Oct/Nov 2022

The photomicrograph shows part of a plant cell. What magnification does the cell have?

The microscope in cell studies

Molecule X is a lipid. Which row gives the correct information for molecule X and a triglyceride?

Carbohydrates and lipids

Bread is made with a blend of polypeptides called gluten. Gluten includes two polypeptides, glutenin and gliadin. Which statement describes the tertiary structure of a protein?

Proteins

A student was given two test-tubes: one contained $10\,\text{cm}^3$ of solution P and the other contained $10\,\text{cm}^3$ of solution Q. After the solutions were mixed and left standing for $24$ hours, the concentration of P fell, but the concentration of Q did not change. The student then recorded the following conclusions. 1. P may decompose over time. 2. Q may function as a biological catalyst. 3. P may act as the substrate for Q. Which conclusions could be supported by the evidence?

Mode of action of enzymes

Which statements are correct for the lock and key hypothesis and the induced fit hypothesis of enzyme action?

Mode of action of enzymes

A student studied how enzyme activity rate changed as substrate concentration increased. The investigation was then repeated after a reversible non-competitive enzyme inhibitor had been added. The results were then plotted on a graph. Which graph shows the results of the two experiments?

Factors that affect enzyme action

A cuboidal epithelium cell measures $2\,\mu\text{m}$ in length. This cell is roughly cube-shaped. What is the best estimate for the surface area : volume ratio of this cuboidal epithelium cell?

Cells as the basic units of living organisms

Which statement accurately describes facilitated diffusion and active transport?

Movement into and out of cells

Potato pieces of equal size were put into a test tube and then covered with a sucrose solution. The test tube was left for $30$ minutes, with every other variable kept constant. After $30$ minutes, the potato piece had stayed the same size. What can be concluded from this result?

Movement into and out of cells

How many of the following processes result in genetically identical cells? • increase in the length of plant roots • replacement of dead skin cells in humans • healing of injured muscle tissue • asexual reproduction in coral

Replication and division of nuclei and cells

Which row indicates the correct number of each component in one chromosome at the end of prophase of mitosis?

Chromosome behaviour in mitosis

Which row correctly pairs each organelle with its function?

Cells as the basic units of living organisms

What processes take place during interphase?

Replication and division of nuclei and cells

Embryonic stem cells can keep dividing indefinitely. During successive mitotic cell cycles in embryonic stem cells, what occurs to the telomeres?

Replication and division of nuclei and cells

Which nitrogenous bases are classified as pyrimidines?

Structure of nucleic acids and replication of DNA

DNA replication in bacteria was studied. The bacteria were first cultured in a medium containing only heavy nitrogen, $^{15}\text{N}$, until every bacterial DNA molecule became heavy. The bacteria were then transferred from the heavy nitrogen medium and grown in a medium containing only light nitrogen, $^{14}\text{N}$. This produced the first generation. The bacteria went on to divide again, and a sample was taken from the second generation and the DNA examined. Hybrid DNA is made up of both heavy and light DNA. Which row shows the correct result for the second generation?

Replication and division of nuclei and cells

The base sequence at the beginning of a gene is shown below. TAC CGA CCA CCA CAA CCA CGA... Following transcription, mRNA was then translated by tRNA into amino acids. Analysis of this section of the polypeptide showed the amino acids listed in the table. Ala: 2; Gly: 3; Met: 1; Val: 1 What is the amino acid order in this section of the polypeptide?

Proteins

The table outlines how two antibacterial drugs act and how they can influence protein synthesis. rifampicin: attaches to RNA polymerase streptomycin: leads to mistakes in translation If bacteria are treated with rifampicin and streptomycin, what immediate effects would occur?

Proteins

The electron micrograph presents a cross-section through a leaf vein and a number of cells beside it. Which structure is involved in mass flow through the action of proton pumps?

Movement into and out of cells

The diagrams illustrate some tissue types in plant organs. Which row correctly identifies the tissue types?

Structure of transport tissues

Which statement gives the correct description of xylem vessel elements?

Structure of transport tissues

Which properties of lignin are important for the role of xylem vessels in the stem of a tall plant, such as a tree?

Carbohydrates and lipids

In which places are $80\text{S}$ ribosomes located? 1 within chloroplasts 2 in the cytoplasm of eukaryotes 3 inside mitochondria 4 in the cytoplasm of prokaryotes

Protein synthesis

At 12:00 p.m., which row correctly shows the sucrose concentrations and the water potentials in a source and a sink in a potato plant?

Movement into and out of cells

The diagram illustrates one possible method by which sucrose can be loaded into a sieve tube element. Which stages need ATP?

Movement into and out of cells

Which of the following statements about arteries is correct?

The microscope in cell studies

What occurs during ventricular systole in a mammalian heart?

The heart

If children have too little protein in their diet, this may cause a disease in which excess tissue fluid collects in the abdomen. What accounts for the build-up of excess tissue fluid in this disease?

Movement into and out of cells

Red blood cells can contain a molecule called 2,3-bisphosphoglycerate (2,3-BPG). When 2,3-BPG binds to haemoglobin, a greater partial pressure of oxygen is required to cause 50% saturation of haemoglobin with oxygen. Which statements about the effect of 2,3-BPG are correct?

Proteins

Carbon dioxide is produced continuously by respiring cells. It passes by diffusion into red blood cells and splits into hydrogen ions ($\text{H}^+$) and hydrogen carbonate ions ($\text{HCO}_3^-$). $\text{HCO}_3^-$ then moves out of the cell in exchange for chloride ions ($\text{Cl}^-$) in the chloride shift. What is the role of the chloride shift?

Movement into and out of cells

The photomicrograph displays a cross-section of a bronchus. Which labelled annotation is correct?

The microscope in cell studies

Penicillin is an antibiotic for treating bacterial infections. Which events help to explain how bacteria develop resistance to penicillin?

Mode of action of enzymes

Which statements explain why some vaccines can be swallowed but the tuberculosis (TB) vaccine must be given by injection?

Factors that affect enzyme action

Which characteristic, if found in an organism, allows it to be classified as a prokaryote?

Cells as the basic units of living organisms

A student made the following statements about how monoclonal antibodies are produced. Which statement is incorrect?

Proteins

What is the role of the nucleolus?

Cells as the basic units of living organisms

The diagram presents the outcomes of several tests carried out on a solution of biochemicals. Benedict’s test: blue; non-reducing sugar test: yellow; iodine test: blue-black; biuret test: blue. Which substances are present in the solution?

Testing for biological molecules

Which diagram illustrates the ring form of $\beta$-glucose?

Carbohydrates and lipids

Which row correctly pairs the example with the type of molecule?

Testing for biological molecules

The enzyme $\alpha$-amylase hydrolyses amylopectin, but it cannot hydrolyse certain of its glycosidic bonds. • It hydrolyses only $1,4$ glycosidic bonds. • It cannot hydrolyse the final bond in a chain. • It cannot hydrolyse the bonds in a chain of three units joined by a $1,6$ glycosidic bond to a different chain. Which glycosidic bond is hydrolysed by $\alpha$-amylase?

Mode of action of enzymes

The diagram depicts a stage micrometer, with divisions $0.10\,\text{mm}$ apart, as seen through an eyepiece that contains a graticule. The microscope’s field of view area may be worked out by using the formula $\text{area} = \pi r^2$. Using the information given and taking $\pi$ as $3.142$, a student found the area of the microscope’s field of view. Which answer has been rounded correctly to an appropriate number of significant figures?

The microscope in cell studies

Which of these statements about triglycerides and phospholipids are correct?

Carbohydrates and lipids

Silk moth caterpillars have been genetically modified so that they make a blend of their own silk and the much stronger spider silk from the golden orb web spider. The spider silk polypeptide chain contains many repeating pairs of the amino acids glycine and alanine, organised into a crystalline structure. What is the correct description of the structure of spider silk?

Proteins

Which feature of the tertiary structure of a globular protein allows it to catalyse a metabolic reaction?

Mode of action of enzymes

A student carried out an investigation into how substrate concentration affected enzyme activity. The graph displays the findings. Which factors, if they increased, could cause the enzyme’s activity at point X on the graph to alter?

Factors that affect enzyme action

The Michaelis-Menten constant, $K_m$, is the substrate concentration at which an enzyme operates at half of its maximum rate. Which statement is correct when the $K_m$ value is low?

Mode of action of enzymes

What roles do glycoproteins carry out on the outer surface of a cell surface membrane?

Fluid mosaic membranes

The diagram shows a process in which molecules leave a cell by crossing the cell surface membrane. Which process is this?

Movement into and out of cells

The photomicrograph shows how onion epidermal cells look after being soaked in solution X for one hour. What substance occupies the space labelled Y?

Movement into and out of cells

After many mitotic cell cycles, telomerase stops telomeres from being lost. Which cells must transcribe the telomerase enzyme?

Replication and division of nuclei and cells

Which cell-cycle processes are shown in the diagram?

Replication and division of nuclei and cells

In which part of a cell are cisternae located?

Cells as the basic units of living organisms

A gene contains the instructions for making the protein p53, which attaches to damaged DNA during interphase and stops it from being copied. A carcinogen in cigarette smoke changes the gene that codes for the p53 protein, so the protein is not produced. Which statement explains why this mutation may cause cancer?

Replication and division of nuclei and cells

A microscope was used to examine stained onion cells that were undergoing mitosis. Which row gives the correct statement for mitosis in plant cells?

Chromosome behaviour in mitosis

How many of the following statements about semi-conservative replication of DNA in a eukaryotic cell are true?

Replication and division of nuclei and cells

The part of the polypeptide that codes for the haemoglobin $\beta$-chain contains the following amino acids. - Pro - Glu - Glu - In patients with sickle cell anaemia, the $\beta$-polypeptide chains are mutated. The corresponding part of the mutated polypeptide contains the following amino acids. - Pro - Val - Glu - The table gives the possible anticodons for Val. What is the matching DNA triplet code for the substituted amino acid in the mutated polypeptide?

Proteins

Which diagram correctly shows temporary hydrogen bonding during transcription?

Protein synthesis

The diagram presents a section of the DNA sequence of a gene together with a mutated version of the same gene. normal DNA sequence $\ldots \text{CCG GAT TAT TGC GAG AAA TGG CAT TCT AGG} \ldots$ mutated DNA sequence $\ldots \text{CCG GAT GTA TTG CGA GAA ATG CAT TCT AGG} \ldots$ What are some possible consequences of the mutated sequence?

Proteins

In the electron micrograph, a lengthwise section of part of a plant stem is shown. Identify X.

Structure of transport tissues

Sodium chloride is introduced into a culture solution that contains freshwater single-celled plant cells. What happens to the water potential of the culture solution when the sodium chloride is introduced, and what may happen to the plant cells after $5$ minutes?

Movement into and out of cells

Which statements accurately describe transport pathways in dicotyledonous plants?

Movement into and out of cells

Which statement about how water moves from roots to leaves is not correct?

Movement into and out of cells

Which row correctly matches the cell structures to their functions?

Cells as the basic units of living organisms

Which terms name the process by which water is moved through xylem vessel elements?

Movement into and out of cells

What is the primary role of a companion cell in phloem tissue?

Movement into and out of cells

The photomicrograph displays a blood smear. Which cell is a monocyte?

The immune system

The table gives some information about three blood vessels, P, Q and R, from a mammal. Which row correctly identifies blood vessels P, Q and R?

The microscope in cell studies

Ventricular septal defect (VSD) is a heart defect that can be present from birth. In people with VSD, there is a hole in the wall (septum) separating the left and right ventricles. What might happen in a person with VSD?

The heart

Which statement regarding the structure of the heart is correct?

The heart

What structures are present in the wall of an alveolus in the lungs of a human?

The microscope in cell studies

What functions do cilia have in the gas exchange system?

The gas exchange system

Cholera and tuberculosis are infectious diseases that can spread when people are forced to live in overcrowded conditions. Which strategies would help to control the spread of cholera and tuberculosis?

Infectious diseases

When a person is vaccinated, immunity to some pathogens develops. Which effects of vaccination are correct?

Proteins

Which structures occur in prokaryotes and eukaryotes?

Cells as the basic units of living organisms

A student produced three statements concerning antibodies. Which of the statements are correct?

Proteins

Which molecules occur in all viruses?

Proteins

The table presents the results obtained from tests for biological molecules on four samples, A, B, C and D. Which conclusion is correct?

Testing for biological molecules

The diagrams display some biological molecules. Which biological molecule makes a polymer that has a structural role in plants?

Carbohydrates and lipids

Which molecule is both a disaccharide and a reducing sugar?

Carbohydrates and lipids

The diagram illustrates bonding in a section of a polysaccharide. Which kind of glycosidic bond is present at position X?

Carbohydrates and lipids

The electron micrograph depicts a chloroplast taken from a tobacco leaf. If the chloroplast’s true length along X-Y is $10\,\mu\text{m}$, what magnification does the image have?

The microscope in cell studies

Which characteristics are true for triglycerides and phospholipids?

Carbohydrates and lipids

A scientist investigating a protein’s structure stated that it is made of two polypeptide chains linked by disulfide bonds. Which level of protein structure is being described?

Proteins

When exposed to ultraviolet light, some molecules show fluorescence. If the structure or shape of these molecules changes, the fluorescence intensity can also change. The enzyme tryptophan synthase shows bluish-green fluorescence because of a phosphate group linked with the active site. The enzyme catalyses the reaction shown. $\text{serine} + \text{indole} \rightarrow \text{tryptophan}$ When serine is added to the enzyme, the fluorescence intensity increases, but if indole is then added as well, the bluish-green fluorescence falls in intensity. What conclusion may be drawn from these observations?

Mode of action of enzymes

Yeast contains the enzyme catalase, which speeds up the decomposition of hydrogen peroxide ($\text{H}_2\text{O}_2$) as follows. $2\text{H}_2\text{O}_2 \xrightarrow{\text{catalase}} 2\text{H}_2\text{O} + \text{O}_2$ Yeast was introduced into a hydrogen peroxide solution, and the total volume of oxygen given off was measured every $30$ seconds over $2$ minutes. Every other variable was kept constant. The results are shown in the table. What explains the pattern in the data?

Factors that affect enzyme action

The Michaelis-Menten constant, $K_m$, shows how strongly an enzyme binds to its substrate. Which of the following statements about $K_m$ are correct?

Mode of action of enzymes

Which features are correct for active transport and facilitated diffusion?

Movement into and out of cells

The diagram shows two solutions, P and Q, which were divided by a partially permeable dialysis tubing. What is the initial movement of molecules 1, 2 and 3 between solution P and solution Q?

Movement into and out of cells

A student measured the mass of a cylinder of potato and then placed it in a test-tube that contained a salt solution. After one hour, the potato cylinder was taken out of the salt solution. It was blotted dry and then weighed again. The student observed that the potato had lost mass. Which row gives the correct explanation for the results the student obtained?

Movement into and out of cells

Which row gives the correct number of each component in one chromosome at the beginning of telophase in mitosis?

Chromosome behaviour in mitosis

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

Replication and division of nuclei and cells

The following cell structures are shown. 1. endoplasmic reticulum 2. Golgi body 3. mitochondrion 4. chloroplast Which of these cell structures lack cristae?

Cells as the basic units of living organisms

The diagram represents the epidermis of human skin. It consists of four layers of cells. The cells in each layer carry out particular functions, which are indicated on the diagram. As new cells are formed, they travel upwards in the direction of the arrow. Which row identifies cells acting as stem cells in the skin epidermis and an organelle required by the keratinocytes?

Replication and division of nuclei and cells

The diagram illustrates some of the stages that occur in the cell cycle. Which two stages occur during interphase?

Replication and division of nuclei and cells

Which components make up a nucleotide? 1 an amino acid molecule 2 a codon triplet 3 a nitrogenous-base 4 a sugar molecule

Structure of nucleic acids and replication of DNA

A diagram may be used to show some relationships between different nucleic acid bases. Which row is correct for the words that can be inserted at positions 1-5?

Structure of nucleic acids and replication of DNA

Escherichia coli, a bacterium, divides once every 50 minutes at $36\,^{\circ}\text{C}$. E. coli were cultured in a medium that contained only heavy nitrogen, $^{15}\text{N}$, until every bacterial DNA molecule contained heavy nitrogen. Some of the bacteria were transferred from the heavy nitrogen medium to a medium containing only light nitrogen, $^{14}\text{N}$ (0 minutes). These bacteria then kept reproducing, and samples were taken out and centrifuged at regular times. Hybrid DNA has both heavy and light nitrogen. The diagram displays the possible band positions of DNA at the upper, middle and lower levels. The actual band positions in the first two samples are shown. What proportion of the DNA in the sample taken at 150 minutes will be at the upper position?

Replication and division of nuclei and cells

After translation, the alpha polypeptide chain of haemoglobin, $\alpha$-globin, is altered. In this alteration, the initial amino acid is removed, so that 141 amino acid residues remain. How many nucleotides are present in the mRNA that codes for $\alpha$-globin?

Proteins

The photomicrograph shows a cross-section of a plant organ. Which statement could be used to describe this organ?

The microscope in cell studies

The statements below outline some properties of water. Which of these properties are also important for transport in xylem?

Water

Which xerophytic adaptations lower the water potential gradient between the leaf surface and the atmosphere?

Movement into and out of cells

The diagram illustrates seven stages in the growth of a tulip bulb. Which row shows the correct stages when the tulip bulb functions only as a source or only as a sink?

Carbohydrates and lipids

Which letter shows the cell structures in which mRNA can be found?

Protein synthesis

What changes would occur if mitochondrial activity were inhibited by a metabolic poison acting on cells in the phloem tissue?

Movement into and out of cells

Through which process does sucrose travel in phloem sieve tube elements?

Movement into and out of cells

Which blood vessels transport blood into the atria?

The heart

Which of these statements about the cardiac cycle are correct?

The microscope in cell studies

At a particular stage of the cardiac cycle, the pressure in the right ventricle is less than the pressure in the right atrium and also less than the pressure in the pulmonary artery. Which row is correct?

The heart

Which of the following statements about how haemoglobinic acid is formed are correct?

Proteins

The graph illustrates the dissociation curves for haemoglobin at two different partial pressures of carbon dioxide. At which position on the graph would the greatest number of chloride ions be present in the red blood cells?

Movement into and out of cells

Oedema results from tissue fluid building up around body cells. What would lead to a larger amount of tissue fluid around body cells?

Movement into and out of cells

Some bacteria become resistant to an antibiotic by pumping the antibiotic out of the cell. This stops the antibiotic from accumulating to harmful levels. What must be present in a bacterial cell for it to develop this type of antibiotic resistance?

Movement into and out of cells

Which statements account for the differences between a primary response and a secondary response after exposure to the same antigen?

The microscope in cell studies

Which row correctly describes typical prokaryotic cells and mitochondria?

Cells as the basic units of living organisms

Which of the following statements about B-lymphocytes and T-lymphocytes is correct?

The immune system

Which of the statements is correct?

Cells as the basic units of living organisms

The Benedict’s test and ethanol emulsion test were performed on a sample of biological molecules. During the Benedict’s test, the solution turned brick-red, and in the ethanol emulsion test it became cloudy. Which molecules were present in the sample?

Testing for biological molecules

Which diagram is the correct one for $\alpha$-glucose?

Carbohydrates and lipids

Which reaction shows one correct way that sucrose can be formed?

Carbohydrates and lipids

The diagram shows a section of an alginic acid molecule. Alginic acid is a polymer that occurs in the cell walls of brown seaweeds. Which statement about alginic acid is correct?

Carbohydrates and lipids