OCR A Level Biology A Biological Processes June 2019 question paper H420/01

Rheumatoid arthritis is a long-term condition that causes pain, swelling and stiffness in the joints.

Which of the following, A to D, explains why stem cells are a potential source of treatment for rheumatoid arthritis?

A Stem cells can be harvested from the umbilical cords of newborn babies.

B Stem cells are cheaper than other drug-based therapies.

C Stem cells allow regeneration of a variety of tissue types.

D Stem cells can be obtained from embryos without any ethical concerns.

Your answer

Myoglobin is a protein found in muscle. Myoglobin has a very high affinity for oxygen at most partial pressures of oxygen.

The figure below shows dissociation curves for

• adult haemoglobin

• fetal haemoglobin

• myoglobin.

Which of the following rows, A to D, shows the correct labels for the lines on the graph?

Your answer

Which of the following, A to D, is not an example of cell signalling?

A The hormone insulin being removed from the blood by the glomerulus.

B The neurotransmitter acetylcholine causing depolarisation.

C The hormone prolactin binding to a cell receptor in breast tissue.

D Epithelial cells releasing cytokines in response to histamine.

Your answer

The image below shows a micrograph of two different types of blood cell.

Questions 4 and 5 refer to this image.

Which of the following rows, A to D, shows the correct cell names from the image above?

Your answer

The image below shows a micrograph of two different types of blood cell.

Questions 4 and 5 refer to this image.

Both of the cell types P and Q develop from haematopoetic stem cells in the bone marrow.

Which of the following statements, A to D, correctly describes haematopoetic stem cells?

A They are neither pluripotent nor multipotent.

B They are pluripotent but not multipotent.

C They are both pluripotent and multipotent.

D They are multipotent but not pluripotent.

Your answer

Which of the following statements, A to D, correctly explains why meristems can differentiate into xylem vessels in plant stems?

A Meristems are living and unspecialised.

B Meristems are living and specialised.

C Xylem vessels are dead and specialised.

D Xylem vessels are dead and unspecialised.

Your answer

The following passage outlines the process of phototropism in plants:

Auxin is synthesised in cells at the........ of the shoot. Auxin causes

the cells to........ on one side, so the stem bends.

Scientists originally thought auxin was........ by light but this was

disproved by the fact that plants growing in the dark and plants growing in

unilateral light had........ auxin levels.

Which option, A to D, is the correct sequence of missing words?

A meristem, shorten, destroyed, different

B tip, elongate, destroyed, similar

C meristem, shorten, synthesised, raised

D tip, elongate, synthesised, similar

Your answer

A scientist tested a plant suffering from water stress. The plant was found to have high levels of abscisic acid (ABA) in its tissues.

Which of the following statements, A to D, explains this observation?

A ABA causes fruit ripening

B ABA prevents leaf drop

C ABA causes phototropism

D ABA stimulates stomatal closing

Your answer

Which of the following statements, A to D, is evidence for geotropism?

A leaves are shed from deciduous plants in the autumn

B roots grow downwards

C shoots grow towards the light

D flowers can change position throughout the day

Your answer

Many trees drop their leaves in the autumn.

Which of the following plant hormones is/are thought to be involved in the control of leaf drop?

1 auxin 2 ethene 3 gibberellin

A 1, 2 and 3

B only 1 and 2

C only 2 and 3

D only 1

Your answer

The image below shows a synaptic bulb.

Which of the following rows, A to D, correctly names the parts labelled H to J in the image?

Your answer

Damage to the hypothalamus results in lower water potential of the blood.

Which of the following, A to D, explains these observations?

A ADH release increases the water potential of blood.

B Mineralocorticoids affect cells in the loop of Henle.

C Fewer water channels are inserted into the cell surface membranes of the collecting duct.

D The anterior pituitary releases hormones into the blood.

Your answer

Collagen is found in tendons. Tendons attach muscles to bones.

Which of the following lists of properties, A to D, makes collagen suitable for this role?

A strong, inflexible, insoluble

B strong, flexible, soluble

C strong, inflexible, soluble

D strong, flexible, insoluble

Your answer

Cyanobacteria are photosynthetic prokaryotes.

A scientist exposed cyanobacteria to light of different colours and intensities and made the following observations:

• Most cyanobacteria are blue in colour.

• At low light intensities, glucose production in cyanobacteria is low.

• When light intensity reaches a certain level the rate of glucose production in cyanobacteria stops increasing.

Which of the following statements, A to D, correctly explains these observations?

A The pigments in cyanobacteria absorb blue light and light intensity is a limiting factor for the rate of photosynthesis.

B The pigments in cyanobacteria absorb red light and light intensity is not a limiting factor for the rate of photosynthesis.

C The pigments in cyanobacteria absorb blue light and light intensity is not a limiting factor for the rate of photosynthesis.

D The pigments in cyanobacteria absorb red light and light intensity is a limiting factor for the rate of photosynthesis.

Your answer

Fig. 16 shows pressure changes during the cardiac cycle.

Using Fig. 16, compare the changes in pressure in the left ventricle with the changes in pressure in the left atrium.

Using Fig. 16, calculate the heart rate of this individual.

Give your answer to 2 significant figures.

Using Fig. 16, calculate the percentage change between minimum and maximum pressure in the aorta.

Give your answer to 2 significant figures.

Name the valve which closes at point X on Fig. 16.

The heart supplies oxygenated blood to the tissues.

VO₂^max is a measurement of the maximum volume of oxygen that an individual can use during intense exercise in a given time.

Smart watches can estimate the VO₂^max of an individual by measuring heart rate while exercising.

Having a higher VO₂^max is associated with improved aerobic fitness.

Two male students exercised for 30 min and used smart watches to record their VO₂^max. Table 16 shows their masses and the VO₂^max values they recorded.

Student 1 drew the following conclusion from this result:

Student 2 said that this conclusion is invalid because several variables have not been controlled.

State three variables necessary for a valid comparison that have not been controlled in the above experiment.

Brown fat is a type of tissue.

Brown fat has a higher need for oxygen because fat cells in this tissue carry out aerobic respiration at a higher rate than fat cells in other tissues.

Suggest which organelle is present in higher numbers in brown fat cells than in other fat cells.

Gibberellin causes stem elongation in plants.

Fig. 17.1 shows the effect of gibberellin on cabbage plants.

Gibberellin causes an increase in the distance between the leaves on the stem, which is known as the internodal length.

Explain why gibberellin is classed as a plant hormone.

A scientist carried out an investigation into the effect of gibberellin on cabbage plants.

The scientist applied a range of volumes of gibberellin and measured the rate of increase of internodal length over 30 days.

Table 17 shows the scientist’s results.

Plot the results from Table 17 as a suitable graph.

Gibberellin causes an increase in internodal length.

State one other role of gibberellin in plants.

A student carried out chemical tests on cabbage leaves to investigate which molecules were present.

The student’s method was as follows:

Name a type of food molecule that the student will not be able to detect using these chemical tests.

The table below is a summary of some of the student’s findings.

Complete the table by writing in the missing observations and conclusions.

The student then used a colorimeter to measure the absorbance of the contents of Tube 2.

Explain how the use of a colorimeter could improve the student’s conclusion.

Mammals and fish both need circulatory systems to transport oxygen to respiring tissues. They have different circulatory systems because they have different oxygen requirements.

Acetylcholine (ACh) is a neurotransmitter in mammals. Studies have suggested that it also functions as a hormone in some invertebrate species, such as squid.

When ACh comes into contact with specialised cells in squid skin, it causes them to change colour. These colour changes allow the squid to communicate and to camouflage itself.

ACh is made by cells in the centre of the squid’s body.

Explain how it is possible for ACh to have an effect on cells in the skin of the squid.

Squid blood contains a blue oxygen-carrying protein called haemocyanin.

High partial pressures of carbon dioxide reduce the affinity for oxygen of haemocyanin.

Suggest a mechanism by which carbon dioxide could reduce the affinity for oxygen of haemocyanin.

Resistance training with weights can increase muscle mass in the body. It can also lead to vascularisation, where blood vessels become more visible through the skin. Fig. 19.1 shows vascularisation.

Vascularisation occurs in bodybuilders because blood vessels are pushed to the surface by increased muscle mass. They can also become more visible due to reduced body fat and dehydration.

Explain why the visible blood vessels are likely to be veins.

Illegal use of steroids is widespread in professional sport.

The International Olympic Committee (IOC) tests the urine of athletes to help prevent steroid abuse.

Fig. 19.2 is a graph showing tests carried out by the IOC between 1986 and 1994.

• The bars represent the number of urine samples tested.

• The line shows the percentage of samples testing positive for the steroid testosterone.

Calculate the change in the number of samples testing positive for testosterone between 1988 and 1991.

Rubredoxin is a protein found in bacteria. It contains around 50 amino acids. One iron ion is bound by the sulphur atoms of four cysteine amino acids.

The structure of rubredoxin is shown in Fig. 20.1.

Rubredoxin is known as a conjugated protein.

Use Fig. 20.1 to explain what is meant by the term conjugated protein.

Using the information provided about rubredoxin, state two similarities between the structures of rubredoxin and haemoglobin.

Rubredoxin and haemoglobin have different secondary and tertiary structures.

Using the information provided about rubredoxin, state two other differences between the structures of rubredoxin and haemoglobin.

Ferritin is a protein that is used to regulate iron levels within plant tissues.

It is a large spherical structure which can hold many iron (Fe³⁺) ions at its centre.

Iron can be toxic to plant tissues. Ferritin prevents the build-up of iron.

Fig. 20.2 shows the internal structure of ferritin.

Explain how hydrophilic and hydrophobic interactions contribute to the spherical shape of ferritin.

Fig. 21.1 shows a transverse section of a human adrenal gland.

Using Fig. 21.1, identify the letter and name of the region of the adrenal gland that secretes adrenaline.

Identify patients X, Y and Z by labelling the traces in Fig. 21.2.

Sketch a trace for a patient who has entered atrial fibrillation.

Suggest why reduced heart rate is sometimes seen in people who are very aerobically fit.

Plants are capable of synthesising a variety of molecules from the products of the light-independent stage of photosynthesis.

Fig 22.1 summarises these processes.

Identify the molecules represented by the letters A, B, C and D in Fig. 22.1

Identify the following variables from the scientist’s method:

independent variable

dependent variable

one control variable

Identify one variable that was not controlled in the scientist’s method.

Fig. 22.2 is a graph of the scientist’s results.

Describe and explain what these results show about photosynthesis in P. pusillus.

The light-independent stage of photosynthesis used to be referred to as the ‘dark reaction’.

Explain why this is both an accurate and an inaccurate way to describe the light-independent stage.

Name the enzyme responsible for fixing CO₂ in the light-independent stage.

The scientist then investigated the effect of auxin on P. pusillus stems.

The growing tips of stems were removed and the stems were placed in solutions containing different concentrations of auxin.

The scientist analysed the results and determined the following relationship:

The higher the concentration of auxin in the solution, the fewer side shoots grew on the P. pusillus stems.

Explain why this relationship occurs in P. pusillus stems.

Give two examples of the commercial uses of auxin.