May/June 2012

Which set of structures can be seen in an appropriately stained plant cell with a high power ($\times 400$) light microscope?

The microscope in cell studies

Which level of protein structure preserves the globular forms of enzymes?

Proteins

Which substances are composed of carbon, hydrogen, oxygen and nitrogen?

Proteins

The graph illustrates how a reaction proceeds with and without an enzyme. What is the activation energy of the reaction when the enzyme is present?

Mode of action of enzymes

Catalase is an enzyme that speeds up the breakdown of hydrogen peroxide into water and oxygen. Two students investigated how enzyme concentration affects the rate of reaction of catalase. They predicted that their results would follow the same pattern. The graphs display the rates measured by each student. Which statement accounts for the different pattern shown by student 2’s results?

Factors that affect enzyme action

The diagram illustrates the fluid mosaic model of membrane structure. Which feature would allow a hormone to identify its target cell?

Fluid mosaic membranes

Which one of the following ways of moving substances across cell surface membranes allows movement in both directions?

Movement into and out of cells

The graphs illustrate the rate at which sugars are absorbed by a culture of animal cells under a range of conditions. How is the sugar absorbed by the cells when air is bubbled through the culture?

Movement into and out of cells

In organisms that reproduce sexually, a reduction division takes place before fertilisation. Which reasons explain why this is needed?

Replication and division of nuclei and cells

What happens during metaphase of mitosis?

Chromosome behaviour in mitosis

What conditions are present in a human cell immediately before it enters prophase?

Replication and division of nuclei and cells

Which structures are always found in prokaryote cells?

Cells as the basic units of living organisms

Which statement explains a process that happens during protein synthesis?

Proteins

In eukaryotic cells, during semi-conservative replication of DNA, these events take place. Which option gives the correct sequence for some of the events?

Replication and division of nuclei and cells

A double-stranded DNA segment contains 120 nucleotides and codes for polypeptide X. What is the greatest possible length of polypeptide X?

Proteins

During transpiration, from which part does water evaporate?

Movement into and out of cells

The diagram illustrates a model used to show the mass flow hypothesis of translocation. 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

The graph illustrates stomatal opening and closing in the leaves of a species of Pelargonium over a 24 hour period. What conclusion can be drawn?

Movement into and out of cells

When transpiration is occurring at its highest rate, tree trunks become smaller in diameter. Which statement accounts for this?

Transport mechanisms

Which statement describes how mass flow develops in sieve tube elements?

Movement into and out of cells

The graph illustrates the pressure in three regions of the heart over one cycle. At $0.2\ \text{s}$, which region of the heart is reacting to the excitatory stimulus?

The heart

Each group of graphs shows data for blood vessels in the order: artery, arterioles, capillaries, venules, veins. Which group is correct?

The circulatory system

All of the items below are characteristics of eukaryotic cells. 1 chloroplast 2 endoplasmic reticulum 3 lysosome 4 mitochondrion 5 nucleus Which of these possess a double membrane?

Cells as the basic units of living organisms

A rise in carbon dioxide concentration within human blood causes the oxyhaemoglobin dissociation curve to move to the right. Why does this happen?

Proteins

Which statement is correct regarding the affinity of haemoglobin for the gases carbon dioxide, carbon monoxide and oxygen?

Proteins

The photomicrographs display cross-sections of arteries taken from a non-smoker and a smoker. Using the evidence shown above, which disease is most likely to develop in the smoker?

Carbohydrates and lipids

Which structures would be visible in an electron micrograph of a bronchus wall?

The gas exchange system

Which cells do memory cells form during the immune response?

The immune system

Which of the following raises the chance of catching cholera?

Infectious diseases

Which statement best characterises a T-helper lymphocyte?

The immune system

Antibodies can protect the body from pathogenic bacteria in several different ways. Which event would not take place after antigen-antibody binding?

Proteins

What does the ecological term community mean?

Cells as the basic units of living organisms

The table presents the findings from a field study of four species in a woodland food chain. What is the pathway of energy flow in the food chain?

Transport mechanisms

The photomicrograph has a magnification of $\times 4000$. What is the real size of the nucleolus?

The microscope in cell studies

The diagram illustrates how energy moves through an ecosystem. Photosynthesis is the gross productivity. Producers lose some energy through respiration, and the energy that remains is the net productivity. This may also be written as an equation: $\text{net productivity} = \text{gross productivity} - \text{respiration}$ Some of the net productivity is transferred to herbivores. Which calculation shows the proportion of net productivity transferred to herbivores?

Cells as the basic units of living organisms

A microscope can resolve details down to $200\,\text{nm}$. Which of the following organelles would not be resolved by this microscope?

The microscope in cell studies

Samples taken from a combination of biological molecules were tested. After iodine in potassium iodide solution had been added to one sample, the mixture changed to black. The biuret test was then done on a different sample, and the mixture became purple. Which biological molecules were present in the mixture?

Testing for biological molecules

Which statement concerning polysaccharides can describe both amylopectin and cellulose? 1 neighbouring glucose molecules are rotated through $180^\circ$ 2 features $1,4$ glycosidic bonds 3 polymer formed from $\alpha$-glucose

Carbohydrates and lipids

In the key, which molecule is sucrose?

Carbohydrates and lipids

Which molecules below have structural formulae that include C=O bonds? 1 fatty acids 2 glucose 3 glycerol

Carbohydrates and lipids

Which size range would encompass most eukaryotic cells?

Cells as the basic units of living organisms

Which carbohydrate produces a brick-red colour when heated with Benedict’s solution?

Testing for biological molecules

The diagram depicts two molecules of glucose. Four possible bonding sites are marked p, q, r, and s, and t, u, v, w. During condensation of these two molecules as a glycogen molecule is formed, at which positions could bonds be made?

Carbohydrates and lipids

Which graph shows the pattern of change in the concentration of a substrate and its product in the same enzyme-catalysed reaction?

Mode of action of enzymes

Glucose in urine may be identified by means of a biochemical test. If the end of a test strip coated with the enzyme glucose oxidase is placed into urine, the appearance of a blue colour shows that glucose is present. This test is dependable and can be done at home by people with diabetes. Which characteristic of the enzyme makes this test so dependable?

Mode of action of enzymes

What function does cholesterol have in the cell surface membrane?

Fluid mosaic membranes

The processes listed below are all ways in which substances may enter a cell. 1 endocytosis 2 facilitated diffusion 3 osmosis Which of these processes are passive?

Movement into and out of cells

The diagram illustrates the water potential of three neighbouring plant cells (top cell $-1200\ \text{kPa}$, bottom left cell $-800\ \text{kPa}$, bottom right cell $-1000\ \text{kPa}$). From which directions will net movement of water by osmosis occur?

Movement into and out of cells

The following events all occur during mitosis. 1 centromeres split 2 chromatids travel to opposite poles of the cell 3 chromosomes arrange along the equator of the spindle 4 chromosomes uncoil 5 two chromatids are linked by a centromere What is the correct sequence for these events?

Chromosome behaviour in mitosis

The diagram illustrates the cell cycle. If radioactive nucleotides are added to cells that are dividing, at what stage will they be incorporated into the chromosomes?

Replication and division of nuclei and cells

What does the process of transcription need?

Proteins

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

The microscope in cell studies

A peptide is made up of ten amino acids belonging to four distinct types. What is the theoretical minimum number of different tRNA molecules needed to translate the mRNA for this peptide?

Proteins

Which of the following statements about tRNA structure are correct?

Proteins

Which statements explain why a large animal has needed to develop a transport system?

Movement into and out of cells

Which row correctly names the tissue that has the Casparian strip and the molecule that makes up this strip?

Movement into and out of cells

Which of the following are part of the apoplast pathway?

Movement into and out of cells

Which statement accounts for why a tree’s circumference (girth) is smaller in the middle of the day than it is at night?

Movement into and out of cells

Sucrose is carried dissolved in the phloem of plants. Movement occurs from sources to sinks. This process relies on differences in hydrostatic pressure between the sources and the sinks. Which tissues act as a source or a sink, and what are the hydrostatic pressures at X and Y inside the phloem?

Movement into and out of cells

Which of the following can be found in all blood vessels, lymph and tissue fluid?

Movement into and out of cells

The diagram illustrates the Bohr effect. What brings about the change from X to Y?

Proteins

The graph illustrates how pressure varies in different regions on the left side of the heart during one cardiac cycle. Which row shows the pressure changes in each part of the heart?

The heart

Which structure occurs in every eukaryotic cell but is absent from prokaryotic cells?

Cells as the basic units of living organisms

Stroke volume is the amount of blood ejected by each contraction of a ventricle. Ventricular end-diastolic volume is the quantity of blood in the ventricle immediately before systole. Which graph shows how stroke volume is related to ventricular end-diastolic volume?

The heart

Which constituent of tobacco smoke results in higher blood pressure?

The circulatory system

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

The gas exchange system

What features would be observable in a photomicrograph of the wall of the trachea?

The gas exchange system

To help prevent a disease, dead bacteria can be injected into the body. What kind of immune response is generated?

Antibodies and vaccination

The graph indicates the amount of antibody produced in response to an antigen. Based on the graph, which statement is correct?

Proteins

Which two of the diseases listed below are caused by viruses?

Infectious diseases

Cholera is now uncommon in many countries. What explains this?

Infectious diseases

The diagram illustrates a food web. How many trophic levels are shown in the food web?

Infectious diseases

What function do decomposers serve in the nitrogen cycle?

Movement into and out of cells

What factor limits the resolution of the light microscope?

The microscope in cell studies

Why was just $4\%$ of the sunlight’s energy able to be fixed by producers in photosynthesis?

Cells as the basic units of living organisms

The diagram shows an electron micrograph of virus particles inside a human nucleus. What is the diameter of the virus particles that are labelled?

The microscope in cell studies

A student performed a set of tests on an extract from a plant. The table displays the results of these tests. Which row indicates the molecules present in the plant extract?

Testing for biological molecules

Glycogen is a polymer made from glucose. Which description best outlines its structure?

Carbohydrates and lipids

Which molecules have $\text{C}=\text{O}$ bonds?

Carbohydrates and lipids

Which statement about polysaccharides can be applied to both amylose and amylopectin?

Carbohydrates and lipids

What is the ecological meaning of the term community?

The microscope in cell studies

Which one of the following means of transporting substances across cell surface membranes permits movement in both directions?

Movement into and out of cells

The graphs illustrate the rate at which sugars are taken up by a culture of animal cells under various conditions. How are the sugars taken up by the cells when air is bubbled through the culture?

Movement into and out of cells

Which molecule in the key represents sucrose?

Carbohydrates and lipids

Samples taken from a combination of biological molecules were tested. After iodine in potassium iodide solution was added to one sample, the mixture became black. A different sample was then tested using the biuret test, and the mixture turned purple. Which biological molecules were present in the mixture?

Testing for biological molecules

Which statement about polysaccharides could be applied to both amylopectin and cellulose?

Carbohydrates and lipids

Which substances are made up of carbon, hydrogen, oxygen and nitrogen?

Proteins

Which molecules have structural formulas that include C=O bonds?

Carbohydrates and lipids

Which level of protein structure is responsible for preserving the globular shapes of enzymes?

Proteins

Catalase is an enzyme that speeds up the conversion of hydrogen peroxide into water and oxygen. Two students investigated how enzyme concentration affects the reaction rate of catalase. The students predicted that their results would display the same pattern. The graphs show the rates measured by each student. Which statement explains the different pattern shown by student 2’s results?

Factors that affect enzyme action

The graph illustrates the course of a reaction with and without an enzyme present. What is the activation energy for the reaction when the enzyme is present?

Mode of action of enzymes

The table presents the findings from a field study involving four species in a food chain within a woodland area. What is the energy flow in the food chain?

Transport mechanisms

In organisms that reproduce sexually, a reduction division takes place before fertilisation. Which reasons account for this requirement?

Replication and division of nuclei and cells

What happens during metaphase of mitosis?

Chromosome behaviour in mitosis

What is the state of a human cell immediately before it enters prophase?

Replication and division of nuclei and cells

A double-stranded DNA molecule contains $120$ nucleotides and encodes polypeptide X. What is the maximum possible length of polypeptide X?

Proteins

Which statement refers to a process that takes place during protein synthesis?

Proteins

In semi-conservative replication of DNA in eukaryotic cells, these processes take place. Which option gives the correct sequence of some of them?

Replication and division of nuclei and cells

Where does water evaporate from during transpiration?

Movement into and out of cells

When transpiration is occurring at its highest rate, the diameters of tree trunks become smaller. Which statement explains this?

Movement into and out of cells

The graph illustrates stomatal opening and closing in the leaves of a species of Pelargonium over a $24$ hour period. What conclusion can be drawn?

Movement into and out of cells

Which statement describes how mass flow develops in sieve tube elements?

Movement into and out of cells

The diagram illustrates how energy moves through an ecosystem. Gross productivity is shown by photosynthesis. Producers use some energy in respiration, and the energy remaining is the net productivity. This may also be written as the equation: net productivity = gross productivity - respiration. A fraction of the net productivity is transferred to herbivores. Which calculation shows the fraction of net productivity transferred to herbivores?

The microscope in cell studies

The diagram presents a model used to illustrate the mass flow hypothesis of translocation. In a plant, what are the structures W, X, Y and Z, and in which direction does the solution flow along W?

Movement into and out of cells

Which one of the following raises the risk of catching cholera?

Infectious diseases

Which cells turn into memory cells in the immune response?

The immune system

Which statement describes a T-helper lymphocyte?

The immune system

Antibodies can protect the body against pathogenic bacteria in several different ways. Which event would not happen after antigen-antibody binding?

Proteins

The graph illustrates the pressure in three regions of the heart during one cycle. At $0.2\,\text{s}$, which section of the heart is responding to the excitatory stimulus?

The heart

For each graph set, the data are arranged for blood vessels in this order: artery → arterioles → capillaries → venules → veins. Which set is correct? The variables plotted are total cross-sectional area, velocity, wall thickness, and pressure.

The microscope in cell studies

Which statement is correct about haemoglobin’s affinity for the gases carbon dioxide, carbon monoxide and oxygen?

Proteins

An increase in carbon dioxide in human blood causes the oxyhaemoglobin dissociation curve to move to the right. What explains this effect?

Proteins

What would an electron micrograph of a bronchus wall show?

The microscope in cell studies

Which structures are always found in prokaryote cells?

Cells as the basic units of living organisms

The photomicrographs display transverse sections of arteries taken from a non-smoker and from a smoker. Using the evidence shown above, which disease is most likely to develop in the smoker?

The circulatory system

All of the following are features of eukaryotic cells. Which of them are surrounded by a double membrane?

Cells as the basic units of living organisms

Which set of structures can be seen in a plant cell that has been suitably stained when a high power (\times400) light microscope is used?

The microscope in cell studies

A microscope has a resolution of $200\ \text{nm}$. Which organelle from the options below would not be resolved by this microscope?

The microscope in cell studies

The magnification of the photomicrograph is \times4000. What is the real size of the nucleolus?

The microscope in cell studies

The diagram illustrates the fluid mosaic model of membrane structure. Which feature would allow a hormone to recognise its target cell?

Fluid mosaic membranes