| Date | November 2015 | Marks available | 1 | Reference code | 15N.3.HL.TZ0.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | State | Question number | 14 | Adapted from | N/A |
Question
The graph shows the oxygen dissociation curve for adult haemoglobin.
State the pathway by which hormones travel from the hypothalamus to the anterior pituitary gland.
State the condition of the blood that would stimulate the release of ADH (vasopressin).
Using the graph, draw a line to show how the oxygen dissociation curve changes with the Bohr shift.
Explain the role of the Bohr shift during vigorous exercise.
Markscheme
(pituitary) portal vein
Do not accept if portal vein is qualified as “hepatic”.
low water content / high blood solute concentration
a. more CO2 is produced which lowers the pH of the blood;
b. hemoglobin releases more oxygen (at lower pH) for same partial pressure of oxygen;
c. more oxygen is available to respiring tissues;
| Date | May 2015 | Marks available | 2 | Reference code | 15M.3.HL.TZ1.13 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Evaluate | Question number | 13 | Adapted from | N/A |
Question
For children suffering from persistent asthma, budesonide may be used in inhalers to suppress airway inflammation. This therapy may continue for many years, so its long-term effect on growth was studied. One thousand children were randomly assigned to receive either budesonide or a placebo, a neutral substance used as the control, and were monitored until adulthood. The graph shows the difference in height between the group who received the drug and others who received the placebo (the control group). The same treatment group was measured at the start of the treatment period, four times during the treatment period and then once again about eight years later.
State the mean height difference between the budesonide group and the placebo group at the start of the study.
The mean age for starting the treatment was nine years. Suggest a reason for the choice of this age.
Describe the effect of budesonide on the mean difference in height, during the period of treatment.
Evaluate the long-term after-effect of budesonide treatment on height.
Suggest one significant shortcoming in the data.
Markscheme
a. 0.3 cm (allow 0.2 to 0.4);
b. no difference (because of large error bars);
growing spurt not yet started/prepuberty
a. causes a reduction in height;
b. biggest drop in first year (of treatment);
c. levelling off after two years;
d. no apparent drop after year two because of overlapping error bars;
a. height difference (seen during treatment period) persists into adulthood;
b. budesonide group on average about 1.3 cm/13 mm shorter than placebo group / height difference is (likely) unnoticeable/insignificant compared to placebo group;
c. benefit from budesonide treatment (probably) outweighs (slight) loss of height;
no information on male versus female/diet/ethnic background/health status/medical treatment or history before study/effects on growth at other ages
| Date | May 2012 | Marks available | 1 | Reference code | 12M.3.HL.TZ2.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | State | Question number | 14 | Adapted from | N/A |
Question
State one example of a steroid hormone.
State one example of a hormone that is a tyrosine derivative.
Outline the hormonal control of digestive juice secretion in the stomach.
Outline how exercise causes an increase in the ventilation rate.
Markscheme
estrogen / testosterone / progesterone
Accept other verifiable examples.
thyroxine/thyroid hormones / epinephrine / adrenaline / noradrenaline
Accept other verifiable examples
gastrin is secreted when food is in the stomach/chemoreceptors/stretch receptors are stimulated;
stimulates gastric acid/pepsinogen production;
when pH drops too low, gastrin secretion is inhibited by (secretin and somatostatin) hormones;
exercise uses energy/ATP/increases metabolic rate/aerobic respiration;
which causes increased CO2 which lowers blood pH;
detected by chemosensors in aorta/carotid arteries;
stimulate medulla/breathing centre of brain;
nerve impulses to diaphragm and intercostal muscles increase contraction (rate);
| Date | May 2010 | Marks available | 1 | Reference code | 10M.3.HL.TZ1.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Define | Question number | 14 | Adapted from | N/A |
Question
Define hormones.
State one type of hormone, giving an example.
Compare gastric juice and pancreatic juice.
Outline the reason for one named substance found in food not being digested and absorbed by humans.
Markscheme
chemical messengers secreted by endocrine glands/specialized cells directly into the blood/body fluid (and transported to specific target cells);
steroid hormone e.g. testosterone / peptide hormone e.g. insulin / tyrosine derivatives e.g. thyroxine;
Award [1] for each pair.
cellulose / lignin;
cellulase not present / no enzymes for digesting lignin;
Accept any other reasonable substance.
| Date | November 2016 | Marks available | 1 | Reference code | 16N.3.HL.TZ0.20 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Outline | Question number | 20 | Adapted from | N/A |
Question
The diagram demonstrates the action of steroid and peptide hormones in a section of cell and adjacent capillary.
On the diagram, label a
(i) second messenger.
(ii) gene regulatory protein.
Outline one characteristic of steroid hormones that allows them to readily diffuse through cell membranes
Compare and contrast the mechanisms of action of peptide and steroid hormones.
Markscheme
(i) a. second messenger correctly labelled
(ii) b. gene regulatory protein correctly labelled
Do not accept steroid hormone/protein complex.
a. lipid-soluble/non-polar/hydrophobic molecules «that readily diffuse through cell membranes»
b. small enough to diffuse through membrane
Since the questions asks to “outline” a brief account is necessary to gain the mark.
Answers do not need to be presented as a table. Award marks for pairs of corresponding elements on the same line of this table.
| Date | November 2017 | Marks available | 1 | Reference code | 17N.3.HL.TZ0.20 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | State | Question number | 20 | Adapted from | N/A |
Question
Thyroxin is a hormone produced in the thyroid gland. State one function of thyroxin.
The action of thyroxin is similar to steroid hormones. Describe the action of steroid hormones.
The World Health Organization recommends that the iodine intake should be supplemented in pregnant women due to their increased requirements. Outline the need for iodine supplementation.
Markscheme
a. regulates the «basal» metabolic rate/BMR
b. controls body temperature
[Max 1 Mark]
a. steroid hormone passes through cell/plasma membrane
b. binds to receptor «proteins» in cytoplasm
c. receptor–hormone complex travels to nucleus
d. binds to DNA/chromatin
e. promotes/inhibits the transcription of specific genes
f. codes for/produces specific proteins
[Max 3 Marks]
a. iodine is an essential nutrient/cannot be synthesized by the body
b. iodine is required for thyroid hormones/thyroxin production
c. some areas in the world have iodine deficient soil/low iodine in their diet
d. supplementation will reduce stunted growth and mental development/cretinism in babies born to mothers associated with thyroid deficiency
e. thyroid deficiency will lead to health problems
[Max 2 Marks]
| Date | November 2010 | Marks available | 1 | Reference code | 10N.3.HL.TZ0.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | State | Question number | 14 | Adapted from | N/A |
Question
Label the section of healthy liver tissue below.
I.
II.
III.
Outline two roles of the liver.
List two materials that are not absorbed but are egested by the body.
State an example of a protein hormone.
Markscheme
I. hepatic cells / hepatocytes / liver cells / liver tissue;
II. hepatic vein / blood cells;
III. sinusoids;
a. storage of nutrients;
b. detoxification of poisons;
c. breakdown of hemoglobin;
d. production of bile pigments;
e. synthesis of plasma proteins;
f. synthesis of cholesterol;
Award [1] for two of the following.
cellulose / lignin / bile pigments / bacteria / intestinal cells
Do not accept fibre.
insulin / glucagon / prolactin / somatotrophin
Award other suitable examples.
| Date | May 2017 | Marks available | 2 | Reference code | 17M.3.HL.TZ1.20 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Outline | Question number | 20 | Adapted from | N/A |
Question
A good marker of dietary intake of iodine is the urinary iodine level (UI). A study was carried out in the UK to establish urinary iodine levels and milk intake in schoolgirls aged 14–15 years.
Urinary iodine values from 50 to 99 μg dm–3 are considered to be mild iodine deficiency. Deduce the effect of milk intake on the iodine status of schoolgirls in the UK.
Outline the need for iodine in the endocrine system.
Growth hormones are examples of peptide hormones. Explain the mechanism of action of peptide hormones.
Markscheme
a. the more milk taken in, the higher the iodine levels
b. when no milk consumed all girls «in study» were iodine deficient
c. in all cases median value is mildly deficient so milk may have no effect
d. increase above 1 cup/day may have no/little effect
Accept answers in the converse.
a. iodine is absorbed/used/needed by the thyroid
b. «needed» to synthesise thyroxin
c. lack of iodine causes swelling of thyroid gland/goiter/hypothyroidism
OR
thyroxin used to regulate metabolic rate/generate heat
a. «peptide hormones» do not enter cells
b. bind to «specific surface» receptors in plasma membrane
c. leads to production /release of a secondary messenger inside cell
d. triggers a cascade of reactions in the cytoplasm
e. usually involves activating or inhibiting enzymes
| Date | May 2017 | Marks available | 2 | Reference code | 17M.3.HL.TZ1.21 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 21 | Adapted from | N/A |
Question
The graph below shows the oxygen dissociation curve at a low CO2 concentration.
Outline the main changes in the lungs that occur in patients with emphysema.
State a treatment for emphysema.
An increase in metabolic activity results in greater release of CO2 into the blood. On the graph, draw the oxygen dissociation curve during intense exercise when the CO2 concentration of the blood is high.
Explain how the increase in CO2 concentration affects the release of oxygen to respiring cells.
Markscheme
a. air sacs/alveoli break down/rupture
b. creating one larger air space instead of many small ones / reduces the surface area of the lungs
c. loss of elasticity of lung tissue
supplemental oxygen / breathing techniques / bronchodilators / inhaled steroids / lung surgery to remove damaged tissue / lung transplant
curve has to be towards the right and starting together
Must start together but can finish slightly below the original curve.
a. increased levels of CO2 lower the pH of the blood
b. «which results in» decreased affinity of the hemoglobin for oxygen / greater release of oxygen
c. this shifts the oxygen dissociation curve to the right/Bohr shift
| Date | November 2009 | Marks available | 2 | Reference code | 09N.3.HL.TZ0.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Define | Question number | 14 | Adapted from | N/A |
Question
The electron micrograph below shows cells from the intestine.
In the electron micrograph above, state the name of the
(i) structure labelled X.
(ii) type of cells labelled Y.
Define hormone.
Outline the circulation of blood through liver tissue.
Markscheme
(i) microvilli/microvillus
(ii) epithelial cell/enterocyte
chemical (messengers) secreted by (endocrine) glands;
into the blood / transported by the blood;
act on target organs/cells;
hepatic artery carries oxygenated blood;
hepatic portal vein carries blood from gut/deoxygenated blood;
blood from hepatic portal vein and hepatic artery mix;
flows through sinusoids;
hepatic vein carries blood away from liver;
| Date | May 2016 | Marks available | 2 | Reference code | 16M.3.HL.TZ0.19 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Identify | Question number | 19 | Adapted from | N/A |
Question
The table summarizes the relative content of essential amino acids in different foods. Cysteine and tyrosine are classified as being “conditionally essential”. The quantity of each amino acid in a hen egg is set as 1.0 and all other values are relative to the hen egg standard.
Outline what is meant by the term essential amino acid.
Phenylalanine is converted to tyrosine by the enzyme phenylalanine hydroxylase.
(i) Deduce the reason that tyrosine is considered to be a conditionally essential amino acid.
(ii) When infants with the condition phenylketonuria (PKU) are left untreated, they have a build-up of phenylalanine in the blood and high levels of phenylalanine in the urine. State the cause of this condition.
Evaluate human milk as an overall source of essential amino acids.
Outline the control of milk secretion by oxytocin and prolactin.
The diagram represents a lobule from a mammary gland. The mammary gland is an example of an exocrine gland.
Identify two features of an exocrine gland visible in the diagram.
Markscheme
«Essential amino acids» must be obtained from the diet
They cannot be synthesized by the body
OR
They cannot be synthesized from other amino acids
(i) Tyrosine can only be synthesized when phenylalanine is in the diet (Accept inverse: if phenylalanine is not in the diet the person will not
be able to synthesize tyrosine).
(ii) Recessive inherited «genetic» condition
OR
They lack «the enzyme» phenylalanine hydroxylase
OR
Mutated form of PAH gene
Contain all of the essential amino acids
Human milk has higher levels of 5 «out of 9» essential amino acids than cow milk
OR
Human milk has the same or more of essential amino acids except histidine and lysine compared to cow milk
Human milk is the same or higher in all essential amino acids except histidine compared with hen egg
OR
Human milk has higher levels of 4 «out of 9» essential amino acids compared with hen egg
Prolactin
Produced by the anterior pituitary
Stimulates mammary glands to grow
Stimulates the production of milk
Oxytocin
Produced in neurosecretory cells «in hypothalamus»
OR
stored/secreted by posterior pituitary
Suckling/nursing stimulates oxytocin release
OR
example of positive feedback
«Contractions» cause ejection/release of milk from mammary glands
Award [2 max] if response only mentions one of the hormones.
Presence of ducts
Presence acini/acinar/secretory cells
Ducts leads to a body surface/cavity/gut
| Date | May 2017 | Marks available | 6 | Reference code | 17M.3.HL.TZ2.22 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Explain | Question number | 22 | Adapted from | N/A |
Question
Explain the role of receptors in mediating the action of both steroid and protein hormones.
Markscheme
a. receptors are proteins
steroid hormones: [3 max]
b. steroid hormones cross plasma membrane
c. bind to receptor «proteins» in the cytoplasm of the target cell
d. to form a receptor–hormone complex
e. «the receptor–hormone complex» promotes the transcription of specific genes
peptide hormones: [3 max]
f. peptide hormones bind to receptors in the plasma membrane of the target cell
g. binding of hormones to «membrane» receptors activates a cascade of reactions
h. mediated by a second messenger inside the cell
i. such as cAmp or Ca2+ calmodulin
| Date | May 2013 | Marks available | 2 | Reference code | 13M.3.HL.TZ1.13 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Distinguish | Question number | 13 | Adapted from | N/A |
Question
Distinguish between the mode of action of steroid and peptide hormones.
Outline the control of gastric juice secretion.
Markscheme
a. peptide hormones do not enter the cell whereas steroid hormones do;
b. peptide hormones bind to a cell surface receptor whereas steroid hormones bind to a receptor in the cytoplasm;
c. peptide hormones act through a secondary messenger/cAMP whereas steroid hormones have (direct) effect on DNA;
d. steroid hormones have effect on gene transcription whereas peptide hormones change activities of cell/influence enzyme activity;
a. involves both nerve impulses and the hormone gastrin;
b. sight/smell of food causes nerve impulses to be sent/reflex action;
c. food in stomach stimulates touch receptors/chemoreceptors/stretchreceptors releasing more gastric juice;
d. stretching of stomach wall stimulates secretion of the hormone gastrin;