Oct/Nov 2016

The diagram illustrates a transverse section of a blood capillary. The lumen has a diameter of $7\,\mu\text{m}$. What is the magnification of the drawing?

The microscope in cell studies

The diagrams illustrate some of the bond types in fatty acids. Which row identifies the bonds present in each type of molecule?

Carbohydrates and lipids

Which of the following could describe the tertiary structure of a protein?

Proteins

In the aftermath of a heart attack, damaged heart muscle allows the enzyme lactate dehydrogenase to enter the blood plasma. Which steps must be taken to estimate lactate dehydrogenase activity in a sample of blood plasma?

Factors that affect enzyme action

Two experiments were done with an enzyme from humans. In the first experiment, X, the temperature was kept constant at $37^b0\text{C}$. In the second experiment, the temperature was raised from $37^b0\text{C}$ to $80^b0\text{C}$. Every other factor remained unchanged. Which graph represents the results?

Factors that affect enzyme action

Which molecules are present on the outer surface of a cell surface membrane?

Fluid mosaic membranes

Which substances are able to move straight through cell surface membranes without needing a carrier protein or a channel protein?

Movement into and out of cells

Which of these statements concerning the proteins in cell surface membranes are correct?

Fluid mosaic membranes

Which row is correct for a human cell immediately before it enters prophase of mitosis?

Chromosome behaviour in mitosis

Which process occurs in the mitotic cell cycle?

Replication and division of nuclei and cells

The diagram illustrates a section of a DNA molecule. Which labels indicate purines?

Proteins

A culture of human cells had their cell surface membranes removed, which caused the cell contents to be released. This material was contaminated with bacteria. The material was then centrifuged, separating the different cell structures by size and mass. Which cell structure would be separated out together with the bacteria?

Cells as the basic units of living organisms

A double-stranded DNA molecule was examined, and adenine made up 29% of its nucleotide bases. What percentage of the nucleotide bases will be cytosine?

Structure of nucleic acids and replication of DNA

If a gene mutation happens, which of the following can be changed so that a non-functional protein is produced?

Proteins

The diagram illustrates the nucleotide sequence for a short part of a gene that is transcribed. GCAGCATGCGCG The table lists the amino acids specified by 10 mRNA codons. What is the sequence of the four amino acids in the polypeptide translated from this short part of a gene?

Proteins

What changes happen to the water potential and the volume of liquid in the phloem when carbohydrate moves from a sink into a phloem sieve tube element?

Movement into and out of cells

A dendrograph measures changes in the diameter of a tree. The diagram shows a dendrograph attached to a tree. Some results are displayed on the recording chart. What accounts for the diameter changes recorded during daytime and nighttime?

Movement into and out of cells

Which description best describes xylem vessel elements?

Structure of transport tissues

Materials such as sucrose and amino acids can be transported in opposite directions through the phloem sieve tube elements. Which statement explains this?

Movement into and out of cells

Which option best explains the potential mechanisms by which sucrose moves from a mesophyll cell into a companion cell?

Movement into and out of cells

Which of the following statements about haemoglobin is correct?

Proteins

The diagram illustrates a cross-section of the heart. Which label is correct?

The heart

Which cell structures contain ribosomes?

Cells as the basic units of living organisms

What causes the increase in the number of red blood cells in humans at high altitudes?

Replication and division of nuclei and cells

Which statement accounts for why the oxygen dissociation curve for haemoglobin has an S-shaped form?

Proteins

Which reactions occur within a capillary in an alveolus? 1. carbon dioxide + water $\rightarrow$ carbonic acid 2. carbon dioxide + haemoglobin $\rightarrow$ carbaminohaemoglobin 3. haemoglobinic acid $\rightarrow$ haemoglobin + hydrogen ions 4. hydrogencarbonate ions + hydrogen ions $\rightarrow$ carbon dioxide + water

Movement into and out of cells

A student examined three slides using both low magnification and high magnification. Each slide was a cross-section through a different airway in the gas exchange system. For each slide, the student saw three features. Slide 1: irregular arrangement of cartilage; highly folded inner layer; cilia on epithelial cells Slide 2: very few goblet cells; cilia on epithelial cells; thick layer of smooth muscle relative to wall thickness Slide 3: smooth muscle tissue; blood vessels; many goblet cells Which row gives the correct identifications for the three slides?

The microscope in cell studies

Which organelle is found in large numbers in ciliated epithelial cells?

Cells as the basic units of living organisms

In certain people with lung disease, the partial pressure of oxygen in the pulmonary veins is lower than the partial pressure of oxygen in the alveoli. What might account for the difference in partial pressure of oxygen? 1. Many alveoli have collapsed, so there are not enough alveolar capillaries. 2. The partial pressure of oxygen in the pulmonary arteries is less than that in the alveolar air. 3. Oxygen diffuses from the alveolar air into the nearby alveolar capillaries too slowly.

Movement into and out of cells

What makes it difficult to control the spread of malaria? 1. International air travel for trade and tourism has risen. 2. The mosquito vector has quickly developed resistance to insecticides. 3. The $\textit{Plasmodium}$ pathogen has very high antigenic variability. 4. Civil unrest and poverty lead to overcrowded living conditions.

Infectious diseases

Which description correctly states the cause and mode of transmission of TB, measles and HIV/AIDS?

Infectious diseases

Which statement describes a function of a T-lymphocyte?

The immune system

A person’s blood group is controlled by the antigens found on the red blood cells. The table lists the antigens and antibodies found in the blood of people with different blood groups. When a blood transfusion is carried out, the recipient’s blood must not contain antibodies against the donor’s blood. Which blood group may be given to someone with blood group AB?

Fluid mosaic membranes

The electron micrograph shows part of two eukaryotic cells. Which features are also present in prokaryotes?

Cells as the basic units of living organisms

Which statement concerning immunity is correct?

The immune system

Which of the following structures occur in photosynthetic prokaryotes?

Cells as the basic units of living organisms

To estimate the amount of glucose in a solution, the same volumes of a set of solutions with known concentrations were each combined with the same excess volumes of Benedict’s solution and then kept in a thermostatically controlled water-bath at $90^\circ\text{C}$ for an identical period of time. After that, the unknown solution was treated in exactly the same manner, and the colours of the known and unknown solutions were compared. What is the independent variable in this procedure?

Testing for biological molecules

Which process cannot take place as a result of a condensation reaction?

Carbohydrates and lipids

Which two monosaccharides make up sucrose?

Carbohydrates and lipids

The diagram illustrates how different polysaccharides are related and the glycosidic bonds that join the monomers. Which row is correct?

Carbohydrates and lipids

Before this, the viruses most widely known to science measured $20$-$150\,\text{nm}$ in size. In 2003, the Mimivirus was discovered, with a size of about $680\,\text{nm}$. In 2013, the Pandoravirus was discovered, and it has a size of more than $1000\,\text{nm}$. Which viruses are visible with both a light microscope with a maximum resolution of $0.25\,\mu\text{m}$ and an electron microscope?

The microscope in cell studies

The table lists several characteristics of collagen and haemoglobin. Which row represents collagen?

Proteins

A sugar’s ring form can also be drawn as a straight-chain structure, as the diagram shows. Which of these sugar molecules could be shown by this formula?

Carbohydrates and lipids

What is the least number of carbon atoms that an amino acid can contain?

Proteins

HIV-1 protease is an enzyme made by the HIV virus. The enzyme consists of two identical chains, each containing 99 amino acids. In each chain, amino acids 25, 26 and 27 along the sequence make up part of the active site. Which levels of protein structure determine the shape of the active site?

Proteins

The graph presents findings from an investigation into how amylase acts on starch at three different temperatures. Which statements are valid conclusions from these results?

Factors that affect enzyme action

Furanocoumarins are compounds present in some fruits, and they inhibit the enzyme CYP3A4. This enzyme is required to break down toxins in the human digestive system, so harmful amounts of these toxins could build up if these fruits are consumed. What does this information indicate about molecules of the enzyme CYP3A4?

Mode of action of enzymes

Which observations provide evidence of a connection between active transport and ATP production?

Movement into and out of cells

A technique known as freeze-fracture can be used to investigate the structure of cell membranes. Which statement about the findings from freeze-fracture studies is correct?

Fluid mosaic membranes

A dandelion flower stalk is a hollow tube. Sections of the stalk are cut as shown and placed into sucrose solutions with different water potentials. Which diagram shows the section that is put into the sucrose solution with the highest water potential?

Movement into and out of cells

The three molecules listed below occur in prokaryotes. 1 phospholipid 2 protein 3 peptidoglycan Which of these molecules are present in prokaryotic cell surface membranes?

Fluid mosaic membranes

The electron micrograph of a leaf section shown here has a magnification of $\times 210$. See image. What is the true length along the line X-Y?

The microscope in cell studies

Which row correctly indicates how the nuclear envelope, the centrioles and the spindle behave during a stage of mitosis?

Chromosome behaviour in mitosis

Which set of cells are all able to divide by mitosis?

Replication and division of nuclei and cells

Which row shows the correct characteristics of the nitrogenous base cytosine?

The microscope in cell studies

Bacteria were cultured in a medium containing $^{15}\text{N}$. After a number of generations, every DNA molecule contained $^{15}\text{N}$. Some of these bacteria were then moved to a medium containing the usual nitrogen isotope, $^{14}\text{N}$. The bacteria were left to divide once. DNA from some of the bacteria was taken out and analysed. This DNA consisted entirely of hybrid DNA, with equal quantities of $^{14}\text{N}$ and $^{15}\text{N}$. In a different experiment, some bacteria from the $^{15}\text{N}$ medium were transferred to a medium of $^{14}\text{N}$. The bacteria were allowed to divide three times. DNA from some of these bacteria was extracted and analysed. What is the composition of this DNA?

Replication and division of nuclei and cells

Which processes are responsible for the bulk movement of water through xylem vessels? 1 hydrogen bonding between water molecules 2 cohesion between water molecules 3 adhesion between water molecules and lignin

Water

The diagrams show transverse sections of different parts of a plant. In the transverse sections, which tissues move most mineral ions?

Movement into and out of cells

Which alterations occur in the water potential and the volume of liquid in the phloem when amino acids are moved from leaves to be carried to a sink in the phloem sieve tube element?

Movement into and out of cells

Environmental conditions alter the rate of transpiration, and this also influences the water potential gradient in the cells of the leaf. Which combination of statements is correct?

Movement into and out of cells

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 solution move along W?

Movement into and out of cells

Which blood vessels deliver blood to the atria of the heart?

The heart

In what sequence do organelles carry out the processes of making and secreting an enzyme?

Protein synthesis

Which statement explains how a higher carbon dioxide concentration affects the oxygen dissociation curve of human haemoglobin and why this matters?

Proteins

Which substance reacts with haemoglobin to produce carbaminohaemoglobin?

Proteins

The graph displays the pressure in three sections of the heart over one cardiac cycle. At $0.2$ seconds, which section of the heart is reacting to the excitatory stimulus?

The heart

The diagram illustrates a section of the circulation system of a mammal. In which location are both the blood pressure and the flow speed at their lowest?

The circulatory system

A student used the high-power lens of a light microscope to produce some labelled drawings of lung tissue, but two airways, P and Q, were left unnamed. In the drawing of the lining of P, both ciliated cells and goblet cells were present, whereas the drawing of the lining of Q contained ciliated cells but only a very small number of goblet cells. Which airways are P and Q?

The microscope in cell studies

Which factors maintain the steep concentration gradients needed for effective gas exchange in the lungs?

Movement into and out of cells

The photomicrograph shows a section of the lung viewed with a light microscope. Which row is correct for the features marked 1, 2 and 3?

The microscope in cell studies

Which disease is least likely to be transmitted straight from parents to offspring?

The microscope in cell studies

Why is it hard to keep the spread of measles under control?

Infectious diseases

The statements below describe responses made by cells of the immune system to a pathogen. Which response is correct for $$-lymphocytes?

The immune system

In the diagram, a stage micrometer scale is shown, with divisions spaced $0.1\,\text{mm}$ apart, as seen through an eyepiece that has a graticule. What is the area of the microscope’s field of view at this magnification? ($\pi = 3.14$)

The microscope in cell studies

What happens when active immunity is produced artificially?

The microscope in cell studies

A scientist performed an experiment to separate the organelles in an animal cell according to mass. First, the scientist combined the cells with a buffer solution that had the same water potential as the cells. The cells were then broken open using a blender so that the organelles were released. After the mixture had been filtered, it was placed in a centrifuge and spun at high speed so that the heaviest organelle was separated out. This settled at the base, producing a solid pellet 1. The liquid above pellet 1 was transferred into a fresh centrifuge tube and spun in the centrifuge at a greater speed to separate the next heaviest organelle. This organelle also settled at the bottom, forming a solid pellet 2. He carried out this method twice more to produce pellet 3 and pellet 4, each of which contained one organelle. What is the function of the organelle extracted in pellet 2?

The microscope in cell studies

Which option gives a correct comparison between a typical prokaryotic cell and a typical eukaryotic cell?

Cells as the basic units of living organisms

The diagrams illustrate four monosaccharides with the formula $\mathrm{C_6H_{12}O_6}$. Which of the diagrams does not depict glucose molecules?

Carbohydrates and lipids

For polysaccharides to be fully digested, every glycosidic bond linking the monomers must be hydrolysed. Amylase catalyses the breaking of only $\alpha$-1,4 glycosidic bonds. To what extent can amylase digest molecules of amylose, amylopectin or glycogen?

Mode of action of enzymes

Which statements concerning a triglyceride molecule are correct?

Carbohydrates and lipids

Which structure occurs exclusively in typical eukaryotic animal cells?

Cells as the basic units of living organisms

Which characteristic explains the solubility of haemoglobin?

Proteins

An investigation was carried out into the speed of an enzyme-catalysed reaction. In the investigation, the concentration of the substrate was maintained above the concentration of the enzyme. In this investigation, which change to the variables would always cause the reaction rate to increase?

Factors that affect enzyme action

In the liver, the enzyme glucokinase and, in the brain, the enzyme hexokinase both catalyse the phosphorylation of glucose: $\text{glucose} + \text{ATP} \rightarrow \text{glucose phosphate} + \text{ADP}$ The activity of each enzyme was recorded at a range of glucose concentrations. The graph presents the results. What describes the different activities of the two enzymes?

Factors that affect enzyme action

The value $K_m$ is the substrate concentration at which the rate of an enzyme-catalysed reaction is half of the maximum rate, $\frac{V_{\max}}{2}$. The $K_m$ was determined in the presence of a competitive inhibitor and in the presence of a non-competitive inhibitor. What might the value of $K_m$ with inhibitor be compared with the value of $K_m$ with no inhibitor?

Mode of action of enzymes

Which molecules in cell surface membranes enable the immune system to recognise cells?

Fluid mosaic membranes

The following are all ways substances may enter a cell. Which of these processes are passive?

Movement into and out of cells

Equal amounts of five different sodium chloride concentrations were added to five containers. In each container, the same-sized piece of plant tissue was inserted and left there for 48 hours. After this, the plant tissues were taken out and the volumes of the sodium chloride solution were measured with precision. The results are shown below. Which statements account for the results from $0.80$ to $1.00\,\text{mol dm}^{-3}$ sodium chloride?

Movement into and out of cells

Chromosome telomeres are needed for DNA replication and are not fully renewed in mitosis. Substance X fully replaces telomeres in mitosis. What effect will there be when cells are grown with and without substance X?

Chromosome behaviour in mitosis

Mutations in either the BRCA1 gene or the BRCA2 gene account for most inherited breast cancer in humans. The proteins made by these two genes move into the nucleus, where they interact with other proteins, including those produced by the tumour suppressor gene p53 and the DNA repair gene RAD51. Which combination of gene activity is most likely to lead to breast cancer?

Replication and division of nuclei and cells

The information outlines several events that happen during mitosis. 1. chromosomes condense and spiralise 2. centromeres are drawn apart by the shortening of spindle fibres 3. sister chromatids are arranged across the middle of the cell 4. centrioles move away from each other 5. spindle fibres disperse Which row correctly states the stages of mitosis in which these events take place?

Chromosome behaviour in mitosis

On the logarithmic scale, which letter represents the size of a typical prokaryote?

The microscope in cell studies

Which diagram illustrates a correct ring structure and a named nucleic acid base?

Structure of nucleic acids and replication of DNA

The diagram represents the nucleotide sequence of a short section of a gene that is transcribed. GCGCGCGGCCGC The table gives the amino acids specified by 10 mRNA codons. What is the sequence of the four amino acids in the polypeptide translated from this short section of a gene?

Proteins

These events take place during transcription. 1. Bonds are broken between complementary bases. 2. Bonds are formed between complementary bases. 3. Sugar-phosphate bonds are formed. 4. Free nucleotides pair with their complementary nucleotides. Before the mRNA molecule leaves the nucleus, which of these events will have happened twice?

Protein synthesis

Which of the following statements about water movement in plants are correct?

Movement into and out of cells

The diagrams display transverse sections of three plant parts: leaf, stem and root. In these transverse sections, which tissues move water and which tissues move sucrose?

Structure of transport tissues

Which diagram shows how atmospheric humidity affects the rate of transpiration?

Movement into and out of cells

Which plant structures contain plasmodesmata?

Movement into and out of cells

The items below are all structural parts of blood vessels. 1 collagen fibres 2 elastic fibres 3 endothelial cells 4 smooth muscle cells Which row shows the components found in an artery and a vein?

The circulatory system

Scientists have found that the oxygen dissociation curves for haemoglobin in smaller mammals lie to the right of those for larger mammals. What does this indicate about the haemoglobin of smaller mammals?

Proteins

Which row could be right for the average blood pressure in different regions of the human circulatory system?

The circulatory system

Which calculation is used to determine the actual length of an organelle from an image?

The microscope in cell studies

Which of the statements are true?

Cells as the basic units of living organisms

The diagram illustrates pressure changes throughout the cardiac cycle. Which arrow shows atrial systole?

The microscope in cell studies

The picture is a photomicrograph of a transverse section of a part of the gas exchange system. Which description matches the image?

The microscope in cell studies

The table gives some of the consequences of smoking. Which row indicates the effect of nicotine and carbon monoxide?

Transport of oxygen and carbon dioxide

Which of the following statements about chronic obstructive pulmonary disease (COPD) is correct?

Movement into and out of cells

Which row is the correct one?

Movement into and out of cells

What shared characteristic do the pathogens of HIV/AIDS, malaria and TB have?

Infectious diseases

Which factor could have helped HIV/AIDS to spread?

Infectious diseases

Which event happens after antigen-antibody binding?

Proteins

Which of the following statements about macrophages are correct?

The immune system

Which of the following statements is correct?

Cells as the basic units of living organisms

The graph illustrates the concentration of antibody in blood after vaccination and then a booster vaccination 28 days later. Which statements about how the antibody concentration changes are correct?

Antibodies and vaccination

The diagram depicts a typical animal cell. Which features are present in both plant cells and prokaryotic cells as well?

Cells as the basic units of living organisms

A student performed Benedict’s test on four glucose solutions of different concentrations and then noted the time taken until the colour first changed (the end-point). The student was unable to judge the very first sign of a colour change and therefore timed each solution for 2 seconds after the change had already begun. This added a source of error to the investigation. Which statements about this error are correct?

Testing for biological molecules

For each molecule, which row is the correct one?

Carbohydrates and lipids

The diagram illustrates the way in which the $\beta$-glucose units within cellulose are linked together. What does it mean that the OH groups on carbon 2 of neighbouring glucose molecules lie on opposite sides of the molecule?

Carbohydrates and lipids

Threonylvaline is a dipeptide made by combining the two amino acids threonine and valine. A peptide bond is created between the carboxyl group of threonine and the amine group of valine. The side-chains (R groups) of both amino acids are shown. Which molecular structure represents threonylvaline?

Proteins