Chapter 11

Question 1

What do membranes do?

Answer 1

Define external boundaries of cells and control the molecular traffic.
Divide internal space in compartments

Question 2

What do membranes consist of?

Answer 2

Lipid bilayer with proteins of various functions

Question 3

What does covalently altered mean?

Answer 3

Refers to a physical change in proteins due to the break of a covalent bond

Question 4

What are rafts?

Answer 4

Functionally specialised regions with unique lipid and protein compositions

Question 5

What are glycerophospholipids?

Answer 5

A form of lipid consisting of 2 long-chain fatty acids and a head group of glycerol and polar charged substituents

Question 6

What are sphingolipids?

Answer 6

A lipid constructed from a long-chain alkyl amine(sphingosine), a saturated long-chain fatty acid and a polar head group that can vary greatly in complexity

Question 7

What are sterols?

Answer 7

Cholesterol in animal membranes
A nonpolar steroid nucleus of four fused rings and a polar hydroxyl group at one end of the ring system

Question 8

What are hydrophobic interactions?

Answer 8

This describes clustering of hydrophobic molecules. Not a chemical reaction

Question 9

What are micelles?

Answer 9

A type of lipid aggregate.
Spherical structure containing only 1 layer of lipids. Hydrophobic regions together in middle.

Question 10

What is a bilayer sheet?

Answer 10

A type of lipid aggregate. A two lipid monolayer also called a leaflet.
Relatively unstable due to exposed hydrophobic regions at edge

Question 11

What is a leaflet?

Answer 11

Monolayer sheet

Question 12

What is exocytosis?

Answer 12

When 2 membranes fuse

Question 13

What is endocytosis?

Answer 13

When a single membrane enclosed compartment undergoes fission and splits into 2.

Question 14

What does the endomembrane system consist of?

Answer 14

Consists of the endoplasmic reticulum, golgi apparatus, lysosomes, varius small vesicles that carry lipids/ proteins, the nucleus, mitochondrion and chloroplast

Question 15

What 3 organelles has double membranes?

Answer 15

The nucleus, mitochondrion and chloroplast

Question 16

How to lipids and proteins move through the endomembrane system?

Answer 16

Synthesised in ER, moves through golgi apparatus to cell surface/to organelles
Individual lipid molecules can be carried throughout the cell by lipid transfer proteins LTPs

Question 17

What is the cis golgi apparatus?

Answer 17

The entrance point to the golgi apparatus

Question 18

What is the trans golgi apparatus?

Answer 18

The exit point of the golgi apparatus

Question 19

What types of lipids are typically found in the extracellular/exoplasmic leaflet?

Answer 19

phosphatidylcholine and sphingomyelin

Question 20

What types of lipids are typically found in the inner cytoplasmic leaflet?

Answer 20

phosphatidylserine, phosphatidylathanolamine and phosphatidylinositols

Question 21

Why are phosphatidylserine and phosphatidylinositols more commonly found in the inner cytoplasmic leaflet?

Answer 21

The negatively charged serine and inositol phosphate head groups can interact electrostatically with the positively charged regions of peripheral or amphitropic membrane proteins

Question 22

What does LTP mean?

Answer 22

Lipid Transfer Protein

Question 23

What does bispecific mean?

Answer 23

It refers to the ability to transfer 2 types of something. For example, certain LTPs can carry one specific lipid from one membrane to another and another specific lipid back.

Question 24

Membrane dysfunction can lead to?

Answer 24

Cancer, neurodegenerative diseases, cardiovascular diseases, bacterial infections

Question 25

How can membrane dysfunction lead to cancer?

Answer 25

Membrane receptor signalling can lead to uncontrolled cell growth

Question 26

How can membrane dysfunction lead to neurodegenerative diseases?

Answer 26

Through abnormalities in membrane proteins such as ion channels or transporters

Question 27

How can membrane dysfunction lead to cardiovascular diseases

Answer 27

Membrane lipids and proteins are crucial in atherosclerosis

Question 28

What allows the membrane to transport/exchange molecules?

Answer 28

Selective permeability, transport through ion channels/membrane proteins, endocytosis/exocytosis

Question 29

What parts of the endomembrane system has single membranes?

Answer 29

ER, golgi apparatus, lysosomes and various small vesicles

Question 30

What parts of the endomembrane system has double membranes?

Answer 30

Nucleus, mitochondrion and chloroplasts

Question 31

What is GPI anchored proteins?

Answer 31

Proteins found on the outer face of the bilayer which are anchored by a GPI anchor

Question 32

What does a GPI anchor consist of?

Answer 32

Phospholipid tail, a glycan chain and a phosphoethanolamine linker

Question 33

What are postranslational modifications?

Answer 33

Chemical modifications that occur after a protein has been synthesized

Question 34

What is a hydropathy index?

Answer 34

A numerical scale used to quantify the hydrophobic or hydrophilic nature of amino acids or regions within proteins

Question 35

What is a hydropathy index used for?

Answer 35

Used to determine how well an amino acid/protein interacts with water.

Question 36

What is a hydropathy plot?

Answer 36

A plot that shows the average hydropathy index plotted against average residue number

Question 37

What is a fluid mosaic?

Answer 37

A pattern formed by individual lipid and protein units in a membrane. This pattern can change while maintaining the permeability membrane

Question 38

What characterizes beta barrels?

Answer 38

They consist of arrangements of 20+ beta strands forming a cylindrical or barrel-like shape. Stabilizes hydrogen bonds between adjacent beta-strands

Question 39

What characterizes an alpha-helical structure?

Answer 39

The hydrophobic side chains face outwards and interact with the lipid bilayer whilst the hydrophilic amino acids face inward, shielded from the hydrophobic environment.

Question 40

How can proteins bind to the bilayer?

Answer 40

Monotopic Bitopic or polytopic

Question 41

What characterizes a monotopic protein?

Answer 41

Has a small hydrophobic domain that interacts with only a single leaflet of the membrane. Attached but not imbedded

Question 42

What characterizes a bitopic protein?

Answer 42

Has a single hydrophobic sequence somewhere in the molecule. Spans the bilayer once and extends on either surface

Question 43

What characterizes a polytopic protein?

Answer 43

Crosses the membrane several times, has multiple hydrophobic sequences of at least 20 residues that each cross the membrane when in the alpha helical conformation. Polytopic due to more domains

Question 44

What types of membrane proteins exist?

Answer 44

Integral membrane proteins, peripheral membrane protein, amphitropic proteins

Question 45

What characterizes an integral membrane protein?

Answer 45

It is firmly embedded within the lipid bilayer

Question 46

What characterizes a peripheral membrane protein?

Answer 46

Associated with the membrane through electrostatic interactions and hydrogen bonding. Can be attached to integral membrane proteins Can be attached to either inner or outer side of membrane

Question 47

What characterizes amphitropic proteins?

Answer 47

Associate reversibly with membranes, bind weakly and can be broken apart again Found in both membranes and the cytosol

Question 48

What is the functions of proteins embedded in or associated with the lipid bilayer?

Answer 48

Transporters, receptors, ion channels and adhesion molecules

Question 49

What forces exist in membrane biophysics?

Answer 49

Hydrophobic effect, electrostatic interactions, elastic forces and Van der Waals forces.

Question 50

What is the general structure of sterols?

Answer 50

They have four fused carbon rings, are almost planar and are relatively rigid

Question 51

What is the general structure og glycosphingolipids?

Answer 51

They have a head group with 1+ sugars which connect directly to the -OH at the C1 of the ceramide half. It does not contain phosphate and occur largely in the outer face of plasma membranes

Question 52

What is the general structure of sphingomyelins?

Answer 52

They are a subclass of sphingolipids that contain phosphocholine or phosphoethanolamine as the polar head group

Question 53

What is the general structure of sphingolipids?

Answer 53

They have a polar head and two nonpolar tails. They contain one molecule of the long-chain amino alcohol sphingosine or one of its derivatives and they contain no glycerol.