Cell Membranes

Question 1

What properties must a cell membrane have?

Answer 1

Flexibility & deformabilitySelective permeabilityFluid environmentReceptorsTransporters, carriers, channelsEnzymesAssociation with cell cytoskeletonJunction and adhesion proteins

Question 2

Why does a cell membrane need to be flexible?

Answer 2

So that its shape can be altered, for molecules to insert themselves into the membrane

Question 3

Why do cell membranes need a permeability barrier?

Answer 3

To prevent free movement of ions, solutes (charged particles) into the cell

Question 4

Why does a cell membrane need receptors?

Answer 4

To recognise hormones, growth factors, neurotransmitters, lipoproteins, transferrin, the extracellular matrix and other molecules.

Question 5

Why do cell membranes need junction and adhesion proteins?

Answer 5

To link proteins together

Question 6

True or false? The lipid bilayer is symmetrical.

Answer 6

False. It has an asymmetric structure

Question 7

True or false? Eukaryotic cells have many membrane systems

Answer 7

True. This is what makes the organelles separate from the cell.

Question 8

What is the benefit of specialised compartments (membrane-bound organelles) in the cell?

Answer 8

Increased complexity of function

Question 9

What do complex lipids provide in the membrane?

Answer 9

Plastic, deformable, fluid, dynamic environmentCreates the permeability barrierPlays key roles in signal transduction

Question 10

What is the role of proteins, glycoproteins and glycolipids in the cell membrane?

Answer 10

Provide receptors, enzymes, junctions with adjacent cellsLinks to the cytoskeleton and extracellular matrixAllow for active transport and carrier functionsPlays a role in signal transduction

Question 11

How do proteins associate with membranes?

Answer 11

Extrinsically/ PeripherallyIntrinsically/ IntergrallyUsing lipid anchors

Question 12

What are some functions of membrane proteins?

Answer 12

TransportingLinkingReceptorsEnzymes

Question 13

What do polar amino acids as part of a polypeptide do in the cell membrane?

Answer 13

Interact with lipid head groups

Question 14

What is the shape of the main membrane lipids in the bilayer?

Answer 14

Cylindrical

Question 15

What factors influence fluidity between lipids?

Answer 15

cis-double bonds in fatty acids, acyl chain length, headgroup size, hydration

Question 16

Complex lipids have a dual affinity. What is the technical term for this?

Answer 16

Amphipathic

Question 17

What are the benefits of amphipathic complex lipids in a bilayer?

Answer 17

Most favourable arrangement energeticallyVery stable structure (bilayer)

Question 18

What configuration are most double bonds in unsaturated fatty acids?

Answer 18

Cis

Question 19

What angle does the cis-configuration of the double bond introduce in fatty acids?

Answer 19

120º

Question 20

Diffusion rate is proportional to what?

Answer 20

Concentration gradient and hydrophobicity

Question 21

What does hydrophobicity have to do with the rate at which a water-soluble molecule diffuses across the bilayer?

Answer 21

The greater the hydrophobicity, the faster it diffuses across the bilayer

Question 22

What molecules cannot cross the membrane on their own?

Answer 22

Polar molecules, large molecules, ions

Question 23

What are uniporters?

Answer 23

Transporters that move one molecule at a time down their gradient

Question 24

What are the two types of cotransporters?

Answer 24

SymportersAntiporters

Question 25

What do symporters/ antiporters do?

Answer 25

Move one or more ions/ molecules down their concentraion gradient with movement of another ion/ molecule against its concentration gradient

Question 26

What are the three major classes of membrane transport proteins?

Answer 26

TransportersATP powered pumpsChannel proteins

Question 27

What are transporter proteins?

Answer 27

Bind to one substrate molecule at a time, transports it down it’s concentraion gradient

Question 28

What are ATP powered pumps?

Answer 28

ATPases that use energy of ATP hydrolysis to move ions or small molecules across the membrane against their concentration/ electrical gradient

Question 29

How is glucose transported into cells?

Answer 29

Uniporter carries them down a concentration gradient

Question 30

How are amino acids transported into most cells?

Answer 30

Uniporter carries them down a concentration gradient

Question 31

What is the electric potential range of animal cells?

Answer 31

-20 to -200 mV

Question 32

What are the major classes of ATP-powered ion and small molecule pumps?

Answer 32

ABC classF classP classV class

Question 33

What does the P class ATP pump transport?

Answer 33

H+, Na+, K+, Ca2+

Question 34

What does the Fclass ATP pump transport?

Answer 34

H+ only

Question 35

What does the Vclass ATP pump transport?

Answer 35

H+

Question 36

What does the ABCclass ATP pump transport?

Answer 36

Ions and small molecules

Question 37

How does signal transduction work?

Answer 37

Seven span receptors in the plasma transduce signals from molecules (that have bound to the receptors). The effects vary from tissue to tissue.

Question 38

What do the effects of signal transduction depend on?

Answer 38

The receptor type

Question 39

Why is there a potential across biological membranes?

Answer 39

10% - Na+/ K+ ATPase pump actionMostly - K+ leak channels open; K+flows down itsconcentration gradient leaving negative ions behind