Stem cells

Microscopy can be used to examine the structure of stem cells.

The image shows a stem cell from a fish embryo viewed under a light microscope.

Identify two pieces of evidence that suggest that the image was produced by a light microscope rather than a scanning electron microscope.

Calculate the horizontal diameter of the cell shown in the image.

Give your answer in m.

Diameter =........ m

Explain why staining is useful in microscopy.

Use structures visible in the image to support your answer.

State two features of stem cells, not visible under the microscope, that distinguish them from specialised cells.

Stem cells have a number of uses in medicine.

Explain why stem cells are useful tools in medical research.

* The development of body form begins in embryonic stem cells.

Using examples, explain the importance of mitosis and apoptosis as mechanisms controlling the development of body form.

Extra answer space if required.

Type 1 diabetes mellitus is characterised by a lack of insulin production. Type 2 diabetes mellitus can involve reduced production of insulin and a decreased response to insulin.

* Scientists analysed the occurrence of diabetes in identical and non-identical twins.

Identical twins have the same DNA. Non-identical twins share approximately 50% of each other’s DNA.

The scientists selected 614 pairs of twins in which at least one of the individuals had diabetes: 109 pairs had type 1 diabetes; 505 pairs had type 2 diabetes.

The scientists calculated the percentage probability of an individual having diabetes when their twin has the disease.

The table shows the percentage probability of both individuals in a pair of twins developing either type 1 or type 2 diabetes.

Explain what conclusions can be drawn from the data in the table about the influence of the environment and genetics on the probability of developing diabetes.

Extra answer space if required.

Insulin is secreted from cells in the pancreas.

This is a photomicrograph of pancreatic tissue.

Identify the structures labelled A, B and C.

The graph shows the changes in the rate of insulin secretion in a person with type 2 diabetes after consuming glucose.

The table shows the changes in the rate of insulin secretion in a person with normal glucose tolerance after consuming glucose.

Plot the data from the table on the graph and draw a line of best fit.

The table lists statements about a molecule of insulin.

Complete the table by stating the level of protein structure (primary, secondary, tertiary or quaternary) to which the statement relates.

Bacteria can be genetically modified to produce insulin.

State how a plasmid containing the gene coding for insulin can be transferred into a bacterial cell.

Suggest how bacterial cells can be screened to check if they have taken up a recombinant plasmid.

In the future, type 1 diabetes could be treated by giving patients new pancreatic -cells that have been produced in a laboratory from stem cells.

State a feature of stem cells that allows them to be used to produce pancreatic -cells.

Future treatments for type 1 diabetes may be able to use stem cells from a patient’s body to produce new -cells.

Explain why patients receiving these new -cells would still need to be given immunosuppressant drugs.

Glands can be either endocrine or exocrine.

Describe what is meant by an endocrine gland.

The pancreas contains endocrine glands such as the Islets of Langerhans. It also contains cells that produce digestive enzymes.

Suggest why the cells that produce digestive enzymes are described as exocrine rather than endocrine.

Hormones can be classed as either steroid or non-steroid. Steroids are lipid soluble.

Suggest the location of the receptors for steroid hormones and state a reason for your suggestion.

The Society for Endocrinology has produced a booklet about adrenal failure to help patients understand their illness.

The following statements are adapted from this booklet.

• Adrenal failure is caused by inability of the adrenal glands to produce sufficient amounts of cortisol and aldosterone.

• In healthy people, the hormone ACTH is produced by the pituitary gland and causes the adrenal cortex to release more cortisol and aldosterone.

• A pituitary tumour can stop ACTH production by the pituitary. This leads to adrenal failure.

• Symptoms of adrenal failure include severe fatigue and weakness, weight loss, low blood pressure and salt craving.

Explain the symptoms of adrenal failure.

Explain why patients with a pituitary tumour have adrenal failure but still respond normally to situations of danger or excitement.

Hypothyroidism (underactive thyroid gland) is treated by taking thyroxine tablets.

Scientists are investigating the use of stem cell transplants to treat hypothyroidism in which the thyroid glands of mice are destroyed using radioactive iodine.

The scientists obtained mouse embryonic stem cells (ESCs) and incubated them in culture with or without a mixture of growth factors for 30 days before transplanting them into the mice.

They divided the mice into four groups as shown in the table.

After eight weeks they measured the thyroxine concentration in the four groups of mice. Their results are shown in the graph. Each cross represents a single mouse and the mean ± 2 standard deviations is shown for each group.

The ESCs are described as pluripotent. Explain what is meant by pluripotent.

The scientists concluded that growing the ESCs with growth factors caused them to differentiate into functional thyroid tissue.

Evaluate this conclusion.

The scientists then repeated their experiments with adult stem cells taken from the skin of patients with hypothyroidism. These cells were artificially transformed into pluripotent stem cells (iPSCs).

The scientists concluded that use of human iPSCs would be safer than using human ESCs to treat hypothyroidism.

Use your knowledge of stem cells to suggest one reason that supports and one reason that does not support the scientists’ conclusion.

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

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