Membrane Structure

Question 1

Function of membrane

Answer 1

maintain the characteristic differences between the contents of each organelle and the cytosol.

Regulates the transport of molecules

Cell signalling (muscle & nerve cells, receptors)

Cell adhesion

Question 2

2 Faces of cellular membrane membranes

Answer 2

Internal face: Cytosolic face
External face: Exoplasmic face

Question 3

Lipid bilayer is ________

• Allow cells to be interact with watery environment but remain water resistant

Hydrophobic
- Impermeable barrier
Hydrophilic

Answer 3

amphipathic

Question 4

Membrane Lipids Are Amphipathic Molecules, Most Of Which Spontaneously Form Bilayers

Examples are…

Answer 4

Micelle
Liposome

Question 5

Liposomes have a bilayer structure, while micelles are single-layered.

Question 6

Characteristics of a lipid bilayer

Answer 6

Stable
- By hydrophobic and van der Waals interaction between lipid layers
Fluid

Question 7

driven by induced electrical interactions between two or more atoms or molecules that are very close to each other.

Answer 7

van der Waals interaction

Question 8

Fluid-Mosaic model

Answer 8

describes cell membranes as a dynamic, flexible structure composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates, allowing for lateral movement and a mosaic-like appearance.

Question 9

Organelles with 2 membranes

Answer 9

1. Nucleus
2. Mitrochondrion
3. Chloroplast

Question 10

most abundant class of lipids in most membranes, are derivatives of __________

Answer 10

glycerol 3-phosphate

Question 11

hydrophobic tails are made up of

Answer 11

2 esterified fatty acids (16-18 carbon)

1 or more cis-double bonds (i.e., it is unsaturated), while the other tail is not (i.e., it is saturated)

• Makes lipid bilayer fluid

Question 12

Hydrophilic head is made up of

Answer 12

Choline
Phosphate
Glycerol

Question 13

Hydrophilic heads are classified according to the nature of its head group

Most abundant phospholipids in plasma membrane are ___________
- Head group: choline

Answer 13

Phosphatidylcholines (PC)

Question 14

a positively charged alcohol

Answer 14

Choline

Question 15

Derived from sphingosine: an amino alcohol with a long hydrocarbon chain

Answer 15

Sphingolipids

Question 16

4 Classes Of Phospholipids (in mammalian plasma membranes)

Answer 16

1. Phosphatidylcholine =outer
   monolayer
2. Sphingomyelin = outer monolayer
3. Phosphatidylethanolamine = inner monolayer
4. Phosphatidylserine = inner monolayer

Question 17

ASYMMETRY OF LIPID BILAYER
¢ Cellular signaling
¢ Determination of viable and dead cells

When animal cells undergo programmed cell death, or apoptosis, ___________, which is normally confined to the cytosolic monolayer of the plasma membrane lipid bilayer, rapidly translocates to the extracellular monolayer

Answer 17

phosphatidylserine

Question 18

Classes of membrane lipids:

Answer 18

Phospholipids
Glycolipids
Cholesterol

Question 19

constitute 2%–10% of the total lipid in plasma membranes; they are most abundant in nervous tissue.

It is a type of sphingolipid

Maintain the stability of the cell membrane

cell-recognition processes

Answer 19

Glycolipids

Question 20

the polar head group is composed of sugar

Answer 20

Sphingolipids

Question 21

Which cell membrane has the most lipid composition in terms of cholesterol?

Answer 21

RBC plasma membrane

Question 22

________ molecules enhance the permeability barrier properties of the lipid bilayer
-> orient themselves in the bilayer with their hydroxyl groups close to the polar head groups of the phospholipid molecules
-Makes the layer less fluid but this prevents the hydrocarbon chains from coming together and crystallizing.

Answer 22

cholesterol

Question 23

Which cell membrane has the most lipid composition in terms of phosphatidylethanolamine?

Answer 23

E. coli bacterium

Question 24

Which cell membrane has the most lipid composition in terms of phosphatidylserine?

Answer 24

Myelin

Question 25

Which cell membrane has the most lipid composition in terms of phosphatidylcholine?

Answer 25

Mitochondrion (inner and outer membranes)

Question 26

Which cell membrane has the most lipid composition in terms of sphingomyelin?

Answer 26

Liver plasma membrane

Question 27

Which cell membrane has the most lipid composition in terms of glycolipids?

Answer 27

Myelin

Question 28

Membrane proteins:

Answer 28

1. Lipid-anchor protein 2. Lipid-anchored protein 3. Integral membrane protein 4. Peripheral membrane protein

Question 29

8 major types of membrane proteins based on how they associate with the lipid bilayer:

Answer 29

1. Single-pass transmembrane protein 2. Multipass transmembrane protein 3. β-barrel transmembrane protein 4. Lipid-anchored protein (on the cytosolic side) 5. Lipid-anchored protein (on the cytosolic side, different lipid) 6. GPI-anchored protein 7. Peripheral protein bound to integral membrane protein 8. Peripheral protein bound directly to membrane lipids

Question 30

Membrane protein functions:

Answer 30

1. Attachment to cytoskeleton & extracellular matrix 2. Cell signaling 3. Enzymatic activity 4. Transport 5. Intercellular joining 6. Cell-cell recognition

Question 31

CLASSIFICATION OF PROTEINS (NATURE OF THE MEMBRANE PROTEIN INTERACTIONS) ___________ = proteins contain membrane spanning hydrophobic a helices and hydrophilic domains that extend from the cytosolic and exoplasmic faces of the membrane.

Answer 31

Integral membrane/transmembrane protein

Question 32

INTEGRAL PROTEINS Membrane-spanning domain: ¢Hydrophobic amino acids ** α helices or multiple β strands

Question 33

EXAMPLE OF INTEGRAL PROTEINS ¢ Channel in the cell membrane that mainly transports water

Answer 33

Aquaporin

Question 34

_______ - β sheet in the form of a closed barrel - comparatively rigid and tend to crystallize readily E.g. ______

Answer 34

βbarrel; Porin

Question 35

_________ are found in the outer membrane of gram-negative bacteria such as E. coli and in the outer membranes of mitochondria and chloroplasts. Certain antibiotics must pass through -------- to reach their targets in gram negative bacteria.

Answer 35

Porin

Question 36

Associated with integral proteins or membrane lipids by specific noncovalent interactions Usually bound to the membrane indirectly by interactions with integral membrane proteins or directly by interactions with lipid head groups

Answer 36

Peripheral proteins

Question 37

_______: A fatty acyl group attached to the N-terminal glycine residue eg. _____: ¢ a mutant form of a cellular tyrosine kinase (c-Src) from avian Rous sarcoma virus (chicken) ¢is oncogenic

Answer 37

Acylation; v-Src

Question 38

__________: an unsaturated fatty acyl group attached to a cysteine residue a or near the C-terminus ¢eg. ____, ____ (GTPase superfamily)

Answer 38

Prenylation; Ras; Rab

Question 39

two fatty acyl chains ¢ eg. heavily glycosylated proteoglycans of the extracellular matrix

Answer 39

Glycosylphosphatidylinositol (GPI)

Question 40

Carbohydrate layer is a protection from damage

Question 41

Help distinguish one cell from another cell (cell-cell recognition) Cell-pathogen interaction

Answer 41

Membrane CHOs Ex. Blood type antigens

Question 42

Human ABO blood group antigens

Answer 42

Ends in GalNAc = A antigen Ends in GalFuc = O antigen Ends in Gal = B antigen

Question 43

Carbohydrate-binding proteins

Answer 43

Lectin

Question 44

Membrane proteins can be solubilized and purified in ______

Answer 44

Detergents