Feb/March 2016

A student has produced a drawing of a cell structure as observed with a light microscope. The drawing has a magnification of $\times 600$. On the drawing, the structure measures $6\ \text{mm}$. What is the true length of the cell structure?

The microscope in cell studies

When proteins are combined with certain organic solvents, hydrophobic interactions and hydrogen bonding change within the protein molecules. Which levels of protein structure would be affected?

Proteins

The speed of enzyme-catalysed reactions in human cells is controlled. What might be involved in this control?

Factors that affect enzyme action

The graphs illustrate how temperature and pH affect enzyme activity. Which statement correctly explains the enzyme activity?

Factors that affect enzyme action

Which statement accurately describes how competitive enzyme inhibitors act?

Mode of action of enzymes

Which row shows the correct association between molecules in the cell surface membrane and their functions?

Fluid mosaic membranes

Antimycin is a chemical that stops mitochondria from working. Which methods of transport across the cell surface membrane would be inhibited by antimycin?

Movement into and out of cells

Which statements regarding the cell cycle are correct?

Replication and division of nuclei and cells

The diagram illustrates cells at various phases of the cell cycle. Which stage comes immediately before cytokinesis?

Chromosome behaviour in mitosis

Of the structures listed, how many normally have genetic material containing telomeres? • bacterial cell • chloroplast • mitochondrion • nucleus

Structure of nucleic acids and replication of DNA

What does the enzyme DNA polymerase produce in a cell?

Mode of action of enzymes

The electron micrograph shows a section of a eukaryotic cell. Which labelled organelle is the site where protein synthesis occurs?

Protein synthesis

In a DNA molecule, $21.2\%$ of the bases are cytosine. What percentage would adenine be?

Structure of nucleic acids and replication of DNA

A gene contains the instructions for making what kind of molecule?

Proteins

The table outlines the mode of action of two antibacterial drugs that can affect protein synthesis. If bacteria are treated with both drugs, what immediate effects will occur?

Proteins

The diagrams illustrate transverse sections of parts of a plant. In the transverse sections, which tissues move sucrose?

The microscope in cell studies

Which statement describes movement within a plant via the apoplast pathway?

Movement into and out of cells

What changes happen to the water potential and to the volume of liquid in the phloem when sucrose is transferred from the phloem sieve tube to an actively dividing root tip?

Movement into and out of cells

The diagram presents the findings from an experiment that used leaves from two different plant species with the same surface area. Each leaf was placed on a balance in daylight inside a closed room, and its mass was measured at $1$ hour intervals. Which characteristics of leaf $2$ might account for these results?

Movement into and out of cells

Which observation provides evidence for the cohesion-tension theory in the transport of water in flowering plants?

Transport mechanisms

Cardiac muscle consists of numerous fibres that make up the walls of the heart chambers. As the heart contracts, these fibres become shorter, so the muscle produces a force that applies pressure to the blood and makes it flow. Which statement explains why the walls of the ventricles of the heart are different in thickness?

The heart

Which reactions happen at a faster rate in a capillary in an alveolus than in a capillary in active muscle?

Movement into and out of cells

Within a cell, a damaged mitochondrion may be wrapped by a membrane to make a vesicle. What occurs following fusion of a lysosome with this vesicle?

Cells as the basic units of living organisms

The diagram illustrates how three different carbon dioxide concentrations affect the oxygen dissociation curve for human haemoglobin. $X$ = partial pressure of carbon dioxide: $3.0\,\text{kPa}$ $Y$ = partial pressure of carbon dioxide: $5.0\,\text{kPa}$ $Z$ = partial pressure of carbon dioxide: $7.0\,\text{kPa}$ What effect does a rise in carbon dioxide concentration have on haemoglobin?

Proteins

The graph illustrates the changes in the volume of the left ventricle over a single cardiac cycle. Which point on the graph indicates the beginning of atrial systole?

The heart

The tissues listed below conduct an electrical impulse during the cardiac cycle. In which sequence does the electrical impulse pass through the cardiac cycle?

The heart

Some effects of smoking are shown below. Which components of tobacco smoke are responsible for these effects?

The gas exchange system

The photomicrograph shows a cross-section of part of a bronchus wall. What function does the tissue labelled X have?

The microscope in cell studies

Which of the following raise the chance of catching TB?

The microscope in cell studies

One way to lower the spread of malaria is to apply an insecticide. This may be used to treat mosquito nets. A further control method is to cover water surfaces entirely with insoluble polystyrene balls that remain floating. From this information, what are the reasons for these control methods?

The microscope in cell studies

Which of the following is not an example of antibiotic action?

Factors that affect enzyme action

Which row correctly states the functions of B-lymphocytes and T-lymphocytes?

The immune system

A person's blood group depends on the antigens found on the red blood cells. The table gives the antigens and antibodies present in the blood of people with different blood groups. In a blood transfusion, it is vital that the recipient's blood has no antibodies against the donor's blood. Which blood groups may be given to a person with blood group B?

Fluid mosaic membranes

Which units are most suitable for recording the diameters of a lymphocyte and a red blood cell?

The microscope in cell studies

An enzyme hydrolyses the two heavy polypeptide chains in an antibody molecule. This hydrolysis takes place at the hinge region and splits the antibody into three fragments. How many of these fragments can bind to antigens?

Proteins

Which structures are found in a cell that causes cholera?

Cells as the basic units of living organisms

What can happen in a hydrolysis reaction?

Water

The table presents some details about four carbohydrate polymers. Which two polymers make up starch?

Carbohydrates and lipids

Which molecule in the key represents sucrose?

Carbohydrates and lipids

Which of these statements about triglycerides and phospholipids are correct?

Carbohydrates and lipids

Statements A to E are about biological molecules. For each one, identify the term that best fits the description.

Protein synthesis

Fig. 2.1 illustrates a root tip cell during interphase.

Structure of nucleic acids and replication of DNA

Erythropoietin, or EPO, is a large glycoprotein made by specialised kidney cells. These cells detect changes in the oxygen concentration of the blood flowing through the kidney and, when oxygen concentration is low, they increase EPO synthesis. EPO acts on the surface of certain target cells, such as cells in the bone marrow. These bone marrow cells are then stimulated to make red blood cells.

Protein synthesis

Morbillivirus, the cause of measles, and human immunodeficiency virus (HIV) have these features in common: • an outer envelope enclosing the protein coat • RNA as the genetic material • infection of cells in the immune system.

Infectious diseases

Fig. 5.1 shows an ATP molecule as a diagram. Statements A, B, C and D belong to the chain of events that takes place when sucrose is loaded into a phloem sieve tube.

Transport mechanisms

Fig. 6.1 illustrates the first three parts of the human gas exchange system that inhaled air from the outside atmosphere passes through.

The gas exchange system

The rate of photosynthesis is influenced by several environmental factors. Fig. 1.1 shows how light intensity changes the rate of photosynthesis.

Investigation of limiting factors

Explain how genetic diseases can be treated by using gene therapy.

Genetic technology applied to medicine

The IUCN Red List gives details on species conservation status across the world, including the American badger, $\textit{Taxidea taxus}$, and the black-footed ferret, $\textit{Mustela nigripes}$. Fig. 2.1 depicts an American badger and Fig. 2.2 depicts a black-footed ferret. Fig. 2.3 presents the IUCN conservation status of the American badger and the black-footed ferret in 1987 and in 2013.

Conservation

Myofibrils in striated muscle are made up of contractile units known as sarcomeres. When an impulse causes striated muscles to contract, calcium ions are discharged from the sarcoplasmic reticulum.

Control and coordination in mammals

Gamete formation in male and female vertebrates, humans included, happens by meiosis.

Passage of information from parents to offspring

Fig. 5.1 shows how hormones A and B help to regulate blood glucose concentration.

Homeostasis in mammals

Paramecium is a single-celled protoctist with cilia. Their cilia are built in a similar way to those in the human trachea. The cilia beat to propel Paramecium through the water in which it lives. Fig. 6.1 shows Paramecium.

Fluid mosaic membranes

Fig. 7.1 shows a diagram of part of a mitochondrion in section.

Respiration

In one snail species, shell colour is determined by a gene with three alleles: allele $C^B$ gives a brown shell; allele $C^P$ gives a pink shell; allele $C^Y$ gives a yellow shell. Allele $C^B$ is dominant over both $C^P$ and $C^Y$, whereas $C^P$ is dominant over $C^Y$. Snail shells may also be banded, meaning they have dark stripes, or non-banded. The allele for non-banded, $N$, is dominant over the allele for banded, $n$.

Passage of information from parents to offspring

Answer only one question.

Genetically modified organisms in agriculture