Oct/Nov 2013

Which cell structure is visible only by using an electron microscope?

The microscope in cell studies

The three lists, 1, 2 and 3, each include some substances present in animal tissues. 1 glucose, cholesterol, triglycerides, water. 2 glycogen, antibodies, adenine, phospholipids. 3 haemoglobin, carbon dioxide, mRNA, monosaccharides. Which list contains one or more substances with nitrogen atoms?

Proteins

Which of the following statements about competitive inhibitors of enzyme action are correct? 1 Raising the concentration of the enzyme’s substrate will lessen their effect. 2 They attach to an enzyme at its active site. 3 They lower the activation energy needed for a reaction to occur. 4 They decrease the maximum rate of reaction.

Mode of action of enzymes

At $50^{\circ}\text{C}$, an enzyme is totally denatured. A fixed concentration of this enzyme is mixed with a fixed concentration of its substrate. The time required for the reaction to finish is recorded at several different temperatures. Which graph shows the results?

Factors that affect enzyme action

The molecules numbered 1, 2 and 3 are present in cell surface membranes. 1 glycolipids 2 glycoproteins 3 phospholipids Which of these contribute to cell recognition?

Fluid mosaic membranes

What characteristics does facilitated diffusion have?

Movement into and out of cells

The flower stalk of a dandelion is a hollow tube. Sections of the stalk are cut as shown and put into sucrose solutions with different water potentials. Which diagram shows the piece placed in the sucrose solution with the highest water potential?

Movement into and out of cells

What occurs to an animal cell when it is placed in a solution with a more negative water potential?

Movement into and out of cells

Exposure to which one of the following raises the chance of developing a cancerous growth?

Replication and division of nuclei and cells

The diagram outlines the process of sexual reproduction. Which row states the type of cell division taking place in stages 1 and 2 and the number of chromosomes present in cells P and Q?

Replication and division of nuclei and cells

A DNA segment 19 base pairs in length was studied to determine the number of nucleotide bases in each polynucleotide strand. Some of the results are shown. How many nucleotides containing C were present in strand 1?

Structure of nucleic acids and replication of DNA

Which statement does not correctly describe a light microscope or an electron microscope?

The microscope in cell studies

Which statements about complementary base pairing are correct?

Replication and division of nuclei and cells

What does the enzyme DNA polymerase make in a cell?

Mode of action of enzymes

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

Water

Which row is the correct one?

Movement into and out of cells

Which characteristic of xylem vessel elements enables them to offer less resistance to movement?

Structure of transport tissues

An investigation was conducted into how light intensity affects the rate of transpiration. Every other variable was kept constant. A student was asked to explain the results displayed in the graph. Which explanation is correct?

Movement into and out of cells

Different substances, such as sucrose and amino acids, may travel in opposite directions within the phloem sieve tubes. Which statement explains this?

Movement into and out of cells

Which reactions are occurring in the blood as it flows through active tissues?

Movement into and out of cells

Throughout a 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 statement correctly describes an event in the cardiac cycle that comes after atrial systole?

The microscope in cell studies

The electronmicrograph shows part of an animal cell. Which substance will be produced in large amounts by this cell?

Proteins

‘Heart block’ is a disease that can cause the heart rate to be lower than normal. A doctor discovered that electrical impulses were started normally, but they were not conducted correctly to the ventricles, so ventricular contraction rate was reduced. Which structure may be working incorrectly in the patient?

Movement into and out of cells

Which statement correctly explains how carcinogens affect lung tissue?

Replication and division of nuclei and cells

A disease damages the walls of the alveoli. What effect does this have on the surface area for gas exchange and on the volume of the lungs?

Movement into and out of cells

Which statement gives the correct description of part of the gas exchange system?

Movement into and out of cells

Which statement is correct about TB, measles and malaria?

Infectious diseases

What characteristic do the pathogens that cause HIV/AIDS, malaria and TB have in common?

Infectious diseases

In the photomicrograph of human blood, three kinds of white blood cell are labelled. Which row correctly names these white blood cells?

The microscope in cell studies

What functions do T-lymphocytes carry out during an immune response?

The microscope in cell studies

A student recorded three statements about antibodies. Which of the statements are correct?

Proteins

An insect ingests $180\ \text{J}$ of plant material. From this, $95\ \text{J}$ of energy leaves in the insect’s faeces and $58\ \text{J}$ is released in respiration. What percentage of the energy in the original plant material absorbed by the insect is turned into biomass?

Transport of oxygen and carbon dioxide

Which of the following statements about a typical eukaryotic cell are correct?

Cells as the basic units of living organisms

The breakdown of organic matter can make the ammonia concentration increase in a fish tank. If ammonia builds up to a high level in the tank, it is poisonous to fish. Bacteria can be introduced to remove the ammonia. Which type of bacteria ought to be added?

Infectious diseases

Which animal cells are likely to contain the greatest amount of Golgi apparatus?

Cells as the basic units of living organisms

Which diagram illustrates the reaction used to join two monomers that make cellulose?

Carbohydrates and lipids

During hydrolysis of a glycogen molecule, which bonds are cleaved?

Carbohydrates and lipids

Collagen is a macromolecule made up of three polypeptides positioned very close together in a triple helix. In each polypeptide, every third amino acid has the smallest possible R-group or side chain so that the polypeptides can pack closely. Which amino acid is it?

Proteins

The diagrams illustrate the structures of two amino acids, and each contains two amine ($-\text{NH}_2$) groups. A peptide bond is created between the two amino acids. Which groups are joined to form the peptide bond?

Proteins

Which structure is measured in the units displayed with a light microscope?

The microscope in cell studies

What is the reason haemoglobin can transport oxygen?

Proteins

Which statement is correct for a non-competitive inhibitor of enzyme action?

Factors that affect enzyme action

The enzyme lysozyme, released by tear glands, builds up on contact lenses. Which ingredient would be suitable in a cleaner for contact lenses to remove these deposits?

Mode of action of enzymes

Which statement is correct about the components of a cell surface membrane?

Fluid mosaic membranes

A technique known as freeze-fracture can be used to investigate the structure of cell membranes. The membrane is frozen, and then it is split through the centre, so that the two phospholipid layers separate from each other. Any proteins present in one layer stay within that layer. Proteins that extend across the membrane may be found in either layer after freeze-fracture, depending on the protein’s properties. Which statement(s) about the results of freeze-fracture studies are correct?

Fluid mosaic membranes

Which statements describe both facilitated diffusion and active transport?

Movement into and out of cells

Which statement about the fluid mosaic model of membrane structure is right?

Fluid mosaic membranes

Which statements about cancer are correct?

Replication and division of nuclei and cells

The diagram shows the life cycle of a sexually reproducing animal. Which row correctly identifies meiosis and mitosis?

Replication and division of nuclei and cells

The statements below outline events that occur during DNA replication and transcription. Which row is incorrect?

Replication and division of nuclei and cells

A student examined two photographs of a palisade mesophyll cell, both at the same magnification, one taken with a light microscope and the other with an electron microscope. The student noticed the following features. Which features can only be observed because the electron microscope has a higher resolution?

The microscope in cell studies

Which of the following statements about complementary base pairing are correct?

Replication and division of nuclei and cells

What is the least number of base substitutions needed to alter the nucleotide sequence of the $\text{HbA}$ (normal) allele into the $\text{HbS}$ (sickle cell) allele?

Proteins

Which plant cell feature is adapted for absorbing water from the soil solution?

Movement into and out of cells

A student used a potometer to determine the rate of water loss from a plant through transpiration. The internal diameter of the capillary tube and the distance travelled by the bubble in $30\ \text{s}$ were noted. The volume of water moved $= \pi r^2 \times$ distance moved by the bubble. Which calculation correctly shows how to work out the rate of transpiration in $\text{mm}^3\ \text{s}^{-1}$?

Movement into and out of cells

Which characteristic of xylem vessel elements assists the cohesion of water?

Water

Which factors determine how quickly water moves from the roots to the leaves?

Movement into and out of cells

The photomicrograph shows a cross-section of a leaf. Which xerophytic leaf features can be seen in this section?

The microscope in cell studies

The graph shows information about blood vessels and blood flow. Which row correctly names the curves?

The microscope in cell studies

What happens during ventricular systole in a mammalian heart?

The heart

The diagram illustrates a defect in the walls separating the atria. What impact would this defect have on the blood circulatory system?

The microscope in cell studies

A sample of mammalian tissue was homogenised and then centrifuged. The biochemical activity of the subcellular fractions was examined. Which diagram shows the fraction with the greatest synthesis of messenger RNA?

Protein synthesis

Which substance is not formed in the plasma in capillaries surrounding active tissue?

Movement into and out of cells

Goblet cells occur in the trachea. Which organelles would be present in large numbers in a goblet cell?

Cells as the basic units of living organisms

Which tissues can be found in a bronchus?

The gas exchange system

Which of the following statements correctly describe the effects of tar in tobacco smoke on the human gas exchange system?

The gas exchange system

The diagram illustrates how cholera, measles and TB are related. Which option is correct?

Infectious diseases

New-born babies possess natural passive immunity. Which statement explains this correctly?

Proteins

Which option correctly describes the different types of immunity?

The immune system

The World Health Organization (WHO) aimed to eliminate polio through the use of vaccines by the year 2000. Even so, cases are still being reported in some regions of the world after this date. What accounts for these new cases of polio?

The microscope in cell studies

The graph illustrates the yearly variation in these factors in a lake: light intensity per day; numbers of producers; numbers of primary consumers; nutrient quantity. Which curve shows the numbers of producers?

Transport mechanisms

Which processes may occur in the nitrogen cycle?

Proteins

Which row identifies the features of a typical eukaryotic cell?

Cells as the basic units of living organisms

Two ecosystems, X and Y, that are equal in size were compared. They share the same climate. The comparison results are displayed. Based on the information in the table, which statement is not a valid inference about X and Y?

Transport mechanisms

Many single-celled animals that live in fresh water have vacuoles that contract at regular intervals to expel excess water. Why do the cells of freshwater plants not need such vacuoles?

Movement into and out of cells

Which structure shows $\beta$-glucose?

Carbohydrates and lipids

Which row is correct when a single molecule of sucrose is hydrolysed?

Carbohydrates and lipids

Polymerisation of biological molecules occurs through the formation of glycosidic bonds and peptide bonds. Which bonds occur in which molecules?

The microscope in cell studies

The diagrams illustrate the structures of two amino acids, and each one contains more than one amine ($\text{-NH}_2$) group. A peptide bond is made between the two amino acids. Which groups join to make the peptide bond?

Proteins

Which process relies on the mitochondria having a large surface area on the cristae?

Cells as the basic units of living organisms

Which pair of bond types correctly indicates the weak and strong bonds in a protein molecule that determine its shape?

Proteins

Which statement about competitive inhibitors of enzymes is correct?

Mode of action of enzymes

The graph illustrates the progress of an enzyme-catalysed reaction at $30\,^{\circ}\text{C}$. Which statement is correct at time X?

Mode of action of enzymes

Which statement about cholesterol’s role in the cell surface membrane is correct?

Fluid mosaic membranes

Of the processes that contribute to transport across cell surface membranes, which are active and which are passive?

Movement into and out of cells

In an investigation, four sucrose solutions were divided from one another by partially permeable membranes. Solution 1: $1.1\,\text{mol dm}^{-3}$ Solution 2: $0.8\,\text{mol dm}^{-3}$ Solution 3: $0.5\,\text{mol dm}^{-3}$ Solution 4: $0.1\,\text{mol dm}^{-3}$ Which option shows the direction in which water moves between the solutions?

Movement into and out of cells

The diagram illustrates a plant cell that has become partly plasmolysed. What is located at Z?

Movement into and out of cells

The diagram illustrates part of the life cycle of the honey bee, \textit{Apis mellifera}. In which stage does mitosis take place?

Replication and division of nuclei and cells

The graph illustrates the change in the amount of DNA in a cell throughout a reduction division. A cell with one pair of chromosomes $(2n = 2)$ undergoes meiosis. Which nucleus is produced by this division?

Replication and division of nuclei and cells

What is the least number of hydrogen bonds in a DNA strand section containing 700 base pairs?

Structure of nucleic acids and replication of DNA

Which of the following is not a limitation of an electron microscope?

The microscope in cell studies

Which term most accurately names the section of DNA that contains the instructions for polypeptide synthesis?

Protein synthesis

Which of these statements about complementary base pairing are correct?

Replication and division of nuclei and cells

What is transpiration, and what benefit does it provide to a plant?

The microscope in cell studies

What structural feature of xylem vessel elements enables them to remain open as the rate of transpiration rises?

Structure of transport tissues

What takes place in the sieve tube elements of a leaf that is photosynthesising and a root that is actively growing?

Movement into and out of cells

What takes place along the apoplast and symplast pathways?

Movement into and out of cells

Certain fungi make crop plants wilt by growing inside the xylem vessels. Which process would be directly affected by these fungi?

Movement into and out of cells

Which statement correctly shows a similarity between blood plasma and tissue fluid?

Movement into and out of cells

Which reactions are unlikely to occur in blood flowing through active tissues?

Movement into and out of cells

The pressure of blood as it enters capillaries is roughly seven times greater than the pressure of blood as it leaves the capillaries. Which statement best accounts for this?

Movement into and out of cells

What accounts for the fact that cells without nucleoli die?

Protein synthesis

People have a higher red blood cell count when they live at high altitudes. What causes this?

Transport of oxygen and carbon dioxide

Goblet cells occur in the trachea. Which organelles would be present in large numbers in a goblet cell?

Cells as the basic units of living organisms

The photomicrographs display a TS of an artery from a non-smoker and a TS of an artery from a smoker. What explains the appearance of the smoker’s artery?

Carbohydrates and lipids

Which row gives the description of emphysema?

The gas exchange system

Which row is the correct one?

Cells as the basic units of living organisms

Scientists are worried that avian (bird) flu caused by the H5N1 virus might spread to humans and trigger a pandemic. What action could help stop humans from passing on the disease?

Infectious diseases

What roles do plasma cells play during an immune response?

Proteins

Some details about the pathogen P are: 1 it is spread through food and water 2 it inhabits the human intestines 3 it contains many genes that code for surface proteins 4 it alters its surface antigens 5 it may or may not cause an immune response. Which of these explains why it is hard to produce an effective vaccine for P?

Proteins

Which statement correctly describes B-lymphocytes?

Antibodies and vaccination

Within a mangrove ecosystem, leaves shed by grey mangrove plants drop into the water and settle in the mud beneath. Bacteria and fungi then decompose them. Invertebrates such as crabs, prawns, and molluscs live in the mud and consume the dead leaves. The bullseye fish feeds on the invertebrates. Humans eat prawns, crabs and fish. Herons and other wading birds live and reproduce in the mangroves. These birds feed on invertebrates and fish. Which statement about this ecosystem is correct?

Cells as the basic units of living organisms

Which statements about a typical prokaryotic cell are correct?

Cells as the basic units of living organisms

Two bird species eat different insects that live on the same tree, so they do not compete for food. Which statement best describes these two species of birds?

The microscope in cell studies

After mitochondria have been removed from cells for biochemical investigation, they are typically maintained in a $0.25\,\text{mol dm}^{-3}$ sucrose solution. Why is a sucrose solution used?

Movement into and out of cells

Which option represents the basic unit of cellulose?

Carbohydrates and lipids

Which statement best explains why haemoglobin is suitable for carrying oxygen?

Proteins

Which diagram depicts a section of a structural polysaccharide?

Carbohydrates and lipids

The diagrams display the structures of two amino acids, and each contains more than one amine ($-\text{NH}_2$) group. A peptide bond is produced between the two amino acids. Which groups join to make the peptide bond?

Proteins