Membranes I&II

Question 1

What controls membrane fluidity?

Answer 1

fatty acid composition and cholesterol content

Question 2

List the common features of biological membranes.

Answer 2

Sheet like structures that form closed boundaries between different compartments.

Mainly, consist of lipids and proteins. They also contain carbohydrates that are linked to lipids and protein.

Membrane lipids have both a hydrophilic and hydrophobic unit (amphipathic).

Specific proteins are embedded in lipid bilayers and mediate distinct functions.

Question 3

List the properties (other common features) of biological membranes.

Answer 3

form non-covalent assemblies

asymmetric

fluid structure

electrically polarized

Question 4

List the two forms of membrane lipids.

Answer 4

Micelle

Bilayer

Question 5

Describe a micelle.

Answer 5

limited, usually less than 20 nm in diameter

is formed when a variety of molecules including soaps and detergents are added to water

Question 6

Describe a lipid bilayer.

Answer 6

favored structure for most phospholipids and glycolipids in water

self-assembly process

forces: hydrophobic interaction, Van der Waals, electrostatic, Hydrogen bonding

Question 7

What is the driving force for self assembly?

Answer 7

hydrophobic interactions

Question 8

What are the three significant consequences of membrane lipid hydrophobic interactions?

Answer 8

have an inherent tendency to be extensive

will tend to close on themselves so there are no edges with exposed hydrocarbon chains, and so they form a compartment

are self-sealing

Question 9

True or False, lipid bilayers have a very low permeability for ions and most polar molecules.

Answer 9

True

Question 10

What is the order from increasing permeability for molecules?

Answer 10

Na+, K+, Cl-, glucose, tryptophan, urea glycerol, indole, H2O

Question 11

What are the types of membrane proteins?

Answer 11

integral (transmembrane) proteins, peripheral proteins, lipid-linked proteins

Question 12

List the 3 kinds of modification for lipid-linked proteins.

Answer 12

Palmitoylation of cysteine residues

Farnesylation of cystein residues

Glycosylphophatidylinositol-link

Question 13

What are the 2 specialized membranes of the mitochondria?

Answer 13

permeable outer membrane

impermeable inner membrane (matrix)

Question 14

True or False, many integral membrane proteins extend across the lipid bilayer.

Answer 14

True

Question 15

True or False the alpha helix is the most membrane spanning structure.

Answer 15

True

Question 16

What forces bind peripheral proteins to the membrane surfaces?

Answer 16

electrostatic and hydrogen-bonding interactions

Question 17

Where does oxidative phosphorylation take place in the mitochondria?

Answer 17

in the innermembrane space

Question 18

What is the site of most of the TCA cycle and fatty acid oxidation?

Answer 18

in the matrix of the mitochondria

Question 19

What is referred to by lateral movement of the membrane proteins?

Answer 19

Membrane proteins and lipids diffuse laterally along the membrane

Question 20

What technique is used to observe the dynamics of membrane molecules?

Answer 20

FRAP = fluorescence recovery after photo-bleaching technique

Question 21

How does transverse diffusion across the membrane compare to lateral diffusion?

Answer 21

Transverse diffusion (flip-flop) is very slow, while lateral diffusion is rapid.

Question 22

What contributes to membrane asymmetry?

Answer 22

different composition of inner and outer leaflets

proteins have unique orientations

lipid molecules are asymmetrically distributed

large amounts of cholesterol in both leaflets

Question 23

Why are carbohydrates placed on cell membranes?

Answer 23

glycosylation occurs on the extracellular surface of the plasma membrane

antibodies recognize RBC blood types by its extracellular carbohydrates

Question 24

How do the membranes of eurkaryotes, bacteria and archaea differ?

Answer 24

Some bacteria and archaea only have a single membrane surrounded by a cell wall

eukaryotes, except for plants, have a lipid bilayer and no cell wall for their plasma membrane

Question 25

Eukaryotic cells have _______ inside their cell membrane.

Answer 25

membrane bound organelles: peroxisomes, mitochondria, endoplasmic reticulum, golgi aparatus

Question 26

True or False, eukaryotic nuclear envelope is continuous.

Answer 26

False

Question 27

What must membranes be able to do?

Answer 27

separate and join together so cells and compartments can take-up, transport, and release molecules

Question 28

What is another word for receptor-mediated endocytosis (RME)?

Answer 28

budding, fusion

Question 29

Describe budding.

Answer 29

Invaginated membrane breaks off and fuses to form a vesicle

Question 30

What is key for neurotransmitter release into the synaptic cleft?

Answer 30

fusion of a vesicle to a membrane

Question 31

What does SNARE do?

Answer 31

gathers the appropriate membranes to initiate the fusion process

Question 32

Describe mitochondrial fission.

Answer 32

Insertion of new components will cause mitochondria to grow

must be a signal for fission

mitochondria have to multiply to be divided between daughter cells

analogous to bacterial division

Question 33

Describe mitochondrial fusion

Answer 33

occurs between identical organelles

excludes all other intracellular membranes

salvage process

requirements: sufficiently large electrochemical gradient must be present across inner membrane, elevated GTP levels must be available for hydrolysis

Question 34

True or False, proteins have to be unfolded to be imported.

Answer 34

True

Question 35

True of False, ATP is required if a protein crosses the matrix membrane.

Answer 35

True