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Cell Bio > Final Topic 21 - Protein Sorting and Endocytosis > Flashcards

Final Topic 21 - Protein Sorting and Endocytosis Flashcards

1
Q

Virtually all proteins are synthesized in

A

The cytoplasm

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2
Q

Some proteins contain

A

Signal sequence

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3
Q

Proteins that are targeted to organelles must be able to

A

cross the membrane

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4
Q

Three mechanisms to cross the membrane

A
  1. Nuclear Pore Complex (only for nuclear proteins)
  2. Protein Translocators (ER, golgi, mitochondria)
  3. Vesicles - fuse with organelles
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5
Q

Proteins that are targeted to other organelles contain a

A

Signal sequence

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6
Q

Typically 15-60 amino acids long and is usually removed after the protein has reached it destination

A

Signal Sequence

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7
Q

The signal sequence is ___________ and ____________ to target a protein to the destination

A

Necessary and Sufficient

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8
Q

The nucleus is surrounded by a

A

Nuclear envelope

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9
Q

Contains a double membrane

A

Nuclear envelope

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10
Q

The nucleus contains

A

Nuclear pore complex

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11
Q

A large multi-protein assembly that forms a channel through the nuclear envelope

A

The nuclear pore complex

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12
Q

Proteins destined for the nucleus contain

A

A nuclear localization sequence (NLS)

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13
Q

Nuclear import requires

A

Cargo protein, Nuclear localization sequence, Nuclear transport receptor, Ran

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14
Q

Protein destined for the nucleus

A

Cargo protein

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15
Q

R and K amino acids

A

Nuclear localization sequence

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16
Q

Binds the NLS containing protein

A

Nuclear transport receptor

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17
Q

GTP binding protein that is involved in releasing cargo protein

A

Ran

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18
Q

Nuclear Import Process

A
  1. Nuclear transport receptor binds to the NLS
  2. Cargo protein and nuclear transport receptor move into the nucleus
  3. Ran-GTP (active form of the protein) Binds to nuclear transport receptor and releases cargo protein
  4. Ran-GTP/nuclear transport receptor move out of the nucleus
  5. Ran-GTP hydrolyzes GTP–>GDP + Pi and releases the nuclear transport receptor
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19
Q

The entry point for proteins destined for the golgi, lysosome, and the plasma membrane

A

ER

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20
Q

In order for proteins to get into the ER, they must pass through

A

The ER membrane

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21
Q

Proteins destined for the ER contain

A

An N-terminal ER signal sequence

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22
Q

A stretch of 8 or more hydrophobic amino acids

A

ER signal sequence

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23
Q

Proteins that enter the ER being to be translocated at

A

The same time they are synthesized

24
Q

Being translocated at the same time they are synthesized requires that the ribosome be

A

Bound to the ER plasma membrane

25
Q

Steps of Protein Import into the ER

A
  1. An ER signal sequence is exposed on the N-terminus of the growing polypeptide (in the cytoplasm)
  2. A signal-recognition particle (SRP) binds to the ER signal sequence
  3. A SRP receptor, embedded in the ER membrane, binds to the complex
  4. After binding, the SRP is release. The SRP receptor directs the complex to a translocation channel
  5. Once attached to the translocation channel, protein synthesis resumes
26
Q

Stops translation and directs the complex to the ER membrane

A

Signal-recognition particle (SRP)

27
Q

Two main types of Endocytosis

A
  1. Pinocytosis

2. Phagocytosis

28
Q

The ingestion of fluid molecules by small vesicles

A

Pinocytosis

29
Q

Cellular drinking

A

Pinocytosis

30
Q

Undergo Pinocytosis

A

All eucaryotic cells

31
Q

The ingestion of very large particles, such as organisms or cellular debris

A

Phagocytosis

32
Q

Undergo Phagocytosis

A

Only certain phagocytic cells

33
Q

One form of pinocytosis

A

Receptor-mediated endocytosis

34
Q

Uses receptors that bind to specific molecules in the extracellular fluid

A

Receptor-mediated endocytosis

35
Q

Endocytose the receptor/macromolecule complex

A

Clathrin coated vesicles

36
Q

The cell uses ______________ to endocytose the receptor/macromolecule complex

A

Clathrin coated vesicles

37
Q

A protein that forms a multi-protein assembly like a “cage” around a vesicle

38
Q

During receptor mediated endocytosis:

A
  1. A receptor binds to some cargo protein
  2. Adaptin then binds to the receptor
  3. Clathrin binds to adaptin and the vessicles form
  4. The vesicle is cleaved from the membrane by Dynamin
  5. After the vesicle is released, clathrin and adptin disassemble (uncoat) from the vesicle
  6. The vesicle then fuses with the endosome
  7. The endosome sorts the receptor/cargo complex to the plasma membrane or the lysosome
39
Q

A GTP-binding protein that hydrolyzes GTP to cut the membrane

40
Q

Insoluble in the blood

A

cholesterol

41
Q

Carried through the blood stream by binding to LDL

A

Cholesterol

42
Q

LDL

A

Low-density lipoprotein (bad cholesterol)

43
Q

HDL

A

High-density lipoprotein (good cholesterol)

44
Q

Gell take up LDL to get cholesterol through RME by the

A

LDL receptor

45
Q

The cholesterol in the cells is used in three ways:

A
  1. Goes to plasma membrane
  2. Is used to produce steroid hormones - cortisol
  3. Gets converted to bile acids - help digestion
46
Q

4 mutations in the LDL receptor that cause Familial Hypercholesteremia

A
  1. Mutation of the synthesis of LDL receptor
  2. Mutation in the transport from ER to plasma membrane
  3. Mutation that disrupts binding to LDL
  4. Mutation in clustering in clathrin vesicle formation
47
Q

Presence of high levels of cholesterol in the blood

A

Familial Hypercholesteremia

48
Q

Mutations in the cytoplasmic domain of the LDL receptor causes

A

The clathrin/adaptin complex to fail to cluster around the receptor

49
Q

How do we treat high cholesterol?

A

Statins and Fiber

50
Q

Inhibit HMG-CoA reductase

A

Statin Drugs (Lipitor, etc)

51
Q

Enzyme required for cholesterol biosynthesis

A

HMG-CoA reductase

52
Q

Prevents the cells ability to recycle bile acid, forcing the cell to use cholesterol to make more bile acid

A

Fiber (Bile acid binding resin)

53
Q

Create a cholesterol deficit inside the cell

A

Statins and fiber

54
Q

Turns on the gene to produce more LDL receptors to take more cholesterol from the blood stream

A

Cholesterol deficit inside the cell

55
Q

Increase LDL uptake efficiency and decrease LDL levels in the blood

A

More receptors

Cell Bio (30 decks)

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