Feb/March 2022

Which cell organelles can be seen clearly when a light microscope is used at high power $(\times 400)$?

The microscope in cell studies

Which row presents the characteristics of a carbohydrate polymer located within animal cells?

Carbohydrates and lipids

The statements outline the structure of a polysaccharide present in the cell walls of some plants. Which of the statements are also true of cellulose?

Carbohydrates and lipids

The formula for a saturated fatty acid is $\text{C}_n\text{H}_{2n}\text{O}_2$. Which of these fatty acids would be unsaturated?

Carbohydrates and lipids

What feature allows triglycerides to carry out their roles in living organisms?

Carbohydrates and lipids

The diagrams illustrate three examples of various bonds. Which bonds are able to keep the quaternary structure of proteins joined together?

Proteins

Which row gives the correct description of the primary structure, secondary structure, tertiary structure and quaternary structure of certain proteins?

Proteins

Which relationships could be studied by means of a colorimeter?

Factors that affect enzyme action

Which transport mechanism does not need a concentration gradient to be present for it to occur?

Movement into and out of cells

At high concentrations, ethanol disrupts cell membrane structure because it denatures proteins and increases the distance between neighbouring phospholipid molecules. Consequently, cell membranes may reduce in thickness by as much as $30\%$ and become more permeable. Yeast cells produce ethanol as a waste product of metabolism. When the ethanol concentration in their surroundings rises, yeast cells can increase the tolerance of their cell membrane to ethanol. Which statement correctly explains a response to ethanol that could account for the increase in tolerance of yeast cell membranes to ethanol?

Fluid mosaic membranes

A plant cell was put into pure water during an investigation. At the start, the rate at which water molecules moved into the cell, $R$, was higher than the initial rate at which water molecules moved out of the cell. In a separate investigation, a plant cell of the same type was placed in a solution whose water potential was the same as that of the cell contents. What will happen in the second investigation over a period of five minutes?

Movement into and out of cells

Microvilli and root hairs are distinctive features of certain cell types. Which row correctly identifies some characteristics of a microvillus and a root hair?

Cells as the basic units of living organisms

The protein p53 is made in a cell when DNA has been damaged. It temporarily halts the cell cycle just before DNA is replicated, allowing the DNA to be repaired. In which phase of the cell cycle does this halt take place?

Replication and division of nuclei and cells

In a typical human chromosome, some sections occur in larger numbers than others. Which sections are given in order from the greatest number to the smallest number?

Chromosome behaviour in mitosis

Which row gives the correct description of a stage of mitosis?

Chromosome behaviour in mitosis

The diagram shows a nucleotide with adenine. Which of the following statements about this nucleotide are correct?

Structure of nucleic acids and replication of DNA

Which row is the correct one for the replication of a DNA molecule?

Replication and division of nuclei and cells

Some students were shown a photomicrograph of a cross-section of an unfamiliar material and asked to state what they could observe. They described the cross-section of F as: 1 circular, 2 a hollow tube, 3 spherical. Which descriptions of the cross-section of F correctly state what the students could actually observe?

The microscope in cell studies

The diagram illustrates the relationship between phloem sieve tube elements, xylem vessel elements and companion cells. Which row correctly shows what the numbers 1, 2, 3, 4 and 5 could stand for?

Structure of transport tissues

Why does an air bubble inside a xylem vessel element bring the water flow to a halt?

Movement into and out of cells

What changes in water potential and in the volume of solution inside a phloem sieve tube happen when amino acids are transported from the phloem sieve tube into a sink?

Movement into and out of cells

Which characteristic of some xerophytic leaves lowers the transpiration rate by reducing the water potential gradient between the leaf’s internal surface and the atmosphere?

Movement into and out of cells

This photomicrograph shows a plant cell. The cell measures $25\,\mu\text{m}$ across from X to Y. What magnification does the photomicrograph have?

The microscope in cell studies

The diagram shows a cross-section of a mammalian heart. Which heart chambers are shown by G and H?

The microscope in cell studies

Blood that enters the heart from the vena cava moves past several structures before reaching the lungs. Five structures from this list are shown here: - atrioventricular node - aorta - semilunar valve - left atrium - pulmonary vein - Purkyne tissue - sinoatrial node - pulmonary artery Once these five structures have been placed in the correct sequence for blood flow from the vena cava to the lungs, which structure comes third?

The heart

The bar charts indicate the amounts of endothelial tissue, elastic tissue and muscle tissue present in the walls of three blood vessels, P, Q and R. Which row correctly names the three blood vessels?

Structure of transport tissues

During one cardiac cycle, the highest pressure in each of the four chambers of a healthy human heart was measured. The highest pressures obtained were 3 mm Hg, 10 mm Hg, 25 mm Hg and 120 mm Hg. Which of these values was measured for the right ventricle?

The microscope in cell studies

The graph illustrates how the pressure varies in three structures on the right side of the heart throughout the cardiac cycle. What does the line labelled T show?

The microscope in cell studies

Which statement explains why the walls of the bronchioles contain no cartilage?

The gas exchange system

The photomicrograph shows a transverse section of part of the gas exchange system of a mammal. What does the line labelled V indicate?

The microscope in cell studies

Which characteristic of cholera reduces the transmission of the pathogen Vibrio cholerae?

Movement into and out of cells

Which row indicates the way penicillin kills bacteria?

Movement into and out of cells

Within the hybridoma method, what is cultured by cell culture to make monoclonal antibodies?

Proteins

Which eukaryotic cell structures each contain nucleic acids?

Structure of nucleic acids and replication of DNA

At birth, what kind of immunity does a baby possess?

The microscope in cell studies

Which of the following statements about viruses are correct?

Infectious diseases

What characteristics do prokaryote cells, chloroplasts and mitochondria have?

Cells as the basic units of living organisms

A student used Benedict’s solution to test a sample that is known to contain carbohydrate. When the test was finished, the solution remained blue. Which carbohydrate might be present in the sample?

Testing for biological molecules

Sugars that have a ring form can also exist in a linear form. Which sugar molecules might be shown by the linear structure in the diagram?

Carbohydrates and lipids

Which row correctly pairs each molecule with a bond type that is present?

Carbohydrates and lipids

Table 1.1 presents three of the ways in which dissolved substances can cross cell membranes. It also gives five statements that may or may not describe each of these three processes. Fill in Table 1.1 to indicate which statements apply to each of the three processes shown. Put a tick (✓) where a statement applies, or a cross (✗) where it does not. Every box must contain either a tick or a cross. The first row has already been completed.

Transport mechanisms

Fig. 2.1 shows a cell during one of the key stages of mitosis in the mitotic cell cycle.

Structure of nucleic acids and replication of DNA

Enzymes consist of polymers made from amino acids. Complete Fig. 3.1 so that it shows the general structure of an amino acid.

Protein synthesis

Tuberculosis (TB) remains a major worldwide cause of ill health.

Infectious diseases

Heartbeat is controlled myogenically. This means that the electrical signals setting the pace of a regular heartbeat begin in the heart muscle itself. Atrial fibrillation (AF) is an abnormal heart rhythm that makes the atria contract quickly and irregularly. If AF is left untreated, it can cause a stroke.

The heart

Fig. 6.1 presents a diagram of part of the structure of a DNA molecule.

Protein synthesis

The European hedgehog, Erinaceus europaeus, is a small mammal that eats both plant and animal matter. Its body is covered with spines, which are usually brown. A rare variant, which does not have the brown pigment, has blonde (pale yellow) spines. This characteristic is controlled by a recessive allele. Fig. 1.1 shows a European hedgehog with blonde spines. Alderney is a small island between the UK and France. Hedgehogs were absent from Alderney until the 1960s, when three pairs of hedgehogs were brought onto the island. The hedgehogs began to breed and some of the offspring had blonde spines. By 2017, the hedgehog population, including individuals with brown spines and individuals with blonde spines, had risen to approximately 600.

Natural and artificial selection

Fig. 10.1 illustrates the arrangement of two guard cells.

Control and coordination in plants

Giant axonal neuropathy (GAN) is an uncommon autosomal recessive disorder that affects neurones. Mitochondria are able to move freely inside the axons of neurones. In GAN, the axons of neurones enlarge and become obstructed by the build-up of particular proteins. This stops mitochondria moving freely and interferes with the transmission of action potentials along the axon membrane.

Respiration

People with sickle cell anaemia have red blood cells with a lower capacity for carrying oxygen.

Homeostasis in mammals

Meiosis is a key process that adds to genetic variation within a population. Fig. 4.1 shows one pair of homologous chromosomes in prophase I of meiosis.

Passage of information from parents to offspring

Factor VIII may be produced as a recombinant human protein.

Principles of genetic technology

The banana plant, Musa acuminata, is a tall herbaceous species with very large leaves. An investigation was carried out to find the net carbon dioxide uptake of a banana plant at different light intensities. Fig. 6.1 shows a banana plant. Fig. 6.2 presents the investigation results, with mean net carbon dioxide uptake measured in $\mu\text{mol m}^{-2}\text{s}^{-1}$ plotted against light intensity in lux.

Investigation of limiting factors

During aerobic respiration, ATP is made by substrate-linked reactions and by oxidative phosphorylation.

Respiration

Natural selection and artificial selection (selective breeding) both play major roles in evolutionary change.

Evolution

Describe what is meant by the biological species concept.

Classification