AQA AS Level Biology Paper 1 with
Definition and correct answers
Define the primary structure of all proteins (2) - 1- sequence of amino acids
2- joined by peptide bonds
Define universal, non overlapping and degenerate (3) - 1- universal: Same codon/triplet
always codes for the same amino acid
2- non overlapping: Each base only part of 1 triplet/codon OR triplets/codons do not
overlap
3- degenerate: More than 1 codon/triplet codes for each amino acid
Figure 1 shows transmission electron microscope image of a streptococcus bacterium.
Describe how the appearance of the area containing DNA in a TEM image of a
eukaryotic cell would differ from that shown in figure 1
(2) - 1- nucleus
2- nucleolus OR nuclear membrane/envelope
3- mitochondria/chloroplast contain DNA
(can also say membrane bound nucleus for 2 marks)
describe one difference between the structure of DNA in a prokaryotic cells and in a
eukaryotic cell (1) - 1- no introns
OR
circular not linear in prokaryotes
OR
not associated with proteins/histones
streptococcus bacteria can infect the lungs when air is breached in and cause lung
disease.
describe the mechanism of breathing that causes air to enter the lungs (3) - 1-
diaphragm muscles contact AND diaphragm flattens
2- external intercostal muscles contract AND rib cage pulled up and out
3- causes volume increase AND pressure decrease in thoracic cavity to below
atmospheric pressure
some strains of streptococcus bacteria are more likely to cause lung disease than other
strains.
, strains that do not cause lung disease are quickly destroyed by phagocytes. phagocytes
are stimulated when they bind to mute in on streptococcus bacteria.
each stain of streptococcus bacteria has a capsule of different thickness from the
others.
suggest how streptococcus bacteria with a thicker capsule are more likely to survive
AND so cause lung disease (2) - 1- thicker capsule so phagocytes are less likely to bind
to murein in cell wall
OR
thicker capsule so phagocytes less likely to be stimulated by murein in cell wall
2- reduced phagocytosis SO more bacterial growth/division/reproduction/binary fission
figure 2 shows a fatty acid that contains 20 carbon atoms and 4 double bonds. On figure
2 draw a box around the R group of the fatty acid (1) - everything except COOH should
have a box around it
figure 3 shows a triglyceride.
describe 2 differences between the structure of the triglyceride shown in figure 3 and a
phospholipid (2) - 1- triglyceride has 3 fatty acids rather than 2
2- has 3 ester bonds rather than 2
3- no phosphate group
explain why phospholipids can form a bilayer but tricky exercises cannot (3) - 1-
phospholipid both hydrophobic and hydrophilic
OR
phospholipid is polar
OR
phosphate group is charged
2- triglycerides only hydrophobic
OR
fatty acid/triglyceride is non-polar
3- phosphate group attracts water to either side of bilayer
figure 4 shows 2 fatty acids A and B.
scientists fed rats diet with added fish oil for 4 months.
they obtained samples of red blood cells from rats before starting diet (0 months) and
after 4 months on diet.
for each red blood cell sample they separated cell-surface membranes and measured:
• percentage of phospholipids containing each fatty acid A and B
• fluidity of membrane
Definition and correct answers
Define the primary structure of all proteins (2) - 1- sequence of amino acids
2- joined by peptide bonds
Define universal, non overlapping and degenerate (3) - 1- universal: Same codon/triplet
always codes for the same amino acid
2- non overlapping: Each base only part of 1 triplet/codon OR triplets/codons do not
overlap
3- degenerate: More than 1 codon/triplet codes for each amino acid
Figure 1 shows transmission electron microscope image of a streptococcus bacterium.
Describe how the appearance of the area containing DNA in a TEM image of a
eukaryotic cell would differ from that shown in figure 1
(2) - 1- nucleus
2- nucleolus OR nuclear membrane/envelope
3- mitochondria/chloroplast contain DNA
(can also say membrane bound nucleus for 2 marks)
describe one difference between the structure of DNA in a prokaryotic cells and in a
eukaryotic cell (1) - 1- no introns
OR
circular not linear in prokaryotes
OR
not associated with proteins/histones
streptococcus bacteria can infect the lungs when air is breached in and cause lung
disease.
describe the mechanism of breathing that causes air to enter the lungs (3) - 1-
diaphragm muscles contact AND diaphragm flattens
2- external intercostal muscles contract AND rib cage pulled up and out
3- causes volume increase AND pressure decrease in thoracic cavity to below
atmospheric pressure
some strains of streptococcus bacteria are more likely to cause lung disease than other
strains.
, strains that do not cause lung disease are quickly destroyed by phagocytes. phagocytes
are stimulated when they bind to mute in on streptococcus bacteria.
each stain of streptococcus bacteria has a capsule of different thickness from the
others.
suggest how streptococcus bacteria with a thicker capsule are more likely to survive
AND so cause lung disease (2) - 1- thicker capsule so phagocytes are less likely to bind
to murein in cell wall
OR
thicker capsule so phagocytes less likely to be stimulated by murein in cell wall
2- reduced phagocytosis SO more bacterial growth/division/reproduction/binary fission
figure 2 shows a fatty acid that contains 20 carbon atoms and 4 double bonds. On figure
2 draw a box around the R group of the fatty acid (1) - everything except COOH should
have a box around it
figure 3 shows a triglyceride.
describe 2 differences between the structure of the triglyceride shown in figure 3 and a
phospholipid (2) - 1- triglyceride has 3 fatty acids rather than 2
2- has 3 ester bonds rather than 2
3- no phosphate group
explain why phospholipids can form a bilayer but tricky exercises cannot (3) - 1-
phospholipid both hydrophobic and hydrophilic
OR
phospholipid is polar
OR
phosphate group is charged
2- triglycerides only hydrophobic
OR
fatty acid/triglyceride is non-polar
3- phosphate group attracts water to either side of bilayer
figure 4 shows 2 fatty acids A and B.
scientists fed rats diet with added fish oil for 4 months.
they obtained samples of red blood cells from rats before starting diet (0 months) and
after 4 months on diet.
for each red blood cell sample they separated cell-surface membranes and measured:
• percentage of phospholipids containing each fatty acid A and B
• fluidity of membrane
