[Maximum number: 4]

Male Lepidoptera (butterflies and moths) commonly drink from pools of water or from moist soil. This behaviour, called puddling, was investigated in an undisturbed area where male tiger swallowtails, Papilio glaucus, had been seen puddling.

Four successive sets of experiments were performed under similar conditions of temperature and humidity. In each set, equal samples of sand were spread out evenly on trays and then treated differently. Except for one dry sample (in the first set), all others were saturated with a different liquid. Results of the observations are given in the table below.

(a)

Study of the male moth Gluphisia septentrionis revealed that their puddling behaviour can last for hours. Though drinking results in the uptake of hundreds of gut-loads of fluid, this fluid becomes rapidly expelled from the digestive system through frequent anal ejections. In this experiment, the ion concentration change was calculated by subtracting ions ejected from ions taken in. The following data was collected from males drinking laboratory solutions and from natural puddles.

[ 4 ]

(i)

Identify which ion the moths are retaining in their body from the laboratory solutions.

[ 1 ]

(ii)

Compare the gain and loss of ions in the male moths which have drunk from laboratory solutions with the changes in those that have drunk from natural puddles.

The diagram below shows the digestive system anatomy of the male and female moth.

[ 3 ]

[Maximum number: 1]

Hypertension (blood pressure exceeding 140 mmHg ) affects millions of people worldwide. Many modern societies consume more sodium in the form of salt (NaCl) than is required for normal physiology. The effect of changing the levels of dietary sodium has been studied in various organisms.

Scientists recorded the blood pressure changes in chimpanzees (Pan troglodytes) fed a diet without added sodium (control) or a sodium supplemented diet (experimental) as follows
- 5 grams of salt per day from December 1991 until May 1992
- 10 grams of salt per day until June 1992
- 15 grams of salt per day until August 1993
after which no more salt was added to the diet until the experiment ended.

(a)

Suggest how sodium-potassium pumps in the membranes of nephron cells in the kidney could allow blood sodium concentrations to be reduced, if there is sufficient potassium in the diet.

[ 1 ]

[Maximum number: 3]

Hypoxia is a condition in which tissues of the body are deprived of an adequate oxygen supply. A study was carried out in rats to examine the effects of continuing hypoxia on the structure of the diaphragm, and to determine whether nitric oxide is implicated in adaptation of the diaphragm to hypoxia. The diaphragm helps to supply oxygen to tissues and organs in the body by ventilating the lungs.

A group of 36 adult male rats were kept for 6 weeks in low oxygen while 36 adult male rats were kept in normal oxygen levels.

(a)

The sodium-potassium pump plays a role in muscle activity. Nitric oxide may have a role in the recovery of hypoxic muscles. The production of nitric oxide can be blocked with an inhibitor of the enzyme nitric oxide synthase. The graph shows the concentration of sodium-potassium pumps in the diaphragm of control and hypoxic rats without and with nitric oxide synthase inhibitor.

[ 3 ]

(i)

Analyse the graph to obtain two conclusions about the concentration of sodium-potassium pumps.
1.
2.

[ 2 ]

(ii)

Muscle fibres are stimulated to contract by the binding of acetylcholine to receptors in their membranes and the subsequent depolarization. Suggest a reason for increasing the concentration of sodium-potassium pumps in the membranes of diaphragm muscle fibres.

[ 1 ]

[Maximum number: 3]

The Chinese soft-shelled turtle, Pelodiscus sinensis, lives in salt water marshes. The turtle can live under water and out of water.

These turtles have fully developed lungs and kidneys, however, many microvilli have been discovered in the mouth of P. sinensis. A study was undertaken to test the hypothesis that oxygen uptake and urea excretion can simultaneously occur in the mouth.

Initial experiments involved collecting nitrogen excretion data from P. sinensis. The turtle urinates both in water and out of water. When in water it allows waste products to be washed out of its mouth. When out of water it regularly dips its head into shallow water to wash its mouth. The table shows the mean rates of ammonia and urea excretion from the mouth and kidney over six days.

(a)

Deduce with a reason whether a urea transporter is present in the mouth of P. sinensis.

[ 2 ]

(b)

Expression of the urea transporter gene by cells in the turtle's mouth was assessed by measuring mRNA activity. Turtles were kept out of water for 24 hours and then injected with either a salt solution that matched the salt concentration of the turtle, dissolved ammonia or urea, followed by another 24 hours out of water.

[ 1 ]

(i)

Identify which of these turtle groups represent the control, giving a reason for your answer.

[ 1 ]

[Maximum number: 1]

Which function is accomplished by structures X and Y in the Paramecium?

excretion

digestion

homeostasis

feeding

movement

food storage

respiration

DNA replication

[Maximum number: 2]

Two models of plasma membrane structure are shown.

(a)

(i)

Label the model A diagram to show a region of protein.

[ 1 ]

(ii)

Label the model B diagram to show a phospholipid.

[ 1 ]

[Maximum number: 4]

Membrane structure can be investigated using a technique known as freeze fracture. Cells are frozen and then split. Fracturing often occurs between the two phospholipid layers of membranes in the cell. An electron micrograph of such a fractured membrane is shown.

(a)

Using the scale bar, calculate the magnification of the image.

[ 2 ]

(b)

Explain how the amphipathic nature of phospholipids allows them to form bilayers.

[ 2 ]

[Maximum number: 1]

How is facilitated diffusion in axons similar to active transport?

They both require the energy of ATP.

They both move substances against a concentration gradient.

They both use sodium-potassium pumps.

They are both carried out by proteins embedded in the axon membrane.

[Maximum number: 1]

An experiment on aerobic respiration was performed using a plant in a pot containing fertile soil. The apparatus was set up as shown in the diagram. Sodium hydroxide and limewater (calcium hydroxide) are both alkaline solutions. Limewater goes cloudy when carbon dioxide is bubbled into it.

(a)

Suggest a reason that the pot was covered with a plastic bag.

[ 1 ]

(a)

The electron micrograph shows human sperm.

Magnification 6300x

Calculate the actual length of the head of the sperm indicated by the arrow, showing your working.

[ 1 ]