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Biol 130 > Intracellular Compartments > Flashcards

Intracellular Compartments Flashcards

1
Q

What is the proposed origin of the mitochondria

A

An aerobic bacteria fused with a cell, its plasma membrane degraded inside the cell, and resulted in two separate mitochondria within the cell

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2
Q

What is protein sorting

A

Transfer of proteins into compartments where they are needed

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3
Q

Where does protein sorting occur

A

In the cytosol, on free ribosomes

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4
Q

Does protein transport require energy

A

Yes

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5
Q

What is a signal sequence

A

A specific chain of amino acids that directs proteins to specific organelles

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6
Q

When are signal sequences removed

A

After sorting

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7
Q

What is the double membrane of the nucleus called

A

The nuclear envelope

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8
Q

What is the space in between the outer and inner nuclear membranes called

A

Perinuclear space

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9
Q

What is the nuclear pore complex

A

Nuclear pores contain cytosolic fibrils, nuclear basket, and pore-complex proteins - they provide access to the nucleus and regulate the transfer of proteins and RNA across the nuclear envelope

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10
Q

Is the flow in nuclear pores selective

A

Yes

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11
Q

What identifies the proteins that are required to be imported

A

They have a nuclear localization sequence

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12
Q

What moves OUT of the nucleus

A

Matured processed RNA, and ribosomal RNA

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13
Q

What moves INTO the nucleus

A

Histones, proteins required for DNA transcription and replication, and dNTPs/rNTPs

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14
Q

What are the three ways to import proteins to organelles

A
  • Nuclear transport
  • Transport across membranes
  • Transport by vesicles
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15
Q

Similarities of mitochondria and chloroplasts in plants in relation to protein transport

A

Each has double membranes (chloroplasts have a third membrane called thylakoids), most of their proteins are encoded by nuclear genome, so those proteins must be transported

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16
Q

Transport of proteins in mitochondria and chloroplasts

A

Proteins are made by free ribosomes in the cytoplasm (signal sequence at N terminus, proteins must move across both outer and inner membranes at special sites where layers are in contact), proteins must unfold to be imported and refold once signal sequence is removed

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17
Q

Subsequent transport within the mitochondria requires what extra sequence

A

Another signal sequence, revealed after first one is removed

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18
Q

Vesicular transport

A

ER most extensive of the endomembrane system, serves as an entry point for proteins in itself as well as proteins for the Golgi body, lysosomes, endosomes, etc., and once in the ER proteins will never re-enter the cytosol

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19
Q

What is protein translocation

A

For example, when the signal sequence is being formed on mRNA, the SRP binds to it and brings it to the SRP receptor in the membrane (like a binding site), which leaves the signal sequence at the translocation channel to be transported across the membrane

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20
Q

What two types of protein are transported to the ER

A
  • Water soluble proteins (destined for lumen)
  • Prospective transmembrane proteins (destined for plasma membrane of ER or another cell)
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21
Q

Which proteins cross all the way over membranes

A

Soluble proteins

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22
Q

What are single-pass transmembrane proteins

A

The signal sequence binds to the peptidase and draws it through the translocation channel until the stop sequence is read at some distance on the protein, where it then stops feeding - part of the protein moves over the membrane but some does not due to the stop signal

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23
Q

Temporary vesicles

A
  • allow material to enter and leave cells
  • move material between endomembrane compartments
  • carry soluble proteins (in the lumen) to the plasma membrane for secretion
  • move membrane proteins to be expressed on the cell surface
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24
Q

What is vesicle budding driven by

A

Formation of protein coat

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25
Q

What does vesicle docking depend on

A

Tethers and SNAREs

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26
Q

How does docking of a vesicle work

A

Once budded, they must find their proper destination, where it recognizes and docks
- each displays molecular markers that must be recognized by complementary receptors on target membrane

27
Q

What are RAB proteins

A

Family of monomeric GTPases displayed on vesicle surface

28
Q

Where are tethering proteins

A

Displayed on cytosolic side of target membrane

29
Q

SNAREs

A

Transmembrane protein on vesicle (v-snare) and transmembrane protein on target (t-snare) that consolidate docking and catalyze membrane fusion

30
Q

Docking, Fusion and Tethering are three steps done in what specific order

A
  1. Tethering
  2. Docking
  3. Fusion
31
Q

ER processing steps along secretory pathway

A
  • Most proteins are covalently modified in the ER, which leads to the formation of disulphide bonds and stabilizes protein shape
  • Addition of sugar groups (glycosylation) which have various functions depending on the sugar - protects protein from degradation, helps direct protein to proper organelle, and if displayed on the surface it allows for cell-cell recognition
32
Q

What is an interchain disulfide bond

A

Disulfide bonds between different proteins

33
Q

What is an intrachain disulfide bone

A

Disulfide bonds within a folded protein

34
Q

What is the function of oligosaccharide transferase protein

A

The oligosaccharide enter the ER, the N-acetylglucosamine group disattaches from the phosphate group and attaches to the amine group of asparagine side chains

35
Q

Only properly ______ proteins can enter the ER

A

Folded

36
Q

What is the unfolded protein response (UPR)

A

If protein production exceeds the amount able to be folded, the result is misfolded proteins accumulate
- this signal increases the expression of chaperone proteins and other proteins that assist in folding; which expands the ER
- If the cell cannot keep up, the UPR triggers cell death: apoptosis

37
Q

What is apoptosis

A

The death of cells which occurs as a normal part of cell growth and development

38
Q

How can the Golgi body be described in physical make up

A

Flattened sacs called cisternae that are organized into compartments

39
Q

What is the cis network of the ER

A

Newly formed, the “entry” part near the ER

40
Q

What is the trans network of the ER

A

Breaking away, the “exit” part away from the ER

41
Q

What are the functions of Golgi apparatus

A

Modify proteins coming from the ER:
- peptides shortened by proteases
- amino acids modified
- CHO groups added in ER are modified or removed
- glycosylation

Most complex proteins are synthesized in the Golgi
- glycos amino glycans in the extracellular matrix in animals
- pectins, hemicellulose in plants

42
Q

What are proteases

A

Enzymes that break down proteins

43
Q

What is constituted secretion

A

Proteins are secreted from the cell at a constant rate, no matter the outer environment

44
Q

What is regulated secretion

A

Proteins secreted from cell in large amounts when a signal is read from the outer environment

45
Q

What are the two main endocytic pathways

A

Pinocytosis (cell drinking) and phagocytosis (cell eating)

46
Q

What is pinocytosis

A

“Cell drinking”: tiny vesicles are formed called endosomes - done in all eukaryotic cells

47
Q

What is phagocytosis

A

“Cell eating”: much larger vesicles are formed called phagosomes - done only by specialized cells

48
Q

What is the extra type of endocytosis in animal cells

A

Receptor-mediated endocytosis
- very selective concentrating mechanisms
- requires specialized receptors

49
Q

What particles are involved in pinocytosis

A

Solutes, fluid, and macromolecules

50
Q

What particles are involved in phagocytosis

A

Larger particles, other cells, debris

51
Q

What particles are involved in receptor-mediated endocytosis

A

Particular molecules (ligands) for which the membrane has receptors, and receptors grouped in patches of membranes called “coated pits”

52
Q

What are coated pits

A

Receptors grouped together in patches of membranes - in relation to receptor-mediated endocytosis

53
Q

What is the site of cellular digestion

A

Lysosomes

54
Q

What part of the cell membrane is most extensive in terms of surface area

A

ER

55
Q

If the ER signal sequence in the gene encoding a large protein were deleted, where would the protein end up

A

In the cytosol

56
Q

If gold nanoparticles are smaller than small proteins, and upon injection into the cell can later be found in the nucleus, how is this explained

A

Molecules that are small can diffuse non-selectively across the nuclear pore complex

57
Q

Proteins encoded by the nuclear genome destined for the mitochondria, enter the mitochondria via…

A

Binding to mitochondrial import receptors, unfolding, and passing through translocator proteins in the mitochondrial membrane

58
Q

In eukaryotic cells, RNA polymerase is synthesized by…

A

Cytosol, by free ribosomes

59
Q

While not actively involved in translation processes, ribosomes…

A

Are scattered in cytosol, with large and small subunits dissociated from one another

60
Q

Phosphofructokinase, a key enzyme in glycolysis, would reach its destination by…

A

Having no localization sequence

61
Q

A UPR monitors protein folding in the _______, releasing signals into the _______ that increases the protein folding capacity in the ER

A

ER lumen, cytosol

62
Q

A cell in which the rate of constitutive secretion secretes rates of pinocytosis…

A

Increases in membrane surface area

63
Q

What would be the fate of a membrane that is associated with a vesicle that has just secreted its cargo via exocytosis

A

The vesicle membrane fuses with the plasma membrane and becomes part of it

64
Q

A transmembrane protein destined for the plasma membrane protrudes from the cytosolic face of the ER membrane. On its journey to the destination, where would you expect the protein to protrude?

A

On the cytosolic face of the Golgi, and the cytosolic face of the plasma membrane

Biol 130 (5 decks)

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