Ans 9
a) D
Cholesterol
E
Protein/glycoprotein/intrinsic protein/protein channel/transport
protein/carrier protein
F
Phospholipid (bilayer)/phospholipids head
b) D
Stabilises the membrane; maintain fluidity; reduce permeability to polar
(charged) particles
E
allow communication across membrane; allow polar/charged, particles to
pass through
F
Act as a barrier to polar/charged particles/ selectively permeable
c) Communication between cells; cell recognition/identification
d) Allow cells/ tissues/organs to work together
Coordination between actions of different cells; to trigger response/reaction inside
the cell
Glycoprotein has a specific shape/tertiary structure
Complementary to shape of ligand (signalling/communicating molecule)
Ligand attaches/binds to receptor
1
Qs 10
Describe the roles of the different components of the plasma membrane
Ans 10
Phospholipids , separates cell contents from exterior / acts as (physical) barrier ;
(Phospholipid) allows diffusion (of suitable substance) / selective / stops some substances
passing through / allows some substances through ;
(carrier / transport / transmembrane) protein used for , active transport (e.g. ions against a
concentration gradient, utilising energy)
(channel / carrier / transport / transmembrane) protein used for facilitated diffusion (e.g.
glucose) ;
hydrophilic channel / water-lined pore ;
protein changes shape ; aquaporins for transport of water ; transport proteins are specific ;
glycoprotein / glycolipid , for cell recognition / for signalling / act as antigens ;
(glycoproteins / glycolipids are) receptors for / attachment of , hormones / neurotransmitters /
antibodies
(glycoproteins / glycolipids allow) attachment of one cell to another ;
cholesterol , determines fluidity / maintains mechanical stability (of membrane)
(cholesterol) allows , bulk flow / endocytosis / exocytosis / pinocytosis / phagocytosis ; (as)
membrane is self sealing ;
(some proteins are) enzymes attached to membrane
carbohydrate chains form hydrogen bonds with water to stabilise membrane
2
Qs 11
A student investigated the effect of temperature on the release of pigment from pieces of
beetroot.
She cut a fresh beetroot into four pieces and placed each piece into water at a different
temperature.
After 10 minutes she removed the beetroot and used a colorimeter to test how much pigment
had entered the water.
She placed the coloured water into the colorimeter and measured the percentage
transmission of light through the water. Her results are shown in the Table
The results show that below 50 °C little pigment had entered the water.
a) Explain why there was no transmission of light after the beetroot had been placed
in water at 100 °C.
b) Suggest three ways in which the student could have improved her investigation
3
Ans 11
a) cell surface / plasma, membrane damaged
pigment, released / leaks out
pigment, absorbs / takes up, the light
ACCEPT description of damage - e.g. proteins denatured / phospholipids separate /
bilayer melts
ACCEPT ‘cell contents’ for pigment
b) more samples at each temperature
same / fixed, volume of water
all samples same, size / surface area
ref to further cutting to increase surface area
pieces, rinsed / blotted, after cutting
more (intermediate) temperatures
same beetroot used / same part of beetroot used
4
Qs 12
The equation below represents Fick’s. first law of diffusion.
a) Use Fick’s law to explain why some cells which are concerned with absorption by
diffusion:
(i)
possess a brush border of microvilli.
(ii) make a very thin membrane.
b) In some membranes absorption involves active transport. Explain why cells in
these membranes:
(i)
contain many mitochondria.
(ii) possess large quantities of cholesterol and other lipids in their cell membranes.
c) Explain how the following substances cross the plasma membrane.
(i)
carbon dioxide.
(ii) glucose.
5
Ans 12
a)
i)
increases surface area/value of A; if A is increased then J is increased; thus more
absorption per unit time
ii)
(if membrane is thin) Dx is small; thus J is large; thus more absorption per unit time
(b)
i)
provide ATP; for active transport; to maintain/work against concentration gradient
ii)
ref. cholesterol will mix with water and allows passage of some water soluble
substances; will accelerate diffusion/entry of non-polar substances; e.g. oxygen/carbon
dioxide;
c)
i)
diffusion; down concentration gradient; as hydrogen carbonate ions / as dissolved CO2
ii)
either: facilitated diffusion; glucose binds to carrier/protein; protein changes
shape/carries glucose across;
or: active transport; glucose binds to carrier/protein; energy or ATP required; protein
changes shape; carries glucose across; ref. needs Na+ to be carried at the same time;
Qs 13
The diagram shows part of the cell-surface
membrane of a cell from the small intestine.
Molecule Y acts as a cell-surface receptor for
growth hormone.
a) State the likely nature of molecule Y.
b) State the approximate length of molecule Y.
c) Explain why molecule Y is only able to recognise growth hormone.
d) Suggest why pygmies are unable to achieve normal growth despite producing normal
amounts of growth hormone.
Ans 13
a) protein
b) 7.0 - 10 nm
c) shape of receptor site is specific to growth hormone/only growth hormone fits
d) receptor damaged / mutation affects protein; unable to recognise/bind with growth
hormone
7
Qs 14
The figure shows the fluid mosaic model of the plasma membrane.
a) State the approximate width of the membrane.
b) Identify,
A
B
C.
c) Explain why the membrane may be described as fluid.
d) Distinguish each of the following pairs.
1. exocytosis and endocytosis.
2. phagocytosis and pinocytosis.
8
Ans 14
a) range 7 - 10 nm
b) A = glycocalyx
B = intrinsic/integral/internal protein;
C = phospholipid bilayer;
(c) lipids/proteins can move laterally/change places
d) exocytosis: when material is passed out from the cell using a vesicle
endocytosis: is the uptake of material into the cell by forming a vesicle with the plasma
membrane
phagocytosis takes solid material into the cell
pinocytosis takes fluid into the cell
9
Qs 15
The graph below shows the rate of movement
of solute molecules across a plasma membrane
by simple diffusion and facilitated diffusion.
a) Which type of uptake is shown by line Y.
Explain your answer.
b) State two factors which may limit the rate of
simple diffusion.
c) Explain how the concentration of ions such as sodium and chloride are kept at high levels
outside cells but low levels within.
Ans 15
a) facilitated
rate of transport levels off; when number of solute molecules exceeds number of carriers /
proteins
b) any two of: concentration gradient/difference / size/shape of molecule /polarity of molecule /
temperature
c) active transport / use of ATP; sodium/chloride pumps move ions out
cannot re-enter because cell membrane is impermeable to these ions
10
Qs 16
A student investigated the effect of putting cylinders cut from a potato into sodium chloride
solutions of different concentration. He cut cylinders from a potato and weighed each cylinder.
He then placed each cylinder in a test tube. Each test tube contained a different concentration of
sodium chloride solution. The tubes were left overnight. He then removed the cylinders from the
solutions and reweighed them.
a) Before reweighing, the student blotted dry the outside of each cylinder. Explain why.
The student repeated the experiment several times at each concentration of sodium chloride
solution. His results are shown in the graph.
Qs 16 (continued)
The student made up all the sodium chloride solutions using a 1.0 mol dm-3 sodium chloride
solution and distilled water.
b) Complete the table to show how he made 20 cm3 of a 0.2 mol dm-3 sodium chloride
solution.
c) The student calculated the percentage change in mass rather than the change in mass.
Explain the advantage of this
d) The student carried out several repeats at each concentration of sodium chloride
solution. Explain why the repeats were important.
e) Use the graph to find the concentration of sodium chloride solution that has the same
water potential as the potato cylinders.
12
Ans 16
a) Water will affect the mass / only want to measure water taken up or lost;
Amount of water on cylinders varies / ensures same amount of water on outside
b) 4 cm3 (of 1.0 mol dm-3 sodium chloride solution), and,
16 cm3 (of distilled water)
c) Allows comparison / shows proportional change; Idea that cylinders have different
starting masses / weights
d) (Allows) anomalies to be identified / ignored / effect of anomalies to be reduced / effect of
variation in data to be minimised;
Makes the average / mean/ line of best fit more reliable / allows concordant results
e) 0.35 (mol dm-3) – whwre line crosses x axis
13
Qs 17
A scientist investigated the effect of cyanide on the uptake of sodium ions by animal tissue. He
set up two beakers, J and K. He put equal volumes of a solution containing sodium ions and
equal masses of an animal tissue in each beaker.
●
●
He added cyanide to beaker J
He did not add cyanide to beaker K
He measured the concentration of
sodium ions remaining in the
solution in each beaker, for 80
minutes.
The graph shows his results
a) Calculate the rate of uptake of sodium ions by the tissue in beaker K for the first 30
minutes. Show your working.
b) Adding cyanide affects the uptake of sodium ions by the tissue. Use the graph to
describe how
Cyanide is a substance which affects respiration.
c) Use information in the question to explain the effect of cyanide on the uptake of sodium ions
by the tissue.
Ans 17
a) 0.2 (concentration / time = 6 / 30)
b) (Uptake) decreases / slower, then no further uptake / uptake / stops
(Decreases) to 20 -22 / no uptake after 20 / 22minutes
c) Stops/ reduces / inhibits respiration
No / less energy released / ATP produced; (ATP / energy needed) for active transport
15
Qs 18
Amoeba is a single-celled aquatic organism. Substances in the water can enter the cell by a
variety of mechanisms.
An experiment was carried out to compare the uptake into Amoeba of substance A
and substance B.
Some of these organisms were placed in a solution containing equal concentrations
of both substances and kept at 25 °C. The concentration of substances A and B, in the
cytoplasm of these organisms, was measured every 30 minutes over a period of
5 hours.
The results of this experiment are
shown in the graph
a) Using the information in the
graph, compare the uptake of
substance A with the uptake of
substance B during this period
of 5 hours.
b) Substance B enters the cells by
diffusion. Describe and explain
how the results of this
experiment support this
statement.
c) Substance A enters the cells by active transport. Give two differences between active
transport and diffusion.
Ans 18
a)
1. rate is same for up to 30 minutes
2. faster (uptake) for A than B
3. (uptake of) A is linear throughout whereas (uptake of) B is not
4. uptake of substance B levels off at {2 to 2.2} hours whereas uptake of A does not
5. credit correct manipulation of comparative figures
b)
1. correct ref to diffusion (of substance B) occurring due to concentration difference
2. idea of rate of uptake decreases
3. as the concentration gradient decreases
4. (net) uptake stops
5. when concentration inside cell equals that outside the cell
c)
1. active transport is {against concentration gradient }
2. active transport requires ATP
3. ref to involvement of (membrane) proteins in active transport
17
Qs 19
When blood is collected from a donor, technicians sometimes separate the red blood cells from
the plasma and other blood cells. They store these red blood cells at 4oC.
They mix the red blood cells with an isotonic solution before giving them to a patient.
a) Suggest one reason why red blood cells are stored at 4oC
The red blood cells are mixed with an isotonic solution before they are used.
b) Explain why it is important that this solution is isotonic with the red blood cells
A large volume of isotonic solution containing red blood cells is often given to injured people
who have lost a lot of blood.
c) Suggest how this treatment might help to save their lives.
Ans 19
a) Reduces enzyme / metabolic activity
that might damage / break down cells
OR
it slows respiration / metabolism; conserving energy reserves / so cells can
live long
b) water potential is the same as the cells
so water doesn’t enter or leave cells
by osmosis
so cells don’t burst / shrinks
c) Isotonic solution:
increases blood volume;
so keeps circulation to (vital) organs/tissues
prevents osmotic damage
red cells
Red cells:
carry oxygen
so improve supply for / maintain respiration
19
A*
20
1
The diagram below shows a small
polypeptide integrated into a membrane
2
The diagram shows some of the main
structures which form the cell
membrane.
Which line in the table below correctly
classifies amino acids in this polypeptide?
Which two structures, when
hydrolysed, would release amino
acids?
A
B
C
D
2 and 3
1 and 4
2 and 5
4 and 5
21
3
The diagram below shows the
arrangement of molecules in part of a cell
membrane
4
The diagram below refers to the
plasma membrane of an animal cell
Identify the two processes X and Y.
What types of molecule are represented
by X and Y?
.
22
5
The experiment below was set up to demonstrate osmosis.
Visking tubing is selectively permeable.
The following results were obtained.
Initial mass of visking tubing + contents = 10·0g
Mass of visking tubing + contents after experiment = 8·2g
The results shown above could be obtained when
A
B
C
D
R is a 5% salt solution and S is a 10% salt solution
R is a 10% salt solution and S is a 5% salt solution
R is a 10% salt solution and S is water
R is a 5% salt solution and S is water.
23
6
The diagram below shows cotransport
(symport) of sodium ions (Na+) and
glucose into a cell lining the gut.
Which line in the table below represents
the relative concentrations of glucose
and Na+ on the two sides of the plasma
membrane when cotransport occurs?
7
Cortisol is a steroid hormone – it is lipid
soluble. Which letter in the diagram
below shows the first stage in cell
signalling for this hormone?
8
Carrier molecules involved in the
process of active transport are made of
A
B
C
D
protein
carbohydrate
lipid
phospholipid.
24
10
9
The diagram below represents part of
the plasma membrane of a red blood
cell
The following diagram illustrates the
fluid mosaic model of a cell
membrane
The membrane is shown magnified 2
million times.
What is the width of the membrane?
(1 nanometre= 1 × 10–6mm)
A
B
C
D
Which line in the table below
describes correctly the uptake of
substances P and Q and the nature
of substances R and S?
0·6 nanometres
6 nanometres
24 nanometres
60 nanometres
25
11
Which of the following statements is/are true?
1 Electron transport chains are located in the thylakoid membranes
2 Phospholipid bilayers are impermeable to protons
3 ATP synthase maintains chemiosmotic gradients
A
B
C
D
12
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
Vitamins and minerals need to cross the
plasma membrane. Vitamins A, D, E and
K are fat soluble; vitamin C is water
soluble
Which of the following combinations
utilises facilitated diffusion to cross the
plasma membrane
A
B
C
D
vitamin A and calcium atoms
vitamin C and calcium ions
vitamin C and calcium atoms
vitamin A and calcium ions
13
Which of the following is responsible
for cell-cell recognition?
A
B
C
D
Glycoprotein
Phospholipid
Hormones
Peptidoglycan
26
14
The diagram below shows the distribution
of protein molecules in a cell membrane.
15
Which line in the table below correctly
identifies a peripheral and an integral
membrane protein?
The diagram below represents a
cross-section of a membrane
magnified 2 million times.
What is the actual width of the
membrane?
1 nm = 1 × 10–6 mm
A
B
C
D
1·6 nm
3·2 nm
8·0 nm
16·0 nm
27
Qs
Answer
Qs
Answer
1
A
11
B
2
C
12
B
3
B
13
A
4
A
14
B
5
A
15
C
6
B
7
B
8
A
9
B
10
D
28
Multiple Choice Questions – Blank Answer Grid
Qs
Answer
Qs
1
11
2
12
3
13
4
14
5
15
Answer
6
7
8
9
10
29
30