Final Topic 21 - Protein Sorting and Endocytosis

Question 1

Virtually all proteins are synthesized in

Answer 1

The cytoplasm

Question 2

Some proteins contain

Answer 2

Signal sequence

Question 3

Proteins that are targeted to organelles must be able to

Answer 3

cross the membrane

Question 4

Three mechanisms to cross the membrane

Answer 4

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

Question 5

Proteins that are targeted to other organelles contain a

Answer 5

Signal sequence

Question 6

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

Answer 6

Signal Sequence

Question 7

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

Answer 7

Necessary and Sufficient

Question 8

The nucleus is surrounded by a

Answer 8

Nuclear envelope

Question 9

Contains a double membrane

Answer 9

Nuclear envelope

Question 10

The nucleus contains

Answer 10

Nuclear pore complex

Question 11

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

Answer 11

The nuclear pore complex

Question 12

Proteins destined for the nucleus contain

Answer 12

A nuclear localization sequence (NLS)

Question 13

Nuclear import requires

Answer 13

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

Question 14

Protein destined for the nucleus

Answer 14

Cargo protein

Question 15

R and K amino acids

Answer 15

Nuclear localization sequence

Question 16

Binds the NLS containing protein

Answer 16

Nuclear transport receptor

Question 17

GTP binding protein that is involved in releasing cargo protein

Answer 17

Ran

Question 18

Nuclear Import Process

Answer 18

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

Question 19

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

Answer 19

ER

Question 20

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

Answer 20

The ER membrane

Question 21

Proteins destined for the ER contain

Answer 21

An N-terminal ER signal sequence

Question 22

A stretch of 8 or more hydrophobic amino acids

Answer 22

ER signal sequence

Question 23

Proteins that enter the ER being to be translocated at

Answer 23

The same time they are synthesized

Question 24

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

Answer 24

Bound to the ER plasma membrane

Question 25

Steps of Protein Import into the ER

Answer 25

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

Question 26

Stops translation and directs the complex to the ER membrane

Answer 26

Signal-recognition particle (SRP)

Question 27

Two main types of Endocytosis

Answer 27

1. Pinocytosis | 2. Phagocytosis

Question 28

The ingestion of fluid molecules by small vesicles

Answer 28

Pinocytosis

Question 29

Cellular drinking

Answer 29

Pinocytosis

Question 30

Undergo Pinocytosis

Answer 30

All eucaryotic cells

Question 31

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

Answer 31

Phagocytosis

Question 32

Undergo Phagocytosis

Answer 32

Only certain phagocytic cells

Question 33

One form of pinocytosis

Answer 33

Receptor-mediated endocytosis

Question 34

Uses receptors that bind to specific molecules in the extracellular fluid

Answer 34

Receptor-mediated endocytosis

Question 35

Endocytose the receptor/macromolecule complex

Answer 35

Clathrin coated vesicles

Question 36

The cell uses ______________ to endocytose the receptor/macromolecule complex

Answer 36

Clathrin coated vesicles

Question 37

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

Answer 37

Clathrin

Question 38

During receptor mediated endocytosis:

Answer 38

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

Question 39

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

Answer 39

Dynamin

Question 40

Insoluble in the blood

Answer 40

cholesterol

Question 41

Carried through the blood stream by binding to LDL

Answer 41

Cholesterol

Question 42

LDL

Answer 42

Low-density lipoprotein (bad cholesterol)

Question 43

HDL

Answer 43

High-density lipoprotein (good cholesterol)

Question 44

Gell take up LDL to get cholesterol through RME by the

Answer 44

LDL receptor

Question 45

The cholesterol in the cells is used in three ways:

Answer 45

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

Question 46

4 mutations in the LDL receptor that cause Familial Hypercholesteremia

Answer 46

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

Question 47

Presence of high levels of cholesterol in the blood

Answer 47

Familial Hypercholesteremia

Question 48

Mutations in the cytoplasmic domain of the LDL receptor causes

Answer 48

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

Question 49

How do we treat high cholesterol?

Answer 49

Statins and Fiber

Question 50

Inhibit HMG-CoA reductase

Answer 50

Statin Drugs (Lipitor, etc)

Question 51

Enzyme required for cholesterol biosynthesis

Answer 51

HMG-CoA reductase

Question 52

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

Answer 52

Fiber (Bile acid binding resin)

Question 53

Create a cholesterol deficit inside the cell

Answer 53

Statins and fiber

Question 54

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

Answer 54

Cholesterol deficit inside the cell

Question 55

Increase LDL uptake efficiency and decrease LDL levels in the blood

Answer 55

More receptors