2 - September 16 membrane - Pg. 63-82 Flashcards
1
Q
Most membrane phospholipids are —-
A
unsaturated
2
Q
how does unsaturated phospholipids help the membrane?
A
kink in the tail creates more space = increased membrane fluidity
3
Q
chemical make up of glycolipids
A
lipids with sugar groups attached
4
Q
where are glycolipids located?
A
outer plasma membrane
5
Q
glycolipids account for only —% of total membrane lipids
A
5
6
Q
the sugar group makes the molecule —-
A
polar
7
Q
20% of the membrane lipid is?
A
cholesterol
8
Q
what is the purpose of cholesterol? how does it achieve this?
A
hydrocarbon rings wedge between the phospholipid tails to stabilize the membrane and decrease the mobility of the phospholipids and fluidity of the membrane
9
Q
what are integral proteins? where are they located?
A
firmly in the lipid bilayer, usually spanning across the whole membrane from both sides, consist of both hydrophobic and hydrophilic regions
10
Q
functions of transmembrane proteins?
A
involved in transport by acting as a channel or act as carriers
11
Q
peripheral proteins
A
loosely attached to the integral proteins and can be removed without membrane disturbance
12
Q
peripheral proteins function
A
helps support membrane from the cytoplasmic side
13
Q
some times peripheral proteins are
A
enzymes or motor proteins, or used to link cells
14
Q
lipid rafts importance and function
A
important components of cell membranes - involved in essential cellular processes, including endocytosis, exocytosis and cellular signalling
15
Q
what are lipid rafts made up of
A
enriched in cholesterol, glycophospholipids and receptors.
16
Q
glycocalyx is a ——–rich area at the cell surface
A
carbohydrate
17
Q
glycocalyx on each cell surface is enriched by both
A
glycoproteins and glycolipids
18
Q
the glycocalyx provides what to help in cell-to-cell recognition
A
highly specific biological markers
19
Q
another name for selectively permeable membrane
A
differentially permeable membrane
20
Q
selectively permeable membrane definition
A
membrane that’s selectively about what substances can penetrate - allows some but not others
21
Q
passive process definition
A
substances move across the membrane without any energy input from the cell
22
Q
active process definition
A
cell provides metabolic energy, usually ATP, to help move substances across the membrane
23
Q
selective permeability is a characteristic of what kind of cell?
A
healthy and intact
24
Q
severe damage to a cell creates what kind of imbalance?
A
homeostatic
25
what are the two main types of passive transport?
diffusion and filtration
26
diffusion
tendency of molecules/ions to move from an area of higher concentration to lower concentration area down or along their concentration gradient
27
the greater the difference in concentration between two areas, the ----- collisions occur and the ----- the net diffusion of the particles
more and faster
28
what is the driving force behind diffusion?
kinetic energy of the molecules
29
speed of diffusion is based off of
molecule size and temperature
30
what are the 3 things that need to be met for a molecule to pass by the plasma membrane?
1 - lipid soluble
2 - small enough to pass through membrane channels
3 - or assisted by a carrier molecule
31
simple diffusion definition
direct diffusion of non polar and lipid soluable substances
32
facilitated diffusion
when a larger molecule either binds to protein carriers or moves through water filled protein channels
33
types of diffusion through plasma membrane
simple diffusion, carrier-mediated facilitated diffusion, channel-mediated facilitated diffusion, osmosis
34
carriers are
transmembrane integral proteins that are specific for transporting certain polar molecules or classes of molecules that are too large for membrane channels alone
35
alterations to the shape of the carrier allows for shielding the molecule from ?
non polar regions of the membrane
36
substances using carrier mediated facilitated diffusion more down, --- ---- ----, just as in simple diffusion
its concentration gradient
37
glucose transport in the body is typically ----- into the cells
unidirectional
38
carrier mediated facilitated diffusion definition
when carriers bind to large substances to help cross through the membrane - carrier helps protect substance from non polar region of the membrane
39
channel-mediated facilitated diffusion analogy
channel acts as a bridge over water than can open and close
40
channel-mediated facilitated diffusion channels are ------ due to --------- and --------- that line the channel
selective, pore size, charges of amino acids
41
channels definiton
transmembrane proteins that transport substances, like water or ions, through aqueous channels from one side of the membrane to the other
42
leakage channels are
always open to allow ions or water to mov according to concentration gradients
43
gated channels are
controlled (open or closed) by chemical or electrical signals
44
channels can be
inhibited by certain molecules, show saturation, tend to be specific
45
In channel-mediated facilitated diffusion, substances moving through also follow ?
concentration gradient
46
rate of diffusion is ------- through simple diffusion because?
uncontrollable , lipid solubility of membrane is not immediately changeable
47
rate of diffusion is ------ in facilitated diffusion because
controllable , permeability of membrane is altered through regulating the activity or number of individual carriers/channels
48
osmosis
diffusion of a solvent through a selectively permeable membrane
49
even though water is highly ------------, it passes through the lipid bilayer via ------
polar , osmosis
50
aquaporins (AQPs)
transmembrane proteins that created water specific channels to allow free and reversible movement of water
51
Aquaporins are believed to be present in all cell types but are most abundant where?
red blood cells and cells that are involved in water balance i.e. kidney tubule cells
52
osmosis occurs whenever
the water concentration differs on two sides of a membrane
53
as solute concentration increases, water concentration?
decreases
54
what is the membrane type in osmosis
selective permeable membrane - hence why water is moving to higher solute concentration since the solutes cannot
55
(a solution's) osmolarity is
the total concentration of all solute particles in a solution
56
what would happen if two equal volumes of aqueous solution, but different osmolarity solutions were to be separated by a membrane that is permeable to all molecules?
net diffusion of both solute and water molecules occurs, each moving down their own concentration gradient. water and concentration would be equal
57
what would happen if two equal volumes of aqueous solution, but different osmolarity solutions were to be separated by a membrane that is impermeable to solutes particles?
water alone moves to reach equilibrium and the water volumes would be different
58
hydrostatic pressure
The force exerted by a fluid pressing against a wall
59
in living cells, net water entry ends when equilibrium of what two things?
hydrostatic pressure and osmotic pressure
60
the higher the amount of non-penetrating solutes in a cell, the higher the osmotic pressure and the greater the hydrostatic pressure must be to?
resist further net water entry
61
Hydrostatic Pressure is found in
any type of homogenous fluid
62
osmotic pressure and hydrostatic pressure is different in plant cells than living because of?
the rigidity of cells - plant cells have more rigidity than living cells. Living cells die/pop if the pressure is too much
63
osmotic imbalances cause animal cells to ----- or -------
swell or shrink
64
swelling or shrinking of the cell occurs until ?
equilibrium of solutes is reached on both sides of the plasma membrane or until the membrane stretches and breaks
65
tonicity
the ability of a solution to change the shape or tone of cells by altering the cells's internal water volume
66
tono =
tension
67
are intracellular proteins able to diffuse through the plasma membrane?
no
68
isotonic
same tonicity - solutions have same concentrate as non-penetrating solutions and cell shape is maintained
69
hypertonic solutions
higher concentration of non-penetrating solutes than seen in the cell - cell shape shrinks due to water loss
70
hypotonic solutions
have less non-penetrating solutes than cell, therefore cell swells due to osmosis and water going to the cell
71
what is the most extreme example of a hypotonic solution?
distilled water
72
what happens to cells placed in distilled water?
usually die because no solutes in distilled water, so water continuously enters the cell
73
a solutions osmolarity is based off of
total solute concentration
74
tonicity is based off of
how the solution affects cell volume which depends on (1) solute concentration & (2) solute permeability of plasma membrane
75
what are 2 processes that are not selective?
simple diffusion and osmosis
76
what process is often highly selective?
facilitated diffusion
77
what energy source does simple diffusion, osmosis and facilitated diffusion use?
kinetic energy
78
facilitated diffusion is similar to simple diffusion but the diffusing substance ?
Is either attached to a lipid-soluable membrane protein carrier, or moves through a membrane channel
79
active transport requires carrier proteins to combine ---- and ----- with transported substances
specifically and reversibly
80
facilitated diffusion follows concentration gradients because?
its using genetic energy
81
active transport (or solute pumps) move solutes how and where?
uphill, against the concentration gradient by using energy
82
active transport moves solutes, which is the most important type?
ions
83
active transport is distinguished according to their?
source of energy
84
primary active transport, the energy comes from
directly from hydrolysis of ATP
85
in secondary active transport, the energy comes
indirectly by the energy stored in ionic gradients created by primary active transport pumps
86
why are secondary active transports called coupled systems?
they move more than one substance at a time
87
symport system
the two transported substances move in the same direction
88
anti port systems
the transported substances 'wave to each other' as they cross the membrane in different directions
89
what does the hydrolysis of ATP result in?
phosphorylation of the transport protein = protein changes shape in a way that 'pumps' the bound solutes across the membrane
90
what types of systems does primary active pump consist of?
calcium-hydrogen and sodium-potassium pump
91
what is the name of the 'pump' (carrier) of sodium-potassium pump?
NAK atpase
92
in the body the concentration of K inside the cell is ---- times higher than that outside the cell
10
93
Na is ----- times higher on the outside of the cell than the inside the cell
10
94
why is the ion concentration of K and Na important?
for excitable cells like muscle and nerve cells to function normally & for cells to maintain normal fluid volume
95
why does the NA-K pump almost always is an anti porter?
because of the slow but continuous leakage of Na-K through leakage channels in the membrane
96
the Na-K pump does what exactly as an anti porter?
drives Na out the cell against the concentration gradient and pumps K back in
97
ions diffuse according to
electrochemical gradients
98
what two things need to be in mind when speaking of gradient?
electrical and concentration gradient
99
The electrochemical gradient is a combination of the
concentration gradient and the electrical potential
100
the electrochemical gradient maintained by Na-K pump underlies?
most of the secondary active transport of nutrients and ions
101
the maintenance of the secondary active pump for nutrient and ions is essential for
cardiac, skeletal muscle and neuron function
102
active transport system provides a way for cells to be?
very selective in cases where substances can't pass by diffusion
103
secondary active transport
transport of a solute in the direction of its increasing electrochemical potential coupled to the facilitated diffusion of a second solute (usually an ion) in the direction of its decreasing electrochemical potential
104
how does the electro gradient and concentration gradient fuel secondary transport?
concentration gradient pushes the Na from outside to the inside due to high and low concentration then the electrical potential wants to go from more positive side to the negative side to balance it out
105
Na electrochemical gradient is what is used to provide
energy
106
vesticular transport
fluids containing large particles and macromolecules are transported across cellular membrane inside membranous sacs called vesicles
107
exocytosis
the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell
108
endocytosis
the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane, and bringing it into the cell
109
which direction does vesicle transport move substances?
inside and outside
110
what are other tasks for vesicular transport besides molecules
transcytosis and vesicular trafficking
111
how is vesicular transport energized?
by ATP, but sometimes by GTP
112
transcytosis definition
moving substances into, across and then out the cell
113
vesicular trafficking
moving substances from one area (or membraneous organelle) in the cell to another
114
all forms of vesicular transport involve what two things?
an assortment of protein-coated vesicles of 3 types and (usually) are mediated by membrane receptors
115
what is the main route for endocytosis and transcytosis
protein-coated vesicles
116
what is the name of the sorting vesicle that the uncoated vesicle fuses with?
endosome
117
clathrin
acts in both selecting the cargo and deforming the membrane to produce the vesicle
118
where is transcytosis common?
endothelial cells lining blood vessels
119
what are the three types of endocytosis that use clathrin-coated vesicles
phagocytosis, pinocytosis, receptor-mediated endocytosis
120
phagocytosis
cell engulfs large material (like debris or bacteria) and forms pseudopods around it and enclosed the membrane around it.
121
what is a phagosome
endocytotic vesicle - the cell with engulfed materials with pseduopods
122
what happens once the phagosome is formed?
fuses with a lysosome for the contents to be digested
123
what if there's nothing digestible for the lysosome and phagosome?
material is ejected from cell by exocytosis
124
pinocytosis is also called
fluid-phase endocytosis
125
pinocytosis is a daily routine for
most cells, especially ones that absorb nutrients like cells in the intestines
126
pinocytosis
the cell membrane folds and creates small pockets and captures the cellular fluid and dissolved substances and forms into a tiny vesicle
127
what's the purpose of pinocytosis
clearing extracellular fluids and as part of immune surveillance
128
receptor-mediated endocytosis is used mainly for
specific endocytosis and transcytosis
129
the receptors in RM-endocytosis are
plasma membrane proteins that bind to specific substances
130
EM - endocytosis
Extracellular substances bind to specific receptor proteins that allows ingestion and concentrate of specific substances (ligands) in protein-coated vesicles
131
what happens to the ligands once they're in the vesicle
released in the cell or they're combined with lysosomes to be digested
132
caveolae
tubular/flask-shaped inpocketings of the plasma membrane seen in many cell types and used for a unique kind of receptor mediated endocytosis
133
caveolae provides
sites for cell signalling and cross talk between signalling pathways
134
what is the most important thing to remember about coat proteins in general?
they play a significant role in all forms of endocytosis
135
exocytosis
vesicular transport protein processes that eject substances from inside the cell to the outside by enclosing substance in membrane vesicle which fuses to plasma membrane to rupture and kick the substance out
136
how does exocytosis get stimulated?
through cell-surface signal
137
what does exocytosis account for?
hormone secretion, neurotransmitter release, mucus secretion
138
secretory vesicle
enclosed protein-coated membraneous sac involved in exocytosis
139
voltage
electrical potential energy resulting from the separation of oppositely charged particles
140
what are the oppositely charged particles in cells?
ions
141
what is the barrier that keeps ions apart?
plasma membrane
142
resting membrane potential
resting state of plasma membrane, ranges from -50 to -1000 mV
143
voltage only exists
at the membrane
144
the negative before the voltage number indicates what
the inside of the cell is negative compared to the outside
145
how does the resting membrane potential come about and maintained? short answer*
diffusion causes implantes that polarize the membrane and active transport processes maintain the membrane potential
146
resting membrane potential is mainly determined by
concentration gradient of potassium and by differential permeability of the plasma membrane to K and other ions
147
the loss of K is due to the fact that the membrane at it's resting potential is
semi permeable to K via leakage channels, which allows it to flow out, but not other anion proteins creating the interior more negative but then K is attracted to the negative so it makes its way back in
148
which of Na or K is more responsible to resting membrane potential and why
K because the membrane is more permeable to k when resting although Na still does play a role
149
resting membrane potential is based off a -------- number of K ions that it actually doesn't cause ?
small, a change in ion concentration in a major way
150
the rate of active transport is equal to and depends on
the rate of Na diffusion into a cell
151
each 'turn' of the Na-K pump, how much of each is exchanged?
3 Na out, 2 K in
152
the ATP -dependent Na-K pump maintains bother
membrane potential and osmotic balance
153
regardless if cells interact with this directly or indirectly, what is always involved
glycocalyx
154
what are the two families that glyxocalyx molecules fall into
cell adhesion molecules and plasma membrane receptors
155
a group of membrane proteins, voltage-gated channel proteins are important for
cells that respond to electrical signals
156
what are CAM's
cell adhesion molecules
157
what are the key role of CAM's
embryonic development, wound repairing, immunity
158
membrane receptors
integral proteins and glycoproteins that serve as binding sites - function in contact signalling and chemical signalling
159
contact signalling
cells come together and touch as a form of recognizing one another
160
why is contact signalling important
for normal development and immunity
161
most plasma membrane receptors are involved in?
chemical signalling
162
ligands
chemicals that bind specifically to plasma membrane receptors
163
ligands includes most
neurotransmitters, hormones and paracrines
164
paracrines
chemicals that acts locally and are rapidly destroyed
165
paracrines example
responses to allergens or blood clotting
166
why do different cells respond differently to the same ligand?
the target cell response depends on the internal machinery that the receptor is linked to, not the specific ligand it's binding to
167
what happens when ligand binds to a membrane receptor?
the receptor's structure changes and cell proteins are altered in some way
168
g protein-linked receptors
exert their effect indirectly through G protein
169
what's a g-protein
a regulatory molecule that acts as a middle man or a relay, to either activate or deactivate, a membrane bound enzyme or ion channel
170
second messengers
intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers, typically caused by G protein-linked receptors
171
what are the two important second messengers
cyclic AMP and ionic calcium
172
what do cyclic amp and ionic calcium do
typically activate protein kinase enzymes which transfer phosphate groups from ATP to other proteins
173
the protein kinase enzyme can do what
trigger a whole series of enzymes that bring out desired cellular activity
174
G protein signalling system is involved in
neurotransmission, smell, vision and hormone action
175
NO (nitric acid) molecule is important for
signalling
176
in electrical signalling, certain plasma membrane proteins acts as
channel proteins that open or close channels based on membrane potential changes
