Biology 9700 · AS & A Level
Transport mechanisms
100 practice questions on Transport mechanisms, with worked solutions and instant marking.
Which observation provides evidence for the cohesion-tension theory in the transport of water in flowering plants?
Feb/March 2016
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.
Feb/March 2016
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.
Feb/March 2017
Fig. 4.1 shows a diagram of a cross-section through part of a young root.
Feb/March 2018
Which terms are used to describe the way water is transported in xylem vessel elements?
Feb/March 2019
Fig. 1.1 and Fig. 1.2 show photomicrographs of cross-sections through the leaves of two different plants. Fig. 1.1 is a photomicrograph of a section through a leaf of Cornish heath, Erica vagans. Fig. 1.2 is a photomicrograph of a section through a leaf of Himalayan cedar, Cedrus deodara. Fig. 1.1 and Fig. 1.2 are not shown at the same magnification.
Feb/March 2019
Human prolactin (hPRL) is a globular protein made up of one polypeptide chain containing 199 amino acids. It moves in the bloodstream and affects only cells whose cell surface membrane protein is called PRLR. One function of hPRL is to stimulate mammary gland cells to produce breast milk. Cells that have been stimulated by hPRL need a larger supply of glucose, so passive glucose uptake rises.
Feb/March 2019
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.
Feb/March 2022
Which row gives the correct identification of sources and sinks of sugars?
Feb/March 2023
Table 1.1 shows cell structures that may occur in eukaryotic cells or in prokaryotic cells. A number of these structures are shared by both cell types.
Feb/March 2023
Fig. 3.1 shows an area of phloem tissue from a transverse section through the stem of a squash plant, Cucurbita pepo.
Feb/March 2023
Fig. 1.1 shows a diagram of part of the phospholipid bilayer in a cell surface membrane.
Feb/March 2024
Smilax china is a herbaceous plant. Fig. 1.1 displays part of a transverse section through a root of S. china, with root hair cells shown.
Feb/March 2025
Which process does not make nitrogen available for plants to use?
May/June 2011
Which processes take part in transport in both phloem and xylem?
May/June 2011
Anaerobic bacteria occur in large numbers in waterlogged soils. What impact does this have on soil fertility, and what is the reason for this?
May/June 2011
What role do nitrifying bacteria play in the soil?
May/June 2011
Which process does not involve supplying nitrogen to plants?
May/June 2011
Mineral ions enter plants through root hair cells. This can occur by a process that transfers the ions from a lower concentration in the soil to a higher concentration inside the root hair cell.
May/June 2011
Fig. 5.1 shows an electron micrograph of a transverse section of part of a plant stem.
May/June 2011
When transpiration is occurring at its highest rate, tree trunks become smaller in diameter. Which statement accounts for this?
May/June 2012
The table presents the findings from a field study of four species in a woodland food chain. What is the pathway of energy flow in the food chain?
May/June 2012
The table presents the findings from a field study involving four species in a food chain within a woodland area. What is the energy flow in the food chain?
May/June 2012
Fig. 2.1 is a drawing based on an electron micrograph showing two neighbouring cells in a leaf.
May/June 2012
One function of the cell surface membrane is to regulate the movement of substances into and out of the cell.
May/June 2012
Using the structure of a leaf as your reference, explain how evaporation differs from transpiration.
May/June 2012
Fig. 2.1 shows an apparatus for measuring how quickly leafy parts of plants absorb water.
May/June 2012
Transpiration is often referred to as an "unavoidable outcome of gas exchange in plants".
May/June 2013
Fig. 5.1 illustrates part of a cell surface membrane.
May/June 2013
Fig. 1.1 shows an electron micrograph of a transverse section through palisade mesophyll tissue from the leaf of the flowering plant Zinnia elegans.
May/June 2013
The diagram illustrates how nutrients move through an ecosystem. Which letter indicates decomposers?
May/June 2014
In an ecosystem, the producers have a total of $3 \times 10^6\ \text{kJ m}^{-2}\ \text{yr}^{-1}$ available to them. In theory, what amount of this energy would be passed on to tertiary consumers?
May/June 2014
In a food chain, which link is associated with the least efficient transfer of energy?
May/June 2014
Fig. 2.1 shows a transmission electron micrograph of cells taken from a spinach leaf.
May/June 2014
The enzyme glutamyl-tRNA reductase (GluTR) is found in many bacteria and is needed to produce a compound that is vital for their survival. GluTR acts on the substrate glutamyl-tRNA, which consists of the amino acid glutamic acid attached to a tRNA. Fig. 3.1 displays the structure of glutamyl-tRNA and another compound, glutamycin.
May/June 2014
Fig. 4.1 shows a light micrograph of a leaf section from the xerophytic plant Nerium oleander, with one of the plant’s stomata circled.
May/June 2014
From which part does water evaporate during transpiration?
May/June 2015
At which stage in a tropical grassland food chain is energy transferred most inefficiently?
May/June 2015
A farmer cultivates a different crop in a field during each of the first three years. In the fourth year, he plants a leguminous crop, such as clover, and then ploughs it back into the soil. In the following year, he begins the rotation again. How does the crop grown in the fourth year add mineral ions to the soil?
May/June 2015
The table presents the findings from a field study of four species in a food chain in a given area. Which pyramid of energy is correct based on these data?
May/June 2015
Once a leaf has just been produced, it is regarded as a sink for carbohydrate. As development continues, the leaf begins photosynthesis and then acts as a source of carbohydrates and other assimilates. Fig. 3.1 illustrates how the structure of plasmodesmata in the leaf alters as it grows.
May/June 2015
The cell surface membrane has a fluid mosaic arrangement.
May/June 2015
Fig. 5.1 shows a light micrograph of several unicellular photosynthetic organisms known as Chlamydomonas.
May/June 2015
Explain what the description ‘an inevitable consequence of gas exchange in leaves’ means.
May/June 2016
Fig. 6.1 presents a partially completed diagram of the fluid mosaic model of membrane structure. It depicts the cell surface membrane of a eukaryotic cell.
May/June 2016
Marram grass, $\textit{Ammophila arenaria}$, is a key plant of sand dunes. The leaves of marram grass are adapted to minimise water loss through transpiration. Fig. 2.1 shows a photomicrograph of a section through a marram grass leaf.
May/June 2016
Transport proteins move sugar molecules into cells.
May/June 2017
In the space provided below, draw a diagram showing a hydrogen bond linking two water molecules.
May/June 2017
What role do the hairs (trichomes) on xerophytic leaves have?
May/June 2018
Sucrose is a disaccharide. Fig. 2.1 illustrates sucrose undergoing breakdown in a reaction with hydrochloric acid.
May/June 2018
Water taken up by plant roots moves along different routes from root hairs to the xylem. Fig. 6.1 illustrates these routes in the root of Ranunculus acris.
May/June 2018
Nerium oleander is a xerophytic plant. Fig. 3.1 shows a photomicrograph of a section across a leaf of N. oleander.
May/June 2018
Linoleic acid is an unsaturated fatty acid found in some triglycerides and some phospholipids. Phospholipids are part of cell membranes. Fig. 2.1 shows a linoleic acid molecule.
May/June 2019
In most plants, sucrose is the principal sugar moved from sources to sinks.
May/June 2020
Water and mineral ions travel upward through xylem vessels in the stem to reach the leaves. A proportion of the water and mineral ions leaves the xylem vessel elements and enters the parenchyma tissue in the stem.
May/June 2020
A student performed an investigation to estimate the water potential of potato tissue. The main stages of the method and of the processing of the results are shown in Fig. 6.1. Six sucrose solutions of different concentrations were prepared, and the same volume of each was transferred into a labelled beaker. The concentrations ranged from $0.0$ to $0.5\ \text{mol dm}^{-3}$. Six potato blocks of equal size were cut from the same potato, blotted dry and weighed. One potato block was placed in the solution in each beaker for 30 minutes. After this period, the block was removed, blotted dry and weighed again. The experiment was repeated twice. The mean percentage change in mass of the potato tissue was calculated for each sucrose concentration used, and a graph of mean percentage change in mass of potato tissue against sucrose concentration was drawn.
May/June 2020
Visking tubing may be used to explore the properties of cell membranes. A student performed an experiment with Visking tubing to investigate osmosis. Fig. 3.1 shows an outline of the investigation.
May/June 2021
Fig. 5.1 contains a transmission electron micrograph of portions of two plant cells. The middle lamella serves to hold neighbouring cells together. It is made of the polysaccharide pectin. Pectin interacts with the polysaccharides cellulose and hemicellulose in the cell walls of the plant cells, keeping the walls close together, as illustrated in Fig. 5.1.
May/June 2021
Microvilli are cell structures found on epithelial cells in the small intestine. These microvilli appear only on the side of the cell that faces the gut lumen. Fig. 1.1 contains images of the microvilli of intestinal epithelial cells. The images were produced with a scanning electron microscope and a transmission electron microscope. Fig. 1.1A was taken at a magnification different from Fig. 1.1B.
May/June 2022
Plants have two transport tissues: phloem and xylem. Xylem transports water and mineral ions from the soil solution to the various parts of the plant body. Phloem translocates assimilates and other substances from sources to sinks.
May/June 2022
Hakea spp. are xerophytic plants that originate in Australia. The leaves of Hakea show adaptations for life in xerophytic conditions.
May/June 2022
Fig. 3.1 illustrates some fruits (grapes) from the grapevine, Vitis vinifera. Sucrose is carried in the phloem of the grapevine to the fruits. Inside the fruits, sucrose is broken down by the enzyme sucrase, which is located in cell walls. The glucose and fructose formed by sucrose hydrolysis move through membrane proteins called hexose transporters into the cytoplasm of the fruit cells.
May/June 2023
Fig. 6.1 presents a diagram of how water travels through the tissues of a flowering plant, starting in the soil and ending in the atmosphere; the arrows indicate the route of movement.
May/June 2023
Fig. 2.1 shows a photomicrograph of a longitudinal section (LS) through a root tip. Two separate regions can be seen: the root apical meristem and the root cap. Cells in the root cap produce a gel-like, sticky secretion called mucilage, which helps to reduce friction between the soil and the growing root. It is made mainly of polysaccharides and also contains some amino acids and enzymes.
May/June 2023
Phloem and xylem are specialised plant tissues that transport water, ions and assimilates.
May/June 2023
Which row correctly states the sinks for sucrose transported by mass flow in plants?
May/June 2024
Phosphate ions are taken up from the soil solution by roots and are needed for metabolic processes in every part of the plant. Scientists studied how phosphate ions move in flowering plants. They found that phosphate ions in the leaves are carried from the roots in the xylem. Only a small fraction of the phosphate ions absorbed is transported to the growing regions of the roots and shoots.
May/June 2025
Root hair cells are specialised plant cells found in the outer cell layer of young roots in plants. These cells play a vital part in absorbing water and dissolved mineral ions from the soil solution. Water can move across the root to the central xylem tissue by either the symplast pathway or the apoplast pathway.
May/June 2025
Lysosomes are membrane-bound organelles that occur in mammalian cells.
May/June 2025
The table presents the findings from a field study involving four species in a food chain within one area. Which pyramid of energy is correct from these data?
Oct/Nov 2010
The photomicrograph depicts a transverse section of a leaf. Which xerophytic leaf features can be seen in this section?
Oct/Nov 2010
Many organisms use the enzyme sucrase to carry out hydrolysis of sucrose. Fig. 3.1 presents a diagram of the enzyme together with its substrate.
Oct/Nov 2010
Which box includes only the components of an ecosystem that are classified as a food web?
Oct/Nov 2011
The graph illustrates the yearly variation of these factors in a lake: intensity of light per day; numbers of producers; numbers of primary consumers; quantity of nutrients. Which curve shows the numbers of primary consumers?
Oct/Nov 2011
Which piece of evidence supports the cohesion-tension theory of water movement in plants?
Oct/Nov 2011
The diagram illustrates the tissues involved in sucrose transport in a plant. In which location is the concentration of sucrose highest?
Oct/Nov 2011
Fig. 1.1 shows a diagram of a cell surface membrane.
Oct/Nov 2011
Phloem transfer cells are altered companion cells that transport sucrose and other assimilates from mesophyll tissue into phloem sieve tube elements. Fig. 5.1 shows an electron micrograph of a phloem transfer cell (magnification $\times 10\,000$).
Oct/Nov 2011
Azotobacter vinelandii is a soil bacterium that can fix atmospheric nitrogen. A key feature of nitrogen-fixing bacteria is their ability to make the enzyme nitrogenase, a protein complex containing molybdenum and iron.
Oct/Nov 2011
Fig. 6.1 depicts a phloem sieve tube element, its companion cell and a mesophyll cell from a photosynthesising plant.
Oct/Nov 2011
Fig. 3.1 shows a photomicrograph of a transverse section of a leaf from the tea plant, Camellia sinensis.
Oct/Nov 2011
Which set of conditions causes the transpiration rate in plants to increase?
Oct/Nov 2012
The diagram illustrates a simplified nitrogen cycle. At which stage does nitrification occur?
Oct/Nov 2012
The overall rate at which producers manufacture organic material is known as gross primary productivity (GPP). The rate at which producers keep organic material as fresh tissue is known as net primary productivity (NPP). What illustrates the connection between GPP and NPP?
Oct/Nov 2012
Thale cress, $\textit{Arabidopsis thaliana}$, is employed to investigate the functions of genes and proteins in organisms. In the root hairs of $A.\ thaliana$, the cell membranes contain aquaporin proteins that enable water to move between the soil and the cytoplasm, as shown in Fig. 2.1.
Oct/Nov 2012
In 1972, Singer and Nicolson first put forward the fluid mosaic model of membrane structure. The model explains in detail how the parts of a membrane are arranged.
Oct/Nov 2012
Fig. 4.1 shows an electron micrograph of a transverse section of a plant stem. The vessels can be seen clearly.
Oct/Nov 2012
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?
Oct/Nov 2013
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?
Oct/Nov 2013
Describe the structure of a cellulose molecule and explain why cellulose is a suitable substance for plant cell walls.
Oct/Nov 2013
Fig. 6.1 shows a photomicrograph of phloem sieve tubes taken from a plant stem.
Oct/Nov 2013
The diagram illustrates the transfer of energy among organisms in an ecosystem. Which option correctly names each organism in the ecosystem?
Oct/Nov 2014
In a freshwater food chain, which stage has the least efficient transfer of energy?
Oct/Nov 2014
Which statement about processes occurring in the nitrogen cycle is not correct?
Oct/Nov 2014
Fig. 6.1 illustrates the route followed by water as it enters the root of a flowering plant.
Oct/Nov 2014
Fig. 2.1 illustrates one section of the nitrogen ($N$) cycle, and some parts of the water cycle are also shown.
Oct/Nov 2014
Agrobacterium tumefaciens is a bacterium that can enter plants through wounds and trigger a disorder called crown gall disease. It attaches to the cell surface and transfers a small circular DNA molecule, called a plasmid, into the cell. Some genes on the plasmid produce proteins that alter the plant cell and lead to a plant tumour, or gall.
Oct/Nov 2014
Table 6.1 gives some information about xylem vessels and phloem sieve tube elements in plants.
Oct/Nov 2014
A tree carries out photosynthesis and supplies organic compounds to other organisms in a forest. It removes carbon dioxide from the atmosphere and gives oxygen back to the atmosphere. It absorbs water from the soil through its roots and its leaves lose water to the atmosphere. Many other organisms live on the tree. Which term describes the tree?
Oct/Nov 2015
The diagram illustrates how energy flows through a food chain. Figures are given in $\text{kJ m}^{-2}\,\text{year}^{-1}$. What percentage of light energy is available to the herbivore?
Oct/Nov 2015