CIE AS & A Level Biology Papers 2 prediction - 2025
CIE AS & A Level Biology Papers 2 prediction- 2025
To excel in A level Biology Exam, consistent practice with CIE AS & A Level Revision resources is key. CIE AS & A Level Biology Papers 2 prediction predictions will guide you for exam pattern.
IITian Academy offers a vast collection of questions that can aid your understanding of specific topics and solidify your concepts. By practicing regularly and focusing on these key areas, you’ll be well-prepared for the A level Biology exam
Question 1
Fig. 2.1 is a diagram of the structure of a protein channel for ions in a cell surface membrane.
Fig. 2.1a shows the channel when open and Fig. 2.1b shows the same channel when closed.
(a) (i) Name the process by which ions pass across the membrane using channel proteins.[1]
(ii) Explain why a channel protein is needed for ions to pass across a cell membrane.[2]
(b) The channel protein in Fig. 2.1 is made from five identical polypeptide chains.
(i) Name the level of protein structure which is present when five polypeptide chains form the protein.[1]
(ii) The part labelled C in Fig. 2.1 is another level of protein structure.
Name this level.[1]
(c) Channel proteins are examples of transmembrane proteins. The polypeptides are held together and also interact with phospholipids in the membrane.
Suggest how the polypeptides are held together and suggest how they interact with phospholipids.[3] [Total: 8]
Answer/Explanation
Ans:
2 (a) (i) facilitated diffusion ;
(ii) ions are, charged/water-soluble ; A hydrophilic
unable to pass, through hydrophobic core/ hydrophobic (fatty acid) tails of,
phospholipid bilayer/ phospholipids(s) ;
(channel of) protein lined with amino acids with, hydrophilic/ polar, R groups /
side chains ; A hydrophilic channels
(b) (i) quaternary / 4°, (structure) ;
(ii) secondary structure ; A alpha/α, helix
(c) bonds must be named in the correct context of maintaining 4° structure and interactions with phospholipids
polypeptides held together
bonds between, R groups / side chains ;
two named bond types ; from
ionic
hydrogen
hydrophobic interactions
disulfide
van der Waal’s forces
I peptide bond
polypeptides interact with phospholipids
(regions with) hydrophilic / charged/ polar (R groups / side chains, of) amino acids
interact with, phosphate/ hydrophilic head , of phosholipid ;
(regions with) hydrophobic /non-polar (R groups / side chains, of) amino acids
interact with, fatty acid/ hydrocarbon/ hydrophobic, tails / chains ;
further detail of named bond ;
Question 2
Bone marrow contains stem cells that divide by mitosis to form blood cells. Each time a stem
cell divides it forms a replacement stem cell and a cell that develops into a blood cell.
Fig. 3.1 shows changes in the mass of DNA in a human stem cell from the bone marrow
during three cell cycles.
(a) With reference to Fig. 3.1, state:
(i) what happens to bring about the changes in the mass of DNA per cell at K and at L
K ……………………………………………………………………………………………………………….
L ……………………………………………………………………………………………………………….
(ii) how many blood cells are formed from the stem cell in the time shown
(iii) what happens to the number of chromosomes in the stem cell.
Stem cells in bone marrow give rise to phagocytes, B-lymphocytes and T-lymphocytes.
(b) Describe how a red blood cell develops from a stem cell.
(c) During an immune response, cells divide by mitosis.
Describe how mitosis is involved in an immune response.
(d) Describe the modes of action of T-lymphocytes during an immune response.
Answer/Explanation
Answer:
(a) (i) K – (DNA) replication / synthesis / described ;
L – cytokinesis / cytoplasmic division / cell division ;
(ii) 3 ;
(iii) remain the same / stays constant / stay at 46 / AW ; ignore description of events
occurring before and during mitosis
(b) transcription (of specific genes) ; A reference to gene switching
protein / polypeptide, synthesis ; A translation
production of haemoglobin ;
further detail ; e.g. assembly of quaternary structure
(production of) carbonic anhydrase ;
loss of, mitochondria / named organelles ;
loss of nucleus ;
adopts biconcave disc shape ;
(c) occurs in both primary and secondary (immune) responses ;
selected / specific / AW ;
lymphocytes / B -cells / T-cells / divide (by mitosis) ;
clonal expansion / described in terms of producing, clone / many cells ;
A idea that different types of immune cell can result
reference mitosis in memory cells (for rapid) secondary response ;
(d) T helper / Th,
secrete, cytokines / interleukins ;
activate B-lymphocytes to, divide / form plasma cells ; A idea that leads to enhanced
antibody levels
enhances / AW, phagocyte / macrophage, response ; A angry macrophages ;
T cytotoxic / Tc / T killer / Tk
attach to / kill / AW, infected cells / damaged cells / tumour cells / cells with non-self
antigens / AW;
mechanism of killing ; e.g. perforin
T memory / Tm
already exposed to antigen ;
reference to role in secondary response ;
AVP ; ; e.g. T suppressor cells
function of suppressor cells
Question 3
(a) Fig. 1.1 shows a section through part of a dicotyledonous leaf of the tea plant Camellia sinensis.
On Fig. 1.1, use label lines and letters to label each of the following parts:[2]
X – xylem tissue
P – palisade mesophyll tissue.
(b) The leaves of C. sinensis have a large surface area and are thin.
Explain how each of these two features help the leaf to carry out photosynthesis.[2]
(c) The lower epidermis contains stomata.
(i) State one structural difference between a guard cell and other lower epidermal cells.[1]
(ii) Abscisic acid has an important role in the closure of a stoma. It promotes the loss of potassium ions from guard cells.
Outline how the loss of potassium ions from guard cells will lead to the closure of a stoma.[3] [Total: 8]
Answer/Explanation
Ans:
1 (a)
(b) large surface area
(to get) more, light/ carbon dioxide ; A gas exchange I oxygen
thinness
small(er)/ short(er)/reduced, diffusion distance for gases OR
fast(er) diffusion of gases ; A named gas, either CO2 or O2
1 mark only if both points made but not related to features in italics
(c) (i) have chloroplasts / varying thickness of (cell) walls / no plasmodesmata ;
(ii) water potential/Ψ, of (guard) cell(s), increases /becomes less negative ; water leaves cell(s) ;
(by) osmosis / down a water potential gradient ; I diffuses
(guard cell) becomes, flaccid/ less turgid/AW ;
Question 4
Table 5.1 shows the triplets of bases on the template polynucleotide of DNA for some amino acids.
Fig. 5.1 shows the base sequences in DNA and mRNA for the first seven amino acids of the β chain of haemoglobin.
(a) (i) Use Table 5.1 to complete Fig. 5.1. [3]
(ii) State the term used to describe the sequence of amino acids in a polypeptide.[1]
(b) In sickle cell anaemia, the amino acid at position 6 in the β chain is valine and not glutamic acid.
Explain how a single change in the DNA triplet for the sixth amino acid of the gene coding for the β chain leads to the production of a different amino acid sequence.[5] [Total: 9]
Answer/Explanation
Ans:
5 (a) (i) GTG ;
ACU ;
leu ;
(ii) primary structure ;
(b) 1 mutation ;
2 base substitution/T→ A in template strand of DNA/AW ;
transcription
3 DNA has CAC as 6th triplet ;
4 (so) mRNA has GUG as (6th) codon ;
allow one mark for altered mRNA codon if no marks gained for mps 3 and 4
translation
5 different tRNA involved/ tRNA specific to val and not glu ;
6 anticodon on tRNA has CAC (with valine) ;
7 tRNA brings, incorrect amino acid/ val, to ribosome ;
8 further detail ; e.g. incorrect amino acid incorporated into growing polypeptide chain
Question 5
(a) Explain how the virus that causes measles is transmitted. [2]
(b) Antibodies against measles are produced by plasma cells during an immune response.
Fig. 2.1 shows a diagram of an antibody molecule.
Explain the functions of the parts labelled A, B and C.
(i) A [2]
(ii) B [1]
(iii) C [1]
[Total: 6]
Answer/Explanation
Ans:
2 (a) (infected) person, sneezes / coughs / talks / breathes out, (airborne)
droplets / aerosol/ moist air ;
ignore contact
inhaled/ inspire/ breathed in, by uninfected, person ;
ignore transplacental transmission
(b) (i) variable region
binds / attaches / combines, to antigen ;
R receptor site R ‘fit’
ref. to specificity ;
ignore complementary shape (to antigen)
R same/ similar shape
(ii) disulphide bond
ignore ref. to hinge
holds, polypeptides /heavy chains / long chains, together ;
ignore constant as description of chains
maintains, tertiary / quaternary / 3D, structure/ shape ;
R shape unqualified
(iii) constant region
binds to, receptors / cell (surface) membrane, on, phagocytes / macrophages ;
antigen, marking/ tagging, for, phagocytosis / macrophage action ; AW
A ref. to opsonisation
R agglutination
Question 6
(a) Define the term disease.[1]
Fig. 2.1 is a flow chart that shows the four different ways that a person can become immune to an infectious disease.
(b) Complete Fig. 2.1 by writing in the boxes provided the four types of immunity described. [4]
Fig. 2.2 shows the number of cases of smallpox from 1950 to 1980:
- in all the countries of the world
- in India.
(c) Describe the changes in number of cases of smallpox as shown in Fig. 2.2.[3]
The World Health Organization (WHO) declared the world to be free of smallpox in 1980.
(d) Outline some of the factors that led to the successful eradication of smallpox from the world population.[4] [Total: 12]
Answer/Explanation
Ans:
2 (a) abnormal condition/abnormal state/disorder/ill-health/AW, qualified
e.g. having an adverse effect (on an organism)
reduces the effectiveness of functions
produces (specific) signs/symptoms
infectious and non-infectious causes ;
(b) natural active ; artificial active ; natural passive ; artificial passive ;
Allow one mark for active and passive correct
(c) number of cases fluctuates ; A description of increases and decreases over time
(overall trend) number of cases decreases (over time) ;
overall decrease, data quote to support ;
e.g. (India) 155000/160000 cases in 1950 to 0 in 1980
(all countries) 330000 cases in 1950 to 0 in 1980
(India) 250000/160000 cases in 1951 to 0 in 1980
(all countries) 485000 cases in 1951 to 0 in 1980
India/all countries, three major peaks ;
data quote to support ; e.g. 1951, 1958, 1974
eradication, no cases from 1975/1976, for India or 1978 for world ;
A (almost zero) from 1976 for world
(d) 1 smallpox virus was stable/did not mutate ;
2 same vaccine was used for whole programme/vaccine did not need to be changed ;
3 vaccine was live/gave a strong immune response ; A effective
4 one dose was enough to give life-long immunity/no boosters required ;
5 heat stable/freeze dried vaccine ;
6 suitable for hot countries/isolated areas/rural areas ;
7 bifurcated/steel, needle, could be re-used/easier delivery/AW ;
8 herd/mass, vaccination/immunity ; A (many countries) mandatory vaccination
9 ring vaccination/ref. to contact tracing ;
10 few/no symptomless carriers ;
11 no animal reservoir/only in humans ;
12 infected people easy to identify ;
13 isolation of cases to prevent spread ;
14 AVP ; e.g. comparatively low cost, qualified; many volunteers became vaccinators/AW ;