Unit A and C1.1 and 1.2 [59 marks]
1.
Absorption spectra of two photosynthetic pigments are shown. Phycoerythrin is a red pigment
found in many marine red algae, while chlorophyll a is the major pigment in green plants and
algae.
What do the absorption spectra show about the pigments?
A. Phycoerythrin absorbs mostly red light.
B. Chlorophyll a reflects more green light than phycoerythrin.
C. Chlorophyll a photosynthesizes more at 550 nm than phycoerythrin.
D. Phycoerythrin does not absorb blue light.
[1]
2.
The foxglove, Digitalis purpurea, was once classified in the figwort family. The figwort family has
been reclassified and is now much smaller.
[Source: Shiva A., 2008 [image online] Available at:
https://en.wikipedia.org/wiki/File:Purple_Foxglove_(Digitalis_
purpurea)_2008_02.jpg [Accessed 14 January 2023] CC BY SA 4.0.
Funhoff, D., 2017. Figwort (Scrophularia canina) flowers, Theisbergstegen, Pfalz, Germany.
[image online]
Available at: https://www.naturepl.com/stock-photo/figwort-(scrophularia-canina)-flowerstheisbergstegen-pfalzgermany-june/search/detail-0_01550655.html [Accessed 28 October
2021].]
Why were species such as the foxglove moved into other families?
A. The appearance was too dissimilar.
B. The plants are found in different locations.
C. The genera were different.
D. The DNA sequences indicated different ancestry.
[1]
3.
What is the arrangement of subunits in a DNA nucleotide?
A. sugar – base – phosphate
B. sugar – phosphate – base
C. phosphate – sugar – base
D. sugar – phosphate – base – base – phosphate – sugar
[1]
4.
The diagram shows water molecules.
Which property of water is not illustrated?
A. Cohesion
B. Dipolarity
C. Hydrogen bonding
D. Adhesion
[1]
5.
The activity of amylase from two bacterial species and a fungus was measured at different pH
levels and constant temperature. The results are shown in the graph.
[Source: Held, P., 2012. Enzymatic Digestion of Polysaccharides. Part II: Optimization of
Polymer Digestion and Glucose Production in Microplates. Available at:
https://www.agilent.com/cs/library/applications/enzymatic-digestion-of-polysaccharides-part-II5994-3304EN-agilent.pdf.]
Which statement about the effect of pH on amylase can be concluded?
A. A. oryzae amylase has the highest optimum pH.
B. A change in pH affects amylase most in B. licheniformis.
C. The optimum pH is 6 in B. subtilis.
D. Amylase activity at pH 8 is the lowest in B. licheniformis.
[1]
6.
What allows to conclude that viruses might have evolved from cells?
I. Some viruses and eukaryotic cells have enzymes to synthesize DNA from RNA.
II. Some viruses have an envelop made of phospholipids, same as cell membranes.
III. Some viruses have similar genetic material to parasitic bacteria.
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
[1]
7.
Which property of DNA explains how genetic information can be replicated accurately?
A. Complementary base pairing
B. The double helical shape
C. 5’ – 3’ bonding in the sugar-phosphate backbone
D. The ability of DNA to bind to histones
[1]
8.
The image shows a group of enveloped viral particles.
[Source: Murphy, F. and Whitfield, S., n.d. Herpes virus image under the microscope. [image online] Available at:
https://www.bbvaopenmind.com/en/science/research/virus-inspired-science/ [Accessed 3 July 2020].]
What is the most likely composition of the structure labelled X?
A. Membrane derived from the host cell
B. Viral DNA
C. Viral cell walls
D. Viral enzymes
[1]
9.
What is a common feature of enzymes?
A. They all react with substrates.
B. They all decrease the rate of reaction.
C. They are all secreted from cells in vesicles.
D. They all bind to the active site of their substrate.
[1]
10.
What distinguishes aerobic respiration from anaerobic respiration in humans?
A. Mitochondria are only used in anaerobic respiration.
B. Aerobic respiration yields lower quantities of ATP.
C. Only aerobic respiration can use glucose as a starting substrate.
D. Only aerobic respiration produces carbon dioxide.
[1]
11.
22N.2.SL.TZ0.5
The diagram shows the release of a neurotransmitter across a synapse.
[Source: Splettstoesser T., 2015. SynapseSchematic [diagram online] Available at :
https://commons.wikimedia.org/w/index.php?curid=41349083 [Accessed 14 January 2023].]
(a) Identify the structure labelled X.
[1]
(b) Outline how the neuron is stimulated to release the neurotransmitter.
[2]
(c) Explain the action of neonicotinoid pesticides in insects.
[3]
12.
A decline in the number of species of trees of the Dipterocarpaceae family in some regions of
the mixed dipterocarp forest in South-east Asia provides evidence for the present biodiversity
crisis.
[Source: Natasha de Vere https://flickr.com/photos/col_and_tasha/5341116968. CC BY 2.0 https://creativecommons.org/licenses/by/2.0/.]
(a) List two variables, other than species richness, that can be monitored over time to provide
evidence of biodiversity loss in dipterocarp forests.
[2]
(b) Outline the reason for the loss of dipterocarp forest ecosystems in South Asia.
[2]
13.
The micrograph shows a transverse section of a leaf from a flowering plant.
(a) Calculate the actual thickness of the leaf, from upper to lower surface along the line a–b,
showing your working.
[2]
(b) Suggest a reason for using a lower power objective lens when first focusing on a slide under
the microscope.
[1]
14.
Various mechanisms can lead to inhibition in biological systems. A toxin is a substance capable
of disrupting metabolic processes in organisms.
(a) Toxins often act as inhibitors. Compare and contrast competitive and non-competitive
enzyme inhibition.
[7]
(b) Rotenone is a naturally occurring toxin that blocks the electron transport chain in insects and
fish. Outline the consequences of exposure to a toxin like rotenone for cell respiration.
[4]
15.
Biological systems are sensitive to temperature changes, so they have mechanisms to resist
temperature changes.
(a) Explain the relationship between temperature and the activity of enzymes.
[4]
(b) Distinguish between the thermal properties of air and water as they relate to the habitat of
animals.
[4]
16.
Mice (Mus musculus) have various defence systems against predators such as foxes (Vulpus
vulpus) or stoats (Mustela erminea). The mice release specific alarm compounds when under
threat that serve as danger signals for other mice. Predators also release scents that the mice
can detect.
In one study, mice were exposed to paper soaked in compounds taken from other mice, foxes or
stoats in a test chamber. The scientists then measured the reaction of three different groups of
neurons used in smelling: G1, G2 and G3, as shown in the diagram.
The percentage of G1, G2 and G3 neurons responding to the mouse, fox and stoat compounds,
as well as a control compound, are shown in the chart.
Percentage of response of neurons in mice
[Source: Julien Brechbühl, et al., (2013), PNAS, 110 (12), pages 4762–4767]
The scientists recorded the neural traces (action and resting potentials) of six G1 neurons
exposed to the compounds from the different animals. The horizontal bar beneath each trace
corresponds to the time of exposure to the test compound.
[Source: adapted from J Brechbühl, et al., (2013), PNAS, 110 (12), pages 4762–4767]
Another study was carried out on the defence systems in aphids (Myzus persicae) which feed on
thale cress plants (Arabidopsis thaliana). Individual aphids release an alarm compound
containing the chemical (E)-β-farnesene (EBF) when attacked by a predator. Other aphids are
repelled and leave the thale cress plant or hide.
The gene for EBF was inserted to produce transgenic (T) thale cress plants to test aphid
reaction to EBF over several generations. Aphids were raised on wild type (W) thale cress and
then allowed to feed for three generations on either W or T thale cress. Aphids were tested in
each generation for their reaction when EBF was added to a choice chamber. The percentages
of aphids attracted to or repelled by EBF and those which made no choice were recorded.
[Source: M De Vos, et al., (2010), PNAS, 107 (33), pages 14673–14678]
(a) State the percentage of G2 neurons in the mice that respond to the fox scent.
. . . . . . . . . . . . . . . . . . . .%
[1]
(b) Using evidence from the chart, identify, giving a reason, which group of neurons responded
most to the chemicals.
[1]
(c) Distinguish between the effects of the mouse alarm compound and the effects of the control
compound on the G1 neurons.
[1]
(d) Compare and contrast the effects of the mouse alarm compound and stoat scent on the G1
neurons.
[2]
(e) Deduce whether there is a correlation between the neural traces and the percentage of
responding G1 neurons.
[2]
(f) The molecular structures of the mouse alarm compound and fox scent are very similar.
Suggest an evolutionary advantage for this chemical similarity.
[1]
17.
What conveys messages from the central nervous system to an endocrine gland?
A. Sensory neurons
B. Hormones
C. Interneurons
D. Motor neurons
[1]
18.
There are a number of advantages to specificity.
(a) Outline the role of membrane proteins in the movement of specific ions at specific times in
the transmission of nerve impulses.
[4]
(b) Describe the barriers that exist to hybridization between species.
[4]
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