Lecture 13: Cell Membranes

Question 1

What are some functions of the cell membrane

Answer 1

-separate cells and create environment
-selectively permeable
-Cell to cell communication
-Cytoskeleton

Question 2

What is the structure of the cell membrane

Answer 2

phospholipid bilayer

Question 3

What property of phospholipid allows for the formation of the double membrane

Answer 3

Amphipathic
Core of hydrocarbon tails provide a hydrophobic barrier for water and charged solutes

Question 4

Animal cells show lipid asymmetry: the outer leaflet of the membrane
has ______________________ while the inner layer is
richer in ________________________

Answer 4

glycosphingolipids and phosphatidylcholine,

phosphatidylserine (PS), phosphatidylinositol, and
phosphatidylethanolamine.

Question 5

_________________ increase in the outer leaflet is an indicator of low app –> Cell stress and death

Answer 5

phosphatidylserine (PS)

Question 6

___________ are ATPase pumps that bring the PS to the inner leaflet

Answer 6

Flippases

Question 7

________________ are transporter pumps that move lipids from the inner to outer leaflet

Answer 7

Floppases

Question 8

____________ are useful in cell to cell and cell to matrix interactions

Answer 8

glycosphingolipid

Question 9

____________ tend to group together in the outer leaflet forming lipid rafts

Answer 9

Sphingolipids

Question 10

lipid rafts are also rich in _________________ which facilitates transmembrane signaling

Answer 10

glycosphingolipids and cholesterol and membrane receptor

Question 11

_________ are non covalently bonded with integral proteins

Answer 11

integral proteins

Question 12

___________ lipids and proteins on the membrane form distinct units on the surface. However they are not fixed in place and can move along the surface of the membrane

Answer 12

Fluid mosaic model

Question 13

________ have membrane spanning alpha helical domains of about 20 amino acids, some have multiple membrane spanning domains, some proteins are linked to membrane phospholipids via oligosaccharides

Answer 13

integral proteins

Question 14

________ interact with the matrix

Answer 14

adhesion molecules

Question 15

_____________ bind to signal molecules ligands and initiate cellular responses often using an intracellular second messenger (more in the cellular communication sessions)

Answer 15

receptors

Question 16

What are 3 methods of the movement of water

Answer 16

-Pores (always open) and channels (can be closed) to allow ions, water and other molecules

-carriers facilitate transport and do not use ATP

-Pumps move substances across membrane against gradient and use ATP

Question 17

What are two key functions of membrane bound proteins?

Answer 17

-Enzymes that participate in digestion
-Some membrane proteins interact with the cytoskeleton to anchor it and transduce signals

Question 18

____________ the ability of substances to cross the membrane depends of size and charge and stability of the membrane

Answer 18

selectively permeable

Question 19

What types of molecules need help crossing the membrane

Answer 19

polar molecules

Question 20

Describe dynamic equilibrium in terms of the plasma membrane?

Answer 20

Molecules redistribute from areas of high concentration to areas of low concentration until they equalize

Question 21

What are some factors that affect how easily things flow across the membrane according to flicks law

Answer 21

-thickness of membrane
-temperature
-solubility and polarity of solute in the membrane
-size

Question 22

What are the two types of diffusion

Answer 22

-Simple diffusion (through a pore)
-Facilitate diffusion (through a carrier protein)

Question 23

What is active transport

Answer 23

transport that requires energy and carrier proteins

Question 24

What occurs when carrier mediated transport is saturated?

Answer 24

We reach v max. The speed of transport reaches its max.

*Simple diffusion is always dependent on concentration gradient

Question 25

What are some control mechanisms top open ion channels

Answer 25

-ligand mediated
-voltage mediated
-mechanical (stretch) mediated

*can be saturated, size and charge regulate what can cross

Question 26

______________ move one type of molecule, selective, saturable, unidirectional flow, regulation is through hiding from the surface of the membrane (endocytosis)

Answer 26

carrier proteins

Question 27

_________ use atp directly, saturable, unidirectional, can move one or multiple molecules, usually regulated through endocytosis

Answer 27

Pumps

Question 28

Secondary active carrier proteins move multiple molecules at the same time: What must occur for the protein to move

Answer 28

both molecules need to be in the binding site
*selective, unidirectional, saturable, endocytosis

Question 29

______________ are used to speed up the movement of water.

Answer 29

Aquaprorins

Question 30

_______________ the force of water movement

Answer 30

osmolarity

Question 31

in osmolarity water moves to the side with _______________________

Answer 31

higher concentration of solutes

Question 32

What two properties balance dynamic equilibrium

Answer 32

-ion concentration and water concentration

Question 33

_____________ the principle that ions will move across the membrane to balance based on both their concentration and their charge

Answer 33

electrochemical gradient

1. charge
2. concentration

Question 34

What is membrane potential?

Answer 34

The potential at which a specific set of concentrations of an ion would lead to a stable equilibrium

Question 35

In simple terms, membrane potential means ion will move in such a way that the _____________________ and ___________ equalize

Answer 35

equilibrium and membrane potential equalize

Question 36

What is hyperpolarization

Answer 36

membrane becomes more negative

-exit of cations and entrance of anions

Question 37

What is Depolarization

Answer 37

Membrane becomes less negative (more positive)

Entrance of cations

Question 38

____________move ions in the same direction

Answer 38

Symporters

Question 39

____________ move ions in opposite directions

Answer 39

Antiporters