cell 2

Question 1

What enzyme was instrumental in the discovery of GPI-anchored proteins? It was found that
this enzyme releases certain membrane proteins from the membrane.

Answer 1

Phosphatidylinositol-specific phospholipase (cuts GPI anchor)

Question 2

What kind of membrane protein is found entirely outside the bilayer on either the extracellular or cytoplasmic surface? These proteins are covalently linked to a membrane lipid situated within the bilayer.

Answer 2

Lipid anchored membrane protein (maybe GPI)

Question 3

Why are integral membrane proteins difficult to study?

Answer 3

Hydrophobic bilayer; hard to pull proteins out (require detergents)- disrupt structure and function

Question 4

What term describes the characteristic of something being both hydrophilic and hydrophobic?

Answer 4

Amphipathic→ non polar and polar

Question 5

What are the components of phosphatidic acids?

Answer 5

Glycerol backbone, two fatty acid tails, phosphate group

Question 6

What technique below is often used to identify transmembrane segments of integral proteins?

Answer 6

Hydropathy plot (hydrophobic peak around 20-25 amino acids represents a transmembrane alpha helix)

Question 7

On average, how many amino acids engaged in predominantly hydrophobic - helices does it take to cross the hydrophobic part of the membrane?

Answer 7

20-25 amino acids

Question 8

What kind of membrane protein penetrates into the hydrophobic part of the lipid bilayer?

Answer 8

integral/intermembrane proteins

Question 9

What did Davson and Danielli add to their model of enzyme structure to explain the passage of polar solute and ions through the membrane and to account for their selective permeability?

Answer 9

Protein pores/channels

Question 10

What word below characterizes the amino acids that are found in an -helical segment that spans a membrane?

Answer 10

hydrophobic/ nonpolar

Question 11

What property of membranes allows interactions to take place within the membrane, including the assembly of membrane protein clusters at particular sites and the formation of specialized structures?

Answer 11

Membrane fluidity

Question 12

While culturing some cells, you lower the temperature of the culture. What happens immediately to membrane fluidity?

Answer 12

Membrane fluidity decreases

Question 13

Highly gelated cell membrane. Contains Phosphoglycerolipids. High concentration of sphingolipids and cholesterol. What are they? (What is this cell?)

Answer 13

Lipid raft

Question 14

Mouse cells and human cells fuse. Then dye with fluorescent dye. Mouse green, Human Red, what would a cell look like?

Answer 14

Immediately after- half green half red; later=mixed

Question 15

What evidence helped Overton believe membranes are made of lipids?

Answer 15

Lipid soluble (nonpolar) substances cross membranes easier than polar ones

Question 16

Which of these are functions of membranes?

Answer 16

Compartmentalization, scaffolding, barrier, communication, energy transduction, transport

Question 17

Gronter and Grendel extract lipids from red blood cells. The surface area extracted is 41.75. What is the surface area of a cell in water?

Answer 17

Bilayer- double

Question 18

What amino acid replaces another amino acid in alpha helices, mutagenesis, and protein coding

Answer 18

Proline? cysteine?

Question 19

What directly and indirectly affects transition temperature?

Answer 19

Length of tails; degree of saturation—-> cholesterol (ind)

Question 20

What interaction on cell membranes explains interactions with other proteins, protein clusters, and specialized structures?

Answer 20

Membrane fluidity

Question 21

When doing a cell culture, the temperature is lowered. What happens to membrane fluidity?

Answer 21

It decreases

Question 22

The cell membrane is tested with agents. What happens to the membrane skeleton? / what happens when the membrane skeleton is disrupted?

Answer 22

Membrane becomes fragile, deformed, lose shape, can rupture; phospholipid mobility is increased agents help remove fences that restricted diffusion

Question 23

What proteins are equally attracted on sds to a positive electrode

Answer 23

All proteins

Question 24

What protein moves the farthest on sds page

Answer 24

Smallest protein

Question 25

What proteins affect the structure of red blood cells

Answer 25

Spectrin, ankyrin, band 3, actin

Question 26

When ionic reactions open gate what is gate type?

Answer 26

Voltage gate

Question 27

What is the charge inside the cell and how many ions get pumped in and how many are pumped out

Answer 27

Negative charge inside; 3 Na+ out 2K+ in

Question 28

What experiment is used when amino acids are put into tissues for short periods of time

Answer 28

Pulse-chase experiment

Question 29

When the electron micrograph was first used what was seen?

Answer 29

Trilaminar, bilayer?, cisternae, proteins?

Question 30

In a pulse-chase procedure, if the chase is longer, which statement below correctly Which statement below correctly describes the location of the radioactively labeled proteins in the cell?

Answer 30

further along the secretory pathway

Question 31

Which procedure below would lead to the visualization of the dynamic movements of specific proteins as they move through a single living cell? The proteins can be seen through the microscope eyepiece, and the cells do not have to be killed for the protein to be detected.

Answer 31

GFP

Question 32

Cells are infected with a virus carrying a temperature sensitive mutant VSVG gene that encodes a protein that cannot leave the ER of infected cells grown at restrictive temperatures. Thus, at higher temperatures

Answer 32

VSVG protein cannot leave the ER.

Question 33

The endomembrane system when homogenized is broken up into vesicles, which are heterogeneous but similar in size. These vesicles can be purified and, after purification, often retain their biological activity. They are collectively referred to as?

Answer 33

microsomes

Question 34

Enzymes can be purified from the microsomal fraction. They can then be used as antigens to make antibodies. The antibodies can then be exposed to cells and later visualized in the electron microscope. What allows them to be seen in the electron Microscope?

Answer 34

Gold attachment

Question 35

RER has ribosomes, similarly to which structure that it is continuous with?

Answer 35

Nuclear envelope; outer membrane

Question 36

SER function (?)

Answer 36

Lipid synthesis, detoxification, calcium storage

Question 37

Blobel, Sabatini & Dobberstein proposed that the site of protein synthesis is determined by information contained in the N-terminal portion of the protein, the first part to emerge from the ribosome. What did they call their proposal?

Answer 37

Signal hypothesis

Question 38

What allows smooth and rough vesicles (microsomes) to be readily separated by density gradient centrifugation?

Answer 38

Difference in density; presence of ribosomes; what separates? Density centrifugation

Question 39

What effect does the binding of the signal recognition particles (SRP) to the ribosome and the growing polypeptide chain have on protein synthesis?

Answer 39

Temporarily pauses protein synthesis

Question 40

How is the orientation of membrane proteins in the membrane thought to be accomplished?

Answer 40

Signal sequence,translocon, charge model positive charge inside/cytosolic

Question 41

What are the two sites within a cell at which protein synthesis occurs?

Answer 41

Free ribosome in cytosol and rough er ribosomes

Question 42

How do integral proteins enter the lipid bilayer?

Answer 42

Through translocon in ER

Question 43

Why is the ER ideal as a port of entry for secretory proteins?

Answer 43

Large surface area

Question 44

What protein(s) is (are) not made on the membrane of the RER?

Answer 44

Cytosolic proteins and proteins destined for nucleus mitochondria and peroxisomes

Question 45

What residue (amino acid) are n-linked polypeptides attached to when they are entering the RER via translocon?

Answer 45

asparagine

Question 46

What happens when a misfolded protein is bound by calnexin or calreticulin?

Answer 46

Protein is retained in ER and given a chance to refold

Question 47

There are sensors that recognize misfolded proteins, but are kept inactive by ____ & ____?

Answer 47

BiP and chaperons

Question 48

What molecules are bound to AP2 with clathrin

Answer 48

Cargo receptors

Question 49

What molecule is required for GTP proteins to bind and release clathrin coated molecules?

Answer 49

dynamin

Question 50

There are “tags” on polypeptides; what molecule goes in and cleaves(breaks covalent bonds) those “tags”?

Answer 50

deUbiquitin or signal peptidase

Question 51

Which endosome is located on the periphery of the cell

Answer 51

Early endosome

Question 52

Which endosome is located in the interior part of the cell. Near the nucleus.

Answer 52

Late endosome

Question 53

What causes the degradation of late endosomes by lysosomal enzymes?

Answer 53

Fusion of lysosome to endosome

Question 54

A single large protein appears in a single phospholipid layer covering an LDL particle. The protein attaches to the LDL receptors on the cell membrane. What is the protein?

Answer 54

Apolipoprotein B-100

Question 55

What causes LDL particles to be endocytosed?

Answer 55

Binding of LDL receptor

Question 56

What submitochondrial compartment allows proteins to be delivered into it?

Answer 56

everything/matrix

Question 57

What address causes lysosomal enzymes to be delivered into lysosomes?

Answer 57

Mannose 6-phosphate

Question 58

Clarthin coated vesicles/membrane___

Answer 58

TGN to endosomes, lysosomes, vacuoles