Midterm 2 Flashcards
1
Q
can you see plasma membrane with light microscope
A
no, too small
need electron microscope
2
Q
what lead them to find out that membranes are mostly comprised of lipids
A
dissolving power corresponded to that of oil
3
Q
what is most energetically favourable orientation for polar head groups in plasma membrane
A
polar head groups facing the aqueous components outside the bilayer
4
Q
what stabilizes bilayers
A
van der Waals interactions in the fatty acyl chains
also there are h-bonds and ionic bonds between the polar head groups and water
5
Q
how are proteins present in lipid bilayer
A
as individual protein molecules and protein complexes that penetrate bilayer and extend out into the surrounding aqueous environment
6
Q
what makes membranes dynamic
A
membrane fluidity
7
Q
what are the functions of plasma membranes
A
- compartmentalization (define boundaries of cell organelles)
- scaffolding for biological activities (provides framework that organizes enzymes for effective interactions)
- selective permeability barrier (allows regulated exchange of substances between compartments)
- solute transport (membrane proteins facilitate the movement of substances between compartments)
- response to external stimuli (membrane receptors transduce signals from outside the cell in response to specific ligands)
- cell-cell communication ( mediate recognition and interactions between adjacent cells)
- energy transduction (membranes transduce photosynthetic energy, convert chemical energy to ATP, store energy)
8
Q
how are membranes and lipid-protein assemblies held together
A
non-covalent bonds
9
Q
what are the two components of membranes and their function
A
- lipid bilayer: structural backbone and barrier to prevent random movement in/out of cell
- membrane proteins: carryout the more specialized functions
10
Q
does the lipid-to-protein ration vary and what does it depend on
A
yes
depends on: type of cellular membrane, type of organism, type of cell
11
Q
what are the three types of lipids that mammalian membranes are primarily composed of
A
- phosphoglycerides
- sphingolipids
-cholesterol
12
Q
what do phosphoglycerides contain (at a minimum)
A
2 fatty acids (usually one saturated and one unsaturated), a glycerol, and a phosphate
13
Q
what do all phosphoglycerides exhibit
A
a distinct amphipathic character
14
Q
what are sphingolipids derived from / composed from
A
derivatives from ceramides
(sphingosine + a fatty acid)
15
Q
what is a glycolipid
A
singolipid with an added carbohydrate group
16
Q
what is a ganglioside
A
sphingolipid with multiple sugars added
17
Q
where are glycolipids found exclusively
A
ectoplasmic face of plasma membrane
18
Q
where are sugar groups added to glycolipids
A
in lumen of the Golgi
19
Q
why is cholesterol amphipathic
A
the hydroxly group
20
Q
what is cholesterol used for
A
used to stabilize and maintain membranes
important for fluidity
21
Q
what can membrane lipids be precursors for
A
highly active chemical messengers that regulate cellular function
22
Q
what do the hydrophobicnature of chains in membranes result in
A
they cannot be exposed to aqueous environment
membranes always continuous unbroken structures
23
Q
can lipid bilayers self assemble
A
yes
24
Q
what do in vitro phospholipids self assemble spontaneously into
A
spherical vesicles called liposomes
25
do leaflets in same lipid bilayer have different lipid compositions
yes
26
what cab lipid bilayers be thought of as
2 independent monolayers with different physical and chemical properties
27
what side of bilayer are glycolpids always on and why
they are aways on the extracellular side and they serve as ligand receptors
28
what side of the lipid bilayer is negatively charged
cytosol side
29
when can proteins bind to cytosolic side
when they require negatively charged PS for activity
30
what way to all membrane carbohydrates face
away from the cytosol (extracellular space, ER lumen, etc..)
31
what is glycosylation
addition of carbohydrates to proteins
most complex post translational modifications
32
what are the 3 classes of proteins associated with membranes
integral monotonic proteins
single pass proteins
multi-pass proteins
(single and multi pass are transmembrane proteins)
33
What are lipid-anchored membrane proteins
located outside the membrane (either side), but are covalently "anchored" to a membrane lipid
34
what do the hydrophobic regions embedded into the membrane function as
transporters: moving ions across the membrane
anchors: binding intra/extracellular components to membrane
receptors: binding ligands to initiate signal transduction pathways
electron transporters: transfer e- during photosynthesis and respiration
35
what are integral membrane proteins (in terms of hydrophobic/hydrophillic)
amphipathic
36
what arrangement are transmembrane segments normally
alpha helices (sometimes beta barrels)
37
how are the alpha helices held in place in membrane
by van der waals between hydrophobic amino acid side chain and lipids
38
why are integral membranes hard to isolate in a soluble form
they aggregate in water
39
what is a glycophorin A
major integral protein of the erythrocyte plasma membrane
40
in glycophorin A what direction do most of the hydrophobic side chains of the amino acids in the a-helix face
lipid layer
41
what does a hydropathy plot do
measures the hydrophobicity of amino acids
42
what does + and - mean in hydropathy plots
+ hydrophobic
- hydrophilic
43
what provide a transmembrane proton pathway
seven helices that are clustered together
44
do peripheral membrane proteins interact with the hydrophobic core of the lipid bilayer
no
45
how are the peripheral membrane proteins associated with the membrane
interactions with lipid's polar head groups
46
are peripheral membrane proteins removed easier/harder remove from membrane than integral membrane proteins
easier to remove
47
what does removing peripheral membrane proteins do
changes pH
changes ionic strength
since it disrupts electrostatic interactions
48
what are the 3 lipid anchored membrane proteins and where are they synthesized
- fatty acid anchored membrane proteins: in cytosol
- isoprenylated membrane proteins: in cytosol
GPI-anchored membrane proteins: in ER
49
what is the fluid mosaic model
membranes consist of a mosaic of proteins/lipids in a fluidic state
50
why is membrane fluidity important
nearly every function involving a membrane is dependent on this phenomenon ex:
- vesicle formation, cell division, muscle contractions, cell migration, signalling mechanisms
51
what is the central dogma of membrane biology
fluid-mosaic model
52
what state do membranes function properly in
only in the fluid state
53
what happens if a fluid membrane is too rigid
membrane components can't organize properly as proteins can't move and interact with binding partners
54
what happens if a fluid membrane is too viscous
lose mechanical support (ability to orientate properly) with excessive fluidity resulting in an increase in membrane permeability
55
how does membrane fluidity change with temperature
low temp: fluidity decreases
high temp: fluidity increases
56
what is the transition temperature (Tm)
temperature at which membrane becomes fluid
57
how is fluidity affected by tail length
fluidity increases with shorter C tails
fluidity decreases with longer tails
58
what kind of fatty acids pack together better in a membrane
saturated
59
what kind of fatty acids are more fluid
saturated fatty acids
60
do saturated or unsaturated fatty acids have a lower Tm
unsaturated
61
what temperature are high fluidity (more unsaturated fatty acids, shorter tails) at a fluid state
lower temperature
62
what temperature are low fluidity (more saturated fatty acids, longer tails) at a fluid state
higher temperature
63
what layers of plasma membrane is cholesterol found in
both
64
what way does cholesterol orient itself in membrane
with hydroxyl group close to the polar head groups of phospholipids
65
what are the two roles of cholesterol in membranes
- sterols decrease the permeability of membranes to ions and small polar molecules
-cholesterol acts as a fluidity buffer (broadens the temperature range of transition)
66
how does cholesterol decreases the membrane's permeability to ions
cholesterol fills spaces between hydrocarbon chains of phospholipids and block routes that ions and small molecules could take through the membrane
67
hoe does cholesterol alter the fluidity of lipid bilayers
with unsaturated fatty acids, cholesterol decrease fluidity (more packed)
with saturated fatty acids, cholesterols increase fluidity
(less packed)
68
what do most membranes vary in and why
chain length and degree of saturation
helps ensure that membranes are fluid at physiological temperatures
69
what do cells use to alter fatty acids in response to needs
enzymes
70
what are homeoviscous adaptations
the ability of a cell to regulate membrane fluidity in response to temperature changes by altering lipid composition and maintain fluidity
71
what are lipid rafts
localized regios of membrane lipids in association with specific proteins
dynamic structures that change compositions as lipids and proteins move into and out of them
72
what are the functions of lipid rafts
- believed to serve as floating platforms that concentrate proteins into compartments on the membrane
- thought to have roles in deterring and responding to extracellular signals
73
what do lipid rafts have elevated levels of in outer monolayer in animal cells
cholesterol and sphingolipids
74
are lipid rafts more/less fluid than rest of membrane
less fluid
75
are lipids mobile in their monolayer
yes
76
what are the two rapid and random movements in plasma membrane
- rotation of phospholipids about their axis
-phospholipids can also move within monolayer via lateral diffusion (very fast)
77
how do lipids "flip flop"
hydrophilic head of the lipids must pass though the internal hydrophobic sheet of membrane
(slow)
78
what are flippases
enzymes that move certain phospholipids from one leaflet to he other
79
what are flippases essential for
establishing membrane asymmetry
80
does protein mobility vary within a membrane
yes
81
what is fluorescence recovery after photobleaching (FRAP)
cell surface molecules are labeled with a fluorescent dye
laser beam bleaches an area on the cell surface
fluorescent labeled molecules diffuse into bleached area and bleached area disappear as lipids move laterally
82
what did frap studies show
proteins move slower in living cell membranes than pure lipid bilayers
the mobility of many proteins was limited ( not free to diffuse back into bleached area)
83
what is passive transport
down a concentration gradient
no energy is expended
transported proteins may or may not be needed
84
what is active transport
against a concentration gradient
requires input of energy (ATP)
transport protein pumps are required
85
what does simple diffusion require
membrane permeability and favourable gradient conditions
86
what is permeability determines by
properties of the solute:
- molecular size
- partition coefficient
- charge
87
do small or big molecules penetrate lipid bilayer more rapidly faster
small
88
are membranes impermeable to ions
yes
89
how does moving down a concentration gradient affect entropy
increases entropy
90
how does an electric potential gradient work
charged molecules want to move towards the compartment with the opposite charge
91
what is the thermodynamically favourable transport direction for molecules determined by:
no net charge: by concentration gradient
ions: by electrochemical gradient
92
what is the electrochemical gradient
the combined effect of concentration gradient and the electrical potential gradient across the membrane
93
what is simple diffusion only possible for (typically)
gases
non-polar molecules
small polar molecules
94
what direction does diffusion move towards
equilibrium
95
what is passive/simple diffusion
unassisted movement of a molecule across a membrane, down its concentration gradient at a rate proportional to the gradient and the permeability of the membrane
96
is simple diffusion reversible
yes
97
what is osmosis
diffusion of water through a semi-permeable membrane where water moves from an area of lower solute concentration to an area higher solute concentrations
98
what happens in a hypotonic solution
cell swells
(more solutes in cell)
99
what happens in a hypertonic solution
cell shrinks
(less solutes in cell)
100
what happens in an isotonic solution
no net loss/gain of water
101
what is facilitated transport
requires a protein to help get the molecule across the membrane
102
how are transport molecules classified
carriers: bind one or more solute molecules, undergoes a conformational change that transfers the solutes to the other side
channels: form hydrophilic channels through the membrane that allow passage of solutes without a major conformational change
103
what are the three types of transmembrane channel proteins (involved with facilitated diffusion)
ion channels: highly specific channel (often for kind of 1 ion) that can conduct a million ions a second
porins: passage of a variety of hydrophilic solutes, determined by pore size
aquaporins: water flows through and amino acid residues discriminate against other ions of similar size
104
what direction do ion channels move in and what determines it
bidirectional
determined by electrochemical gradient
105
what does ion specificity result from
ion specific associations and from constriction in centre (size filter)
106
are most ion channels gated and do they require conformational changes
most have gates
no need to undergo conformational changes
107
what are the types of ion channel gates
voltage gated: open and close in response to change in membrane potential
ligand gated: triggered by the binding of specific substances to the channel protein
mechxnosensitive gated: respond to mechanical forces that act on the membrane
108
how do porins work
allow for rapid passage of various solutes (low specificity)
109
where are porins found
outer membrane of mitochondria, chloroplasts, and bacteria
110
what is the structure of a porin
beta barrel with water pore at its centre
polar side chains line the inside
nonpolar side chains point into the membrane
111
how does water diffuse across membranes
slowly (through simple diffusion)
flows single file through aquaporins
112
why do kidneys have a high density of aquaporins
reabsorption of water
113
what is the alternate conformation model
how transport with carrier proteins work
where the membrane protein can adopt 2 conformational states to transport solute
114
what are the similarities between carrier proteins and enzymes
carrier proteins are very specific for their target
carrier proteins have their activity regulated
exhibit saturation kinetics
115
what is a uniporter
transports a single solute
116
what is a symporter
transports 2 solutes in the same direction across the membrane
117
what is an anti-porter
transports two solutes in opposite directions across the membrane
118
how does glucose transporter GLUT1 work
facilitated diffusion of glucose by a uniport carrier protein
119
how does chloride bicarbonate exchange work
facilitated diffusion via an antiport protein
(anion exchange protein, facilitates the reciprocal exchange of chloride and bicarbonate in opposite directions)
120
what is a typical membrane potential in a mammalian cell
-60mV to -70mV
121
what side of the membrane is negative with respect to the other side
cytosolic side
122
what direction does active transport move
away from equilibrium
123
what are the membrane proteins involved in active transport called
pumps since they require enegery
124
what direction is active transport
unidirectional, has an intrinsic directionality
125
what are the functions of active transport
uptake of essential nutrients
removal of wastes (even if concentration is higher outside the cell)
creation of gradients and maintenance of non-equilibrium concentration
126
what is direct (primary) active transport
solute accumulation is coupled directly to an exergonic chemical reaction (ATP hydrolysis)
ATP hydrolysis drives the outward transport of protons, thereby establishing an electrochemical potential for protons across the membrane
127
what is indirect (secondary) active transport
an endergonic (uphill against a concentration gradient) is coupled to the exergonic (downhill down a concentration gradient) (may have been pumped uphill by primary active transport)
simultaneous transport of 2 solutes. exergonic inward movement of protons provides energy to move the transported solute against its concentration gradient or electrochemical potential
128
what is the difference between indirect and direct active transport
source of the energy
129
what do ATPases do
harness the energy of ATP hydrolysis to perform active transport
130
what are the similarities and differences between the 4 classes at ATPases
differ in structure, mechanism, localization, and physiological roles
all have one or more ATP binding sites on the cystolic membrane leaflet
131
what are P-type ATPases
members of a large family of ATPases that are reversibly phosphorylated by ATP
132
where are most types of P-type ATPases found
on the plasma membrane
133
what do V type ATPases do
pump protons (H+) into organelles such as vacuoles, vesicles. lysosomes, endosomes, and the Golgi complex
134
where are V type ATPases only found
eukaryotes
135
what is the structure of V type ATPases
have 2 multi-subunit components: an integral component embedded in the membrane and a peripheral component that juts out from membrane surface
136
what do F-type ATPases transport
protons in bacteria, mitochondria, and chloroplasts
137
What does primary active transport maintain
intracellular sodium and potassium concentrations, which maintain osmotic balance and stabilize cell volume
138
what are ABC-type ATPases
ATP binding casette transporterts
involved in uptake of nutrients
139
what do all ABC-type ATPases have
2 nucleotide (ATP) binding domains
2 transmembrane domains
140
what is secondary active transport:
indirect active transport
is not powered by ATP hydrolysis, but instead by potential energy stored in ionic gradients
141
are there indirect active uriporters
no
142
why does indirect transport rely on ATP
because the Na+ and H+ concentration gradient is generated by an ATPase pump
143
what mediates transport of most molecules and ions across biomolecules
membrane proteins
144
what can energy be loosely defined as
the capacity to cause a specific physical or chemical changes
145
what is a chemotroph
no net fixation of carbon into organic compounds
(energy from food)
146
what are the laws of thermodynamics
1st: total energy in universe remains the same
2nd: universe goes towards greater disorder (entropy increases)
147
in a spontaneous rxn does delta S (entropy) - or +
positive
148
does entropy increase or decrease when monomers are ordered into complex molecules
decrease
149
what does enthalpy (H) tell us
heat content (energy) of a system
150
hat are changed I'm enthalpy and entropy related by
Gibbs free energy (G)
151
what does it mean if delta G (Gibbs free energy) is negative
process is exergonic
rxn releases energy
thermodynamically favourable
152
what does it mean if delta G (Gibbs free energy) is positive
process is endergonic
input of energy is needed to drive the rxn forward
thermodynamically unflavoured
153
what does it mean if delta G (Gibbs free energy) is 0
at equilibrium
no net flow in forward or reverse direction
neither direction is favoured
enthalpy and entropy changes are exactly balanced
154
what has a significant effect on delta G of an rxn
concentration of products and reactions
155
what is the equilibrium constant (Keq)
ratio of product concentration to reactant concentration at equilibrium
156
is homeostasis equilibrium
no
living cells are characterized by continuous rxns and maintain themselves in states far from equilibrium
157
what is homeostasis
the maintenance of dynamic steady state by regulatory mechanisms that compensate for external changes
158
what charge does delta G have if its spontaneous
negative
159
what is the metastable state
a result of the activation barrier
for most biologically important rxns (at normal temps) the activation energy is high enough that the number of molecules possessing sufficient energy to react is extremely small
160
what must be overcome before a chemical rxn can occur
activation energy (Ea)
161
what is the transition state
precise point at which weak chemical rxns between substrate and enzyme are at the stage where the rxn has an equal chance of going to product or back to substrate
162
how do enzymes reduce the activation energy
- maintaining precise substrate orientation (substrates can be brought closer together in the current orientation to allow the rxn to occur )
- changing the substrate reactivity ( R-groups of the amino acids in the enzyme can influence the distribution of electrons within the substrate )
- exerting physical stress. (conformational changes can exert a physical force on certain bonds destabilizing the substrate)
all of these help strategies allow substrates to reach the transition state more efficiently
163
what is the active site
region of the enzyme that binds substrate (and cofactor)
complimentary groove that accommodates the substrate with high affinity
every enzyme contains a characteristic cluster of amino acid)
164
what amino acids comprise active site
cysteine, serine, aspartat, glutamate, histidine and lysine
165
Since active site takes up small portion of enzyme, what are the other parts of the enzyme
- support structures
- regulatory sites
- sites of interaction with other properties
- substrate channel
166
how are enzymes characterized
by their sensitivity to temperature and pH
167
how does enzyme activity change with temperature
increases since more kinetic energy
168
are enzymes activated at different pHs
yes
169
how are enzymes sensitive to ionic strength of environment
affects H bonding and ionic interactions needed to maintain tertiary conformations
170
what do enzyme kinetics describe
the quantitative aspects of enzymes catalysis and the rate of substrate conversion into products
171
what are the rxn rates of enzymes influenced by
concentrations of substrates, products, and inhibitors
172
what is allosteric regulation
regulation of enzyme by binding an effector molecule at a site other than the active site
173
where is allosteric regulation common
multi-subunit proteins and enzymes
174
when enzymes are inactive what kind of modification activate them and vice versa
covalent modification
175
how does phosphorylation work
changes a proteins charge and generally leads to conformational change, which can alter ligand binding
results in increase/decrease od activity
176
what 3 elements are always needed for imaging (microscopy)
- source of illumination
-specimen to examine
-system of lenses to focus illumination
177
how does light microscopy work
use visible light and glass lenses to form an image
178
what is a condenser lens
placed in front of the light source to focus the light at desired point on specimen
179
what is the objective lens
forms primary image
closest to the object of interest
180
what is the occult lens
magnifies the primary image produced by objective lens
181
what is resolution
minimum distance that 2 points can be apart can be part and remain apart
182
what is empty magnification
magnification without resolution
at a certain point the resolution is fixed no matter how much magnification
183
what is the refractive index
measure of the change in velocity of light as it passes from one medium to another
184
what does resolution consider
wavelength of illumination
refraction index
angular aperture
185
what does magnification consider
refraction of index of the lens and medium the sample is immersed in
the focal length of the lens
186
what are the different types of light microscopy
bright field (stained/unstained)
phase contrast
fluorescence
differential inference
confocal
187
what is bright field microscopy
visualizing white light passed through a specimen
188
what is phase contrast
takes advantages of differences in refractive index and thickness to image living cells without need to section and stain
189
what is phase contrast most useful for
examination of dynamic events
- since doesn't use fix cells
190
what is differential interference contrast
the technique has a shadow-casting effect that makes cells appear dark on one side and light on the other
- results in an image with a 3D effect
191
what do fluorescence and confocal microscopy detect
fluorescent proteins or dyes to show location of substances in the cell
192
what is immunofluoresence microscopy
uses antibodies to locate specific molecules
193
what are the advantages of immunofluoresence microscopy
high specificity
strong signal
identifies endogenous proteins in their native environment
194
what are the disadvantages immunofluoresence microscopy
experiments are done on dead cells (samples require fixation)
there might not be an available antibody
195
what is green fluorescent protein (GFP) used for
to visualize patterns of gene expression proteins in living cells and organisms
- proteins can be tagged with GFP
196
what are the advantages of GFP
cellular events can be observed in living cells
197
what are the disadvantages of GFP
GFP protein that might negatively affect your target protein
introducing the GFP tagged proteins into the cells
198
what does confocal fluorescence microscopy do
has ability to produce in-focus images of thick specimens, a process known as optical sectioning
images are acquired point by point, allowing a 3D reconstruction
199
what are the advantages of viewing a fixed cell
organisms/organs can be viewed by sectioning thick tissue
easier to manage samples (can look at them anytime)
don't need to introduce a recombinant protein (can disrupt cellular function)
200
what are the advantages of viewing a live cell
can observe the movement of biomolecules within a cell
provides critical context to your observtaios
201
what can live focal microscopy be used to visualize
the location of molecules but also to study dynamic movements and properties of biological molecules
202
what do electron microscopy use
a beam of electrons rather than light and glass lenses
203
what are the 2 types of electron microscopy
scanning electron microscopy (SEM): the surface tension of a specimen is scanned by detecting electrons deflected from outer surface
transmission electron microscopy (TEM): electrons are transmitted through the specimen
204
what is cryo-electron tomography
take multiple 2D images at different angles and using computers, create a 3D image
used for high resolution structure determination of biomolecules in solution
205
what are the 2 membranes the the nuclear envelope consists of
- inner membrane defines the nucleus
- the outer membrane is continuous with the ER
206
what are the nuclear pores for
fuse the 2 membranes together and serve as a conduit for transport between the cystoplasm and nucleoplasm
207
what does the nucleus contain
molecules of DNA organized into chromosomes
208
what do nuclei serve as
info centres for the cell
DNA replication, transcription, and RNA processing occurring here
209
where is rRNA transcribed
nucleus
210
where are ribosome assembled
nucleus
211
what is the structure of ER
consists of tubular membranes and flattened sacs called cisternae
internal space of the ER is the lumen
212
what is the rough ER a critical starting point for
protein biosynthetic pathways
213
where are most membrane lipids synthesized
rough ER
214
what side of rough ER are the ribosomes on
cytoplasmic side
215
what do ribosomes synthesize
polypeptides
216
does the smooth ER have a role in protein synthesis
no
217
what does the smooth ER synthesize
lipids and steroid hormones
218
what is the sarcoplasmic reticulum
type of smooth ER
critical for the storage and release of calcium ions during muscle contraction
219
what is closely related to the ER in proximity and function
Golgi apparatus
220
what is the function of the Golgi apparatus
plays important role in processing and packaging secretory proteins and in complex polysaccharide synthesis
221
what is TGN
vesicle sorting station
segregating proteins into vesicles headed to plasma membrane or other intracellular destinations
222
what is CGN
transition vesicle sorting station
sorting proteins to be sent back to the ER or on to the Golgi
223
what do lysosomes do
digestive organelle
224
what is the structure of a lysosome
have a single membrane and store about 50 hydrolyses (digestive enzyme)
225
what are the 3 degradation pathways utilizing the lysosome
endocytosis
phagocytosis
autophagy (mechanism for degrading intracellular organelles)
226
what make up the endomembrane system
ER, golgi, vesicles, lysosomes
227
what is the endomembrane system responsible for
trafficking substances through the cell
228
are peroxisomes part of the endomembrane system
no
229
what do peroxisomes do
detoxify harmful compounds and catabolize unusual substances
in animals, play a vital role in oxidative breakdown of fatty acids, especially longer chain fatty acids
230
what is the structure of mitochondria
2 membranes creating 3 regions
outer membrane: relatively permeable, contains porins which allow free movement of small molecules and ions
inner membrane: high impermeable, acts as a permeability barrier to most solutes
regions:
matrix: within the inner membrane, contains most of the enzymes associated with mitochondrial function as well as DNA and ribosomes
intermembrane space: area between the inner and outer membranes
intracristal space: localized regions where protons can accumulate during the electron transport process
231
where os the principle site of ATP production in non-photosynthetic cells
mitochondria
232
what kind of cells have more mitochondrias
ones with high energy needs
233
what is a tonoplast
the single membrane of a vacuole
contains numbers of active transporters
234
what do vacuoles store
ions, amino acids, proteins, and polysaccharides
235
are ribosomes organelles and why
no since they aren't enclosed by a membrane
236
what is a cytoskeleton
3D array of interconnected filaments, microtubules, and intermediate filaments
237
what is the extracellular matrix (ECM) composed of
mainly of proteins and glycoproteins
238
what are the functions of ECM (extracellular matrix )
support for cells to form tissues
substrate for attachment, motility
growth promoting signals
righty in plants
