2.5 biological membranes Flashcards
(112 cards)
1
Q
what is tonoplast
A
the membrane surrounding the vacuole
2
Q
is the nuclear envelope a membrane
A
yes
3
Q
the membrane at the outside of the cell can be called…
A
the plasma membrane or the cell surface membrane
4
Q
membranes are - permeable
A
partially
5
Q
cell membranes control…
A
what can enter and exit the cell
6
Q
cell membranes are used in cell
A
signalling
7
Q
cell membranes provide - for enzymes
A
attachment sites
8
Q
cytosol is…
A
an area of cytoplasm with no organelles in it
9
Q
cell membranes compartmentalise, which means that they…
A
produce different compartments inside cells
10
Q
phospholipid heads are
A
hydrophilic
11
Q
phospholipid tails are
A
hydrophobic
12
Q
what are the bonds in phospholipids?
A
ester bonds
13
Q
what is formed when phospholipids are put in water?
A
micelles
14
Q
what did Gorter and Grendel propose and when?
A
that the cell membrane is formed of a phospholipid bilayer, 1925
15
Q
what was Davson-Danielli wrong about?
A
he said that proteins formed a layer on top of the membrane, but they are actually embedded in the membrane
16
Q
who proposed the fluid mosaic model?
A
Singer and Nicholson
17
Q
what model do we use for the plasma membrane structure?
A
the fluid mosaic model
18
Q
proteins move more freely in - phospholipids, because…
A
unsaturated, they are bent and less rigid
19
Q
what makes ATP?
A
ATP synthase (in the mitochondria)
20
Q
can fat soluble molecules go through the phospholipid bilayer?
A
yes
21
Q
a glycocalyx consists of…
A
a lipid and a glycolipid
22
Q
what proteins are present in the plasma membrane?
A
peripheral proteins, enzyme or signalling proteins, glycoproteins, transport proteins, integral proteins
23
Q
what are the transport proteins? 4
A
passive carrier protein, active carrier protein, channel protein, gated channel protein
24
Q
integral and intrinsic proteins…
A
span the whole plasma membrane
25
peripheral and extrinsic proteins...
are found in one layer of the plasma membrane only
26
channel proteins are - in the plasma membrane
pores
27
channel proteins allow movement of - or - molecules, eg.
large or hydrophilic, glucose
28
channel proteins are often gated so that...
they only allow one type of ion through
29
channel proteins may be gated, which means they can...
open and close to allow certain things through
30
carrier proteins are often used in - using - energy
active transport, ATP
31
carrier proteins often have a particular shape so that
specific molecules fit
32
a glycocalyx is a - chain
carbohydrate
33
glycocalyxs form - bonds with -, helping to stabilize the membrane structure
hydrogen, water
34
aggregating means
bringing together
35
glycocalyxs are involved in cell adhesion for
aggregating cells into tissues
36
glycocalyxs act as receptors for
chemical signals
37
glycolipids in the glycocalyx act as cell identity markers or -, allowing...
antigens, the immune system to recognise them as self or non-self
38
cholesterol is found between - of a plasma membrane
the tails in the phospholipids
39
the function of cholesterol in the plasma membrane is...
to regulate fluidity
40
at high temperatures, cholesterol makes the plasma membrane more/less fluid
less
41
at low temperatures, cholesterol makes the plasma membrane more/less fluid
more
42
the plasma membrane being more fluid when it is colder is useful as it prevents...
the membrane from freezing
43
lipid soluble molecules go through
the phospholipid bilayer
44
polar or soluble molecules go through
hydrophilic channels created by channel proteins
45
endocrine systems signal to cells
over large distances
46
panacrine systems signal to cells
to other cells locally
47
autocrine systems signal
within the cell or to cells of the same type
48
the 'message molecule' sent is called the - or the -
signal or stimuli
49
the most common types of signal or stimuli are
hormones
50
the detect signals, cells must have sensors called -
receptors
51
receptors are often
proteins
52
non polar signals (such as testosterone and oestrogen) are able to... and bind to ...
diffuse directly through the phospholipid bilayer, intracellular receptors
53
polar signals must bind to the membrane bound receptors, which are the - proteins
intrinsic
54
5 steps of cell signalling:
1. stimuli
2. receptors
3. transducers
4. amplifiers
5. intracellular responses
55
a ligand is the
primary messenger
56
hormones are - messengers transported in the -
chemical, blood
57
target cells are any cells with a - for
receptor, the hormone
58
the hormone and the receptor on the target cell bind due to
their complementary shapes
59
channel proteins travel to- to let - into the cell
the cell membrane, glucose
60
binding causes the target cell to
react in a certain way
61
under normal circumstances, are there any channel proteins present in the plasma membrane?
yes
62
when blood glucose levels rise, the hormone - is secreted into the blood by the -
insulin, pancreas
63
medicinal drugs can interfere with
receptors
64
beta blockers block receptors to prevent...
the heart muscle increasing the heart rate if it would be dangerous for the patient
65
some drugs mimic natural receptors which people lack, eg in
schizophrenia
66
drugs blocking receptors form
drug- receptor complexes
67
painkillers attach to receptors and block - from travelling along the -
pain signals, nerve
68
drugs can do 2 things:
- mimic natural receptors
| - block receptors
69
how does botox work?
it uses a toxin from the bacterium clostridium botulinum, the toxin binds to the receptors on muscle fibres, prevents them working and causes paralysis, reduces wrinkling of the skin
70
what is theory of Brownian Motion?
molecules move around randomly and bump into each other, and so tend to fill out the space that they are in
71
diffusion occurs down a
concentration gradient
72
diffusion is always
passive
73
diffusion can be - or -
simple or facilitated
74
what happens at equilibrium
the reaction rate is equal in both directions
75
which molecules go through channel proteins
large or polar molecules
76
is facilitated diffusion active
no
77
how wide is the phospholipid bilayer
7nm
78
how wide is the channel protein
0.8nm
79
what can move by osmosis
only water
80
pure water has a potential of
0
81
which symbol represents water potential
psi
82
diffusion occurs across a
partially permeable membrane
83
why are plant cells not haemolysed
they have a cell wall which prevents it
84
plant cells, water moves in so cell is
turgid
85
animal cells, water moves in so cell is
haemolysed
86
plant cells, water moves out so cell is
flaccid or plasmolysed
87
animal cells, water moves out so cell is
crenated
88
what is a hypertonic solution
something with a very low water potential
89
what is plamolysis
when water moves out of a cell, causing the vacuole to shrink and cytoplasm to move away from the cell wall
90
what is the incipient point of plasmolysis
when 50% of cells have been plasmolysed
91
what is bulk transport
moving large quantities of material in or out of the cell
92
endocytosis is
moving large quantities of material into the cell
93
exocytosis is
moving large quantities of material out of the cell
94
what type of energy does active transport need
ATP
95
when is active transport used
when diffusion isn't quick enough or when the movement is against a concentration gradient
96
cells involved in active transport have lots of
mitochondria
97
why are most carrier proteins one way
because otherwise particles would want to move back by diffusion
98
the shape of carrier proteins is
complementary
99
carrier proteins are complementary so that
they only allow specific molecules to enter snd exit the cell
100
the two types of endocytosis are
pinocytosis and phagocytosis
101
pinocytosis is
the cell taking in liquids
102
phagocytosis is
the cell taking in solids
103
an example of phagocytosis is
white blood cells engulfing and digesting pathogens
104
is bulk transport active or passive
active
105
why is bulk transport active
because it uses energy to transport material in vesicles along the cytoskeleton
106
exocytosis example
insulin exiting the cell
107
endocytosis example
pathogens entering the cell
108
why is beetroot used to investigate the effect of temperature on cell membranes
because their red cell sap is naturally coloured and easy to see
109
why does temperature effect cell membranes
because phospholipids break and proteins denature, and the plasma membrane melts. The tonoplast is broken and cell sap can escape from the vacuole.
110
what steps happen to the cell membrane as temperature is increased
1. proteins are denatured as the bonds in their tertiary structure are broken
2. phospholipid membrane bonds break
3. rate of diffusion increases
111
how do we conduct an experiment to investigate the effect of temperature on cell membranes?
1. place test tubes with 10cm3 of water into water baths set at 30, 40, 50 and 70, and leave one at room temperature. Leave for 15 mins to equilibrate.
2. cut beetroot into identical cylinders measured with a ruler and rinse and dry them
3. place the beetroot cylinders into test tubes and leave for 10 mins
4. remove the test tubes, remove the beetroot and swirl the liquid
5. place liquid into cuvettes and measure light absorption, record data in table and plot graph
112
how do we investigate osmosis in an artificial cell?
1. create a dilution series of 1.0, 0.8, 0.4, 0.2 and 0.1 mol dm3
2. cut visking tubing into 5 equal sections and tie then ends in knots
3. fill tubing 1/3 full with 0.4 mol dm3 solution
4. measure the mass of each concentration initially
5. place the artificial cells into each concentrated solution for 20 mins and then remove and weigh mass
6. create a table recording concentration, initial mass, final mass, mass change, and percentage change
