Feb/March 2017

The diagram illustrates the ultrastructure of a typical animal cell. Which structure synthesises and moves lipids?

Cells as the basic units of living organisms

The molecules present in animal tissues can be arranged into three groups. 1 glucose, cholesterol, triglycerides, water 2 glycogen, antibodies, adenine, phospholipids 3 haemoglobin, carbon dioxide, mRNA, monosaccharides Which of these groups contain one or more molecules that always have nitrogen atoms?

Proteins

Haemoglobin is made up of two $\alpha$ chains and two $\beta$ chains. About $5\%$ of all humans have a change in one amino acid in the $\beta$ chain, which alters the structure and stability of haemoglobin. Which levels of protein structure could be affected in the haemoglobin of these humans?

Proteins

Which row shows the correct description of both a collagen molecule and a collagen fibre?

Proteins

The structures of two amino acids are shown in the diagrams; each one contains two amine ($-\text{NH}_2$) groups. A peptide bond is made between these two amino acids. Which groups could make the peptide bond?

Proteins

An enzyme was mixed with a slight excess of its substrate. Every variable was held constant. A student had to draw a graph showing how the concentration of the enzyme-substrate complex varies with time. Which graph represents this accurately?

Mode of action of enzymes

The table shows data gathered by a student during an investigation into how temperature affects an enzyme-catalysed reaction. All other variables were kept constant. What is the correct conclusion?

Factors that affect enzyme action

Which range of measurements is correct for the width of the cell surface membrane?

Fluid mosaic membranes

Beetroot root cells contain a red pigment. If small pieces of root tissue are placed in cold water, some of the red pigment escapes from the cells into the water. An experiment was performed to examine how temperature affects the amount of red pigment lost from the root cells. It was observed that as the water temperature increased, the rate at which red pigment left the root cells also increased. Which of the following statements could account for this pattern?

Fluid mosaic membranes

The cell surface membrane has been described as a ‘fluid mosaic’. Which statement describes the ‘mosaic’ part of the cell surface membrane?

Fluid mosaic membranes

The diagram illustrates two routes, X and Y, by which molecules can diffuse across a cell surface membrane. Which row correctly indicates the possible routes for lipids, water and glucose?

Movement into and out of cells

A light microscope is used to view two structures separated by $200\ \text{nm}$. What is the distance between the structures when the magnification changes from $\times 40$ to $\times 400$?

The microscope in cell studies

Some stem cells undergo division and produce phagocytes. In which part of the human body do these stem cells divide?

Replication and division of nuclei and cells

Which is the correct order of the stages in the mitotic cell cycle?

Replication and division of nuclei and cells

Telomerase is an enzyme that maintains telomeres. It prevents telomeres from becoming shorter each time a chromosome is replicated. In human body cells, telomerase is usually inactive, although it can be switched on in some diseases. In which disease is the enzyme telomerase activated?

Replication and division of nuclei and cells

The statements refer to events in the mitotic cell cycle. Which is the correct sequence for three of these events in the mitotic cell cycle?

Replication and division of nuclei and cells

Which statement concerning nitrogenous bases is correct?

Structure of nucleic acids and replication of DNA

Rifampicin is an antibiotic used for treating tuberculosis. Its action is to block RNA polymerase in bacteria. Which of the following processes would be directly blocked by this antibiotic?

Proteins

Meselson and Stahl carried out an investigation on DNA in bacteria. First, they cultured the bacteria in a medium containing only heavy nitrogen, $^{15}\text{N}$, until every bacterial DNA molecule had heavy nitrogen only. The bacteria were then transferred out of the heavy-nitrogen medium and grown in a medium containing only light nitrogen, $^{14}\text{N}$. Samples of bacteria were taken from each of the next three generations and the DNA was examined. Hybrid DNA has both heavy and light nitrogen. Which row indicates the correct DNA for the first and third generations?

Replication and division of nuclei and cells

The diagram illustrates the stages involved in producing part of a polypeptide. DNA nucleotide sequence (template strand): $\text{TACGACAATCGC}$. mRNA sequence: $\text{AUGCUGUUAGCG}$. Amino acid sequence: met leu leu ala. Which feature of the triplet code is shown by the information provided?

Proteins

Which combination of features is typical of a phloem sieve tube element as it unloads into a sink?

Movement into and out of cells

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

Movement into and out of cells

The diagram illustrates a stage micrometer scale as seen through an eyepiece that contains a graticule. Each of the smaller divisions on the stage micrometer scale measures $0.1\ \text{mm}$. A slide of a plant cell is used instead of the stage micrometer scale. What is the length of the nucleus in the plant cell?

The microscope in cell studies

The diagrams illustrate transverse sections of parts of a plant. Which labelled structures are responsible for transporting mineral ions?

Structure of transport tissues

Which characteristic of transport in plants is true for both xylem and phloem?

Movement into and out of cells

What is the chief function of a companion cell in phloem tissue?

Movement into and out of cells

The heart’s contraction is synchronised by electrical impulses moving through the cardiac muscle. What is the correct order for part of the sequence of these impulses?

Movement into and out of cells

As blood moves from an artery to a vein, the wall thickness of the vessels changes. Which bar chart shows these changes correctly?

The microscope in cell studies

The graph displays the oxygen dissociation curves of haemoglobin taken from two mammal species, S and T. Which statements might account for the difference between the oxygen dissociation curves of species S and species T?

Proteins

Which tissues might be present in bronchioles?

The gas exchange system

Which of the following statements could describe the effect of carbon monoxide in cigarette smoke?

Proteins

The table shows the worldwide mortality figures for some diseases in 2002. How many millions of people died from the viral diseases named in the table in 2002?

Infectious diseases

Which statement could apply to both B-lymphocytes and T-lymphocytes?

The immune system

Some cell features are shown below. 1 cytoplasm 2 cell surface membrane 3 ribosomes Which of these features are present in both animal and prokaryotic cells?

Cells as the basic units of living organisms

People G and H each received an injection intended to protect them from a specific pathogen. One of them was given antibodies by injection. The other was given a vaccine by injection. The graph shows how the concentration of the antibody against this pathogen in the blood of G and H changes during the 20 days after the injection. Which row gives the correct description of the type of immunity shown by G and H?

Proteins

What size ribosomes are present in chloroplasts?

Protein synthesis

Within which of these organelles is ATP produced?

Cells as the basic units of living organisms

A milk sample is heated with Benedict’s solution. Once boiling has occurred, a yellow colour is seen. Which conclusion is correct?

Testing for biological molecules

The table presents some information about carbohydrate polymers. Which row refers to amylose?

Carbohydrates and lipids

Which table row concerning $\alpha$-glucose and $\beta$-glucose molecules is correct?

Carbohydrates and lipids

Fig. 1.1 shows a diagram of a chromosome taken from a dividing cell.

Structure of nucleic acids and replication of DNA

Cholera is an infectious disease brought about by a bacterium.

Structure of nucleic acids and replication of DNA

Catalase is an enzyme that speeds up the decomposition of hydrogen peroxide, a toxic waste product of metabolism. The reaction is $2\text{H}_2\text{O}_2 \xrightarrow{\text{catalase}} 2\text{H}_2\text{O} + \text{O}_2$. Fig. 3.1 presents the findings of an investigation into how hydrogen peroxide concentration affects the rate of the catalase-controlled reaction, both in the absence of inhibitors and in the presence of two different inhibitors.

Structure of nucleic acids and replication of DNA

In both plants and mammals, transport systems work to move substances into and out of cells.

The heart

Smooth muscle and cartilage are two of the tissues present in the walls of structures in the mammalian gas exchange system. Complete Fig. 5.1 to indicate how these tissues are distributed in the gas exchange system of mammals. Select from the four structures listed below: alveolus, trachea, bronchus, bronchiole.

The gas exchange system

A student carried out an investigation into how altering the surface area to volume ratio affects diffusion. Two agar blocks of different sizes, X and Y, were prepared. The agar included Universal Indicator solution. Universal Indicator solution changes colour when acid is added. The blocks were then put into dilute hydrochloric acid at the same temperature. The student recorded how long each block took to become completely colour-changed. Blocks X and Y are shown in Fig. 6.1. All dimensions are in cm.

Transport mechanisms

Fig. 1.1 contains nephron diagrams taken from the kidneys of three mammals, P, Q and R. Each one has been drawn to the same scale.

Homeostasis in mammals

Describe the core principles of the polymerase chain reaction (PCR).

Principles of genetic technology

An athlete carries out aerobic respiration while taking part in a sporting event.

Respiration

One example of chemical control and co-ordination in plants is the breakdown of stored food reserves during the germination of cereal grains such as wheat.

Control and coordination in plants

An experiment was done to find the photosynthesis rate at a range of carbon dioxide concentrations. The two plants, barley and sugar cane, were investigated at two temperatures, $10^\circ\text{C}$ and $25^\circ\text{C}$. The results are presented in Fig. 4.1.

Investigation of limiting factors

The foxglove, \textit{Digitalis purpurea}, is a plant commonly found in many regions of the world. Fig. 5.1 shows a foxglove. In foxgloves, flower colour is determined by two genes that interact with one another. Dominant allele $M$ codes for an enzyme involved in the production of a purple pigment. Recessive allele $m$ codes for a non-functioning enzyme, so no purple pigment is produced, giving a white colour. Dominant allele $D$ interacts with allele $M$ to produce dark purple flowers. Recessive allele $d$ does not interact with allele $M$. Neither allele $D$ nor allele $d$ interact with allele $m$. A double homozygous foxglove with dark purple flowers was crossed with a double homozygous recessive foxglove with white flowers. All of the offspring had dark purple flowers.

Passage of information from parents to offspring

The Hardy-Weinberg principle can be applied to work out allele frequencies and genotype frequencies for a gene in a population. The Hardy-Weinberg principle is expressed by these equations: $p^2 + 2pq + q^2 = 1$ $p + q = 1$

Evolution

Most reflex arcs pass through the spinal cord and include more than one type of neurone. Name and state the functions of the three neurone types in a spinal reflex arc.

Control and coordination in mammals

Palm oil is an edible vegetable oil obtained from the fruit of oil palm trees. Palm oil is inexpensive. It is the most widely used vegetable oil in the world. The oil yield per hectare from oil palm trees is thirty times higher than the oil yield from maize. About 85% of the world’s palm oil is now produced in Indonesia.

Conservation

Explain the meanings of ecosystem and niche.

Biodiversity