May/June 2016

Under the high power $(\times 400)$ of the light microscope, which cell organelle will be clearly visible?

The microscope in cell studies

The diagrams display the structures of two amino acids, one containing two amine (-NH$_2$) groups and the other containing two carboxylic (-COOH) groups. A peptide bond is made between the two amino acids. Which groups join to form the peptide bond?

Proteins

Proteins that move sugars out of cells have been identified. These proteins are known as SWEETs. Each SWEET contains seven coiled, cylindrical sections which together form a pore through the cell surface membrane bilayer, as shown in the diagram. What describes each of the seven coiled regions (1-7) of a SWEET shown in the diagram?

Fluid mosaic membranes

Influenza virus contains an enzyme named neuraminidase, which breaks down glycoproteins in the membrane of the cell that the virus will infect. The glycoprotein binds to the active site of neuraminidase by induced fit. Which statements concerning the induced fit hypothesis of enzyme action are correct?

Mode of action of enzymes

Which row concerning competitive inhibitors of enzymes is correct?

Mode of action of enzymes

The graph illustrates how raising substrate concentration affects the rate of an enzyme-catalysed reaction. What is limiting the rate of the enzyme-catalysed reaction at 1, 2, 3 and 4 on the graph?

Factors that affect enzyme action

The diagram shows a cell surface membrane of a metabolically active cell and the direction in which some molecules move through the membrane. Which row indicates a process that the molecules may be using to cross the membrane at each of the points 1, 2, 3 and 4?

Movement into and out of cells

Batrachotoxin is a toxin present in frogs from the Colombian jungle. Native Indians use the toxin to make poisoned darts. It acts by making some cell surface membranes more permeable to sodium ions, which then move out of the cells. Which statements are true for cells affected by batrachotoxin?

Movement into and out of cells

Which processes take place in prophase of the mitotic cell cycle in an animal cell?

Chromosome behaviour in mitosis

Protein p53 is made within a cell when DNA damage occurs. It briefly halts the cell cycle immediately before DNA is copied, allowing the DNA to be repaired. During which phase of the cell cycle does this halt take place?

Replication and division of nuclei and cells

What characteristic of stem cells allows them to replace cells in tissues such as the skin?

Replication and division of nuclei and cells

The sketch made from an electron micrograph shows a ciliated epithelial cell, magnified $\times 1500$, and it is located in the trachea. Line $X-Y$ represents the cell’s greatest width. What number of these cells could fit along a $1\ \text{cm}$ length of the trachea?

The microscope in cell studies

In DNA, the X base Y pairs with adenine through Z hydrogen bonds. Which row correctly finishes the statement about DNA?

Proteins

The diagram presents the nucleotide sequence for a short part of a gene that is transcribed: CGCCGCACGCGC. The table lists the amino acids coded for by 10 mRNA codons. In what sequence do the four amino acids appear in the polypeptide translated from this short section of a gene?

Proteins

The statements below outline the characteristics of some nucleic acids. Which functions are performed by tRNA?

Proteins

A student was instructed to make a plan diagram of the plant tissue visible in the photomicrograph and to label two features that can be seen. Which annotations are correct?

The microscope in cell studies

Water inside a root hair cell can move out of the cell and enter the vascular tissue. Which pathway must the water follow?

Movement into and out of cells

Which statement gives an accurate definition of transpiration?

Movement into and out of cells

What changes happen to the water potential and to the volume of liquid in the phloem sieve tube element as sucrose is moved from a photosynthesising leaf into the phloem sieve tube element?

Movement into and out of cells

Which statement provides evidence for the active loading of sucrose into companion cells?

Movement into and out of cells

The diagram shows the outside of the mammalian heart together with the blood vessels linked to it. Which statement about the blood vessels linked to a normal, healthy heart is correct?

The heart

The graph illustrates how blood pressure changes over one cardiac cycle. What is taking place at time X?

The heart

Which locations of ribosomes in a typical eukaryotic cell are correct?

Cells as the basic units of living organisms

Which event does not take place when a red blood cell reaches the alveolus?

Movement into and out of cells

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

Proteins

Which of the following statements about events that take place in the heart is correct?

The heart

What features would be visible in an electron micrograph of a bronchus wall?

The gas exchange system

Which regions of the human gas exchange system can typically contain macrophages?

The microscope in cell studies

An oxygen molecule moves by diffusion from the air within an alveolus, through cells, to haemoglobin in a red blood cell. What is the minimum number of cell surface membranes that this molecule must cross?

Movement into and out of cells

Which short-term effects of smoking result from carbon monoxide?

Transport of oxygen and carbon dioxide

A person whose immune system is suppressed may be more prone to certain diseases. Which disease would this person not be more prone to?

The immune system

Which disease is treated using drugs whose molecular structure is similar to DNA nucleotides?

Infectious diseases

Rabies is a viral disease that may be transmitted to humans through a bite from an infected animal. One treatment method is to inject the patient with antibodies that are specific to the rabies virus. Which of the following statements about this treatment are correct?

Proteins

Visking tubing is an artificial, partially permeable membrane that is used to show diffusion. Glucose molecules are able to move through the membrane pores, which have a diameter of about $2.4\ \text{nm}$. Which one of the following could pass through the pores?

Movement into and out of cells

What functions do T-lymphocytes perform during an immune response?

The immune system

What structures are present in both chloroplasts and typical prokaryotic cells?

Cells as the basic units of living organisms

Two solutions, 1 and 2, were examined using a range of reagents to establish their identities, with one solution containing starch and sucrose and the other containing glucose and protein. The table presents the conclusions drawn from the results obtained for the different tests. Which row correctly matches the two solutions?

Testing for biological molecules

$X$ and $Y$ are two monomers present in biological polymers. In which of cellulose, glycogen, amylopectin and amylose is each monomer found?

Carbohydrates and lipids

Chitin is a polysaccharide made up of long, unbranched chains of the monosaccharide acetylglucosamine, joined by $1,4$ glycosidic bonds. Acetylglucosamine has a structure similar to glucose, but it also contains nitrogen, which enables hydrogen bonds to form between neighbouring chains of chitin when they are aligned parallel to one another. Which polysaccharide has the closest structural similarity to chitin?

Carbohydrates and lipids

Which of the following statements about triglycerides is correct?

Carbohydrates and lipids

A student is shown a photomicrograph of a cell organelle. The magnification of the photomicrograph is known. Which calculation gives the true length of the organelle in $\mu\text{m}$?

The microscope in cell studies

In two investigations, the rate of an enzyme-catalysed reaction was measured when either a competitive inhibitor or a non-competitive inhibitor was present. What could happen to each rate of reaction if the substrate concentration is increased?

Factors that affect enzyme action

In an experiment, enzymes X and Y were tested. Enzyme X came from bacteria living in rivers and lakes at temperatures from $5\,^{\circ}\text{C}$ to $20\,^{\circ}\text{C}$. Enzyme Y came from bacteria living in hot water springs at temperatures from $40\,^{\circ}\text{C}$ to $85\,^{\circ}\text{C}$. The experiment recorded the concentration of product made by each enzyme at temperatures between $0\,^{\circ}\text{C}$ and $100\,^{\circ}\text{C}$ after 5 minutes. Which graph shows the results?

Factors that affect enzyme action

What role does cholesterol have in a cell surface membrane?

Fluid mosaic membranes

Which functions of the cell surface membrane arise from the properties of the phospholipids?

Fluid mosaic membranes

Which statements about active transport are always true?

Movement into and out of cells

A high concentration of molecule X is present outside the cell, and it enters the cell by facilitated diffusion. The graph shows how the concentration of X inside the cell changes at $30\,\text{s}$ intervals. Why does the concentration of X inside the cell remain unchanged after $150\,\text{s}$?

Movement into and out of cells

The photomicrographs display cells at different stages of the cell cycle. Which cells have twice the number of DNA molecules as a cell from the same organism following cytokinesis?

Replication and division of nuclei and cells

A group of chemicals used to treat cancer stops the spindle from forming during mitosis. Which phase of mitosis is affected first?

Chromosome behaviour in mitosis

Mitosis is a vital process in organisms. Which characteristics of mitosis matter for single-celled organisms?

Replication and division of nuclei and cells

Which statements concerning complementary base pairing are correct?

Structure of nucleic acids and replication of DNA

Which of the following statements about both mitochondria and chloroplasts are correct?

Cells as the basic units of living organisms

Bacteria were cultured in a medium that contained $^{15}\text{N}$. After a number of generations, every DNA molecule contained $^{15}\text{N}$. Some of these bacteria were then moved into a medium containing the usual nitrogen isotope, $^{14}\text{N}$. They were permitted to divide once. The DNA from some of these bacteria was removed and examined. It was entirely hybrid DNA, with equal proportions of $^{14}\text{N}$ and $^{15}\text{N}$. The rest of the bacteria were kept in the $^{14}\text{N}$ medium and allowed to divide once again. The DNA from some of these bacteria was then extracted and analysed. What is the composition of this DNA?

Replication and division of nuclei and cells

Which of the following statements about tRNA are correct?

Proteins

The diagram gives the nucleotide sequence for a small part of a gene that is transcribed: TTCTTCCCGTTC. The table shows the amino acids encoded by 10 mRNA codons. What is the sequence of the four amino acids in the polypeptide translated from this small section of a gene?

Proteins

The graph illustrates the diameter of a tree trunk at various times. Which statement is correct?

Replication and division of nuclei and cells

Certain plant species are able to absorb poisonous heavy metal ions that are dissolved in water within the soil. These ions build up in the aerial regions of the plant, which can then be harvested and disposed of safely. An investigation was done into the capacity of a plant species to remove a heavy metal ion from soil. The following observations were obtained: some heavy metal ions had accumulated in the cells of the root cortex; inside these cells, most of the ions were located in the vacuole; in both the roots and the leaves, the ions were moved while dissolved in water. Which statements about the movement and build-up of heavy metals are correct?

Movement into and out of cells

The diagram presents the outcomes of an experiment on transpiration with two different leaves. Each leaf was placed on a balance in daylight in a closed room, and its mass was measured at 1 hour intervals. Which conclusions could be correct?

Movement into and out of cells

Which statement concerning the transport of sucrose is correct?

Movement into and out of cells

Which of the tissue types listed below can be found in the walls of every blood vessel?

The circulatory system

Which blood components are found in tissue fluid?

Movement into and out of cells

The graph illustrates how the percentage saturation of haemoglobin with oxygen varies in the blood of a human and another animal. The partial pressure of carbon dioxide is kept constant at $1.0\ \text{kPa}$, and the temperature is kept constant at $25^{\circ}\text{C}$. Which conclusion does the graph support?

Proteins

What size range would encompass most eukaryotic cells?

Cells as the basic units of living organisms

Which statements concerning the formation of haemoglobinic acid are correct?

Proteins

The photograph depicts one kind of blood cell. Which of the following statements about these cells are correct?

Transport of oxygen and carbon dioxide

A student was asked to compare the features seen on four microscope slides of sections from different regions of the gas exchange system. slide 1 lacks cartilage and glands has few goblet cells, ciliated epithelial cells and smooth muscle slide 2 contains incomplete cartilage rings, glands, goblet cells, ciliated epithelial cells and smooth muscle slide 3 lacks cartilage, glands, goblet cells and smooth muscle has squamous epithelial cells slide 4 contains plates of cartilage, glands, goblet cells, ciliated epithelial cells and smooth muscle Which is the correct identification of the parts of the gas exchange system?

The microscope in cell studies

Which parts of the human gas exchange system assist in reducing the effects of carcinogens in tar?

The microscope in cell studies

Which statement correctly describes haemoglobin’s affinity for the gases carbon dioxide, carbon monoxide and oxygen?

Proteins

The table lists the names of five pathogens. Which row correctly matches each pathogen to the disease it causes?

Infectious diseases

Which disease has all of the following characteristics? • It may pass from animals to other animals, including humans. • One way it spreads is through transfusion of infected blood. • The pathogen responsible can develop resistance to several drugs. • Most humans who die from this disease are children.

The microscope in cell studies

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

Infectious diseases

Which statement explains how passive natural immunity is acquired?

The immune system

What is meant by a non-specific immune response?

The immune system

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 apart with a blender so that the organelles were released. The resulting mixture was filtered and then placed in a centrifuge at a speed sufficient to separate the heaviest organelle. This organelle moved to the bottom, where it formed a solid pellet, 1. The liquid remaining above pellet 1 was transferred into a clean centrifuge tube and spun in the centrifuge at a higher speed to separate the next heaviest organelle. This organelle also sank to the bottom, producing a solid pellet, 2. He carried out this process twice more to produce pellet 3 and pellet 4, with each pellet containing one organelle. What function does the organelle in pellet 4 carry out?

Cells as the basic units of living organisms

What accounts for the fact that monoclonal antibodies can be used to target cancer cells?

Proteins

Which row indicates the monomer and the type of bond that make up the polymer?

The microscope in cell studies

Which biological molecules invariably include the element nitrogen?

Proteins

Which of the following statements about the quaternary structure of proteins is correct?

Proteins

Which group of statements gives the correct description of haemoglobin?

Proteins

The diagrams illustrate different bond types present in biological molecules. Which bonds occur in proteins that have a tertiary structure?

Proteins

A stage micrometer can be used to calibrate an eyepiece graticule. Why is an eyepiece graticule calibrated?

The microscope in cell studies

As the temperature of an enzyme is raised, which bond will be the last one to break?

Factors that affect enzyme action

Which statement applies only to the induced fit theory of enzyme action?

Mode of action of enzymes

The influence of substrate concentration on an enzyme-catalysed reaction was recorded under three separate conditions: • without inhibitor • with inhibitor X • with inhibitor Y. The graph presents the data. Which statement is correct?

Factors that affect enzyme action

The following list names some of the molecules present in a cell surface membrane. 1 glycoprotein 2 glycolipid 3 surface protein 4 trans-membrane protein Which of these molecules take part in cell signalling?

Fluid mosaic membranes

Which of these statements about fatty acids are correct?

Carbohydrates and lipids

Which substances are able to move directly through cell surface membranes without a carrier protein or channel protein? 1 $\text{Ca}^{2+}$ and $\text{Na}^+$ ions 2 $\text{O}_2$ molecules 3 glucose, $\text{C}_6\text{H}_{12}\text{O}_6$

Movement into and out of cells

Which of the following statements about endocytosis are correct?

Movement into and out of cells

Which process takes place during prophase in the mitotic cell cycle of an animal cell?

Chromosome behaviour in mitosis

Which processes take place in bone marrow cells during the mitotic cell cycle? 1 phosphate groups attach to ADP molecules to make ATP 2 bonds are formed between nucleotides in a DNA strand 3 tRNA anticodons form hydrogen bonds with codons on mRNA

Replication and division of nuclei and cells

Which diagram shows the correct ring structure and a correctly named nucleic acid base?

The microscope in cell studies

Which cell component would be best measured using nanometres?

The microscope in cell studies

Which of the following statements are correct?

Cells as the basic units of living organisms

A DNA fragment that was 18 base pairs in length was examined to determine how many nucleotide bases were in each of the polynucleotide strands. A few of the findings are given below. How many nucleotides containing thymine were found in strand 2?

Structure of nucleic acids and replication of DNA

The diagram presents the nucleotide sequence for a short part of a gene that is transcribed. CGGGCCCCGCGG The table gives the amino acids encoded by 10 mRNA codons. What is the sequence of the four amino acids in the polypeptide translated from this short gene section?

Proteins

During transpiration, where in the leaves does water evaporation take place?

Movement into and out of cells

Water moves through leaf tissues along different pathways because of: • variations in water potential • the pull passed on through cohesive forces between water molecules. The diagram illustrates three pathways along which water can move. Which row correctly shows why water moves through leaf tissues by the different pathways?

Movement into and out of cells

Which factors cause the transpiration rate to increase as temperature rises?

Movement into and out of cells

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

Movement into and out of cells

What changes happen to the water potential and the volume of liquid in the phloem sieve tube element when sucrose is transported from the phloem sieve tube element to an actively dividing shoot tip?

Movement into and out of cells

Which events take place during ventricular systole?

The heart

Which blood components are found in lymph?

Movement into and out of cells

Which organelles are needed to make lysosomes that contain hydrolytic enzymes?

Cells as the basic units of living organisms

Which row shows the correct labels for the diagram illustrated?

Cells as the basic units of living organisms

A rise in carbon dioxide in human blood causes the oxyhaemoglobin dissociation curve to shift to the right. What explains this effect?

Proteins

An individual has two blood tests taken one month apart. For each test, the number of each cell type in a fixed sample volume is counted. What might this indicate about the individual from the findings after one month?

Replication and division of nuclei and cells

Goblet cells occur in the trachea. Which organelles would be present in large numbers in a goblet cell?

Cells as the basic units of living organisms

What is the smallest number of phospholipid layers that one molecule of oxygen crosses as it diffuses from the alveoli, through the cells, to haemoglobin in the red blood cells?

Movement into and out of cells

Which symptoms might be seen in a person who has chronic obstructive pulmonary disease (COPD)?

The microscope in cell studies

A larger number of people face the danger of catching malaria because Anopheles mosquitoes are being distributed more widely. What might have led to this rise?

The microscope in cell studies

An antibiotic prevents cross-links from forming between the molecules that make up bacterial cell walls. Which statements account for bacteria being killed by the antibiotic?

Antibiotics

Which one of these pathogens is able to be spread through the air?

Infectious diseases

The graph illustrates the antibody response after a person is injected first with antigen X and then, at a later time, with antigens X and Y. Which curve represents the primary response to antigen Y?

Antibodies and vaccination

Which features are present in both chloroplasts and mitochondria?

Cells as the basic units of living organisms

Which row gives the description of passive immunity?

Proteins

What kinds of RNA are present in both prokaryotic and eukaryotic cells?

Proteins

Benedict’s solution was used to test a milk sample, and a yellow colour was seen. Which conclusion is correct?

Testing for biological molecules

The diagrams depict four monosaccharides that have the formula $\text{C}_6\text{H}_{12}\text{O}_6$. Which diagram shows $\beta$-glucose?

Carbohydrates and lipids

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

Carbohydrates and lipids

When a small amount of phospholipid is placed in a test-tube containing water and the mixture is shaken strongly, an emulsion is produced with tiny droplets known as liposomes. Which diagram shows how phospholipid molecules are arranged in a cross-section through a liposome?

Fluid mosaic membranes