Lecture 4: Cell Membrane

Question 1

basic function of the cell membrane

Answer 1

to separate the outer and inner cell environments

to separate two aqueous compartments

Question 2

phospholipid structure/formation

Answer 2

formed from a neutral fat in which one of the groups of the fat is replaced by a phosphate group
each P has 2 amino acid tails associated with it

Question 3

hydrophilic head

Answer 3

phosphate groups

Question 4

hydrophobic tails

Answer 4

amino acid tails, 2 per head

Question 5

bilayer composition

Answer 5

two phospholipids that are arranged with tails on the inside

Question 6

singer and nicholson

Answer 6

fluid mosaic model of cell membrane

backed up by freeze-fracture technique

Question 7

outer leaflet

Answer 7

cholesterol
phosphatidylcholine, -ethanolamine
sphingomyelin
glycolipids
GPI

Question 8

what does GPI stand for? significance?

Answer 8

glycosylphosphatidylinositol
important in cell signaling
GPI anchoring proteins for peripheral proteins

Question 9

inner leaflet

Answer 9

cholesterol

phosphatidylethanolamine, -serine, -inositol

Question 10

located on inner and outer leaflet

Answer 10

cholesterol

Question 11

cholesterol functions

Answer 11

moderates membrane fluidity

functions in changing tempertures

Question 12

cholesterol at high temperatures

Answer 12

interferes with FA chain mvt
makes outer less fluid
reduces permeability to small molecules

Question 13

cholesterol at low temperatures

Answer 13

prevents membrane from freezing

maintains fluidity

Question 14

location of glycolipids

Answer 14

outer leaflet only

Question 15

function of glycolipids

Answer 15

function to create a cell coat --- involved in cell to cell interactions
conveys antigenicity

Question 16

what portion of a glycolipid faces the extracellular matrix?

Answer 16

the carbohydrate portion

Question 17

what are lipid rafts composed of?

Answer 17

cholesterol and sphingolipids

Question 18

function of lipid rafts

Answer 18

to compartmentalize cellular processes by serving as organization center
examples:
assemble cell signaling molecules
influence membrane fluidity – cholesterol
protein and neurotransmitter trafficking

Question 19

____ proteins will cluster in lipid rafts.

Answer 19

GPI-anchoring proteins

Question 20

tips of microvilli

Answer 20

glycocalyx

Question 21

functions of glycocalyx

Answer 21

protect cell from ionic/mechanical stress
barrier against microorganisms
involved in cell-cell interactions

Question 22

mechanisms for moving materials across cell membranes

Answer 22

diffusion
osmosis
facilitated diffusion
active transport

Question 23

mvt of particles based upon a concentration gradient

Answer 23

diffusion

Question 24

diffusion of water across a semipermeable membrane

Answer 24

osmosis

Question 25

diffusion that requires transport molecules

Answer 25

facilitated diffusion

Question 26

mvt of particles against a gradient

Answer 26

active transport

Question 27

categories of transport proteins

Answer 27

Unitransporters = uniporters 
co-transporters = symporters
counter-transporters = antiporters

Question 28

difference between symporters and antiporters

Answer 28

carry 2 molecules in same or opposite directions