Cell Membranes Flashcards Preview

Phase I Medicine > Cell Membranes > Flashcards

Flashcards in Cell Membranes Deck (39):
1

What properties must a cell membrane have?

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

2

Why does a cell membrane need to be flexible?

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

3

Why do cell membranes need a permeability barrier?

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

4

Why does a cell membrane need receptors?

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

5

Why do cell membranes need junction and adhesion proteins?

To link proteins together

6

True or false? The lipid bilayer is symmetrical.

False. It has an asymmetric structure

7

True or false? Eukaryotic cells have many membrane systems

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

8

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

Increased complexity of function

9

What do complex lipids provide in the membrane?

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

10

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

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

11

How do proteins associate with membranes?

Extrinsically/ PeripherallyIntrinsically/ IntergrallyUsing lipid anchors 

12

What are some functions of membrane proteins?

TransportingLinkingReceptorsEnzymes

13

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

Interact with lipid head groups

14

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

Cylindrical

15

What factors influence fluidity between lipids?

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

16

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

Amphipathic

17

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

Most favourable arrangement energeticallyVery stable structure (bilayer)

18

What configuration are most double bonds in unsaturated fatty acids?

Cis

19

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

120º

20

Diffusion rate is proportional to what?

Concentration gradient and hydrophobicity

21

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

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

22

What molecules cannot cross the membrane on their own?

Polar molecules, large molecules, ions

23

What are uniporters?

Transporters that move one molecule at a time down their gradient

24

What are the two types of cotransporters?

SymportersAntiporters

25

What do symporters/ antiporters do?

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

26

What are the three major classes of membrane transport proteins?

TransportersATP powered pumpsChannel proteins

27

What are transporter proteins?

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

28

What are ATP powered pumps? 

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

29

How is glucose transported into cells?

Uniporter carries them down a concentration gradient

30

How are amino acids transported into most cells?

Uniporter carries them down a concentration gradient

31

What is the electric potential range of animal cells?

-20 to -200 mV

32

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

ABC classF classP classV class

33

What does the P class ATP pump transport?

H+, Na+, K+, Ca2+

34

What does the F class ATP pump transport?

H+ only

35

What does the V class ATP pump transport?

H+

36

What does the ABC class ATP pump transport?

Ions and small molecules

37

How does signal transduction work?

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

38

What do the effects of signal transduction depend on?

The receptor type

39

Why is there a potential across biological membranes?

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