DP Biology Questionbank

Mucus traps pathogenic bacteria. Mucus also attracts viruses that attack pathogenic bacteria.

[Source: EYE OF SCIENCE/SCIENCE PHOTO LIBRARY]

What part of the immune system do these viruses resemble in their function?

A. Antigens

B. Antibodies

C. Memory cells

D. Antibiotics

The diagram shows the female reproductive system.

[Source: © International Baccalaureate Organization 2017]

Which structures do K and L identify?

In which image are polysomes visible? (The images do not have the same magnification)

Describe the process of photolysis in photosynthesis.

To calculate chi-squared, expected values must first be calculated. Assuming that there is no association between the two species, calculate the expected number of quadrats in which both species would be present, showing your working.

State the number of degrees of freedom for this test to determine the critical value of chi-squared.

On the diagram, label the testa and the radicle.

What could account for this distribution of height in a population?

[Source: Graph adapted from Six Minutes http://sixminutes.dlugan.com/good-public-speaker-average/]

A. Gene linkage

B. Dominant alleles

C. Independent assortment

D. Multiple genes

Which letter (A–D) indicates where a new nucleotide would attach?

State the name of the process which occurs in the chloroplasts of Chlorella, that uses CO₂.

The diagram shows a section through a seminiferous tubule.

[Source: © International Baccalaureate Organization 2020.]

Which labelled cells are diploid and haploid, respectively?

The diagram shows the link reaction between glycolysis and the Krebs cycle.

[Source: © International Baccalaureate Organization 2019]

Which type of reaction is occurring?

A. Pyruvate is carboxylated.

B. CO2 is oxidized.

C. NAD+ is reduced.

D. Pyruvate is phosphorylated.

Outline how the compounds produced by chloroplasts are distributed throughout the plant.

Autosomal genes are located in chromosomes that are not sex chromosomes. The inheritance of autosomal genes is affected by whether the genes are linked or unlinked. Explain the two types of inheritance, using the example of parents that are heterozygous for two genes A and B.

Calculate the difference (in mm²) in the mean leaf area of L6 at the start of stage 4 between the leaves of plants grown in long days and short days.

Outline how the muscle attachment of insects differs from humans.

Some bacteria can synthesize the amino acid isoleucine from threonine, a process involving five enzymes (E₁ to E₅) and four intermediary products (P, Q, R and S). The production of isoleucine is controlled by end-product inhibition.

Which statement describes this end-product inhibition?

A. If isoleucine accumulates, it inhibits the production of P.

B. End-product inhibition causes a build-up of intermediary products.

C. Isoleucine inhibits E₅, so no more isoleucine is produced.

D. Isoleucine affects the structure of threonine.

The image shows part of a myofibril from a relaxed muscle fibre.

[Source: Sarcomere. Sameerb. Available at https://commons.wikimedia.org/wiki/File:Sarcomere.gif
[Accessed 30 November 2021].]

What occurs during muscle contraction?

A. Myosin binding sites are blocked.

B. The bands labelled Y get shorter.

C. The bands labelled X get shorter.

D. Calcium ions bind to myosin.

The micrograph shows a glomerulus and Bowman’s capsule, where ultrafiltration takes place in the kidney.

[Source: MICROSCAPE/SCIENCE PHOTO LIBRARY.]

What facilitates the formation of glomerular filtrate?

A. Many fenestrations in walls of capillaries in the glomerulus

B. High pressure in the Bowman’s capsule

C. ADH secreted by the pituitary gland

D. Osmosis caused by a high concentration of urea in the blood

In a plant, what tissue(s) is/are specially adapted to transport sucrose?

Which structure in the chloroplast diagram is adapted to carry out chemiosmosis?

[Source: © International Baccalaureate Organization 2019]

Identify the following processes as either anabolism or catabolism by placing a tick (√) in the correct box.

The diagram shows a method for the production of monoclonal antibodies.

The graph shows how the mass of a bean seed from which all water has been removed (dry mass) changes during germination.

What can be deduced from the graph?

A. The plant loses more water during period X than during period Y.

B. During period Y, photosynthesis occurs but not respiration.

C. During period Y, more CO₂ is fixed in photosynthesis than is released by cell respiration.

D. The seeds were not exposed to the correct temperature for germination during period X.

What is the difference between the DNA of adult identical (monozygotic) twins?

A. Order of genes

B. Sequence of nucleotides

C. Methylation pattern

D. Ratio of complementary base pairs

The image shows a portion of a cell containing a mitochondrion.

[Source: ‘TEM of a mitochondrion’ by Prof. R. Bellairs. Credit: Prof. R. Bellairs. CC BY 4.0.]

Where do glycolysis and electron transport occur?

Which kidney adaptation would be expected in the desert kangaroo rat (Dipodomys deserti)?

A. Increased nephron density
B. Longer proximal convoluted tubule
C. Longer loop of Henle
D. Increased ADH receptors on the collecting duct

 

Label with an R the tissue where the red dye would appear.

Label region X and structure Y on the diagram of the kidney.

[Source: PeterHermesFurian/iStock]

Outline the role of tRNA activating enzymes in translation.

Label a peptide bond in the diagram of a polypeptide.

The image shows part of a section through the stem of a non-woody plant.

The diagram shows the chromosomes derived from a single homologous pair following meiosis in a diploid cell.

Which diagram represents the homologous pair from which these chromosomes were derived?

[Source: © International Baccalaureate Organization 2019]

The image shows a light micrograph of tissue stained with a dye that binds to the nucleic acids in a cell.

[Source: by Jose Luis Calvo/Shutterstock]

What is the major purpose of the tissue depicted in the image?

A. Absorption of digested food

B. Production of insulin

C. Spermatogenesis

D. Fertilization

William Bateson and Reginald Punnett used the sweet pea (Lathyrus odoratus) in genetics studies in the early 20^th century. Pure-breeding plants that produced purple flowers and long pollen grains were crossed with pure-breeding plants that produced red flowers and round pollen grains. The resulting offspring all produced purple flowers and long pollen grains. Two of the F₁ generation plants were crossed. The table shows the ratio of phenotypes in the F₂ generation. 

What is an explanation for these experimental results?

A. Purple flowers and long pollen grains are dominant and the alleles have assorted independently.

B. The genes for flower colour and pollen shape are linked and all plants producing long pollen grains are recombinants.

C. The genes for flower colour and pollen shape are linked and all plants producing red flowers are recombinants.

D. Plants producing purple flowers and round pollen grains arose through crossing over.

The image is a cross section through an Ammophila leaf, which grows on coastal sand dunes.

[Source: Charles Good: The Ohio State University at Lima]

What feature suggests that Ammophila is a xerophyte?

A. The leaf surface area is increased.

B. The rolled leaf reduces the upper epidermis area.

C. The rolled leaf protects the lower epidermis from the wind.

D. The lower epidermis can transpire more easily.

The cheetah (Acinonyx jubatus) is a large cat found in Africa. It has been discovered that organs could be transferred between any two individuals without rejection of the organ.

What is the probable reason for this?

A. Cheetahs have poor reproductive success.

B. Cheetahs have high heterozygosity.

C. Cheetahs have a large gene pool.

D. Cheetahs have a small gene pool.

The mean stomatal density for the lower epidermis of P. decandrum was around 600 per mm². Predict how the stomatal density for the upper epidermis would compare.

Cell biologists play an important role in research into disease, fertility, evolution and many
other areas of science.

Compare and contrast the processes of spermatogenesis and oogenesis.

The electron micrograph shows sarcomeres in myofibrils of striated muscle during muscle contraction. The lines P–Q and R–S show two regions of one sarcomere.

[Source: Republished with permission of Elsevier - Health Sciences Division from Cell by Don W. Fawcett 1981 ; permission conveyed through Copyright Clearance Center, Inc.]

How would regions P–Q and R–S change when the muscle relaxes?

Explain the reasons for variation in human height.

In which process(es) do nucleosomes play a role in eukaryotes?

I. tRNA activation

II. Transcription regulation

III. DNA supercoiling

A. I only

B. II only

C. II and III only

D. I, II and III

Plants have widespread influences, from food chains to climate change.

Draw a labelled diagram of the internal structure of a seed.

The micrograph shows the cross-section of the vascular tissue in a dicotyledonous root. Which letter identifies phloem sieve tubes?

[Source: Wendy Paul]

The image shows seedlings that have been exposed to unidirectional light.

[Source: The Micro Gardener (https://themicrogardener.com/prevent-fix-leggy-seedlings/)]

Which statement explains the growth towards the light source?

A. Light causes auxin to inhibit cell division in the shoot meristem.

B. Light causes auxin to promote cell division in the shoot meristem.

C. Auxin is concentrated in the side of the shoot with light and inhibits cell elongation.

D. Auxin is concentrated in the side of the shoot without light and promotes cell elongation.

The graph shows the relationship between mass at birth and the percentage that die shortly after birth for Scottish Blackface lambs.

[Source: Dwyer, C.M., Conington, J., Corbiere, F., Holmoy, I.H., Muri, K., Nowak, R., Rooke, J., Vipond, J. and Gautier,
J.-M., 2016. Invited review: Improving neonatal survival in small ruminants: science into practice. Animal, 10(3),
pp. 449–459.]

What type of selection for the lambs is shown in the graph?

A. Disruptive selection, as there is a drop in mortality at intermediate birth masses

B. Stabilizing selection, as lambs with low or high birth mass are less likely to survive

C. Directional selection, as lambs with a high birth mass have high mortality

D. There is no evidence in the graph of selection, as survival frequency is not shown

The micrograph shows part of a human sperm cell. Which region of the cell is responsible for the greatest production of ATP?

Explain the mechanism that prevents polyspermy during fertilization.

In the micrograph of a plant stem, which letter indicates the xylem?

[Source: adapted from Kelvinsong/https://creativecommons.org/licenses/by/3.0/deed.en]

The grey line in each of the graphs below represents the rate of reaction catalysed by an uninhibited enzyme as substrate concentration is increased.

Which graph shows expected results if a competitive inhibitor was added to the reaction?

[Source: © International Baccalaureate Organization 2019]

Describe the production of hybridoma cells.

The apparatus in the diagram was used to assess the effects of factors on transpiration rates.

[Source: Republished with permission of Springer-Verlag from Experimentelle Pflanzenphysiologie: Band 2, Peter Schopfer, 1st edition, 1st Jan 1989; permission conveyed through Copyright Clearance Center, Inc.]

Which factor would be a controlled variable in an experiment designed to assess the effects of temperature on transpiration rate?

A. The opening and closing of stomata

B. The intensity of light striking the plant

C. The height of the water in the reservoir

D. The evaporation of water from the leaves

The diagram shows a section through the seminiferous tubules. What is the cell labelled X?

[Source: © International Baccalaureate Organization 2019]

A. Spermatid that will differentiate into sperm

B. Primary spermatocyte that will undergo meiosis to form secondary spermatocytes

C. Sertoli cell that provides nutrients

D. Stem cell that will divide by mitosis to form spermatogonia

The diagram shows a section through a thylakoid. Electrons move from X to Y.

[Source: Courtesy Alyse Da Quynh.]

What do the letters X, Y and Z represent?

This DNA sequence was used to synthesize a polypeptide.

DNA (sense strand): 3′ T A C T G A 5′

DNA (template strand): 5′ A T G A C T 3′

Which are the bases of the tRNA (anticodons)?

A. T A C   T G A

B. U A C   U G A

C. A U G   A C U

D. A T G   A C T

Outline how plants make use of the different wavelengths of light.

Hershey and Chase used a bacteriophage (a virus that infects bacteria) to investigate the chemical nature of genes. The diagram shows a bacteriophage.

Which equation is an example of decarboxylation?

A. Pyruvate $\to$ Acetyl CoA + CO₂

B. CO₂ + H₂O H₂CO₃

C. CH₄ + 2O₂ CO₂ + 2H₂O

D.

A hybridoma is a cell produced by the fusion of a plasma cell with a tumour cell. Explain the advantages of using hybridoma cells in the production of monoclonal antibodies.

Which letter identifies phloem?

[Source: E R DEGGINGER/Getty Images]

Suggest how the graph would differ for a human during a long period of inactivity.

Explain how water balance is restored in mammals when they are dehydrated.

Describe how monoclonal antibodies are produced.

The diagram shows the structure of a nucleosome.

The diagram shows the structure of E. coli ribonuclease HI, a bacterial protein consisting of one polypeptide chain.

When a cell divides by meiosis, chiasmata can be observed. Which are features of chiasmata?

I. They are points of attachment between chromatids of non-homologous chromosomes.

II. They occur during meiosis I.

III. They increase stability of bivalents.

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

There are multiple tandem repeats of nucleotide segments of DNA found in the non-coding DNA between genes. Outline how tandem repeats are used for DNA profiling.

Explain how speciation occurs, including the different processes of isolation and selection.

Humans need to balance water and solute concentrations and also excrete nitrogenous wastes. Explain how the different parts of the kidney carry out these processes.

Describe adaptations in mammals living in desert ecosystems to maintain osmolarity in their bodies.

Describe the role of ADH in human osmoregulation.

A plant is allowed to photosynthesize in an atmosphere containing radioactive ¹⁴C. Where in the plant stem would radioactive sugars be found?

[Source: sinhyu/123rf.com.]

Explain the role of the kidney in osmoregulation.

Nitrogen is part of many important substances in living organisms.

Explain how insects excrete nitrogenous wastes.

The pregnancy test for humans is based on detection of the hormone HCG. What is the reason for detection of this hormone indicating pregnancy?

A. HCG is involved in milk production.

B. HCG production is blocked by negative feedback during menstruation.

C. HCG is produced by an embryo.

D. HCG is released during the acrosome reaction.

The graph shows three hormones circulating during pregnancy in the rat, with birth occurring at 22 days.

[Source: Dr Paul Kenyon University of Plymouth (retired).]

What are hormones X and Z?

The picture shows lentils sprouts growing towards a light source from the left.

The salt marshes where these turtles live periodically dry up to small pools. Discuss the problems that this will cause for nitrogen excretion in the turtles and how their behaviour might overcome the problems.

Where in the nephron is most glucose reabsorbed?

[Source: National Institute of Diabetes and Digestive and Kidney Diseases, n.d. [Nephron]. [diagram online] Available at:
https://www.niddk.nih.gov/news/media-library/9164 [Accessed 23 March 2020].]

Growth in living organisms includes replication of DNA. Explain DNA replication.

Explain how organic compounds are transported within plants.

The diagram shows the three-dimensional structure of tRNA.

[Source: Structure reproduced with the kind permission of N.R. Voss.]

What can attach to the region marked X?

A. mRNA

B. An amino acid

C. An anticodon

D. The P site of the ribosome

Describe the secondary structure of proteins.

In fruit flies (Drosophila melanogaster), grey bodies (b⁺) are dominant to black bodies (b) and normal wings (vg⁺) are dominant to vestigial wings (vg). Homozygous vestigial winged, black bodied flies were crossed with individuals that were heterozygous for both traits. 2300 individuals were counted and the phenotypes observed were recorded as shown.

965 normal wings, grey bodies
944 vestigial wings, black bodies
206 vestigial wings, grey bodies
185 normal wings, black bodies

Which statement is valid?

A. The predicted phenotypic ratio was 9:3:3: 1.

B. There is independent assortment of wings but not body colour.

C. The expected number of vestigial winged, grey bodied flies was 575.

D. The traits are on different chromosomes.

The image shows part of a section through the stem of a non-woody plant. Where does transport of sucrose occur?

[Source: Courtesy of Kelly Cude, PhD, Professor Biological Sciences, College of the Canyons.]

What is a feature of transcription in the single-celled organism shown in the electron micrograph?

[Source: George E. Palade Electron Microscopy Slide Collection Harvey Cushing/John Hay Whitney Medical Library Yale University Library.]

A. mRNA splicing

B. Removal of introns

C. Codon-anticodon binding

D. Synthesis of RNA in a 5′ to 3′ direction

The diagram shows structures involved in contraction of a sarcomere.

Evaluate the limitations of using a potometer in the investigation you suggested in (a).

Explain the scientific reasoning for your hypothesis.

Explain gene linkage and its effects on inheritance.

Distinguish between the xylem and phloem of plants.

Describe how the structure of the chloroplast is adapted to its function in photosynthesis.

The Hershey and Chase experiment supported DNA as the hereditary material. Describe the experiment.

Describe the transport of organic compounds in vascular plants.

Suggest reasons for the difference in end of day starch concentrations in stage 2 (S2) for the plants grown in long days and short days.

Explain the role of the electron transport chain in the generation of ATP by cell respiration.

Label with a C the tissue where organic compounds are transported.

Explain how some plant species are able to respond to changes in their abiotic environment and flower at a precise time of the year.

Compare and contrast mitochondria and chloroplasts in terms of the substrates they use and the products they produce. 

Plasma cells secrete antibodies against specific antigens. Outline how plasma cells become activated.

Outline how the hormone auxin controls phototropism in plant shoots.

Describe the processes that cause water to move from the roots of plants to their leaves.

The colours of the indicator in the jars ranged from yellow to purple after five hours.

Predict the distribution of indicator colours in jars 1 to 9.

Compare and contrast the location of ATP synthase and the movement of protons during aerobic cell respiration and photosynthesis.

Describe the changes that occur in gene pools during speciation.

State one use of monoclonal antibodies.

Explain the factors that affect the rate of enzyme-controlled reactions in cells.

The graph shows results of an experiment by Hershey and Chase in 1952 in which bacteria were infected with a mixture of virus particles labelled with either ³²P or ³⁵S. A suspension of the infected bacteria was agitated with a blender, and samples collected from the suspension were centrifuged to record the percentage of isotope remaining on the outside of the cells.

[Source: Republished with permission of ROCKEFELLER UNIVERSITY PRESS, from Independent functions of protein and nucleic acid in growth of bacteriophage. Hershey, A.D. and Chase, M., 1952. (Journal of General Physiology, 36(1), p.47). Society of General Physiologists, Rockefeller Institute for Medical Research, Rockefeller Institute; permission conveyed through Copyright Clearance Center, Inc.]

What do curves X and Y represent?

The Hill reaction occurs when isolated chloroplasts are exposed to sunlight in the presence of DCPIP. DCPIP replaces NADP as the final electron acceptor for the light-dependent reactions of photosynthesis. What are products of the Hill reaction?

A. H₂O and ATP

B. ATP and CO₂

C. O₂ and ATP

D. C₆H₁₂O₆ and O₂

What function is maintained as a result of the release of HCG?

A. Production of milk by the mammary glands

B. Release of oxytocin by the posterior pituitary gland

C. Production of FSH by the anterior pituitary gland

D. Production of progesterone by the ovary

Describe the process of crossing over.

The image shows a polysome in a bacterial cell.

[Source: © International Baccalaureate Organization 2019]

How many genes have been transcribed?

A. 1

B. 2

C. 3

D. 4 

The image shows a cross-section of a flower.

[Source: © International Baccalaureate Organization 2019]

Where does production of haploid gametes occur?

A. I and II only

B. III and IV only

C. I and III only

D. II and IV only

What is/are the effect(s) of auxin in plants?

I.   Increasing the rate of cell elongation in stems
II.  Changing the pattern of gene expression in shoot cells
III. Detecting the direction of light

A. I only
B. I and II only
C. II and III only
D. I, II and III

Three-spined stickleback fish (Gasterosteus aculeatus) vary in the number of armour plates. The graph shows the frequency of individuals with low, partial or complete plating in a three-spined stickleback population living in Kennedy Lake, Vancouver Island, Canada.

[Source: Reprinted from Current Biology, 24, Marchinko, K.B., Matthews, B., Arnegard, M.E., Rogers, S.M. and Schluter, D., Maintenance of a Genetic Polymorphism with Disruptive Natural Selection in Stickleback.
2014.  pp.1289–1292 with permission from Elsevier.]

Which type of natural selection could result in this pattern of variation in the population?

A. Disruptive

B. Directional

C. Stabilizing

D. Convergent

The photomicrograph shows a section through the top of a plant shoot.

[Source: Charles Good: The Ohio State University at Lima]

What are the structures labelled X and Y?

Outline the roles of estrogen and progesterone in females during human reproduction.

The diagram represents a sarcomere. Which structure is myosin?

[Source: MPI of Molecular Plant Physiology. [Sarcomere]. [diagram online] Available at: http://www.macroevolution.net/sarcomere.html [accessed 4 April 2019]. Source adapted.]

Plants have widespread influences, from food chains to climate change.

Explain the process of water uptake and transport by plants.

The diagram shows the arrangement of introns and exons in a segment of pre-mRNA. Pre-mRNA is immature mRNA containing introns and exons.

Which is a mature mRNA molecule derived from the pre-mRNA by splicing?

[Source: © International Baccalaureate Organization 2019]

The image shows a transverse section through a collecting duct in a vertebrate kidney.

[Source: Professor Peter Takizawa, Yale University]

How is the movement of materials across the wall of the collecting duct affected by the release of ADH from the pituitary gland?

A. There is increased movement of water in the direction of arrow I.

B. There is increased movement of sodium in the direction of arrow I.

C. There is increased movement of water in the direction of arrow II.

D. There is increased movement of sodium in the direction of arrow II.

The diagram shows compounds in the Krebs cycle labelled as X, Y and Z.

[Source: © International Baccalaureate Organization 2019]

How many carbon atoms are there in Y and in the acetyl group of acetyl CoA?

The first enzyme in the metabolic pathway that produces isoleucine is threonine deaminase. Which graph illustrates the relationship between threonine deaminase activity and threonine concentration?

[Source: © International Baccalaureate Organization 2019]

Suggest reasons for the high percentage of fatal cases at Ebola treatment centres.

Explain the process of muscle contraction.

DNA has regions that do not code for proteins. State two functions of these regions.

1.

2.

Draw a half-view of an animal-pollinated flower.

The table shows the results of blood type tests on samples from four individuals. Which row represents an individual who can accept transfusions from people with blood type AB?

[Source: © International Baccalaureate Organization 2019]

Explain the production and role of antibodies in defense against bacterial pathogens in humans.

Compare the pattern of GH3 transcription with the pattern of auxin concentration in the stem base control cuttings. You may use the table provided to help you to record the patterns before you compare them. (Please note: a simple
comparison in the table will not gain marks)

Concerns have been raised about the effect of rising pollution levels on sperm production in men. To investigate the possible effects of pollution on spermatogenesis, sperm samples from men of similar ages were collected in Kolkata in the 1980s and 2000s. The box plot represents the mean and range of sperm counts in the 1980s and 2000s.

[Source: Republished with permission of Elsevier Science and Technology Journals, from ‘Semen quality and age-specific changes: A study between two decades on 3729 male partners of couples with normal sperm count and attending an andrology laboratory for infertility-related problems in an Indian city’, Dyutiman Mukhopadhyay, Alex C. Varghese, Manisha Pal, Sudip K. Banerjee, Asok K. Bhattacharyya, Rakesh K. Sharma, and Ashok Agarwal, Fertility and Sterility, 93 (7), 2009; permission conveyed through Copyright Clearance Center, Inc]

A hypothesis has been suggested that pollution may have a negative effect on spermatogenesis. Evaluate whether the data support this hypothesis.

Describe the role of oxygen in aerobic cell respiration.

Nitrogen is part of many important substances in living organisms.

Distinguish between transcription and translation.

The graph shows changes in the concentration of an antibody in the blood of an individual subjected to two separate infections at time X and time Y.

Explain how polypeptides are produced by the process of translation.

ADH (antidiuretic hormone) is a peptide hormone that is produced in the hypothalamus. Explain its action in the human body.

Describe how changes in weather conditions affect the transport and loss of water in plants.

When the data in the table were used to calculate chi-squared, the calculated value was 0.056. The critical value is 3.84. Explain the conclusion that can be drawn from the calculated and critical values for chi-squared.

Explain the role of hydrogen ions used in photosynthesis.

Explain the production of antibodies in humans.

Distinguish between competitive and non-competitive enzyme inhibition.

Explain how the light-independent reactions of photosynthesis rely on the light-dependent reactions.

Draw labelled diagrams to show the structure of RNA nucleotides and how they are linked together to form a molecule of RNA.

Explain transcription.

Outline the extension of the stem in plants.

What structure is indicated by the arrows?

[Source: Courtesy Roger Craig, University of Massachusetts]

A. One muscle fibre

B. One sarcomere

C. One myofibril

D. One Z line

The diagram shows two states of skeletal muscle, relaxed and contracted.

[Source: Provophys/Wikipedia. File licensed under CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/)]

Which process is part of muscle contraction?

A. Myosin filaments cause the actin filaments to shorten.

B. Ca²⁺ from the sarcoplasmic reticulum binds to the myosin heads.

C. ATP provides energy for the movement of the myosin heads.

D. Ca²⁺ binds to tropomyosin and uncovers troponin.

The electron micrograph shows a section through part of an animal cell.

[Source: https://en.wikipedia.org/wiki/Mitochondrion#/media/File:Mitochondria,mammalian_lung_-TEM.jpg,
by Louisa Howard.]

Which process is occurring on the structures labelled X?

A. The Krebs cycle

B. The link reaction

C. Glycolysis

D. Phosphorylation of ADP

In the diagram of a ribosome, which letter indicates the P site?

[Source: iStock.com/ttsz]

Rosalind Franklin produced X-ray diffraction images of DNA.

[Source: © King’s College, London. KCL Department of Biophysics KDBP/1/1.]

Which previously unknown aspect of DNA was deduced from these images?

A. Chromosomes are made of DNA.

B. Deoxyribose sugar is attached to a phosphate group.

C. The base A pairs with T and C with G.

D. The DNA molecule is a double helix.

The diagram shows a plant shoot and the direction of the light which the shoot received.

[Source: USDA-NRCS PLANTS Database. Available at: https://commons.wikimedia.org/wiki/File:Alnus_seedling_drawing.png
[Accessed 30 November 2021].]

What are the direction of movement and the effect of auxin in the tip of a plant shoot when receiving light from one side?

What is the primary function of the free ribosomes shown in the electron micrograph?