Cell Biology Chapter Eleven

Front 1

the simplest bacteria have ______membrane and eucaryotic cells have ____

Back 1

the simplest bacteria have only a single membrane: the plasma membrane

eucaryotic cells however, also contain an abundance of internal membranes that enclose intracellular compartments to form the various organelles

Front 2

regardless of their location, all cell membranes are composed of ____ &____ and share a common general structure

Back 2

lipids and proteins

Front 3

in general what are the three things that a membrane is involved in ?

Back 3

cell communication
(receptor proteins in the plasma membrane enable a cell to receive signals from the environment)

import and export of molecules
(transport proteins in the membrane enable the import and export of small molecules

cell growth and motility
(the flexibility of the membrane and its capacity for expansion allow cell growth and cell movement)

Front 4

list all the membrane enclosed organelles in a typical animal cell

which are enclosed by two membranes?

Back 4

1. endoplasmic reticulum
2. nucleus
3. peroxisome
4. lysosome
5. transport vesicle
6. mitochondrion
7. plasma membrane
8. golgi apparatus

nucleus and mitochondria are each enclosed by two membranes

Front 5

the ______ has been firmly established as the universal basis for membrane structure, and its properties are responsible for the general properties of all cell membranes.

Back 5

lipid bilayer

Front 6

the most abundant lipids in cell membranes are the ______, molecules in which the hydrophilic head is linked to the rest of the lipid through a _____group.

Back 6

phospholipids

phosphate

Front 7

the most common type of phospholipid in most cell membranes is ______, which has the small molecule ____ attached to a phosphate as its hydrophilic head and two long hydrocarbon chains as its hydrophobic tails

Back 7

phosphatidylcholine

choline

Front 8

molecules with both hydrophilic and hydrophobic properties are termed ___

Back 8

amphipathic

Front 9

which type of membrane lipids have sugars as part of their hydrophilic head ?

Back 9

glycolipids

Front 10

how big is the the lipid bilayer

Back 10

5 nm

Front 11

phosphatidylcholine
this particular phospholipid is built from five parts, what are they?

Back 11

the hydrophilic head choline
is linked via a phosphate to glycerol
which in turn is linked to two hydrocarbon chains forming they hydrophobic tail

Front 12

different types of membrane lipids are all amphipathic

phosphatidylserine
cholesterol
galactocerebroside

what is the hydrophilic head for each of this?

Back 12

phosphatidylserine : serine phosphate
cholesterol : -OH group
galactocerebroside : a sugar (galatose) and an -OH group

Front 13

give an example of a hydrophilic and hydrophobic molecule

Back 13

acetone: hydropholic because it is polar it can form favorable interactions with water

2 methylpropane molecule is entirely hydrophobic, it cannot form favorable interations with water, and forces adjacent water molecules to reorganize into a cagelike structure around it

Front 14

fat molecules such as triacylgycerol are ____ whereas phospholipids such as phosphatidylethanolamine are _____.

Back 14

hydrophobic

amphipathic

Front 15

what do phospholipid bilayers tend to do spontaneously?

Back 15

close in on themselves to form a sealed compartment.

the closed structure is stable because is avoids the exposure of the hydrophobic hydrocarbon tails to water

Front 16

why does the membrane behave as a two dimensional fluid?

Back 16

because nothing stops lipids from moving about and changing places with one another within the plane of the bilayer

Front 17

_____ is the ability of the membrane to bend. it sets a lower limit of about ___to the size of vesicle that cell membrane can form.

Back 17

flexibility

25nm

Front 18

what is the name of the synthetic lipid bilayers that are made (closed spherical vesicles)?

Back 18

liposomes

Front 19

individual lipid molecules within a monolayer rotate very rapidly about their long axis

Back 19

flip flop spontaneously

Front 20

describe the fluidity of a cell membrane

Back 20

the ease with which its lipid molecules move within the plane of the bilayer

Front 21

the fluidity of a lipid bilayer depends on its ____

Back 21

composition

Front 22

just how fluid a lipid bilayer is at a given temp depends on its ______, in particular ______

Back 22

phospholipid composition
on the nature of the hydrocarbon tails

the closer and more regular the packing of the tails, the more viscous and less fluid the bilayer will be

Front 23

what are the two major properties of hydrocarbon tails affect how tightly they pack in the bilayer?

Back 23

their length &
the number of double bonds they contain

Front 24

why do lipid bilayers that contain a large proportion of unsaturated hydrocarbon tails more fluid than those with lower proportions?

Back 24

each double bond in an unsaturated tail creates a kink in the hydrocarbon tail , which makes it more difficult for the tails to pack against one another

Front 25

in animal cells, membrane fluidity is modulated by the inclusion of the ____

Back 25

sterol cholesterol

this molecule is present in especially large amounts in the plasma membrane, where is constitutes approximately 20% of the lipids in the membrane weight

Front 26

_____ tends to stiffen cell membranes

Back 26

cholesterol

Front 27

what fits into the gaps between phospholipid molecules in a lipid bi-layer

Back 27

cholesterol (short and rigid) is makes the bi layer more rigid and less permeable

Front 28

cell membranes are generally _____: they present a very different face to the interior of the cell or organelle than they show to the exterior

Back 28

asymmetrical

Front 29

the two halves of the bilayer often include strikingly different sets of ___&___

Back 29

phospholipids and glycolipids

Front 30

____transfer specific phospholipids selectively so that different types become concentrated in each monolayer

Back 30

flippases

Front 31

newly synthesized phospholipid molecules are all added to the ___

___ then transfer some of these molecules to the opposite monolayer, so that the entire bilayer expands

Back 31

cytosolic side of the ER membrane

flippases

Front 32

nearly all new membrane synthesis in eucaryotic cells occurs in the membrane of one intracellular compartment- the ____

Back 32

endoplasmic reticulum

Front 33

new membrane assembled in the ER is exported to the other membranes of the cell through a cycle of ______: bits of the bilayer pinch off from the ER to form small spheres called _____, which then become incorporated into another membrane such as the plasma membrane by ____

Back 33

of membrane budding and fusion

vesicles

by fusing with it

Front 34

gylcolipids are located mainly in the _____, and they are found only in the _____half of the bilayer

Back 34

plasma membrane

non cytosolic

they glycolipid sugar groups are therefore exposed to the exterior of the cell, where they form part of a continuous protective coat of carbohydrate that surrounds most animal cells

Front 35

where do glycolipids acquire their sugar groups?

Back 35

in the golgi apparatus, the organelle to which proteins and membranes made in the ER often go next

Front 36

inositol phospholipids plays a special role in ...

Back 36

relaying signals from the cell surface to the intracellular components that respond to those signals

they are concentrated int he cytosolic half of the lipid bi layer