Oct/Nov 2020

Which row gives the correct sequence for the size of these cell structures? 1 width of a mitochondrion 2 width of a ribosome 3 width of a cell surface membrane 4 width of a chloroplast

The microscope in cell studies

Which row gives the correct match between the function and the structural features of cellulose, collagen, glycogen or triglyceride?

Carbohydrates and lipids

The diagram presents the amino acids making up a polypeptide. An enzyme speeds up the hydrolysis of any peptide bond between a non-polar amino acid and any polar amino acid. By the action of this enzyme, how many small peptides and single amino acids will be produced?

Proteins

Which properties of water help to minimise temperature changes within cells?

Water

Which enzyme is secreted outside the cell?

Mode of action of enzymes

The graph illustrates how the concentrations of the substances in an enzyme-catalysed reaction vary over time. Which line shows enzymes with unoccupied active sites?

Mode of action of enzymes

What effects may non-competitive inhibitors produce in enzyme-controlled reactions?

Factors that affect enzyme action

Which processes can enable transport into or out of a cell?

Movement into and out of cells

Plant cells were placed in one of three sugar solution concentrations, $10\%$, $5\%$ or $2.5\%$. They remained there for $50$ minutes before being viewed with a light microscope. Which statements are correct?

Movement into and out of cells

In telophase of mitosis, a scientist uses a fluorescent dye to stain the chromosomes in a diploid animal cell in order to view the telomeres. The cell contains $22$ chromosomes. How many telomeres will the scientist see in one nucleus?

Chromosome behaviour in mitosis

Methotrexate is a drug that is used in cancer treatment. It works as an enzyme inhibitor, stopping the production of nucleotides that contain thymine. Cells exposed to methotrexate are unable to finish the cell cycle. A cell that has entered telophase is exposed to methotrexate. Which stage of the cell cycle will be affected by methotrexate’s action?

Replication and division of nuclei and cells

The diagram depicts a stage micrometer scale as seen through an eyepiece that contains a graticule. Each small division on the stage micrometer scale measures $0.1\,\text{mm}$. The stage micrometer scale is then substituted with a slide of a plant cell. What is the real length of the nucleus in the plant cell?

The microscope in cell studies

At which stage of mitosis is the description accurate?

Chromosome behaviour in mitosis

The diagram shows a nucleotide that includes cytosine. Which of the following statements about this nucleotide are correct?

Proteins

A segment of DNA contains $73$ base pairs. Which row shows the correct number of bases?

Structure of nucleic acids and replication of DNA

The photograph shows a part of a stem. Which labelled part is xylem?

Structure of transport tissues

Certain fungi induce wilting in crop plants by developing inside the xylem vessel elements. Which process is directly affected by these fungi?

Movement into and out of cells

What characteristics help water to move through xylem vessel elements?

Structure of transport tissues

Several processes are involved in the loading of sucrose into companion cells. Which one is active?

Movement into and out of cells

The statements outline the changes that take place as sucrose is transported. 1 Hydrostatic pressure falls. 2 Hydrostatic pressure rises. 3 Sucrose is loaded into the phloem vessel. 4 Sucrose is unloaded from the phloem vessel. 5 Water enters the phloem by osmosis. 6 Water leaves the phloem by osmosis. 7 Water potential falls in the phloem. 8 Water potential rises in the phloem. Which sequence correctly shows the events in a plant at a source during the movement of sucrose?

Movement into and out of cells

What is found in the walls of capillaries?

Movement into and out of cells

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

The microscope in cell studies

Insulin is a hormone made from two polypeptide chains within cells in the pancreas. Which row identifies the cell structures involved in making insulin and in releasing it from the cells?

Protein synthesis

Which arrangement of letters correctly shows the sequence of events in the cardiac cycle? T the atrial walls contract U the impulse is held up for a fraction of a second V a wave of excitation enters the atrioventricular node W a wave of excitation travels down the Purkyne tissue X a wave of excitation spreads out from the sinoatrial node Y the ventricles contract

The heart

The graph illustrates how three different partial pressures of carbon dioxide affect the oxygen dissociation curve of human haemoglobin. How does a lower partial pressure of carbon dioxide affect haemoglobin?

Proteins

Which statement about the transport of carbon dioxide in blood is correct?

Movement into and out of cells

Which of the following statements about all bronchioles are correct?

The gas exchange system

The graph illustrates the amount of air expelled rapidly and forcefully after a deep inhalation, for three different people, X, Y and Z. What could explain the differences in the volume of air breathed out by these people that are shown?

The gas exchange system

The diagrams illustrate some of the pathogens that cause disease in humans and some of the ways they are passed on. Which pathogen and method of transmission are correct for TB?

Infectious diseases

The proportion of the local population who have malaria in area R is greater than the proportion in area S. Which factor is responsible for this difference?

Infectious diseases

Species X is a unicellular eukaryote. Species X has been genetically engineered to make penicillin, which does not damage the cell walls of species X. What can be inferred from this information?

Antibiotics

If an antigen enters the body again, memory cells trigger a secondary immune response. Which option shows the secondary immune response correctly?

The immune system

Monoclonal antibodies are made for use in the diagnosis or treatment of disease. To collect the antibodies against an antigen, a mouse is injected with the antigen. Several stages in monoclonal antibody production are given below. 1 Plasma cells are fused with cancer cells to produce a hybridoma. 2 Hybridomas that release the needed antibody are found and cloned. 3 B-lymphocytes that recognise the antigen multiply and change into plasma cells. 4 Hybridomas divide by mitosis and secrete antibodies. 5 Plasma cells are taken from the mouse spleen. What is the order of the first four stages in the production of the monoclonal antibody?

Replication and division of nuclei and cells

The electron micrograph displays a cell structure in a eukaryotic cell. Which of these statements about that cell structure are correct?

The microscope in cell studies

Which row gives the description of passive immunity?

Antibodies and vaccination

Four students were asked to pair each function with the appearance of certain cell structures in an animal cell. The functions were given as numbers. 1 synthesis of polypeptides 2 synthesis of lipids 3 packaging of hydrolytic enzymes that will remain in the cell The appearances were given as letters. V membranes that enclose an inner cavity W spherical structures with no membrane X a double membrane with pores between it Y cylindrical structures with no membrane 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

In typical prokaryotes, the DNA is naked and circular. Which statement explains how eukaryote DNA is different from the DNA of typical prokaryotes?

Structure of nucleic acids and replication of DNA

A student investigated two milk samples, X and Y, using Benedict’s test. Each milk sample was heated in a water-bath to $100\,^{\circ}\text{C}$ with Benedict’s solution, and the time until the first colour change appeared was recorded. The findings are given in the table. X: 13 s Y: 26 s Which row identifies the biological molecule detected in each milk sample and the milk sample with the greater concentration of this biological molecule?

Testing for biological molecules

The diagram shows the structure of a monomer. Which molecules include this monomer?

Proteins

Which molecules are produced in condensation reactions involving a carboxyl group?

Proteins

The measles virus, Morbillivirus, has a size of about $150\,\text{nm}$. Mimivirus is about $4.5$ times bigger than Morbillivirus, while Pandoravirus is about $1.5$ times bigger than Mimivirus. Which of these viruses can be observed with a light microscope that has a maximum resolution of $0.25\,\mu\text{m}$, and which can be observed with an electron microscope?

The microscope in cell studies

Which row correctly describes the structure of proteins?

Proteins

Which row correctly identifies the structural characteristics of a collagen molecule and a haemoglobin molecule?

Proteins

Which of the following statements describe some enzyme actions?

Mode of action of enzymes

Lipase is an enzyme that catalyses the hydrolysis of lipids. An experiment was carried out to examine how pH changes when lipase is added to a food sample with a high proportion of lipids. The results are displayed in the graph. Which statements could explain the results of the experiment between 50 minutes and 60 minutes?

Factors that affect enzyme action

The painkiller ibuprofen lowers the activity of an enzyme that is involved in the synthesis of prostaglandin. Ibuprofen attaches reversibly to the active site of the enzyme. Which type of enzyme inhibition is shown by this example, and why?

Mode of action of enzymes

Potato pieces of the same size were put into test-tubes with equal volumes of sucrose solution at different concentrations and left for 30 minutes. All the other variables were kept constant. After 30 minutes, the potato piece in one of the sucrose solution concentrations had stayed the same size. What may be concluded from the result for this potato piece?

Movement into and out of cells

Four agar blocks are coloured green with universal indicator and placed in $1\ \text{mol dm}^{-3}$ hydrochloric acid. The length of time needed for the agar blocks to turn from green to red was measured. Which agar block would turn completely red first?

Movement into and out of cells

As the cell cycle proceeds, the amount of DNA in a cell is doubled. At what stage in the cell cycle is the amount of DNA in a cell reduced?

Replication and division of nuclei and cells

Of the structures listed, how many normally contain genetic material with telomeres? • bacterial cell • chloroplast • mitochondrion • nucleus

Structure of nucleic acids and replication of DNA

In eukaryotes, chromosomes become shorter and more compact during mitosis. This compaction can be greater because of molecules known as protamines. The protamines replace part of the chromosome structure. Which part of the chromosome is replaced by protamines?

Chromosome behaviour in mitosis

The electron micrograph displays a type of virus at a magnification of $\times 60\,000$. What is the real length of the virus?

The microscope in cell studies

How many hydrogen bonds hold the two strands of this section of a DNA molecule together?

Structure of nucleic acids and replication of DNA

Which statement correctly describes a eukaryotic gene?

Structure of nucleic acids and replication of DNA

The DNA sequence $\text{CCAAGAAGTCGACAAAA CA}$ is translated to produce the amino acid chain gly-ser-ser-ala-val-cys. Following a mutation, the length of the amino acid chain is reduced from six to two amino acids. The stop codon in mRNA is $\text{UGA}$. Identify which base in the DNA sequence was altered by the mutation?

Proteins

Which combination of characteristics is correct for a phloem sieve tube element while it unloads into a sink?

Movement into and out of cells

Mass flow is the bulk transfer of materials from one location to another. Which vessels transport fluids by mass flow?

Movement into and out of cells

Which two rows correctly show the movement of water from the soil into a root?

Movement into and out of cells

ATP is used in companion cells to supply the energy needed to load a sieve tube element with sucrose. In what way does the co-transporter mechanism make use of this energy?

Movement into and out of cells

Why is the mammalian circulatory system said to have a double circulation?

The circulatory system

Which letter sequence correctly shows the order of events in the cardiac cycle? T: atrial walls contract U: the impulse is delayed for a fraction of a second V: the wave of excitation enters the atrioventricular node W: the wave of excitation travels down the Purkyne tissue X: the wave of excitation spreads from the sinoatrial node Y: ventricles contract

The heart

What factors influence blood pressure?

The microscope in cell studies

The electron micrograph displays a structure that is located in the cytoplasm of an animal cell. Which biological molecules are present in this structure?

Proteins

The diagram provides a summary of haemoglobin’s function in the transport of carbon dioxide. Which group of labels is correct?

Proteins

The graph plots the oxygen dissociation curves for haemoglobin in two mammal species, S and T. Which of these statements could account for the difference between the oxygen dissociation curves of species S and species T?

Proteins

Which of these are found in bronchioles?

The gas exchange system

The partial pressure of oxygen in the air within the alveoli is $14\ \text{kPa}$. The partial pressure of oxygen in the pulmonary capillaries is $6\ \text{kPa}$. How will these partial pressures affect diffusion?

Movement into and out of cells

Which of these can be directly connected with a decrease in the surface area available for gas exchange in human lungs?

Movement into and out of cells

Which row gives the correct information about haemoglobin’s affinity for the gases carbon dioxide, carbon monoxide and oxygen?

Proteins

An earthquake damaged sanitation systems in a large tropical village. The drinking water was then polluted by sewage. After that, heavy rainfall led to flooding and created extensive pools of standing water in the village. Homes were destroyed, so the villagers had to live in very crowded conditions. Which infectious diseases might become more common in the village population because of the earthquake and heavy rain?

Infectious diseases

Which of the following statements about how antibiotics are used could lead to an increase in antibiotic-resistant bacteria?

The microscope in cell studies

Which row gives the correct information for neutrophils and B-lymphocytes?

The immune system

Rabies is generally a fatal disease. It is passed to people through the saliva of infected animals. Anyone who has been bitten by an infected animal requires treatment without delay. This treatment consists of a vaccination against rabies and an injection that contains antibodies to the rabies antigen. What type of immunity is provided by the injection of antibodies?

Proteins

Four students were told to link each function to the appearance of certain cell structures in an animal cell. The functions were numbered as follows. 1 mRNA moves through to the ribosome 2 production of lipids 3 collection of hydrolytic enzymes that will stay inside the cell The appearances were labelled with letters. V membranes enclosing a cavity inside W spherical structures without a membrane X a double membrane with pores between it Y cylindrical structures without a membrane Z membrane-bound sacs arranged in 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

The body usually rejects a tissue graft, such as skin, if it comes from another person. Which statement is correct about graft rejection?

Fluid mosaic membranes

Which of the following are present in typical prokaryotic cells and in typical plant cells?

Cells as the basic units of living organisms

The diagram illustrates several features found in organisms. Which of these features may also occur in viruses?

Cells as the basic units of living organisms

Diastase is an enzyme that converts starch into maltose. Maltose is a reducing sugar. A starch sample is treated with boiled diastase and left for $15\,\text{minutes}$. After this, portions of the mixture are tested using iodine solution and Benedict’s reagent. What are the results?

Testing for biological molecules

Which two monosaccharides combine to form sucrose?

Carbohydrates and lipids

The diagram illustrates the structures of two amino acids. These amino acids will be part of a protein with tertiary structure. Which numbered groups could make hydrogen bonds to help maintain the tertiary structure of the protein?

Proteins

Which units are suitable for measuring the diameters of alveoli, the diameters of white blood cells and the width of cell walls?

The microscope in cell studies

Which row correctly gives the ratio of carbon atoms to hydrogen atoms for glucose, a saturated fatty acid and sucrose?

Carbohydrates and lipids

Which row gives a correct comparison of a phospholipid molecule with a triglyceride molecule?

Carbohydrates and lipids

Adult human haemoglobin usually contains two $\alpha$ chains together with two $\beta$ chains. Around $5\%$ of humans possess one amino acid in the $\beta$ chain that has been altered. This alteration changes the structure and stability of haemoglobin. Which levels of protein structure might be affected in the haemoglobin of the humans with the altered amino acid?

Proteins

Lysozyme is found in human tears, saliva, milk and mucus. It functions in the immune system and hydrolyses peptidoglycan. Which description of lysozyme is correct?

Mode of action of enzymes

Which letter on the flow diagram indicates the effect of adding a competitive inhibitor to an enzyme-catalysed reaction?

Factors that affect enzyme action

The cell surface membrane is referred to as a ‘fluid mosaic’. Which statement best describes the ‘mosaic’ component of the cell surface membrane?

Fluid mosaic membranes

Solute X has a higher concentration outside a cell than inside the cytoplasm. Which processes could enable solute X to be transported across the cell surface membrane?

Movement into and out of cells

Three molecules present in prokaryotes are shown. 1 phospholipid 2 protein 3 peptidoglycan Which of these molecules occur in the cell surface membranes of prokaryotic cells?

Fluid mosaic membranes

What change occurs to the surface area to volume ratio of a cube when the length of each side is doubled?

Cells as the basic units of living organisms

Three chromosome components and what they do are given below. p1 centromere p2 histone proteins p3 telomere f1 keeps the DNA coils joined together f2 keeps two chromatids joined together f3 stops genes from being lost Which component is paired with the correct function?

Chromosome behaviour in mitosis

A prokaryotic cell has an actual diameter of $0.5\,\mu\text{m}$. The cell is shown in an electron micrograph at a magnification of $\times 50\,000$. What is the diameter of the cell in the image?

The microscope in cell studies

Which aspects of mitosis are important for a unicellular organism?

Replication and division of nuclei and cells

Some stages in the cell cycle are given below. Which of these stages are part of mitosis?

Chromosome behaviour in mitosis

Which row shows the correct characteristics of guanine?

Structure of nucleic acids and replication of DNA

Bacteria were cultured in a medium containing $^{15}\text{N}$. After several generations, every DNA molecule contained $^{15}\text{N}$. Some of these bacteria were then moved to a medium containing the common isotope of nitrogen, $^{14}\text{N}$. The bacteria were allowed to divide once. DNA from some of these bacteria was removed and analysed. This DNA consisted entirely of hybrid DNA with equal amounts of $^{14}\text{N}$ and $^{15}\text{N}$ ($^{14}\text{N}/^{15}\text{N}$). In a different experiment, some bacteria from the medium with $^{15}\text{N}$ were transferred into 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 would be the composition of this DNA?

Replication and division of nuclei and cells

A transfer RNA (tRNA) molecule contains the anticodon sequence UAC. Which nucleotide sequence in the DNA corresponds to this?

Proteins

Some features of transport tissues in plants are given below. Which of these features occur in xylem vessel elements?

Structure of transport tissues

The diameter of a tree trunk usually becomes a little smaller during the day and a little larger at night. Which three environmental factors, if increased, could produce the biggest decrease in diameter?

Movement into and out of cells

Sucrose is carried in a phloem sieve tube from a source to a sink by mass flow. Which type of gradient inside the phloem sieve tube between the source and the sink causes the movement of sucrose?

Movement into and out of cells

What structures are found in the walls of veins?

The circulatory system

Which row shows the correct location of a type of molecule or cell?

Fluid mosaic membranes

An electron micrograph is shown and it includes some cell structures. A list of cell structures is given. 1 nucleolus 2 chloroplast 3 microtubules 4 ribosomes 5 mitochondria 6 plasmodesmata Which of these cell structures can be observed in the electron micrograph?

The microscope in cell studies

How does a lower carbon dioxide concentration affect haemoglobin?

Proteins

What causes the red blood cell count in humans to rise when they begin living at high altitude?

Replication and division of nuclei and cells

The diagram displays a photomicrograph of part of a bronchus. Which label shows smooth muscle?

The microscope in cell studies

Which of these statements about every bronchiole is correct?

The gas exchange system

Which row indicates the effects of emphysema?

Movement into and out of cells

Which row is the correct one?

Movement into and out of cells

The diagrams illustrate the outcome of incubating two species of bacteria, P and R, on separate Petri dishes, each of which contains nutrient agar. Three filter paper discs have been placed on each Petri dish. Which statement is correct?

Movement into and out of cells

The statements relate to infectious diseases. 1 Disease can pass from one human to another through contact. 2 The disease-causing organism has many antigenic variations. 3 The spread of disease may be affected by climate. 4 A vaccination programme is available. Which row correctly links the statement numbers to each disease?

Infectious diseases

Muscle cells possess receptors on their cell surface for the neurotransmitter ACh. These receptors enable the muscle to respond to a nerve impulse. In myasthenia gravis, helper T cells cause a clone of B cells to differentiate into plasma cells and release antibodies that attach to and obstruct these ACh receptors. As a result, the muscles fail to be stimulated and start to deteriorate. A short-term treatment for myasthenia gravis is to inject monoclonal antibodies into the blood. What is the target of these monoclonal antibodies?

Fluid mosaic membranes

The diagram illustrates the simplified structure of an antibody. Which statement is correct?

Proteins

Which cell structure is often continuous with the rough endoplasmic reticulum?

Cells as the basic units of living organisms

Why have vaccination programmes eliminated smallpox but not TB?

Antibodies and vaccination

Which of the following statements about ATP are correct?

Cells as the basic units of living organisms

Four students were asked to link each function to the correct appearance of certain cell structures in an animal cell. The functions were numbered as follows. 1 mRNA travels through to the ribosome 2 arranges microtubules to form the spindle during cell division 3 lipid synthesis The appearances were given the letters. V membranes enclosing a cavity inside W spherical structures without a membrane X a double membrane with pores Y cylindrical structures without a membrane Z membrane-bound sacs arranged in a flattened stack Which student matched the numbered functions to the appearance of the cell structure correctly?

Cells as the basic units of living organisms

A student tested one milk sample for biological molecules. The outcomes of the tests were: • When heated to $80\,^{\circ}\text{C}$ with Benedict’s solution, a red colour was produced. • After boiling with acid, then neutralising, and then heating to $80\,^{\circ}\text{C}$ with Benedict’s solution, a red colour was also produced. • On adding Biuret solution, the colour became purple. • On adding iodine solution, the colour became yellow. Which biological molecules have to be present in the milk?

Testing for biological molecules

Which row gives the correct answer for carbohydrates?

Carbohydrates and lipids

Which molecules include $1,6$ glycosidic bonds?

Carbohydrates and lipids