Oct/Nov 2017

Which row gives the correct answer for a typical plant cell?

Cells as the basic units of living organisms

Lysozyme is an enzyme present in tears and saliva. Which statement relates only to the tertiary structure of lysozyme?

Proteins

Certain RNA molecules, known as ribozymes, are able to catalyse reactions in much the same way as protein enzymes. The majority of these ribozymes use other RNA molecules as their substrates and catalyse reactions that cleave particular sugar phosphate bonds in the substrate molecules. Which statements about these ribozymes are correct?

Mode of action of enzymes

The graph illustrates how an enzyme affects a reaction. Which labels are correct?

Mode of action of enzymes

Which of the following statements about non-competitive enzyme inhibitors are correct?

Factors that affect enzyme action

Each of the following is a process that permits substances to move into cells. 1 phagocytosis 2 active transport 3 facilitated diffusion Which processes need ATP?

Movement into and out of cells

The fluidity of the cell surface membrane can be altered by several factors. If the fluidity of cell surface membranes decreases, which process would be affected the least?

Fluid mosaic membranes

The diagram illustrates the cell cycle. In which phase do chromosomes condense and become visible?

Chromosome behaviour in mitosis

Colchicine is a chemical that prevents chromatids from separating during mitosis. A cell is exposed to colchicine. Which stage of mitosis will this cell enter but fail to finish?

Chromosome behaviour in mitosis

The statements below outline the translation process. 1 A peptide bond is formed between neighbouring amino acids. 2 Hydrogen bonds are formed between the anticodon and the codon. 3 mRNA attaches to the ribosome. 4 tRNA moves into the ribosome, carrying a particular amino acid. In what sequence does this process occur?

Proteins

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

Structure of nucleic acids and replication of DNA

An electron micrograph of a cell reveals extensive rough endoplasmic reticulum and numerous Golgi bodies. What type of cell is being viewed?

Cells as the basic units of living organisms

UGU and UGC are codons for the amino acid cysteine, and this amino acid can form disulfide bonds in a polypeptide. UGG is the codon for the amino acid tryptophan, which contains no sulfur atom. UGA functions as a stop signal. The DNA triplet code for the 10th amino acid in a particular polypeptide is ACA. Which single-base substitutions in this triplet code would mean that no disulfide bond is formed with the 10th amino acid in the polypeptide?

Proteins

A student made a table showing the differences between RNA and DNA. There is one error in the table. Which row contains the error?

Proteins

The diagrams display transverse sections of parts of a plant, with some transport tissues numbered 1-6. Which tissues mainly carry water, and which tissues mainly carry sucrose?

Movement into and out of cells

Which feature of plants results in transpiration?

Movement into and out of cells

Mass flow is the movement of substances in bulk from one location to another. How many of the vessels in the list transport fluids by mass flow? • artery • phloem sieve tube • vein • xylem vessel

Movement into and out of cells

The diagram illustrates a xerophytic leaf in two conditions, P and Q. Which statements describe how the cells in layer X differ between conditions P and Q?

Movement into and out of cells

What might increase the rate of transpiration?

Movement into and out of cells

What takes place during ventricular systole in a mammalian heart?

The heart

Which substances are able to displace oxygen from oxyhaemoglobin?

Proteins

The graph illustrates the affinity of haemoglobin for oxygen at two distinct concentrations of carbon dioxide. Which point on the graph indicates the percentage saturation of haemoglobin as it enters the pulmonary artery?

Proteins

Which cell structures are able to produce vesicles?

Fluid mosaic membranes

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

Mode of action of enzymes

How many phospholipid bilayers does oxygen cross when diffusing from an alveolar air space to form oxyhaemoglobin inside a red blood cell in a mammalian lung?

Movement into and out of cells

Which of the following statements about the human gas exchange system are correct?

Movement into and out of cells

A disease harms the walls of the alveoli, making the alveoli rupture. What impact does this have on the gas exchange system?

Movement into and out of cells

Which short-term effects does nicotine have on the cardiovascular system?

The circulatory system

Which statement about tuberculosis (TB) is correct?

Infectious diseases

Which factors lead to measles outbreaks following natural disasters?

Infectious diseases

Which of these statements explain why some vaccines can be taken orally but the tuberculosis (TB) vaccine must be injected?

Antibodies and vaccination

Which means of acquiring immunity is referred to as natural active immunity?

The immune system

Which of the following statements about endocytosis are correct?

Movement into and out of cells

Which collection of measurements is correct?

The microscope in cell studies

The statements are about vaccination programmes for the diseases cholera, measles, smallpox and tuberculosis (TB). Which one of the statements is correct for TB?

Antibodies and vaccination

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

The microscope in cell studies

Which carbohydrate produces a brick-red colour when it is boiled with Benedict’s solution?

Testing for biological molecules

Which two polysaccharides each contain $1,6$ glycosidic bonds and are branched?

Carbohydrates and lipids

Three carbohydrate molecules are displayed. Which two molecules join together to make one molecule of sucrose?

Carbohydrates and lipids

The diagram illustrates the amino acids that make up a polypeptide. An enzyme catalyses the hydrolysis of bonds between polar basic amino acids and non-polar amino acids. How many peptides (chains of amino acids) would be produced as a result of the hydrolysis of this polypeptide?

Proteins

Which equation used to calculate the actual size of a specimen, $A$, the image size, $I$, or the magnification, $M$, is correct?

The microscope in cell studies

The diagram illustrates the structure of the polysaccharide chitin, which is present in the cell wall of fungi. Which statements are correct for chitin and for cellulose?

Carbohydrates and lipids

Which row correctly pairs the functional and structural characteristics of cellulose, collagen, glycogen or triglyceride?

Carbohydrates and lipids

A polypeptide contains $n$ amino acids. How many peptide bonds and R groups (side chains) are present in this polypeptide?

Proteins

What characteristics do triglycerides have?

Carbohydrates and lipids

Which of these statements show the action of an extracellular enzyme?

Mode of action of enzymes

An investigation was conducted in which the enzyme lipase was used to hydrolyse a triglyceride. pH was measured at set intervals throughout the reaction. The findings are shown in the table. At 14 minutes, unreacted triglyceride was still present. What is the explanation for the results after 10 minutes?

Factors that affect enzyme action

Which statement correctly describes how substrate concentration affects enzyme activity?

Factors that affect enzyme action

Which row identifies a correct function of the components of the cell surface membrane?

Fluid mosaic membranes

The graph illustrates how the rate at which substance X enters a cell varies as the concentration of substance X outside the cell rises. The diagram shows a section of a cell surface membrane. Which pathways might substance X use to enter the cell?

Movement into and out of cells

The photomicrographs display cells at different points in the cell cycle. In which stage does semi-conservative replication of DNA occur?

Replication and division of nuclei and cells

The polio virus is among the smallest viruses, with a diameter of about 30 nm. The Mimivirus was identified in 2003 and has a diameter of about 680 nm. The Pandoravirus was identified in 2013 and has a diameter of about 1000 nm. Which row gives the correct match between a cell structure and a virus of a roughly similar size?

The microscope in cell studies

The diagram illustrates the structure of one chromosome. Which row is the correct one?

Chromosome behaviour in mitosis

Cancer cells can undergo many more divisions than most other cells in humans. Which statement about cancer cells is correct?

Replication and division of nuclei and cells

What is the greatest possible number of hydrogen bonds in a DNA length containing 700 nucleotides?

Proteins

Which statements about DNA and RNA are correct?

Structure of nucleic acids and replication of DNA

Two groups of bacteria were cultured in different nitrogen-containing growth media. One group was grown in a medium containing the 'heavy' isotope of nitrogen, $^{15}\text{N}$, until every DNA molecule had become labelled. The other group was grown in a medium containing the 'light' isotope of nitrogen, $^{14}\text{N}$, until every DNA molecule had become labelled. The DNA from each bacterial group was extracted and then centrifuged. The diagram shows where this DNA is located in the centrifuge tubes. Bacteria with $^{15}\text{N}$ labelled DNA were moved to a medium containing $^{14}\text{N}$ and allowed to reproduce once. The DNA from the new generation of bacteria was extracted and centrifuged. Which tube shows the position of the DNA from this new generation of bacteria?

Replication and division of nuclei and cells

The diagram illustrates the nucleotide sequence of a short part of a gene that is transcribed. GCGCGCGGCGCG 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 section of a gene?

Proteins

Which factors help water move through the xylem vessel elements?

Movement into and out of cells

The diagram illustrates a xerophytic leaf under two different conditions, P and Q. Which of the following statements about the cells in layer X of the leaf in conditions P and Q are correct? 1. water potential in P is less negative than in Q 2. the cells may be turgid in P and plasmolysed in Q 3. cells are less turgid in P than in Q 4. there is no net diffusion of water into X in either P or Q

Movement into and out of cells

Which features allow root hair cells to take up mineral ions efficiently? 1. many mitochondria 2. many protein carriers in the cell surface membrane 3. a large surface area to volume ratio

Movement into and out of cells

The cross-sections of two plant organs are illustrated. Which pair of tissues has proton pumps?

Movement into and out of cells

Which cell structures occur in every prokaryotic cell?

Cells as the basic units of living organisms

Measurements taken of the stem of a young tree showed that its diameter changed a little. It became smaller in the daytime and larger at night. Which statement accounts for these observations?

Movement into and out of cells

Which statement concerning the human circulatory system is correct?

The microscope in cell studies

The graph illustrates how the volume of the ventricles changes during the cardiac cycle. At P and R, which valves are open and which are closed?

The heart

Haemoglobin is able to bind to carbon dioxide, carbon monoxide and oxygen. 1. carbon dioxide 2. carbon monoxide 3. oxygen Which of the listed gases use the same binding site?

Proteins

An effective gas exchange system helps to keep the diffusion gradient steep, gives a large total surface area and has a short diffusion distance. Which feature of the human gas exchange system helps to keep the diffusion gradient steep?

Movement into and out of cells

Which of the following statements about bronchioles is correct?

The gas exchange system

In which parts of the human gas exchange system does tar in cigarette smoke directly affect the function of some cell types?

The gas exchange system

Identify the causative agent of smallpox and the way it is transmitted.

The microscope in cell studies

A scientist studied how an antibiotic affected the treatment of cholera. 320 people with cholera were separated into two groups. One group received an antibiotic, whereas the other group was not given antibiotics. Both groups were supplied with fluids containing sugars and mineral salts (oral rehydration therapy). The scientist noted the number of days for which each person had diarrhoea. The results are shown in the table. antibiotic and oral rehydration therapy: 3.2 days oral rehydration therapy: 5.3 days Calculate the percentage decrease in the mean time that a person suffered from diarrhoea when they were treated with the antibiotic.

Movement into and out of cells

Which order of events happens during an immune response? 1 formation of plasma cells 2 mitosis of B-lymphocytes 3 recognition of non-self antigens 4 secretion of antibodies

Replication and division of nuclei and cells

The electron micrograph shows a section of an animal cell. Which substance is this cell likely to synthesise in large amounts?

Protein synthesis

An influenza vaccine may be produced by cultivating the viruses in chicken eggs. The viruses are then taken out of the eggs in liquid form and inactivated. After purification, the egg extract that contains the viruses is used as the vaccine. What side-effect can this vaccine cause in some people?

Proteins

Mitochondria are believed to have originated from prokaryotic cells that were taken in by an ancestral cell. Which feature did the prokaryotes lose as they evolved into mitochondria?

Cells as the basic units of living organisms

Which statement is the correct one?

Cells as the basic units of living organisms

A student performed four biological molecule tests on a milk sample. The tests and outcomes were: heating to 80^{\circ}C with Benedict’s solution produced a brick red colour. Adding Biuret solution produced a purple colour. Adding iodine solution produced an orange colour. Boiling with acid, then neutralisation, then heating to 80^{\circ}C with Benedict’s solution produced a brick red colour. Which biological molecules must be present in the milk?

Testing for biological molecules

Which features enable a cellulose molecule to carry out its function?

Carbohydrates and lipids

Maltose and sucrose are two disaccharides. Maltose is made from two glucose molecules, whereas sucrose is made from fructose and glucose. Which row gives the molecular formulae of these two disaccharides?

Carbohydrates and lipids

Which statement concerning the light microscope is correct?

The microscope in cell studies

A person who has diabetes cannot produce a sufficient amount of the protein insulin. Some types of diabetes may be treated with insulin made by animals. Scientists compared the amino acids in animal-produced insulin with those in human insulin. Which level of protein structure were the scientists investigating?

Proteins

The diagrams illustrate four fatty acids, and each contains a chain of 18 carbon atoms. Which fatty acid would, when included in a phospholipid molecule, make the greatest contribution to the fluidity of a cell surface membrane?

Fluid mosaic membranes

Disulfide bonds help preserve which levels of protein structure?

Proteins

An investigation was carried out to examine how temperature affects the activity of the enzyme β-glucosidase. The enzyme was examined both in solution (free) and after being immobilised in alginate beads. The results are presented in the graph below. Which statement about the effect of immobilisation of β-glucosidase is correct?

Factors that affect enzyme action

An investigation was done to find out how increasing the concentration of substrate molecules affects the rate of an enzyme-catalysed reaction. All other variables were kept standardised. Which statement is correct?

Factors that affect enzyme action

Which characteristics are correct for a competitive inhibitor in an enzyme-catalysed reaction?

Mode of action of enzymes

Liver cells have membrane-bound organelles known as peroxisomes, and these contain the enzyme catalase. Catalase breaks down hydrogen peroxide into water and oxygen gas. A student took two liver pieces of identical size and kept one in a refrigerator at $5\,^{\circ}\text{C}$ and the other in a freezer at $-18\,^{\circ}\text{C}$. After 12 hours, both pieces were returned to room temperature and then placed in equal volumes of hydrogen peroxide. The liver that had been kept at $-18\,^{\circ}\text{C}$ gave off oxygen bubbles more quickly than the liver that had been kept at $5\,^{\circ}\text{C}$. Which statement explains why the liver that had been at $-18\,^{\circ}\text{C}$ produced bubbles of oxygen more rapidly than the liver that had been at $5\,^{\circ}\text{C}$?

Factors that affect enzyme action

Which of these processes allows movement in both directions across cell surface membranes?

Movement into and out of cells

The diagram illustrates an experiment where two separate cell surface membranes were fused to make one larger membrane. The outer face of one membrane carried protein P molecules, while the outer face of the other membrane carried protein Q molecules. The locations of the two proteins in each membrane were recorded immediately before fusion and again 1 hour later. Which statements are correct?

Fluid mosaic membranes

Which row gives the correct description of osmosis across a cell surface membrane?

Movement into and out of cells

The diagram depicts a stage micrometer scale seen through an eyepiece graticule at a magnification of $\times 200$. At this same magnification, a chloroplast measures $4$ eyepiece graticule divisions in length. What is the length of the chloroplast?

The microscope in cell studies

What does the term telomere describe?

Chromosome behaviour in mitosis

When cell division is uncontrolled, tumours can form. Which statement is correct for tumour cells only?

Replication and division of nuclei and cells

Which of these events occur during mitosis?

Chromosome behaviour in mitosis

Rifampicin is an antibiotic used for treating tuberculosis. It acts by blocking RNA polymerase in bacteria. Which of the following processes are prevented by this antibiotic?

Mode of action of enzymes

A gene specifies the amino acid sequence in one polypeptide. Haemoglobin is composed of two α-globins and two β-globins. How many genes are required to code for one haemoglobin molecule?

Proteins

A change involving one nucleotide in an allele of the gene that codes for haemoglobin produces sickle cell haemoglobin. For normal haemoglobin, the mRNA base sequence for three amino acids is shown as CCUGAAGAG. For sickle cell haemoglobin, the mRNA base sequence is shown as CCUGUAGAG. The table lists some of the triplet codes for two amino acids. Which row gives the correct substituted DNA nucleotide in the allele and the substituted amino acid in the protein?

Proteins

What is the lowest number of hydrogen bonds in a DNA segment containing 700 base pairs?

Proteins

The photomicrograph shows a cross-section through a plant organ. Which label indicates the xylem vessels?

The microscope in cell studies

Which of the following statements accurately describe transport pathways in dicotyledonous plants?

Movement into and out of cells

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

Movement into and out of cells

A cell was given cytosine containing radioactive carbon. In which cell structure would radioactivity be detected first?

Replication and division of nuclei and cells

Amino acids are transported from a phloem sieve tube element into a root cell. Which changes in water potential and in the volume of liquid inside the phloem sieve tube element are correct?

Movement into and out of cells

The table gives the amount of water absorbed during a 10 minute interval for two plant species, X and Y. The two plants were investigated simultaneously, in the same room, and with identical potometers. A student decided that Y was a xerophyte, so it lost less water. Which aspect of the experiment might cast doubt on this conclusion?

Movement into and out of cells

During left ventricular systole, what occurs?

The heart

The photograph depicts blood cells viewed with a high power light microscope. Which row correctly gives the different types of white blood cell?

The microscope in cell studies

Which of these processes contribute to the Bohr shift?

Proteins

In the photomicrograph, a cross-section of a bronchus is shown. What function do tissues X and Y carry out?

The gas exchange system

Which flow diagram correctly shows the impact of tar entering the lungs?

The gas exchange system

The antibiotic penicillin stops cross-links forming between peptidoglycans during bacterial cell wall synthesis by inhibiting the enzyme transpeptidase. Which statements describe how penicillin acts on bacteria?

Mode of action of enzymes

Which pathogens are transmitted by droplet infection?

Infectious diseases

The flow diagram illustrates the events that occur after a T-lymphocyte is activated by attaching to antigens on an infected cell. Which row correctly names X, Y and Z?

Fluid mosaic membranes

The diagram illustrates some similarities among chloroplasts, mitochondria and typical prokaryotes. Which row is the correct one?

Cells as the basic units of living organisms

Smallpox was eliminated from the human population through a global prevention programme. Which kind of immunity was induced in people who were given treatment as part of this programme?

Antibodies and vaccination

Which statement provides evidence that mature plant cells can perform the same function as lysosomes?

Cells as the basic units of living organisms

A student performed four biological molecule tests on a milk sample. The tests and outcomes were: heating to $80^{\circ}\text{C}$ with Benedict’s solution produced a green colour; adding Biuret solution produced a purple colour; adding iodine solution produced an orange colour; boiling with acid, then neutralising, and afterwards heating to $80^{\circ}\text{C}$ with Benedict’s solution produced a brick red colour. Which conclusion drawn from these results is correct?

Testing for biological molecules

The diagrams display four monosaccharides with the formula $\text{C}_6\text{H}_{12}\text{O}_6$. Which diagrams represent glucose molecules?

Carbohydrates and lipids

In the breakdown of one glycogen molecule, which bonds are broken?

Carbohydrates and lipids

The diagram illustrates the amino acids arranged in a polypeptide. An enzyme speeds up the hydrolysis of any peptide bond linking a non-polar amino acid with any polar amino acid. How many small peptides and single amino acids are produced by this enzyme?

Proteins