1.3 cell membranes and transport Flashcards
1
Q
functions of the plasma
membrane
4
A
-taking in nutrients and other required substances for the cell
- receptor sites for hormone attachment
- secreting chemicals
- cell- cell recognition
2
Q
what’s lateral movement
A
sideways
3
Q
3 main types of proteins in the plasma membrane
A
structural
transport
enzymes
4
Q
what does the polarity of protein molecules affect
A
their position in the membrane
5
Q
what is glycosylation
A
the process of adding carbohydrates onto either a protein (glycoprotein)
or lipid (glycolipid)
6
Q
what is glycocalix
A
is the carbohydrate layer on the outer surface of the plasma membrane
7
Q
what is the cell membrane
A
semi-permeable
8
Q
what is the cell membrane made up of mainly
A
-phospholipids
-proteins
-some polysaccharides and cholesterol
9
Q
what are the phospholipid molecules arranged in
A
in a bilayer
10
Q
explain the arrangement of the phospholipid bilayer
A
hydrophilic heads are polar they are on the outside as they are water loving. and the hydrophobic tails are non polar, they are on the inside because they are water hating
11
Q
who proposed the fluid mosaic model
A
singer and Nicholson
12
Q
what does the fluid mosaic model describe
A
the arrangement of phospholipids and proteins in cell membranes
13
Q
what do the proteins form
(to do with the model)
A
form a mosaic pattern within the phospholipid bilayer
14
Q
description/function of phospholipid bilayer
A
forms the basis of the cell membrane/ allows transport of small non-polar molecules in and out of the cell by simple diffusion
15
Q
description of extrinsic proteins
A
proteins found at the edges of the phospholipid bilayer, they do not span the membrane
found above/below the membrane
polar(hydrophilic head)
16
Q
function of extrinsic proteins
A
-receptor sites
-they bind with proteins such as hormones or neurotransmitters
17
Q
description of intrinsic proteins
A
proteins found within the bilayer, soon the membrane polar and non polar (hydrophobic/hydrophillic)
18
Q
function of intrinsic proteins
A
transport
channels/carries take part in facilitated diffusion
pumps take part in active transport/ form ion channels
19
Q
description/function of the models movement
A
is capable of movement
which is why its called the fluid mosaic model
20
Q
where is cholesterol found
A
animal cells between the phospholipid molecules
21
Q
what does cholesterol do
A
increases the rigidity and stability of the membrane
22
Q
what are glycolipids
A
lipids which have combined with polysaccharides
23
Q
where are glycolipids found
A
in the outer layer of the membrane
24
Q
what are glycolipids involved in
A
cell to cell recognition
25
what are glycoproteins
proteins which have combined with polysaccharides
26
where are glycoproteins found
sticking out of some membranes
27
name the factors affecting the permeability of the plasma membrane
increasing temperature
increasing ethanol concentration
increasing sodium chloride concentration
icreasing detergent concentration
pH
28
explain how increasing the temperature would affect the permeability of the plasma membrane
as the temperature increases cell membrane and tonoplast permeability increases due to increased disruption of the membrane. at temps above 40 the cell membrane and tonoplast become increasingly unstable. more heat energy= more kinetic energy so the phospholipids will vibrate more and move further apart
29
explain how increasing the ethanol concentration would affect the permeability of the plasma membrane
ethanol dissolves phospholipids (organic solvent)
the greater the concentration of ethanol the more permeable the membrane becomes
30
how does increasing sodium chloride concentration affects the permeability of the plasma membrane
as concentration increases, the permeability will decrease
sodium ions attach to the oxygen atoms on the hydrophilic heads of the bilayer. reduces the mobility of the phospholipid molecules so less betaken is released
31
how does increasing detergent concentration affect the permeability of the membrane
as the concentration increased the permeability increases because it reduces the surface tension of phospholipids and sippers the membrane.
32
how does the pH affect the permeability of the membrane
denaturation of enzyme
33
what does directly proportional mean
decrease/increase
at the same time.
if the line is straight and goes through the origin
34
what is diffusion
the passive movement of a small non-polar (lipid-soluble) molecule from an area of high concentration to an area of low concentration
until they are equally distributed
35
what is equilibrium
the concentration of molecules is equal either side of the membrane.
36
what happens at equilibrium
molecules/particles still continue to cross the membrane in both directions, but there is no net movement in a particular direction
37
what are the factors that affect the rate of diffusion
(6)
-concentration gradient
- distance of travel
-the surface area of the membrane
-the thickness of the membrane
-an increase in temperature
-particle size
38
why does the concentration gradient affect the rate of diffusion
the steeper the triangle the faster diffusion would occur.
39
why does the distance of travel affect the rate of diffusion
the shorter the distance of travel the greater the rate of diffusion
40
how does the surface area of the membrane affect the rate of diffusion
the larger the surface area the greater the rate of diffusion
41
why does the thickness of the membrane affect the rate of diffusion
the thinner the membrane the greater the rate of diffusion
42
why does an increase in temperature affect the rate of diffusion
an increase in temperature the greatest the rate of diffusion the diffusion path is short
43
why dies the particle size affect the rate of diffusion
small particles diffuse faster than larger molecules
44
what is co transport
is a type of facilitated diffusion that brings molecules and ions into cells together on the same carrier protein
45
what is osmosis
the passive net movement of water molecules from an area of high water potential to an area of low water potential through a semi permeable membrane
46
factors that effect osmosis
-temperature
-surface area
-thickness of membrane
-water potential
47
how does water pass through membranes
through channel proteins called aquaporins
48
what do aquaporins do
increase the rate water molecules can go in and out of the cell through charged (polar) channels (due to the particular hydrophillic R group of the amino acid)
while preventing the passage of ions and other solutes
49
what is water potential
the tendency of water to move from one place to another
50
is there a tendency for water to move into pure water
no, this means pure water has a water potential of 0KPa
51
what does KPa stand for and what does it describe
kilopascal
it describes the pressure exerted on a surface
52
what does a low concentration of water mean
a low water potential
53
what does the addition of a solute to pure water do
bring water molecules in
lowers the water potential and gives it a negative value
54
how is water potential related to the concentration of the solution
the more concentrated a solution gets the more negative its water potential
55
what does the solute potential show
the reduction in water potential due to the presence of solute molecules
56
what does solute potential measure
how easily water molecules move out of a solution
57
what does the concentration of dissolved substances inside the cell vacuole equal
solute potential
58
what makes the tendency of water to move out lower
the more solute present
59
is the solute potential +/-
always a negative value and lowers the water potential of the cell
a higher concentration solution has a lower, more negative solute potential
60
what is pressure potential
the hydrostatic pressure exerted by the contents on the cell wall.
it is equal and opposite to the pressure exerted by the cell wall on the cell contents
61
turgid.....
a plant cell that holds as much water as possible. further entry of water is reverted a the cell wall cannot expand any further
62
what does water entering the cell via osmosis do
expands the vacuole and pushes the cytoplasm against the cell wall. the cell wall can only expand a little and so pressure (potential) outwards builds up, resisting the entry of more water making it turgid
63
solute potential for pure water
0
or negative
64
solute potential in a cell at incipient or full plasmolysis
0
or positive
65
water potential equation
water potential=solute potential + pressure potential
66
what are the 2 forces plant cells are under the influence of
the solute potential
the pressure potential
67
why are plant cells under pressure from the solute potential
due to the solutes in the vacuole and cytoplasm pulling water in. the higher the concentration the less likely the water to move out
68
why are plant cells under pressure from the pressure potential
a force which increases the tendency of water to move out
69
do animal cells have a pressure potential
no because they have no cell wall
70
what is tonicity
the ability of an extracellular solution to make water move into or out of a cell by osmosis is known as its tonicity
71
what is hypertonic solution
water leaving the cell
the extracellular solution has low H20 and high solute concentration
72
isotonic solution
equilibrium
equal amount of water leaving and entering the cell
73
hypotonic solution
more water entering the cell
extracellular solution has high H20 and low solute concentration
74
what is haemolytic
the destruction of red blood cells by rupture of the cell and release of the contained haemoglobin
75
crenated meaning?
a red blood cell in highly concentrated solution
76
what will happen if the cell is crenated
water leave the cell and it will shrink
77
examples of active transport
reabsorption in kidneys
uptake of inorganic ions in plants
nerve transmissions
78
example of uptake of inorganic ions in plants
magnesium in through root hair cells
79
what is the sodium potassium pump in charge of
generating a gradient of ions
80
what does the sodium potassium pump do
continually pumps sodium ions out of the cell and potassium ions into the cell, powered by ATP
each ATP that is broken down it moves 3 sodium ions out and 2 potassium in
81
what happens to the cell because it is depleted of sodium
an electrical gradient is created and a concentration gradient
82
what is the effect of cyanide
strong poison. it works as a respiratory inhibitor. the enzyme cytochrome oxidase catalyses the reaction
83
what happens in cytochrome oxidase is inhibited
ATP is not produced and the organism quickly dies
84
what are channel proteins
with pores lined with polar groups (hydrophilic) allowing charged ions to pass through (Na+)
they open and close depending on needs of the cell, they are specific for one type of ion.
85
what are carrier proteins
allow the facilitated diffusion of larger polar molecules e.g sugars, amino acids.
molecule will attach to its binding site, it changes shape and releases the molecule the other side of the membrane
86
what is facilitated diffusion
allows the movement of molecules or ions across a membrane down a concentration gradient. it occurs on the cell membrane where there are transport molecules
87
explain the sodium potassium pump
1- pump binda 3 sodium and a molecule of ATP
2- splitting ATP provides energy to change the shape of the channel, the sodium ions are driven through the channel
3- the sodium ions go outside the membrane the new shape of the channel allows to K ions to bind
4- the phosphate releases which allows the channels to go back to its orginal form, releasing the potassium ions from the inside of the ions.
88
what do carrier and channel proteins do to the rate of diffusion?
increase the rate of facilitated diffusion along the concentration gradient without the need for energy in the form of ATP from respiration
89
why does the line flatten out on a facilitated diffusion graph
because carrier proteins are full, the uptake is constant
90
why is facilitated diffusion not affected by a respiratory inhibitor
as ATP is not required
91
what does respiratory inhibitors do
stop ATP production
92
what is the sodium-glucose co-transport significant in
absorbing glucose and sodium ions across cell membranes and into the blood in the ileum and kidney nephron
93
what does active transport allow even when present in a low concentration
the uptake of important solutes
94
what is pumping
an active process, only transport that can transport substances up/against their concentration gradient
only works in one direction
95
explain how the pump works
the molecule/ion that needs to be transported combines with a specific intrinsic protein (pump)
ATP transfers a phosphate group to the pump on the inside of the membrane. the pump will then change shape and transport the ion. this is then released into the cell
96
what does cyanide do
stops active transport as it stops the production of ATP
97
why does the rate of active transport level off at higher concentration differences
due to the pumps being full, this limits the rate of active transport
98
what is lysis
animal cells may burst as they have no cell wall to prevent this happening when too much water moves into the cell
99
what's plasmolysis
when water leaves a plant cell by osmosis the cytoplasm and vacuole shrink and the cell membrane pulls away from the cell wall
100
what is the effect on animal cells when in a hypotonic external medium
cells swell and may lyse (burst)
red blood cells in a hypotonic medium burst. this is called haemolytic
101
what is the effect on plant cells when in a hypotonic external medium
the cytoplasm and vacuole will swell and push against the cell wall; the cells become turgid. turgid plant cells support the plant tissues and structures
(optimum for plant cells )
102
what is the effect on animal cells when in a hypertonic external medium
the cell shrinks
103
what is the effect on plant cells when in a hypertonic external medium
the cytoplasm and vacuole shrink causing the cell membrane to pull away from the cell wall. this is called plasmolysis ad cells in this condition are referred to as plasmolyse
104
what is the effect on animal cells when in an isotonic external medium
this is animal cell optimum
the water potential of the cell is equal to the water potential of the external medium at this point
105
what is the effect on plant cells when in an isotonic external medium
cells become flaccid
point of incipient plasmolysis
106
how do large particles enter the cell
by endocytosis
107
what does endocytosis mean
the cell membrane engulfs particles or liquid forming vesicle which enters the cytoplasm
108
2 types of endocytosis
phagocytosis
pinocytosis
109
what is phagocytosis
cell eating
110
what is pinocytosis
involves the entry of liquid into a cell
111
what can phagocyles do
engulf microbes by phagocytosis
112
briefly explain exocytosis
substances leave the cell after being transported through the cytoplasm in transport vesicles (from the rough ER) to the golgi body and then to the cell membrane via secretory vesicles. secretory vesicles fuse with the cell membrane and the contents are secreted outside the cell
