound vesicles never going into the cytosol

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12
Q

What are the two proteins made in the ER?

A
  1. water-soluble - stay in ER lumen

2. Membrane-bound - these stay within ER membrane

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13
Q

where does the translation of all proteins begin?

A

ribosomes in the cytosol except for protein that are destined for the ER have a signal sequence

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14
Q

what are soluble proteins

A

water-soluble ( hydrophilic) and so can enter the watery lumen of ER

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15
Q

how are soluble proteins translated

A

translated through translocator channels in the ER membrane

signal sequence stays bound to translocator & the rest of the protein is threaded through into lumen

once complete, the signal sequence is cleaved off by peptidase enzyme

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16
Q

How are membrane-bound proteins translated

A

translated through translocator channels in the ER membrane

Proteins are destined to stay in the membrane.

have one or more hydrophobic regions that slide into the ER membrane once translated

the hydrophobic region starts and stops the signal

17
Q

what is the transport of proteins through the endomembrane system

A

proteins are synthesised in the ER and transported through vesicles

Transport vesicles form when a small part of the ER membrane buds off

18
Q

what protein is involved in vesicle budding?

A

clathrin is involved in forming the vesicle. It coats the outside of the vesicle creating the shape

19
Q

how does clathrin make a vesicle?

A

Clathrin forms a basket-like network around the vesicle, and this involves other accessory proteins eg. adaptins, dynamin

20
Q

how do clathrin-coated vesicles form?

A

form from Golgi and also the plasma membrane (endocytosis)

21
Q

what are the Golgi stacks of membrane?

A

proteins move through the stacks from the cis Golgi network closer to the nucleus, to the trans-Golgi network closer to the plasma membrane

22
Q

what is protein secretion

A

secretory proteins are released via exocytosis

23
Q

What is constitutive secretion

A

continually supplies the plasma membrane with newly synthesised lipid and proteins

  • continual or unregulated
    e. g albumin, immunoglobins, collagen
24
Q

what are regulated secretion

A

proteins are stored in vesicles until an extracellular signal stimulates their secretion

requires extracellular signal for secretion

e.g insulin, neurotransmitters

25
Q

what is a chaperone protein

A

hold the protein in the ER until proper folding occurrs

misfolded protein is directed to cytoplasm instead of Golgi and degraded

26
Q

What is cystic fibrosis

A

inherited disease involving secretory glands of mucus and sweat
Thick mucus in lungs

27
Q

What is the CFTR gene?

A

Encodes for chloride ion channel in airway epithelium cells

Chloride ions are transported into the airway lumen, water follows due to osmosis, and this normally keeps mucus fluid

28
Q

CFTR protein is a slightly misfolded chloride ion

A

The misfolded protein is unfortunately recognized by chaperones & degraded, rather than being trafficked to the plasma membrane

29
Q

what is enodcytosis

A

Uptake of material into cell by invagination of plasma membrane & internalization in a membrane-bound vesicle

30
Q

Phagocytosis

A

cell eating

  • ingestion of large particles via vesicles
  • specialised phagocytic cells
31
Q

Pinocytosis

A

cell drinking
receptor mediated
ingestion of fluid & small molecules via small vesicles

32
Q

Receptor-mediated endocytosis

A

Macromolecules (e.g. LDL) bind to complementary receptors (proteins that recognize the molecule) on the cell surface

Bound receptors cluster together in a clathrin-coated pit

Clathrin protein allows the vesicle to form & dynamin enzyme helps to it ‘pinch off’ the membrane

Ingested molecules are transferred to endosomes which remove the receptor, and the endosome then delivers the molecules to the lysosome for digestion

Receptors are usually recycled back to the cell surface

Low density lipoproteins (LDL cholesterol) enter cells via this mechanism

Cell Biology (5 decks)

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