Cell Membranes

Question 1

has both hydrophilic and hydrophobic elements

Answer 1

amphipathic

Question 2

amphipathic molecules that disrupt membranes by shielding non-polar regions of memb. Removes integral membrane proteins

Answer 2

detergent

Question 3

most common phospholipid

Answer 3

phosphatidylcholine

Question 4

membrane sugars (glycolipids, glycoproteins, proteoglycans) are added in the _______ on the ___ face, and therefore are located on the ____ of the plasma membrane

Answer 4

added in the golgi on the lumenal face, and therefore are located on the extracellular face of the plasma memb.

Question 5

increased membrane fluidity results from

Answer 5

• less cholesterol (sterols increase rigidity)
• short, unsaturated phospholipid tails

Question 6

• ______ can diffuse in the plasma memb.
• ____ can easily spin in the memb (____).
• Movement of lipids between bilayers requires ______.
• New phospholipids are added to the _____ of the ____. ____ moves phospholipids to the other face to maintain symmetrical growth of bilayers. _____ moves specific phospholipids between cytosolic and outside bilayers.

Answer 6

• proteins (crucial for signaling) and lipids (lateral diffusion
• Lipids (rotation)
• Scramblase or Flippase
• cytosolic face of the ER. Scramblase moves phospholipids to the other side for even growth…. Flippase moves specific phospholipids…

Question 7

• Tethering of proteins in the plasma memb
• Anchoring of proteins in the plasma memb

Answer 7

• proteins bound to the cytoskeleton or to a neighboring cell
• proteins bound to the extracellular matrix

Question 8

Spherocytosis

1. mechanism
2. symptoms
3. MOI
4. treatment

Answer 8

1. defect of spectrin or ankyrin in RBCs causes them to be spherical instead of bi-concave disc shaped.
2. hemolytic anemia and jaundice
3. AD
4. splenectomy

Question 9

When cells die, flippase moves ____ to the outer membrane, signaling immune cells to bind and digest the dying cell.

Answer 9

phosphatidyl serine

Question 10

outside of the cell is topologically equivalent to:

Answer 10

• ER
• golgi
• endosomes
• lysosomes
• vesicles
  *

Question 11

• proteins enter nucleus if they have:
• prot enter mitochondria if they have:
• prot enter ER if they have:

Answer 11

• nuclear localization signal
• mitochondria import sequence
• signal sequences

Question 12

transport into the ER is ______.

1. _____ is created during translation. Ribosomes have a stop particle called ____ which binds the ____.
2. The ___ binds to a ____ receptor in the memb of the ER, heping the protein bind to a ____.
3. ______ is released from ____ and translation resumes.
4. After translation and translocation, ____ cleaves the signal peptide

Answer 12

co-translational; transmembrane protein transport

1. A signal peptide is created during translation. Ribosomes have a Signal Recognition Particle (SRP) which binds the signal peptide, stopping translation.
2. SRP then binds to an SRP receptor in the memb of the ER, helping the prot bind to a translocation channel.
3. signal peptide is released from SRP and translation resumes.
4. signal peptidase

Question 13

______ is provided in the translocation channel in the ER membrane, and can be activated by _____, which cause the nascent chain to stop within the channel and allows the protein to be _____.

Answer 13

lateral escape hatch

stop transfer sequences

stitched into the ER memb.

multiple stop transfer sequences give a multipass memb protein

Question 14

examines newly synthesized proteins in the ER and destroys misfolded proteins.

Stays int he ER because it has a ____ sequence, which is recognized by ______ in the golgi and brought back via ____ if found.

Answer 14

BiP

KDEL

KDEL receptor

brought back via transport vesicles coated with COP1

Question 15

vesicles coated with COPII move them from________.

Clathrin is involved with:

COPI coats _____ to move them _____.

Answer 15

the ER to the cis golgi

endocytosis and post-golgi transprot

golgi to ER; within golgi

Question 16

Nuclear import: Gated transport

1. protein with NLS binds _____ and _____ in cytosol
2. goes thru nuclear pore
3. _____ exchanges ____, cargo is delivered to the nucleus.
4. _____ exits the nuclear pore.
5. _____ hydrolyzes it ____, freeing the

Answer 16

1. protein with NLS binds importin and Ran-GDP in cytosol.
2. protein goes thru nuclear pore
3. RAN_GEF exchanges GDP for GTP, so cargo is released (delivered to nucleus).
4. Importin-Ran-GTP exits the nucleus.
5. Ran-GAP hydrolyzes it, freeing Ran-GDP, Importin.

Question 17

Ran ____ is present in the nucleus, while Ran ___ is present in the cytosol. Therefore, there is more Ran-GTP in the ____ and more Ran-GDP in the ____.

Answer 17

Ran- GAP in the cytosol; Ran-GEF in the nucleus

more Ran-GTP in the nucleus, more Ran-GDP in the cytosol.

Question 18

Nuclear Export:

Answer 18

1. Exportin and Ran-GTP binds protein with NES.
2. cargo-Exportin-Ran-GTP exits the nucleus.
3. Ran-GAP hydrolyzes to Exportin-Ran-GDP, freeing the cargo (cargo delivered to cytosol) and Ran-GDP
4. Exportin goes back into the nucleus

Question 19

NLS has _____ which associates with channel lining including _____

Answer 19

KKKRK

Phe-glycine repeats

Question 20

amphipathic or not:

1. phosphatidyl serine
2. cholesterol
3. triacylglycerol
4. phosphatidylethanolamine
5. detergent in tide

Answer 20

1. phosphatidyl serine- amphipathic
2. cholesterol- amphipathic
3. triacylglycerol- not amphipathic
4. phosphatidylethanolamine-amphipathic
5. detergent in tide-amphipathic

Question 21

Vesicle budding:

1. Clathrin binds to membrane via ____.
2. ___ wraps around the stalk to pull vesicle free
3. Once free, clathrin dissociates.

Answer 21

1. Clathrin binds to membrane via adaptin and forms budding vesicle.
2. Dynamin wraps around stalk to pull vesicle free.
3. Clatrin dissociates

Question 22

Vesicle fusion:

1. _____ and _____ are on the vesicle. ____ binds target and pulls vesicle clsoe so that _____ can engage with ______ on target membrane.
2. ______ and ______ pull membranes together and exclude water, allowing membranes to fuse.

Answer 22

1. V-Snare and Rab are on the vesicle. Rab binds target and pulls vesicle clsoe so that V-snare can engage with T-snare on target membrane.
2. V-Snare and T-Snare pull membranes together and exclude water, allowing membranes to fuse.

Question 23

regulates COPI and clathrin in golgi

Answer 23

ARF

Question 24

regulates COPII in ER

Answer 24

SAR1

Question 25

for vesicular transport to lysosomes, ____ is added in the \_\_\_\_.

Answer 25

m-6-p signal added in the golgi

Question 26

protein transport into the mitochondria: 1. ____ (outer) and ____ (inner) form translocation channel 2. _____ (outer) and _____ (inner) help insert proteins into the memb. 3. \_\_\_\_\_\_initiates transport. Protein is unfolded, transported into the nucleus, and then refolded in the nucleus w the help of _______ proteins. 4. After translocation,\_\_\_\_\_\_\_.

Answer 26

1. TOM and TIM form translocation channel. 2. SAM (outer) and OXA (inner) help insert proteins into the memb. 3. Signal sequence/mitochondrial import sequence initiates transport. Protein is unfolded, transported into the nucleus, and then refolded in the nucleus w the help of chaperone proteins. 4. After translocation, signal sequence is cleaved and degraded.

Question 27

vesicles are guided to the plasma membrane by

Answer 27

MT tracks guide vesicles

Question 28

m-6-p receptors dissociate from protein and are recycled in:

Answer 28

prelysosomes

Question 29

Rab proteins are

Answer 29

GTPases. After fusion of membrane, Rab dephosphorylates, Rab-GDP is pulled off vesicles, and then Snares can be pulled apart by adaptors-NSF+ATP

Question 30

ARF is: SAR1 is: regulation of SAR:

Answer 30

a GTPase that regulates COPI and clathrin in the golgi a GTPase that regulate COPII in the ER. SAR1-GEF-GTP assembles at ER membrane. Recruits COPII. Buds form from ER.

Question 31

GPI-linked proteins _____ membrane fluidity

Answer 31

increase

Question 32

Calcineurin is a _______ activated by ___ which ____ the NLS in \_\_\_\_\_\_, which are transcription factors important to \_\_\_\_\_. This _____ the NLS, which goes to the nucleus and turns on genes in \_\_\_\_. When ___ levels fall, NES is available and a _____ phosphorylates \_\_\_\_\_, blocking the \_\_\_\_\_, so it leaves the nucleus.

Answer 32

**phosphatase** activated by **Ca** which **dephosphorylates** the NLS in **NF-AT,** which are TFs important to the **immune system. **This **unmasks** the NLS, which goes to the nucleus and turns on genes in **T-cells. ** When **Ca** levels fall, NES is available and a **kinase** phosphorylates **NF-AT**, blocking the **NLS**, so it leaves the nucleus.

Question 33

Cyclosporine inhibits ____ signaling by suppressing \_\_\_\_. As a result, the _____ is blocked, preventing ____ from driving immune responses.

Answer 33

Cyclosporine inhibits **NF-AT** signaling by suppressing **Calcineurin**. As a result, the **NLS** is blocked, preventing **NF-AT** from driving immune responses.