2023 AQA Alevel BIOLOGY 7402/3 Paper 3 Question Paper & Mark scheme (Merged)|| newest 2024
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Course
2023 AQA Alevel BIOLOGY
Institution
2023 AQA Alevel BIOLOGY
2023 AQA Alevel
BIOLOGY
7402/3 Paper 3
Question Paper
& Mark scheme
(Merged)||
newest 2024
Describe how oxygen in the air reaches capillaries surrounding
alveoli in lungs ANSWERTrachea and bronchi and
bronchioles;
Down pressure gradient;
Down diffusion gradient;
Across alveolar epitheli...
2023 AQA A-
level BIOLOGY
7402/3 Paper 3
Question Paper
& Mark scheme
(Merged)||
newest 2024
,Describe how oxygen in the air reaches capillaries surrounding
alveoli in lungs ✔✔✔ANSWER➖Trachea and bronchi and
bronchioles;
Down pressure gradient;
Down diffusion gradient;
Across alveolar epithelium;
Across capillary endothelium/epithelium;
Difference between species richness and index of diversity
✔✔✔ANSWER➖Species richness measures only number of
(different) species / does not measure number of individuals;
Explain how cellulose molecules are adapted for their function
in plant cells ✔✔✔ANSWER➖Long and straight chains;
Become linked together by many hydrogen bonds to form
fibrils;
Provide strength (to cell wall);
Describe how mRNA is produced in the nucleus of the cell
✔✔✔ANSWER➖Helicase;
,Breaks hydrogen bonds;
Only one DNA strand acts as template;
RNA nucleotides attracted to exposed bases;
(Attraction) according to base pairing rule;
RNA polymerase joins (RNA) nucleotides together;
Pre-mRNA spliced to remove introns;
What two types of molecule is a ribosome made from?
✔✔✔ANSWER➖nucleotide and protein
Describe the role of a ribosome in the production of a
polypeptide ✔✔✔ANSWER➖mRNA binds to ribosome;
Idea of two codons/binding sites;
(Allows) tRNA with anticodons to bind/associate;
(Catalyses) formation of peptide bond between amino acids
(held by tRNA molecules);
Moves along (mRNA to the next codon)/translocation described;
, Describe how phagocytosis of a virus leads to presentation of its
antigens. ✔✔✔ANSWER➖Phagosome/vesicle fuses with
lysosome;
(Virus) destroyed by lysozymes/hydrolytic enzymes;
Peptides/antigen (from virus) are displayed on the cell
membrane;
Explain three ways in which an insects tracheal system is
adapted for efficient gas exchange ✔✔✔ANSWER➖Tracheoles
have thin walls so short diffusion distance to cells;
Highly branched/large number of tracheoles so short diffusion
distance to cells;
Highly branched/large number of tracheoles so large surface
area (for gas exchange);
Tracheae provide tubes full of air so fast diffusion (into insect
tissues);
Fluid in the end of the tracheoles that moves out (into tissues)
during exerciseso faster diffusion through the air to the gas
exchange surface;
OR
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