chapter 12

Question 1

membranes are how thick

Answer 1

2 molecules thick

Question 1

membranes are composed of

Answer 1

lipids and proteins

Question 2

membrane lipids are

Answer 2

small amphipathic molecules that form closed bimolecular sheets

Question 3

membrane proteins serve to

Answer 3

mitigate the impermeability or membranes and allow movement of molecules and information

Question 4

membranes are….. (noncovalent or covalent)

Answer 4

noncovalent

Question 5

membranes are (symmetric or asymmetric)

Answer 5

asymmetric (outside is always different than inside)

Question 6

membranes are (nonfluid or fluid)

Answer 6

fluid duh

Question 7

how are membranes formed

Answer 7

phospholipids spontaneously form lipid bilayers in aqueous solution (because the head is hydrophilic and the tail is hydrophobic) and then van der waals stabilize the membrane

Question 8

membranes have _____ permeability for ions and polar molecules

Answer 8

LOW

Question 9

what is melting temperature

Answer 9

temperature at which a membrane transitions from being highly ordered to very fluid

Question 10

the melting temperature is dependent on what

Answer 10

the length of the fatty acids in the membrane lipid and the degree of cis unsaturation

Question 11

what does cholesterol do

Answer 11

maintain proper membrane fluidity in membranes of animals

Question 12

integral proteins

Answer 12

embedded in the hydrocarbon core of the membrane

Question 13

peripheral proteins

Answer 13

bound to the polar head groups of membrane lipids or to the exposed surfaces of integral membrane proteins

Question 14

membrane spanning a helices

Answer 14

integral membrane proteins
bateriorhodopsin (light powered protein pump)

Question 15

porin

Answer 15

B strands that form a pore in the membrane

porin is an example

inside is polar and filled with water

Question 16

fluid mosaic model

Answer 16

describes membranes as two dimensional solutions of oriented lipids and globular proteins

Question 17

lateral diffusion

Answer 17

very fast

Question 18

transverse diffusion

Answer 18

very slow

Question 19

lipophilic molecules pass through how

Answer 19

down their concentration gradients in the process of simple diffusion

Question 20

passive transport

Answer 20

movement (facilitated diffusion) by charged molecules down their concentration gradient

Question 21

active transport

Answer 21

molecule movement across a membrane against concentration gradient that requires energy

Question 22

atp driven pumps

Answer 22

lipid fluidity independent

Question 23

carriers

Answer 23

lipid fluidity dependent

Question 24

channels

Answer 24

lipid fluidity independent

Question 25

Na-K pump or Na-K ATPase

Answer 25

P-type ATPase
goes from low concentration to a high concentration
most animal cells have a high concentration of K and a low concentration of Na relative to the external environment - this pump maintains and generates this gradient

Question 26

what are the 2 conformations of p-type atpase pumps

Answer 26

1: ion binding site facing into the cell
2: ion binding site facing out of the cell

Question 27

what powers the interconversion between the two conformations of p-type atpases

Answer 27

ATP hydrolysis

Question 28

multi-drug resistance protein

Answer 28

atp-dependent pump that extrudes small molecules from the cell

member of ABC transporter family

Question 29

what characterizes ABC transporters

Answer 29

common domain called ATP-binding cassette (ABC)

Question 30

ABC transporters consist of

Answer 30

two ABC domains and two membrane spanning domains (4 in total)

Question 31

what is the difference between MDR (multidrug resistance protein) and MsbA (bacterial lipid transporter)

Answer 31

MDR domains are linked together and are 1 peptide chain with chains linking all domains together

MsbA does dimerization and the dimers are not linked together

Question 32

what is a carrier

Answer 32

protein that transports ions or molecules across the membrane WITHOUT ATP hydrolysis

Question 33

how do carriers transport

Answer 33

facilitated diffusion - high to low concentration
secondary active transport - low to high concentration by using energy of another gradient

Question 34

what do symporters do

Answer 34

power the transport of a molecule against its concentration gradient by coupling the movement to the movement of another molecule down its concentration gradient, with both molecules moving in the same direction

Question 35

what do symporters do for dummies

Answer 35

the molecule going high to low concentration piggy backs on the molecule going low to high concentration and goes with the flow (cheating the system)

the molecules are moving in the SAME (sym) direction

Question 36

what do antiporters do

Answer 36

use one concentration gradient to power the formation of another but the molecules move in the OPPOSITE direction

Question 37

what do uniporters do

Answer 37

transport a molecule in either direction depending on the concentration difference across the membrane

Question 38

what are channel proteins

Answer 38

channels in the membrane for molecules to pass through

Question 39

how are channel proteins selective

Answer 39

there are 2 sections to the channel - a larger channel and a smaller channel

molecules that are just right are the perfect size for both and can pass through both “filters” in the channel without blocking

Question 40

what accounts for the rapid rate of transport in potassium ion channels

Answer 40

charge repulsion among the 4 binding sites