Membrane proteins structure and function

Question 1

Name 3 types of membrane proteins?

Answer 1

Peripheral, integral and lipid anchored

Question 2

How do peripheral membrane proteins associate with the membrane?

Answer 2

Relatively loosely associated via
ionic interactions with lipids
aqueous domains of integral membrane proteins

Question 3

How are peripheral membrane proteins removed?

Answer 3

By disrupting ionic interactions either with high salt or change in pH

Question 4

Purified peripheral membrane proteins are no longer associated with what

Answer 4

any lipids

Question 5

Integral membrane proteins span what

Answer 5

the entire membrane

Question 6

Integral membrane proteins have what type of symmetry

Answer 6

Asymmetrical

Different domains in different compartments

Question 7

How are integral proteins removed

Answer 7

Removed by detergents that disrupt the membrane

Question 8

Purified integral membrane proteins still have what associated with them?

Answer 8

Phospholipids

Question 9

How many different type of integral proteins are there

Answer 9

6

Question 10

Integral membrane proteins in the plasma membrane serve as what 3 things?

Answer 10

Transporters, signal receptors and ion channels

Question 11

Receptors detect what and name 4 of these things it can detect

Answer 11

Detect signals from outside
Light (Opsin)
Hormones (Insulin receptor)
Neurotransmitters (Acetylcholine receptor)
Pheromones  (Taste and smell receptors)

Question 12

Channels, gates and pumps transport what 3 things

Answer 12

Nutrients (maltoporin)
Ions (K-Channels)
Neurotransmitters (Serotonin reuptake protein)

Question 13

Enzymes are used in what 2 synthesis

Answer 13

Lipid biosynthesis

ATP synthesis

Question 14

Majority of multipass transmembrane proteins in eukrayotic cells contain what?

Answer 14

Alpha-helices rich in hydrophobic residues

Question 15

Amino acids in membrane proteins do what

Answer 15

cluster in distinct regions

Question 16

Transmembrane segments are predominantly hydrophobic or philic?

Answer 16

Phobic

Question 17

what 2 amino acids cluster at nonpolar/polar interface

Answer 17

Tyr and Trp

Question 18

Charged amino acids are only found in what domains?

Answer 18

Aqueous

Question 19

Beta Barrels form what

Answer 19

large transmembrane channels

Question 20

3 points about beta barrels

Answer 20

1) Comparatively rigid, easily crystallised
2) Common in outer membrane of mitochondria, chloroplasts and bacteria
3) Some are pore forming generating water filled channels

Question 21

Lipid Anchor are what

Answer 21

Lipoproteins

Question 22

Lipid anchors contain what

Answer 22

A covalently linked lipid molecule

Question 23

What lipid molecule could lipid anchors contain?

Answer 23

Long chain fatty acids, isoprenoids, sterols and glycosylated phosphatidylinositol

Question 24

Is the anchoring of lipoproteins reversible or irreversible?

Answer 24

Reversible

Question 25

Anchoring of lipoproteins allows what

Answer 25

Targeting of proteins

Question 26

What lipid anchor is only found on the outer face of plasma membrane?

Answer 26

GPI

Question 27

Farnesylation is what

Answer 27

A method of targeting proteins to the inner leaflet of the plasma membrane

Question 28

Primary sequence of the protein contains a signature for what

Answer 28

Signature for farnesylation: CaaX

Question 29

What does CaaX stand for

Answer 29

C is a conserved Cys
a is an aliphatic amino acid
X is Met, Ser, Glu and Ala

Question 30

Farnesylation is catalysed by what?

Answer 30

Farnesyl transferase

Question 31

Nonfarnesylated proteins do not go to where?

Answer 31

Do not go to the membrane and are inactive

Promising cancer therapy