Oct/Nov 2021

A student looks at a cell through a light microscope and then makes a drawing of it. Which items does the student need in order to calculate the magnification of the drawing?

The microscope in cell studies

The diagrams illustrate three examples of different bonds. Which bonds are responsible for holding the tertiary structure of proteins together?

Proteins

Which property of collagen allows it to carry out a structural role in skin and tendons?

Proteins

The graph illustrates the way the concentrations of four components, 1, 2, 3 and 4, in an enzyme-catalysed reaction vary over time. Which component is the enzyme-substrate complex?

Mode of action of enzymes

The table presents the Michaelis-Menten constant, $K_m$, for three enzymes. Which explanation of the data is correct?

Mode of action of enzymes

What term explains how a signal molecule made by one cell can be detected by a target cell?

Fluid mosaic membranes

Certain enzymes are made within pancreatic cells. When they are needed, the enzymes are released. Which process moves these enzymes out of the pancreatic cells?

Movement into and out of cells

Plant cells were placed in a solution whose water potential was less negative than the water potential inside the cells. Which statement best describes the state of the plant cells after 20 minutes?

Movement into and out of cells

What will each chromosome contain by the end of the $G_2$ phase of the cell cycle?

Replication and division of nuclei and cells

Which of the listed events are included in the cell cycle?

Replication and division of nuclei and cells

Which organism features are influenced by a drug that destroys cells undergoing mitotic division?

Replication and division of nuclei and cells

Which equations correctly describe the relationship between magnification, image size and actual size in microscopy?

The microscope in cell studies

The graph illustrates how the distance between sister chromatids (curve P) and the distance between chromatids and centrioles (curve Q) changes during part of mitosis. Which statements could be correct?

Chromosome behaviour in mitosis

Which statement explains why the two sugar-phosphate chains in a DNA molecule remain the same distance apart?

Structure of nucleic acids and replication of DNA

In DNA replication, what has to occur before a freshly added nucleotide is joined to the next nucleotide in the strand?

Replication and division of nuclei and cells

An antibiotic is moved into bacterial cells by a membrane channel protein, P. In some bacterial cells, resistance to this antibiotic has appeared after they acquired a mutation that changes P. This mutation stops the antibiotic from entering the cell. Which conclusions can be drawn about how resistance to this antibiotic arose in these bacteria?

Movement into and out of cells

Which tRNA anticodon is correct for the amino acid proline? The table gives: - alanine: DNA triplet code on transcribed strand = CGT - histidine: DNA triplet code on transcribed strand = GTG - proline: DNA triplet code on transcribed strand = GGT

Proteins

The table summarises a student’s observations of three cell types, P, Q and R, taken from a transverse section through a plant stem and viewed using a light microscope. P: ratio of cell wall width to whole cell width = $1:10$, structures seen in cell contents = none Q: ratio of cell wall width to whole cell width = $1:20$, structures seen in cell contents = regular pattern of circles in some cells R: ratio of cell wall width to whole cell width = $1:20$, structures seen in cell contents = granular appearance of all cells What kind of cells are P, Q and R?

Structure of transport tissues

Water molecules are drawn towards one another. This feature is significant in the upward transport of water in xylem. What term describes the attraction between water molecules?

Water

The diagram illustrates a model used to show mass flow. In a plant, what are the structures W, X, Y and Z, and in which direction does the solution travel along W?

Movement into and out of cells

The heart structures that regulate heart action are: - sinoatrial node (SAN) - atrioventricular node (AVN) - Purkyne tissue Which row shows the correct pattern for atrial contraction and ventricular contraction?

The heart

The diagram illustrates part of the circulatory system in a mammal. In which part are blood pressure and flow speed at their lowest?

The circulatory system

Within which cell structures does DNA transcription take place?

Protein synthesis

The photomicrograph depicts human blood cells. What kind of blood cell is X?

The circulatory system

The diagram illustrates some of the reactions that occur when carbon dioxide moves from cells into the blood in a metabolically active tissue. Which reaction is catalysed by the enzyme carbonic anhydrase?

Mode of action of enzymes

The graph presents the oxygen dissociation curves for haemoglobin in animals living at high altitude and animals living at low altitude. What accounts for the oxygen dissociation curve at high altitude?

Proteins

The diagram illustrates three features present in the mammalian gas exchange system. Which structures in the gas exchange system might X represent in the diagram?

The gas exchange system

What are the short-term effects of nicotine on the cardiovascular system?

The circulatory system

A disease has the following characteristics. • It may be passed from animals to other animals, humans included. • One way it spreads is through a transfusion with contaminated blood. • The organism that causes it can be resistant to several drugs. • Most humans who die from the disease are children. Which disease has all of these characteristics?

Infectious diseases

The advice below was given to someone travelling to a country where an outbreak of an infectious disease had occurred. • Cook food thoroughly and eat it while hot. • Remove the skins from fruit and vegetables. • Drink only water that has been boiled and left to cool. • Wash hands frequently with soap and cool, boiled water. Which infectious disease would this advice help to guard against?

Infectious diseases

Which statement correctly describes multiple drug resistance in bacteria?

Antibiotics

Which statement correctly describes a T-lymphocyte?

The immune system

In what location are antibodies present during an immune response?

Proteins

Which rows could accurately show the nucleic acids found in two different virus particles in an air sample?

The microscope in cell studies

Monoclonal antibodies are used for diagnosing and treating disease. They are made by a technique called cell fusion. Which two structures are fused in this technique?

Proteins

Four samples taken from a mixture of biological molecules were tested, and the outcomes are shown in the table. Which biological molecules were present in the mixture?

Testing for biological molecules

A single condensation reaction produces one molecule of X and, in the process, one molecule of water is released. What is the identity of molecule X?

Carbohydrates and lipids

The table presents some information on carbohydrate polymers. Which row gives the description of glycogen?

Carbohydrates and lipids

The diagrams display four phospholipid molecules. Which molecule could make the greatest contribution to the fluidity of a cell surface membrane?

Fluid mosaic membranes

Which features of phospholipids account for the fact that when single layers of phospholipids are added to water, bilayers form at once?

Fluid mosaic membranes

On an electron micrograph, a scale bar measuring 2 cm corresponds to a real length of 1 μm. What is the magnification of the electron micrograph?

The microscope in cell studies

For polysaccharides to be fully hydrolysed, every glycosidic bond joining the monomers must be broken. Enzyme X hydrolyses only $\alpha$-1,4 glycosidic bonds. Which row indicates how far enzyme X is able to hydrolyse glycogen and amylose molecules?

Carbohydrates and lipids

Which molecules have at least two double bonds?

Carbohydrates and lipids

The diagram illustrates an amino acid. Which group is altered to make different amino acids?

Proteins

Which row gives the correct statement about protein structure?

Proteins

Which graph shows, correctly, the possible changes in energy levels as a chemical reaction proceeds with and without an enzyme?

Mode of action of enzymes

The graph illustrates how the concentration of substrate is related to the rate of an enzyme-catalysed reaction. Which row indicates the effect on $K_m$ and $V_{max}$ for this enzyme if the same reaction were conducted with a competitive inhibitor present?

Factors that affect enzyme action

Liver cells possess vesicles whose membranes contain proteins that are specific to glucose transport. When these cells require glucose, the vesicles join with the cell surface membrane. In what way is glucose taken up?

Movement into and out of cells

A learner carried out an investigation into diffusion. A piece of agar measuring $1.0\,\text{cm} \times 1.0\,\text{cm} \times 1.0\,\text{cm}$ was evenly coloured with a water-soluble blue dye. The agar block was placed in a test-tube with $10\,\text{cm}^3$ of distilled water at $20^\circ\text{C}$. After five minutes, the blue colour intensity of the water was measured. Four further experiments, A, B, C and D, were then done using different numbers of agar blocks, different agar block sizes and different temperatures. All the other variables were kept constant. Which experiment would produce a paler blue colour in the water after five minutes than the first experiment?

Movement into and out of cells

Which statement is correct?

The microscope in cell studies

While the cell is in metaphase, a scientist uses fluorescent dye to stain the chromosomes of a diploid animal cell so that the telomeres can be seen. This cell contains 26 chromosomes. How many telomeres will the scientist observe?

Chromosome behaviour in mitosis

An eyepiece graticule is placed in the eyepiece of a microscope, and a stage micrometer scale is positioned on the microscope stage. Which of the following statements about the stage micrometer scale are correct?

The microscope in cell studies

The photomicrographs display cells at different points in the cell cycle. Which cells contain twice the number of DNA molecules found in a cell from the same organism that has just completed a full mitotic cell cycle ending with cytokinesis?

Replication and division of nuclei and cells

If cell division is no longer controlled, a tumour may form. During the development of a tumour, which phase of the cell cycle would take a shorter time?

Replication and division of nuclei and cells

A section of a DNA molecule has 84 base pairs. The table gives the number of adenine and cytosine bases in one or both strands of this section of the DNA molecule. How many guanine bases are present in this section of the DNA molecule?

Structure of nucleic acids and replication of DNA

The three mRNA stop codon sequences are given below. $\text{UAA}\quad \text{UAG}\quad \text{UGA}$ Which mutation in the template (transcribed) strand of a DNA sequence that codes for a polypeptide would make translation end too soon?

Proteins

Which characteristics of companion cells are vital for their role?

Structure of transport tissues

Which statements concerning water movement in plants are correct?

Movement into and out of cells

The diameter of a tree trunk normally becomes slightly smaller over the course of the day. Which changes in environmental factors during the day could make the diameter decrease by a greater amount?

Movement into and out of cells

Which sequence of events could result in mass flow in a phloem sieve tube?

Movement into and out of cells

What occurs when the blood pressure in the right ventricle becomes higher than the blood pressure in the right atrium?

The heart

The graph illustrates pressure changes in various parts of the heart during a mammalian cardiac cycle. W, X, Y and Z show the times when a valve opens or shuts. Which row correctly names W, X, Y and Z?

The microscope in cell studies

Four students had to pair each function with the appearance of certain cell structures in an animal cell. The functions were given by number. 1 mRNA passes through to the ribosome 2 organises microtubules to produce the spindle during cell division 3 synthesis of polypeptides The appearances were given by letter. V membranes enclosing an inner cavity W non-membrane bound, spherical structures X a double membrane containing pores Y non-membrane bound, cylindrical structures Z membrane-bound sacs arranged as a flattened stack Which student made the correct match between the numbered function and the appearance of the cell structure?

Cells as the basic units of living organisms

Which of these statements are correct?

Cells as the basic units of living organisms

Which of the following statements regarding the formation of haemoglobinic acid are correct?

Proteins

What is the explanation for how the greatest volume of oxygen is absorbed while blood flows through the lung capillaries?

Movement into and out of cells

The image provided is a photomicrograph of a transverse section through part of the gas exchange system. Which statement best describes the image?

The microscope in cell studies

Which row identifies the tissues found in the wall of the trachea and in the wall of the bronchus?

The gas exchange system

During an asthma attack, the tubes of the gas exchange system become narrower and more mucus is made. Which changes take place during an asthma attack?

Movement into and out of cells

Which flow chart correctly shows the effect when tar enters the lungs?

The gas exchange system

What control measures would lower the spread of tuberculosis (TB)?

Infectious diseases

Comorbidity refers to a situation in which a person has two or more diseases or medical conditions at the same time. Certain medical conditions are especially likely to lead to comorbidity. In one case, an initial infection by one pathogen can raise the chance of developing a second disease by a factor of 15 or more. This second disease is the main cause of death in these people. Which description could match this example?

Infectious diseases

Which of these conditions is infectious and causes a raised white blood cell count?

The microscope in cell studies

Which cell structures are needed for the formation of lysosomes and the hydrolytic enzymes that they contain?

Cells as the basic units of living organisms

Which type of cell makes the secondary immune response much quicker than the primary immune response?

The microscope in cell studies

Which cell structures include rRNA? 1 chloroplast 2 mitochondrion 3 nucleus 4 smooth endoplasmic reticulum

Cells as the basic units of living organisms

The unicellular organism Thiomargarita namibiensis has a diameter of 700 μm and is surrounded by a cell wall. In T. namibiensis, the genetic material lies freely in the cytoplasm, where it is present as thousands of copies of circular DNA. A large vacuole occupies most of the cell and contains vital chemicals needed for metabolism. Which statement is correct?

Cells as the basic units of living organisms

A student performed four tests on a sample of biological molecules. emulsion test: cloudy Benedict’s test: yellow biuret test: purple iodine test: yellow Which of the following conclusions reached by the student are correct? 1 Fat was present. 2 Glucose was present. 3 Protein was present. 4 Starch was not present.

Testing for biological molecules

What is the correct general formula for monosaccharides such as fructose?

Carbohydrates and lipids

Which statements may be used to describe cellulose structure? 1 a polymer formed from glucose monomers joined by $\beta$-1,4 glycosidic bonds 2 a polysaccharide made from hexose monomers 3 an unbranched macromolecule composed of $\beta$-glucose monomers

Carbohydrates and lipids

A student was told to use the scale bar shown in order to calculate the magnification of a cell in a photomicrograph. The scale bar indicates $2\ \mu\text{m}$. Which method could the student use to calculate the magnification of the cell?

The microscope in cell studies

Which molecules invariably contain at least four double bonds?

Carbohydrates and lipids

Which row concerning protein structure is correct?

Proteins

Which of the following statements about collagen is correct?

Proteins

Which properties of water are caused by hydrogen bonding between water molecules?

Water

Which statements about all enzymes are correct?

Mode of action of enzymes

Root cells of beetroot plants contain a red pigment. If small pieces of root tissue are placed in cold water, part of the red pigment escapes from the cells into the water. An experiment was done to examine how temperature affects the amount of red pigment lost from the root cells. The results showed that, as the temperature of the water increased, the rate at which red pigment was lost from the root cells also increased. Which statements could account for this pattern?

Movement into and out of cells

The diagram shows a plant cell that is partially plasmolysed. What is present at Z?

Movement into and out of cells

A unicellular organism is living in freshwater. Water that moves into the cell cytoplasm by osmosis is gathered in a structure known as the contractile vacuole. To expel the water, the contractile vacuole joins with the cell surface membrane. A student recorded how many times the contractile vacuole filled and then emptied when the cell was placed in solutions with different water potentials. The findings are shown in the table. Which statement accounts for the pattern seen as the water potential of the external solution decreased?

Movement into and out of cells

Which row correctly gives the number of each component found in one chromatid during anaphase of mitosis?

Chromosome behaviour in mitosis

The processes shown are: cytokinesis; differentiation; DNA replication; mitosis. During tissue repair by stem cells, how many of these processes take place?

Replication and division of nuclei and cells

Which of the following statements about light microscopy are always correct?

The microscope in cell studies

The photomicrographs display cells at different stages of the cell cycle. Which stage of mitosis is missing?

Chromosome behaviour in mitosis

Which letter in the key represents uracil?

Structure of nucleic acids and replication of DNA

When a gene for protease becomes active, which nucleic acid is produced?

Proteins

The diagram illustrates a vascular bundle taken from a plant stem. Which row gives the functions of the labelled cells?

Structure of transport tissues

Several features found in the transport tissues of plants are given below: 1. lignified walls 2. cytoplasm 3. mitochondria 4. chloroplasts 5. plasmodesmata Which of these features are found in sieve tube elements?

Structure of transport tissues

Which statements account for why transpiration is an unavoidable result of gas exchange in plants?

Movement into and out of cells

During an investigation, a leafy shoot was connected to a potometer and placed under several different conditions. For each condition, the length of time for the meniscus to travel $50\,\text{mm}$ through the capillary tubing was measured and noted. Which row represents the slowest and fastest rates of water uptake in this investigation?

Movement into and out of cells

When a plant loads sucrose into a phloem sieve tube element at a source, which row shows the correct use of proton pumps ($\text{H}^+$ pumps) and co-transporters?

Movement into and out of cells

The events in the cardiac cycle are listed below, but they are not in the correct sequence: 1. The impulse moves through Purkyne tissue. 2. An excitation wave spreads across the atria. 3. The atrioventricular node delays the impulse for a fraction of a second. 4. The sinoatrial node contracts. 5. The excitation wave moves upwards from the base of the ventricles. 6. The ventricles contract. 7. The atria contract. Which statement describes the sixth event to occur in the cardiac cycle?

The microscope in cell studies

Which tissue types are found in the walls of every blood vessel?

The circulatory system

What is the typical length of a prokaryote, for example the bacterium Escherichia coli?

Cells as the basic units of living organisms

The photomicrograph displays three white blood cells labelled X, Y and Z. Which row correctly identifies these cells?

The immune system

When active tissues contain a high concentration of carbon dioxide, oxyhaemoglobin must release oxygen to the tissues. In what form is carbon dioxide carried away from the tissues in the blood?

Transport of oxygen and carbon dioxide

What effect does a rise in carbon dioxide concentration have on haemoglobin?

Proteins

The diagram presents an enlarged view of a section of the lungs that contains specialised tissues. Which row gives the correct answer for the structures labelled 1 to 6?

The gas exchange system

The table shows several regions of an animal’s lungs that contain different cell types. Which regions of these lungs filter inhaled air, and which regions perform gas exchange?

The gas exchange system

What factor helps keep a steep oxygen concentration gradient between the air inside an alveolus and the blood?

Movement into and out of cells

Goblet cells are present in the trachea. Which cell structures would be found in large numbers in a goblet cell?

Cells as the basic units of living organisms

In a country where malaria has been eliminated successfully, an outbreak of malaria may happen many years later. What might make this later outbreak of malaria possible?

Infectious diseases

Which row correctly describes a person who has leukaemia only and a person who has measles only?

Replication and division of nuclei and cells

What is responsible for the symptoms experienced by people with myasthenia gravis?

Fluid mosaic membranes

Which cell structures does Plasmodium contain?

Cells as the basic units of living organisms

Tetanus is caused by a bacterial infection. The graph shows the blood antibody concentration of two individuals. On day 0, person G was given antibodies against the tetanus toxin and person H was given the tetanus vaccine. What might happen if G and H were infected with tetanus bacteria on day 20?

Proteins

Which cell structures are able to contain nucleic acid?

Cells as the basic units of living organisms

Which row identifies the correct features of ATP?

The microscope in cell studies

Which tests can identify biological molecules whose monomers include a carboxyl group?

Testing for biological molecules

Which polysaccharide is described correctly?

Carbohydrates and lipids

Which formula shows a saturated fatty acid?

Carbohydrates and lipids