Biomembranes I (Lecture 7)

Question 1

The core of the phospholipid bilayer is ______ and the faces of it are ______.

Answer 1

Hydrophobic

Hydrophillic

Question 2

True or False: Biological membranes are impermeable to water-soluble molecules and ions.

Answer 2

True

Question 3

What can you use to measure the lateral diffusion of the phospholipid bilayer.

Answer 3

FRAP

Question 4

True or False: Heat makes the bilayer more rigid.

Answer 4

False, more fluid

Question 5

______ face always faces the cytoplasm and ______ always faces the cell exterior or interior lumen.

Answer 5

Cystolic, Exoplasmic

Question 6

What are the two functions that membrane fluidity and flexibility help with?

Answer 6

Enables organelles to assume their typical shapes

Provides dynamic property that enables membrane budding and fusion

Question 7

What are the 3 types of phospholipid arrangements:?

Answer 7

Liposome, Micelle, Bilayer sheet

Question 8

A smaller polar head favours?

Answer 8

inverted micelles or cubic structures

Question 9

Similar polar head and hydrophobic region favious?

Answer 9

Bilayers

Question 10

Bulky polar head and only one acyl chain favours?

Answer 10

Micelles

Question 11

True or False: All phospholipids are amphipathic.

Answer 11

True

Question 12

True or False: Phosphoglycerides are most common.

Answer 12

True, phosphoglycerides are most common

Question 13

What are the 3 types of sterols found in animals fungal and plants?

Answer 13

Cholesterol (animals) —Ergosterol (fungal)

Stigmasterol (plant)

Question 14

What is the tripartite structure of nucleotides?

Answer 14

Base + Sugar + Phosphate

Question 15

What is the tripartite structure of phosphoglycerides?

Answer 15

Head group + backbone + fatty acyl tails

Question 16

Sphingolipids are attached by what kind of bond?

Answer 16

Amide

Question 17

True or False: Cholesterols are amphipathic lipids.

Answer 17

True, Polar head group

Tail, conjugated four ring hydrocarbon and short hydrocarbon chain

Question 18

True or False: Phosphoglycerides, sphingolipids are all sterols.

Answer 18

False, while all phosphoglycerides are phospholipids, only certain sphingolipids are, and no sterols are.

Question 19

What two lipid components are found mostly in the inner leaflet.

Answer 19

Phosphatidylethanolamine

Phosphatidylserine

Question 20

Where are phospholipids synthesized?

Answer 20

Cytosolic face of endoplasmic reticulum

Question 21

What enzyme allows PC (a phospholipid) found in the exoplasmic face of plasma membrane.

Answer 21

Flippases

Question 22

______ is synthesized on exoplasmic face of Golgi

complex.

Answer 22

Sphingomyelin

Question 23

True or False: There is more sphingomyelin in ER membrane than golgi membrane.

Answer 23

False, more in golgi and ER membranes

Question 24

True or False: Cholesterol helps maintain natural fluidity of membranes.

Answer 24

True

Question 25

______ cholesterol levels the steroid ring separates and disperses phospholipid tails and increases fluidity and at ______ cholesterol level it tends to decrease biomembrane fluidity at typical cholesterol concentrations.

Answer 25

Low, High

Question 26

True or False: Cholesterol has no effect on membrane thickness.

Answer 26

False, it influences membrane thickness

Question 27

Small polar head groups have what type of phosphoglycerides?

Answer 27

PE, PS

Question 28

Similar polar head groups have what type of phosphoglycerides?

Answer 28

PC PG PI

Question 29

Bulky polar head groups have what type of phosphoglycerides?

Answer 29

Lysolipids

Question 30

______ are found more in the outer leaflet, ______ are found in both leaflets and ______ are found more in the inside leaflet.

Answer 30

Lysolipids PC PG PI PE PS

Question 31

Where does excess lipid storage occur?

Answer 31

In ER membrane through insertion of triglycerides and cholesterol esters

Question 32

What are the three types of proteins in the biological membranes?

Answer 32

Integral, lipid-anchored and peripheral proteins

Question 33

______ are membrane proteins (aka transmembrane proteins) contain one or more hydrophobic membrane-spanning domains.

Answer 33

Integral

Question 34

Integral proteins are made ip of ______ typical 20-25 amino acids and typically made up of ______ residues

Answer 34

α-helix, hydrophobic

Question 35

True or False: “Multipass” proteins have multiple transmembrane helices

Answer 35

True

Question 36

True or False: Polar or charged residues in transmembrane helices need to be sequestered away from the hydrophobic lipid bilayer core

Answer 36

True

Question 37

______ are made up of B-barrels and are found in outer membrane of gram negative bacteria, mitochondria and chloroplasts

Answer 37

Porins

Question 38

True or False: The B-barrel has a hydrophilic interior and a hydrophobic exterior.

Answer 38

True

Question 39

______ are proteins that are bound covalently to one or more lipid molecules.

Answer 39

Lipid anchored

Question 40

True or False: In lipid anchored proteins, ther lipid may be at the N- or the C-terminus of the polypeptide

Answer 40

True

Question 41

GPI anchordd is attached to the ______, Prenylation is attached to the ______ and acylation is attached to the ______.

Answer 41

C terminus, C terminal Cys, N-terminal Gly

Question 42

True or False: Membrane proteins do flip-flop when forming a vesicle.

Answer 42

False, do not flip flop

Question 43

______ is the word known as the membrane no flip flopping.

Answer 43

Topology

Question 44

______ proteins do not directly contact the hydrophobic core of the membrane.

Answer 44

Peripheral

Question 45

What are lipid binding motifs used for?

Answer 45

Degrade damaged/aged cellular membranes Generate signaling molecules